Plant Resources Pla nt

Plant Resources Pla nt
Agriculture and food production have a large footprint on the landscape globally and
compete for space with land for nature conservation. This book explores the competition
between the food needs of a growing human population and the conservation of
biodiversity as intensified by the emerging use of crops for energy production.
As concern about the impact of greenhouse gas emissions on climate grows and oil prices
increase, energy production from agricultural crops has become a significant industry.
At the same time, growth in food demand due to population growth has been accelerated
by growing affluence associated with economic growth in major developing countries
increasing per capita consumption. Consumers are concerned that the price of food will
continue to increase sharply as a result of this competition, but a loss of biodiversity may
be another major outcome. Drawing on his expertise in plant conservation genetics, the
author provides a balanced appraisal of the potential for developing new or improved crops
for food or bioenergy production in the context of climate change, while at the same time
protecting biodiversity.
Earthscan strives to minimize its impact on the environment
Cover credits:
‘Ethanol 3 © Jim Parkin/
publishing for a sustainable future
publishing for a sustainable future
Plant Resources
for Food, Fuel
and Conservation
Robert Henry is Director of the Centre for Plant Conservation Genetics
at Southern Cross University, Australia. He is the author or editor of several books
on plant molecular biology, genetics, evolution and biodiversity.
Plant Resources
‘Henry’s book deals with biofuels – an alternative, renewable energy source
in a world that confronts us today with diverse opportunities and challenges due to
climate change. It provides a comprehensive and thoughtful account on the potential
for producing biofuels without harming biodiversity or food security.’
Rodomiro Ortiz, Centro Internacional de Mejoramiento de Maíz y Trigo
(CIMMYT), Mexico
for Food, Fuel and Conservation
‘This is not only an interesting and informative book,
but is highly relevant and well-timed. Robert Henry explores the diverse uses of plants
and challenges the reader to contemplate some of the choices
that future generations will face in terms of food, fuel and environmental protection.’
Kerrie Farrar, Aberystwyth University, UK
Robert Henry
Page i
Plant Resources for Food,
Fuel and Conservation
Page ii
Page iii
Plant Resources for Food,
Fuel and Conservation
Robert Henry
London • Sterling, VA
Page iv
First published by Earthscan in the UK and USA in 2010
Copyright © Professor Robert J. Henry, 2010
All rights reserved
ISBN: 978-1-84407-721-2
Typeset by 4word Ltd, Bristol
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A catalogue record for this book is available from the British Library
Library of Congress Cataloging-in-Publication Data
Henry, Robert J.
Plant resources for food, fuel, and conservation / Robert Henry.
p. cm.
Includes bibliographical references and index.
ISBN 978-1-84407-721-2 (hardback)
1. Botany, Economic. 2. Energy crops. 3. Agrobiodiversity conservation. I. Title.
SB107.H46 2010
At Earthscan we strive to minimize our environmental impacts and carbon
footprint through reducing waste, recycling and offsetting our CO2 emissions,
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The paper used is FSC certified.
Page v
List of Figures, Tables and Boxes
List of Acronyms and Abbreviations
Plants for Food, Energy and the Environment
Plant Resources for Food and Fibre
Impact of Climate Change on Food and Fibre
Energy Resources
Plant Resources for Bio-energy and Chemical
Feedstock Uses
Competition between Food and Fuel Production
Plants, Biodiversity and the Environment
Impact of Climate Change on Biodiversity
Competition between Agriculture and
Biodiversity Conservation
Domestication of New Species
Options for the Future
References and Further Reading
Page vi
Page vii
List of Figures, Tables and Boxes
World cereal production
Wild barley plants are shown growing in a field near
Aleppo, Spain
Genetic origin of bread wheat
World population growth
Global food consumption by industrialized and
developing countries
Global food consumption by region
Global food consumption – world
The concept of the gene pool
Wild grape and rice relatives
Carbon dioxide concentrations in the atmosphere
Global temperature
Oil consumption – regions
Oil consumption – world
Difference in biomass composition in flowering plants
Interactions between biomass, conversion
technology and fuel molecule
Global ethanol production
Ethanol produced from sugarcane on sale in Brazilia
Sugarcane production
Comparison of conventional cultivation of
Eucalypts and growth of a related Melaleuca for
annual harvest
Transportation of biomass for biofuel production
Brazil – land use
Relationships between different groups of flowering plants
Comparison of a weed in a new environment and in
its native habitat
Biodiversity in cultivation – traditional village gardens near
Tsukuba, Japan
Page viii
Plant Resources for Food, Fuel and Conservation
The rare Banksia conferta
Fertile Crescent – site of early domestication
Ancient grain
Loss of genetic diversity in domestication
Domestication in the Proteaceae
Davidson’s Plum
Relationships between higher plants
Mayan ruins on the Yucatan Peninsula, Mexico
Hybrid Eucalypts – Hybrid vigour
Human uses of higher plants
Flowering plant groups used as foods
Domestication of maize
Rice genus
Rice tribe
Seedbanks for major crop germplasm resources
Consultative Group on International Agricultural
Research (CGIAR) Centres
Electricity generation from non-fossil fuel sources
Examples of the composition of plant biomass
and predicted ethanol yields
Examples of different stages of development of
biofuel technology
Biofuel technologies and products
Examples of plants that have been considered as
a source of biomass for biofuels
Examples of arable land estimates
Impact of different levels of biofuel production
on food supply (assuming no expansion in
agricultural land)
Land requirements to satisfy food and fuel
requirements by 2085 – relative to 2005 values
Estimates of yields, conversion efficiencies and
areas of land required to replace oil with biofuel
in a country consuming around 100GL/year
fuel consumption
Water use for electricity and biofuel production
from different crops
Domestication of crop plants
Page ix
List of Figures, Tables and Boxes ix
Barley: the first plant domesticated
Human selection of rice as an attractive food
DNA banks for conservation and support of plant
The Green Revolution
Improving the folate content of cereals
Scientific and popular views of climate change
Pathways of photosynthesis
Gene diversity in relation to climate
Case study – cereals (rice, wheat, barley and sorghum)
in Australia
Approximate conversions for units of energy
Advances in technologies for the analysis of plant
Biomass transportation
Nanotechnology provides greatly improved
tools for analysis of plant genes
Arable land in Western Australia
Case study – Queensland, new species
Coastal Fontainea – an example of a critically
endangered plant species
What is a species?
Ecosystem services
Lismore Rainforest Botanic Gardens
Impact of climate on wild barley populations
Climate change and Banksia conferta
Did plants and animals domesticate humans?
Parallel domestication of plants and animals
The domestication of rice
The case of the Mayan society
Advances in DNA fingerprinting techniques
for use in plant improvement
Plant genomics
Research targeting better health and
functionality in foods
Page x
Page xi
The capacity of the biosphere to support population growth is being challenged by several emerging issues. Climate change may reduce the
productivity of agriculture globally. Growing affluence in major developing countries is creating very strong growth in demand for food. Some
have argued that the ability of agricultural production systems to meet this
demand may be restricted by the emerging use of crops to produce renewable fuels. The production of biofuels is a response to both the threat of
climate change and reducing supplies of affordable oil. These combined
demands on land for agricultural production to support strong growth in
food and energy consumption threaten new pressures on space for biodiversity conservation. At the same time climate change poses a direct threat
to biodiversity. The challenge can be defined as balancing the advantages
to biodiversity and food production of any climate change mitigation
achieved by biofuel production against any loss of biodiversity and food
production resulting from displacement by biofuel crop production. This
indicates that we should also aim to ensure that human energy requirements are met as far as possible from parts of plants not useful as food, or
plants that can be grown on land not suitable for food production. We
need to minimize the land footprint of food and energy production to allow
space for biodiversity conservation.
Global analysis of the strategic options available suggests that land, water
and other resources use needs to be very carefully managed, especially with
the prospects of significant climate change.
Some of the key related global issues are:
Which of the available plants should be allocated the limited land, water
and other resources to produce crops for direct use as human food, pastures for food animals, fibre and energy production?
How do we resolve competition for these resources between these alternative uses of plants?
Should we also be growing plants specifically to protect the environment and to conserve biodiversity?
What plants do we have in cultivation for these applications or can we
develop new varieties from wild plants for these purposes?
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Plant Resources for Food, Fuel and Conservation
How do we balance these needs against nature conservation as an alternative land use option?
This book explores the challenges of selecting from the available plant
genetic resources the varieties necessary to meet these new and increasing
demands. The expansion of agriculture to satisfy human demand for food
and energy will continue to be constrained by the need to support conservation of the biodiversity upon which agricultural production and life itself
Page xiii
I thank Kylie Lindner and Linda Hammond for assistance with back up of
the manuscript and correspondence with the publisher, and Linda
Hammond for assistance in preparation of the figures. Figure 10.2 was
provided by James Helm from the photographs of the late Robert Metzger.
I thank Tim Hardwick, Earthscan, for assistance with source material and
editorial input. I also thank three anonymous reviewers for their constructive criticisms of the manuscript. In an attempt to provide a more
first-hand account of the issues discussed in this book, I have, as far as possible, drawn on personal experience and used examples of research in
which I have been involved, or plant species from agricultural production
systems or wild plant populations with which I am familiar. I thank the
many colleagues, friends and family members who have spent the time to
introduce me to these plants, their biology and utility.
Page xiv
Page xv
List of Acronyms and Abbreviations
C 3, C 4
three-carbon compound, etc.
Consortium for the Barcode of Life
Consultative Group on International Agricultural Research
International Centre for Tropical Agriculture
Centre for International Forestry Research
International Centre for Wheat and Maize Improvement
International Potato Research Centre
carbon dioxide
deoxyribonucleic acid
Food and Agricultural Organization
International Centre for Agricultural Research in the
Dry Areas
World Agroforestry Centre
International Centre for Agricultural Research in the
Semi-Arid Dry Tropics
International Energy Agency
International Food Policy Research Institute
International Rice Research Institute
International Union for Conservation of Nature &
Natural Resources
life cycle assessment
National Aeronautics and Space Administration
polylactic acid
parts per million
Africa Rice Centre
World Health Organization
Page xvi
Page 1
Plants for Food, Energy and the
Not only are the flowering plants the largest and most successful plant
group today but they are of fundamental importance to the life and survival of [humans]. [We] in fact depend on them for major sources of
food and sustenance, either directly through agricultural or horticultural
crops such as cereals, legumes and fruits, or indirectly through their
ability to provide pasture or feed for animals [we] eat. They also provide a source of raw materials for building and shelter, for the
manufacture of paper, fabrics and plastics, and for oils, fibres, waxes,
spices, herbs, resins, drugs, medicines, tannins, intoxicants, beverages –
the list seems endless.
Vernon Heywood, 1978
Plants are a major feature of the landscape over much of the land surface of
the earth except for extreme deserts, very high mountains and the Poles
where it is too cold. Photosynthetic plants are an essential component of the
biosphere, using light energy from the Sun to capture carbon dioxide from
the atmosphere, forming the basic organic compounds on which other life
forms depend and generating the oxygen in the atmosphere. Modern everyday human life still depends on plants for food as much as our ancestors did.
However, many of us, especially those of us living in large cities, are unaware
of these links in our daily lives. More than 10,000 years ago humans began
the domestication of plants and animals and, in developing agriculture, were
able to support large populations that could settle in one place. This process
probably happened first in the Fertile Crescent (an area east of the
Mediterranean Sea) and then separately in several locations around the world.
The development of agriculture was a key factor in humans being able to
establish large communities co-located in permanent structures that became
our towns and cities. Progressively, the development of human societies has
resulted in most people being separated from the daily reality of food production as this task has fallen to an increasingly small and specialized fraction
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Plant Resources for Food, Fuel and Conservation
of the population. In industrialized countries, rural populations account for
only about 20 per cent of the population (FAO, 2005). We have a general
and worrying lack of public appreciation of our continued dependence on
domesticated plants (and animals) for food, as most people living in large
cities have little opportunity to directly experience the food production systems on which they depend.
Current situation
Plant domestication and the production of large quantities of food in agricultural systems have allowed human populations to continue to expand. This
has been possible because of the application of science in the form of plant
breeding and agronomy. These technologies have made possible the increases
in productivity necessary to keep pace with population growth and agriculture
now occupies a large part of the land surface that is suitable for agriculture
(the arable land). The human population passed 6 billion around 2000 and is
projected to rise to as many as 9 billion by 2050 (FAO, 2005), and agricultural productivity has been dramatically increased to meet the demands of this
growing population. However, in very recent times there are signs that we may
have reached some limits in our ability to continue to increase food production faster than that required to match population growth or at least the
growing demands of human populations. The causes of shortfalls in production are difficult to identify: are we reaching the physical and biological limits
of production, are market signals influencing production or have all the benefits of the available technologies been implemented? Sustainable food
production requires conservation of the land and water systems needed to support plant growth on the scale required to feed human populations. The
availability and cost (economic and energy) of the soil nutrient inputs (fertilizers) required to maintain the nutrient status of the soil are an increasing
constraint. The growing economic and environmental cost of energy is making a significant contribution to the cost of producing and distributing these
essential inputs to food production. The establishment of agricultural systems
that will support the human population sustainably long term remains a challenge. The area of arable land per person is predicted to decline from 0.21ha
per person in 1997/99 to 0.16ha per person in 2030 (FAO, 2005).
Recent rising living standards in developing countries have put more
pressure on agricultural production systems. A rapid growth in affluence in
countries with large populations (e.g. China and India) has increased
demand for food beyond that resulting from population growth. Greater per
capita demand for food imposes a larger effective environmental and agricultural footprint per person as populations continue to grow. Increased
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Plants for Food, Energy and the Environment
consumption of meat (or animal products) associated with higher incomes
is a key factor. Human diets with a higher animal content greatly increase
the demand for plant products such as feed grain relative to that of the same
human population eating plant products directly. Significant increases in
food prices were widespread in 2007/8, fuelling concerns about global food
security. If all humans increase their consumption of food to the current levels of developed countries, food demand may be difficult to meet sustainably
and biodiversity may be reduced unless new technologies in the form of
superior plant varieties or better management become available to allow sustainable production at higher levels.
Human societies do not depend on food alone; they are also consumers of large quantities of energy. Many use plant biomass directly as
a source of heating or for cooking. However, fossil fuels such as oil are
used for transport and the production of a diverse range of materials (e.g.
plastics) that are widely used in modern human societies. The general
consensus is that oil is likely to be in short supply in the relatively near
future as we deplete world stocks (Hirsch, 2007). The price of oil has
spiked sharply recently, partly in response to these perceptions. The burning of fossil fuels has increased carbon dioxide concentrations in the
atmosphere. This increase in greenhouse gas concentrations is predicted
to result in dangerous levels of global warming. Increasing global temperatures are a new issue that may pose new constraints on agriculture and
food production. Major and rapid changes in climate risk widespread
extinctions of species of plants, animals and micro-organisms. This situation has created a great interest in developing alternative energy sources
to replace oil. The incentives are two-fold: oil is going to run out eventually so scarcity and the associated rising price will drive the search for
alternatives; and environmental concerns and constraints imposed by
global warming provide another even more compelling incentive. Global
warming resulting from the continued use of fossil fuels may directly
threaten agriculture and food production.
Plants have been co-opted directly to the production of energy with the
recent rapid growth in the conversion of plants to biofuels for use as transport fuel and the burning of plant material to produce electricity. The use of
plants to replace oil in the manufacture of products such as plastics is a significant option. This has immediately put more pressure on the agricultural
production system. Energy and food crops may be competitors for land,
water and other agricultural inputs.
Expansion of human populations has resulted in the displacement of
many other species with the rapid extinction of many plants and animals.
Large numbers of species are currently endangered and if current trends
continue we will see an ongoing rapid loss of biodiversity globally. A major
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Plant Resources for Food, Fuel and Conservation
contributor to the environmental impact of humans is the large area of the
land surface (especially in favourable environments) that is required for agriculture. The continuing growth of human populations, growth in per capita
consumption of food and the additional potential demand for energy crops
with declining oil stocks and the threat of global warming – all contribute to
a potential acceleration of loss of biodiversity.
Human societies are now dependent for survival upon domesticated
plants that are very different in many essential characteristics from the
wild plants that were their ancestors. Despite this we also depend upon
continued availability of the wild populations as a source of new genetic
variation to allow us to adapt our crop plants to environmental variation.
New diseases and plant pathogens (biotic stress) and environmental conditions, including short- or long-term climate change (abiotic stress), are
a continuing threat to food security. Plant breeders are expected to
deliver ongoing food and energy security in an environment that may be
increasingly hostile to crop growth, and with the wild genetic resources
available for their use in delivering these outcomes under growing threat
from development or environmental change. Science is continuing to
offer new technologies that have potential to meet these challenges.
However, growth in human societies and the resulting demand for food
and energy is such that we are required to make major technology
advances (e.g. better plant varieties and effective management systems)
more and more frequently. Unfortunately this is not just an option, especially if we wish to satisfy human requirements sustainably without major
loss of global biodiversity.
Summary of major questions to be addressed
for the future
This book aims to define these issues and explore solutions largely from a
scientific or technical perspective. Many questions need to be answered or
at least raised so that answers can be sought in the future. Can we select
more appropriate plants or more efficient plants for food, feed and energy
applications? Can we learn from the history of domestication of plants to
date? How do we avoid or minimize competition between these uses? Do we
need to domesticate completely new species for these new applications? How
do we protect biodiversity in all of this? Ultimately, how do we minimize the
impact of humans and their agriculture on the global environment and make
life on earth more sustainable? What contribution does science and technology need to make to achieve a sustainable future? What types of innovations
are required and how feasible are they?
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Plants for Food, Energy and the Environment
Outline of this book
Human uses of plants (Table 1.1) for food, feed and fibre will be described
in Chapter 2. Plant domestication was a major step accelerating the development of large human societies that are interdependent with domesticated
plants. The diversity of plants used, their origins and the scale of production
necessary to support human populations will be evaluated. The potential of
climate change to impact upon our ability to produce the food and other
products on which we currently depend will be discussed in Chapter 3. The
needs of human societies for energy and the range of sources of energy will
be explored in Chapter 4. Chapter 5 addresses the use of plants as a source
of energy and specifically the potential of plants to make a major contribution to transport fuel. The resulting potential for competition between food
and energy uses of crops will be examined in Chapter 6. The importance of
plants in the environment, specifically the contribution of plants to biodiversity, will be explored in Chapter 7. We can replace some of the
contributions of natural plant communities to the environment by equivalent
volumes of agricultural and forest plantings. However, these do not support
the biodiversity of more complex plant communities. Chapter 8 will focus
on the continuing competition between the growth of plants for agriculture,
forestry and emerging bioenergy applications, and conservation of plants in
more diverse natural ecosystems. The loss of biodiversity and the impact of
climate change on biodiversity will be examined in Chapter 9. Chapter 10 will
explore the potential for domestication of new plant species to better satisfy
human need for food and energy while preserving biodiversity. Chapter 11
will provide options for the future and will set out scenarios that could be
chosen to deal with the challenges posed by continuing expansion of human
Table 1.1 Human uses of higher plants
Category of use
Animal feed
Cereal, pulses, fruit, vegetables, oilseeds and sugar
Wine, beer, tea, coffee
Pastures, fodder
Cotton, hemp and paper
Housing and furniture
Pharmaceutical products, traditional medicines
Cut flowers, pot plants, garden plants and turf grass
Ethanol for fuel, electricity
Environmental restoration, greenhouse gas sequestration
Perfumes, cosmetics
Source: Henry, 2005a
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Plant Resources for Food, Fuel and Conservation
impact on the global environment. At the end of the book some recommended actions in relation to plant genetic resources will be provided that
will support a sustainable future for life on earth.
This book discusses plants in the environment but most of the discussion relates to all organisms, whether plant, animal and micro-organisms.
Plants are a useful proxy for all life forms when we consider the impact of
human activities and climate change on biodiversity. The diversity of other
organisms in the environment will frequently parallel that of the plants which
are frequently the largest or most obvious components of the ecosystem.
Loss of plant biodiversity directly contributes to a loss of biodiversity of
other organisms by reducing the diversity of habitats or micro-environments.
We will begin by considering the use of plants for food, arguably the
most fundamental and essential use of plants by humans.
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Plant Resources for Food
and Fibre
The history of the world my sweet is who gets eaten and who gets to eat.
Sweeney Todd, The Demon Barber of Fleet Street (as cited by
Lang and Heasman, 2004)
What do we eat? (biological sources)
Human diets are predominantly based upon direct consumption of plants.
Animal products are a smaller part of most human diets, but tend to be
consumed in greater quantities by more affluent human populations.
Animal production is supported by the growth of plants as feed, often
consumed by the animal as pasture or fodder or in more intensive production systems as grain. The production of food in animals is relatively
inefficient. For example, it takes 3000 litres of water to produce 1kg of
rice but 15,000 litres of water to make 1kg of beef, because more than
10kg of feed is needed to produce the 1kg of beef (Millstone and Lang,
Around 300,000 species of flowering plants have been defined.
Relatively few of these species are used as food. However, humans have
explored this diversity extensively to find food plants and as a result foods
are derived from a genetically diverse range of plant species (Table 2.1). A
significant number of species are consumed at least regionally as human
foods, but most human food by volume is accounted for by a very small
number of plant and animal species. Modern human societies are critically
dependent on this small number of species for survival. Despite this remarkable human reliance on these foods, public awareness and as a result
international effort devoted to conservation of the plant genetic resources of
the major crops on which we depend does not always seem to match the
importance of the task.
Food production and consumption has grown to meet the demands of
strong population growth resulting from advances in medical science and
associated longer lifespans. The total amount of food produced continues
to grow largely due to improvements in plant genetics (plant breeding) and
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Plant Resources for Food, Fuel and Conservation
Table 2.1 Flowering plant groups used as foods
Food (seeds and rhizomes)
Beverage (Chloranthus officinalis)
Food white cinnamon
Food pepper
Beverage kava
Food avocado, cinnamon, bay leaves
Food nutmeg, custard apple
Food Sagittaria (tubers)
Food onions, garlic, leek, vanilla, asparagus saffron
Food yams
Beverage sarsaparilla
Food (starchy fruits)
Food coconuts, copra, dates, sago, palm oil
Food rice, wheat, maize, barley, sorghum, millet,
sugarcane, bamboo, pineapple
Animal feed pastures
Food banana, ginger, cardamom, tumeric, arrowroot
Food fruits
Food Macadamia
Food Ammaranthus
Food grapes, gooseberries, currants
Food cloves, lillypilly
Beverage Arabia tea
Beverage tea
Beverage coffee
Food olives
Food potato, aubergine, tomato, pepper, sweet potato
Food carrot, celery, parsley, fennel, dill
Food sunflower, lettuce, chicory, Jerusalem artichoke
Beverage elderberry (wine)
Food cassava, passion fruit
Food peas, beans, peanut (groundnut), soybean
Animal feed clover, lucerne
Food fruits (apple, plum, pear, cherry, mulberries, fig,
raspberries, strawberries)
Beverage hops
Food cucumber, pumpkin, melon
Food chestnut, walnut, pecan
Food oilseed rape, mustard, vegetables
(cabbage, cauliflower), papaw
Animal feed fodder
Food orange, lemon, lime, mango, cashew, pistachio,
lychee, maple sugar
Source: based upon Henry (2005a)
better management of plant production (e.g. improved plant nutrition using
fertilizers). The development of human societies as we know them today
began with the domestication of plants (and animals) more than 10,000
years ago. The expansion of human societies has relied largely on the
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Plant Resources for Food and Fibre
continued genetic selection of these species to refine them to satisfy our
demands for more food and better quality food. Evolving approaches to the
management of agriculture that have advanced the whole crop or animal
production system has complemented genetic strategies to deliver these
Estimated global production of foods for 2004 (FAO, 2007) is as follows:
Fruits & Vegetables
Roots & Tubers
Sugar Crops
2270 million tonnes
1384 million tonnes
718 million tonnes
61 million tonnes
142 million tonnes
1577 million tonnes
622 million tonnes
260 million tonnes
3 million tonnes
The parts of plants that we eat vary widely. The seeds are generally highly
nutritious because they represent a concentrated source of energy and nutrients for a new plant itself. In many cases this has been enhanced by human
selection and domestication. Fruits (the part of a plant surrounding the seed)
have evolved to be attractive to animals to aid plant seed dispersal and we
have also further developed this feature by human selection. Roots and
tubers and sometimes even stems are plant organs for the storage of energy,
often making them attractive foods. The leaves and flowers of many species
are also eaten but are generally less nutritious or attractive as foods. Major
plant food groups contribute to human food needs in specific ways. For
example, the cereals are the primary sources of carbohydrates or energy in
most human diets, while grain legumes or pulses provide significant amounts
of protein.
Cereals are the major source of calories or energy in many human diets.
The three leading cereal species – wheat, rice and maize – are each produced in large quantities (600–700 million tonnes of each per year) and
account for a large part of all human food measured in calories (energy) or
protein. More maize is produced, but much of it is feed to animals and only
contributes to human diets indirectly. In contrast, most wheat and almost all
rice are consumed directly by humans. The wheat is milled to produce flour
which is used in a wide range of foods such as bread and pasta, while rice is
largely consumed as a whole grain food. Barley and sorghum are fourth and
fifth ranked in production (Figure 2.1).
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Plant Resources for Food, Fuel and Conservation
Box 2.1 Cereals
Oryza sativa (and Oryza glaberrima)
Triticum aestivum (and Triticum durum)
Zea mays
Hordeum vulgare
Sorghum bicolor
Secale cereale
Avena sativa
Pearl (Pennisetum glaucum) and finger (Eleusine corocana)
Figure 2.1 World cereal production
Daily average global calorie intake from rice is 557, wheat 521 and maize
117, representing more than 40 per cent of the total of around 2800 from
all foods (FAO, 2007). Rice has been the traditional staple food in Asia and
maize in the Americas, with wheat widely consumed elsewhere. Wheat was
domesticated in the Fertile Crescent and rice in Asia (China). Globalization
of food consumption is resulting in all three species being consumed as a
significant part of diets worldwide. The per capita consumption of cereals
is likely to decline in some regions as diets become more international
and change to include more meat and other foods. Migration has spread
dietary habits globally, and combined with high levels of international travel,
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Plant Resources for Food and Fibre
contributed to consumption of many foods on a widespread global basis.
Cereals have been adapted to the production of a very wide range of human
foods (Henry and Kettlewell, 1996). For example, wheat is used to produce
the following types of products:
fermented (leavened) breads (including pan bread, sandwich buns,
hearth breads, sweet goods, Danish, croissant and raisin bread, and
steamed breads);
flat breads and crackers (including chapatti, roti, naan, paratha, poori,
balady, pita, barabari, tortillas, pizza crust, English muffin, crumpets,
bagels and pretzels);
cookies and cakes;
noodles (including instant noodles, white salted noodles, yellow alkaline
noodles and Udon noodles);
breakfast foods;
starch and gluten as food ingredients.
The production of such a diversity of foods from a single plant species
emphasizes the narrow genetic base of most human food and our great
dependence on cereals for food.
Cereals account for the bulk of energy or calories in many human diets
and are as a consequence important sources of total protein. However, the
proteins in cereals are of relatively poor nutritional quality, requiring other
foods to provide balance in the diet. In addition to the seeds of the grasses
(cereals), our primary source of carbohydrate, we eat the seeds of legumes
(for protein) and those rich in oils (oilseeds).
Grain legumes or pulses are protein rich seeds consumed as a complement
to cereals, especially in many largely vegetarian diets such as those commonly consumed in countries such as India. Increased consumption of
pulses rather than meat as a protein source is an important option to consider in efforts to satisfy food needs from a smaller agricultural footprint.
These crops are critical for food production in other ways; through associated micro-organisms they fix and contribute nitrogen to the soil, enhancing
the yields of other crops such as cereals grown in rotation or following the
legume crop. The contribution of these crops to sustainable food production
is often seriously underestimated because this factor of nitrogen fixation (as
a substitute for fertilizer use) is not considered.
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Box 2.2 Pulses
Pulses include: Adzuki beans, Alfalfa, Beans (Green), Black gram, Borlotti
bean, Broad beans (Faba beans), Carob, Chickpea, Haricot beans, Kidney
beans, Lentil, Lupins, Mung Bean, Pea, Peanut, Pigeon pea, Pinto bean,
Soybeans, Tamarind, Vetches. These foods are the seeds of plants in the
legume family (Fabaceae). They represent an important source of protein
in human diets. Many of these species contain toxic or anti-nutritional factors that have been reduced by breeding selection, or are reduced by
processing or cooking. For example, pulses may contain trypsin inhibitors
(compounds that inhibit the action of trypsin, a protease (protein degrading enzyme) produced in the digestive system, and as a result reduce the
ability of the human or animal to gain nutrition from protein in the diet).
Oilseeds provide an important contribution to human diets. Canola, a product of modern plant breeding, has recently emerged as a major oilseed.
Developed in the early 1970s, canola was produced by selecting cultivars of
rapeseed that were low in both erucic acid and glucosinolates to reduce problems of rancidity and potential toxicity of the oil. Sunflower domesticated in
North America has also been an important oilseed. Oil palms have been a
major source of food oil from more tropical regions. Soybeans are a significant oil source especially in North America. Recent genetic improvement of
soybean has targeted the mutation of three genes to reduce greatly the
linolenic acid (18:3) content to avoid the formation of undesirable trans fats
during the stabilization of the wild type soybean oil by hydrogenation. This
is a good example of how humans have modified oilseeds to suit our food
needs. We now aim to combine the desired function of the oil in the food in
terms of physical properties with desirable nutrition and health attributes.
Fruit and vegetables
Plant parts other than seeds are also major foods. Fruit and vegetables are at
least minor parts of most human diets. However, some fruits are very important regionally. For example, the banana, originally domesticated in South
East Asia, probably having a centre of diversity in New Guinea, is a staple
food in Uganda and is important in other countries. Fruits such as grapes
and citrus are consumed widely throughout the world. Other fruits, especially many tropical fruits, are consumed on a much more regional basis.
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Roots and tubers
The roots and tubers of plants are also important components of many
human diets.
The potato is widely consumed as a staple food; originally from South
America, it has become very important elsewhere. Infamously, the outbreak
of disease in potatoes in Ireland led to major food shortages in the mid1800s. Potatoes have been ranked third in importance as a food, after wheat
and rice. Increased emphasis on potato production contributes to food security by helping to diversify food production and reduce reliance on cereals.
The potato can be produced in many regions and has been more stable in
price because it is produced locally and has not become an exported commodity. Use of potatoes to substitute for some of the wheat in bread is an
option for increased use of potato in human diets.
Cassava, originally from Brazil, is a starchy tuber crop that is especially
important as a food in Africa. Yams (Dioscorea species) are also important
root crops in many tropical regions.
The attractiveness of sweet foods has made the cultivation of crops as a
source of sugar an important activity. Sugarcane in tropical areas and sugar
beet in temperate regions are import food crops. Sugarcane was domesticated in South Asia and New Guinea, and globally it makes a significant
contribution to the energy in human diets (averaging 202 calories per day).
Beverages from plants
Humans consume several beverages made from plants. Tea and coffee are
widely consumed, while alcoholic beverages are produced from several
plants. Barley and to a much lesser extent sorghum and wheat are used to
produce beer by fermentation of the carbohydrates. Grapes and rice are used
to produce wines (sake in the case of rice). Fermented plants are distilled to
produce alcoholic beverages such as whisky. Alcohol is a significant but not
necessarily desirable part of human food energy consumption.
Food from animals
Animals were domesticated by humans at the same time as plants
(Diamond, 2005a). Cows, pigs, sheep and goats were early domesticates and
continue to be important sources of food. The potential for the domestication of a range of both plant and animal species in the one region probably
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explains the location of early domestication and the beginnings of agricultural communities in the Fertile Crescent, and later separately in several
other key regions globally.
Food from animals also depends upon plants. Animals graze plants in
pastures or are fed grain in more modern intensive production. Eggs are produced from chickens fed on grain in similar production systems. Fish
production from the oceans has declined rapidly due to overharvesting.
Increasingly, fish is produced by farming or aquaculture, using increasing
amounts of plant-derived feeds. However, the human consumption of food
from animals is a relatively inefficient mechanism of obtaining nutrients
from plants. Food energy sourced from animals requires relatively large
amounts of plant material as animal feed (around ten times) relative to the
amount of plant material that would be required to supply the energy in
direct plant consumption by humans. Increasing global consumption of
meat associated with increased affluence is resulting in a greater per capita
environmental footprint. Animals also contribute methane, a significant
greenhouse gas, to the atmosphere. A higher proportion of animal food in
human diets results in a greater per capita impact on the environment due
to increased methane production. In this way the choices of food consumers
have a large impact on the global environment.
Maize is the grain crop produced in greatest quantity globally, but most
maize is fed to animals. The amount of maize produced currently exceeds
the amount of wheat or rice, the two major food crops consumed directly by
Human food preferences and plant domestication
Domesticated plants have been selected for genetic attributes that suit human
purposes. The evolution of human populations has necessarily been influenced by food selection and availability. We have selected plants that we find
pleasing (taste good) and that can be produced conveniently (easy to grow
and prepare to eat). This explains the forces that have shaped the selection
of our domesticated crops, but how might plants have influenced human evolution? Humans that prefer or select food that has a high nutritional value and
contributes to good health are more likely to survive and pass on their genes
than those that favour foods that do not meet physiological and nutritional
requirements. In this way domesticated plants and humans co-evolved to be
dependent upon one another. Humans seem well adapted to the omnivorous
diet of our hunter-gatherer ancestors. We may not be so well suited to our
modern domesticated plants that have been selected for human tastes which
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Box 2.3 Barley: the first plant domesticated
Agriculture and the growth of modern human societies began more than
10,000 years ago. Barley has been widely considered as the plant likely to
have been domesticated first. Wild barley (Hordeum spontaneum) is still
abundant in the Fertile Crescent (Figure 2.2) and can be seen growing on
the sides of the citadel (inset) in Aleppo, Syria. Wild and cultivated barley
continue to interbreed (Bundock and Henry, 2004). Domestication of barley and the other cereals was based upon selection of this large seeded
grass that grew in large populations that could be easily harvested. Wild
barley shatters; that is, the seed falls from the plant when ripe to ensure
dispersal and survival of the species. However, domestication has involved
selection of barley that does not shatter but retains its seed, so that it can
be harvested at one time by humans. Selection for similar genetic changes
Figure 2.2 Wild barley. Wild barley plants are shown growing in a field near
Aleppo, Syria
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has been associated with the domestication of other seed crops such as
rice, wheat and maize. Aleppo, together with Damascus, are claimed to be
the longest continuously inhabited existing cities probably owing their
development to the societies established following the foundations of agriculture using the wild barley. The barley plant may have been the first
species domesticated in the Fertile Crescent more than 12,000 years ago.
may have largely been developed for survival in a pre-agricultural environment. We now have human societies that are overwhelmingly dependent
upon domesticated plants for survival. Current world populations greatly
exceed the numbers that could survive on the planet, without agriculture, as
hunters and gatherers of food. Furthermore, we now exceed the populations
that could survive by cultivation of wild plants and depend upon the characteristics of our domesticated plants for survival. It is worth examining the
process of domestication and the ongoing development (more extreme
domestication of these plants) and the potential for additional domestication
of species that have not yet been domesticated by humans. Chapter 10 will
consider these issues in more detail.
Much of the selection during plant domestication and breeding has been
for characteristics which allow the production and harvest of large quantities
of the edible part of the plant. Maize was domesticated in Meso-America
more than 7000 years ago (Thompson, 2006). The wild teosinte plant from
which maize was domesticated is very different in appearance (Table 2.2).
Domestication involved changing the architecture of the plants. Ease of production has been an important consideration driving human domestication
of plants.
Plants have been selected by humans on the basis of their attractiveness
as foods – taste and texture have probably been the key influences on human
behaviour in selection of foods. The ready availability of food that tastes
good has clearly been an important incentive for humans in the development
of agriculture.
Table 2.2 Domestication of maize
Primitive maize
Slender cobs
Short ears
Hard grains
Brownish colour
Source: Henry, 2001a
Domesticated maize
Loss of dormancy
Increased grain size
Loss of hard casing
Common traits
Unisexual inflorescences
Tassle and ear
C4 photosynthesis
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Box 2.4 Human selection of rice as an attractive food
Domesticated rices have many attributes that have been selected by
humans because of their attractiveness in a food (Bradbury et al, 2008).
These include texture, aroma and appearance.
Aroma or fragrance (Bradbury et al, 2005a) Recent research has identified that a loss of function of a gene in rice leads to the highly desirable
aroma or fragrance of Thai and Basmati rices. The fragrant rices of Thailand
are very different to the Basmati rices of India and Pakistan, but they both
share a common fragrance gene suggesting a common ancestor contributed
the fragrance to many of these divergent rices. Fragrance is due to a compound, 2-acetyl-1-pyrroline, that accumulates in parts per billion in the
plants as a result of the mutation selected by humans. Apparently humans
have selected this trait because they have an ability to detect the smell of
this compound at very low concentrations and find it highly desirable.
Modern plant breeders have progressed slowly with the development of fragrant cultivars, until the recent advent of DNA-based tests, probably
because of the genetically recessive nature of the trait (requiring the gene
to be carried by both parents for it to be expressed in the rice plant) and
the difficulty of detecting the fragrance of individual seeds or plants. Most
rices result from a single selection event, but recently other mutations in
this gene have also been found to result in loss of function and the associated fragrance, indicating several separate human selection events.
Recent research has revealed a remarkable twist to this story. Fragrant rices
have been found to be highly susceptible to salt stress. Humans are cultivating
a plant that is very poorly adapted to survival under environmental stresses
because of a defect in metabolism that also happens to give the plant a highly
desirable taste. This provides an excellent example of the conflict between
traits desirable to humans and favoured under domestication and traits that
favour survival in wild populations. The detection of a single fragrant grain is
difficult for most human noses and even modern analytical chemistry. This indicates just how desirable this trait must have been to those originally selecting
it. Fragrance has been difficult to assess on individual grains of rice in breeding,
but can now be assessed by DNA analysis (Bradbury et al, 2005b).
Cooking requirements (Waters et al, 2006) Two different mutations
have been found in some domesticated rices, each of which allows the rice
to be cooked at a temperature around 8oC lower than wild rice. Human
selection for these mutations has allowed rice to be cooked at lower temperatures and to produce a rice grain with more desirable texture. This
selection happened at least twice, possibly at different times or locations, to
account for these two different genetic forms, illustrating the desirable nature
of this trait.
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The domestication of many plants remains a mystery with limited evidence
as to the identity of the wild plants from which they were domesticated or the
time of location of domestication. Some major crop plants for which we do
have some of this type of information have origins that involved complex or
poorly understood genetic processes. For example, common bread wheat is
hexaploid (six copies of each chromosome as compared to a diploid like a
human with two sets of chromosomes – one from each parent (mother and
father)) that has resulted from the combination of three different grass species
(Figure 2.3). Cultivated sugarcane has a very large number of chromosomes
(greater than 100) and is also the progeny of crosses between different wild
species (Dillon et al, 2007). Many cultivated plants have multiple copies of
their genes and chromosomes that have arisen by processes other than the
crossing of different parental species. The presence of multiple copies of
related chromosomes (polyploidy) is a feature of many flowering plants and
is probably especially common in cultivated plants. Polyploidy may be a significant advantage to the plant and is often associated with enhanced plant
Figure 2.3 Genetic origin of bread wheat
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performance and adaptation to environmental variation. Domestication of the
peanut involved human cultivation of a polyploidy plant distinct from the
diploid plants in wild populations. The potential for further domestication of
plant species to meet human needs for food, feed, fibre and energy in the
future is considered in more detail in Chapter 10.
How much do we eat? (growth in food consumption)
The growth in food consumption is being driven by several key factors:
1 Growth in human population is a primary cause of continued growth
in demand for food.
2 However, economic growth in countries such as China and India is also
driving increases in per capita consumption of food. Increased travel
and communication is also changing food preferences, with diets
becoming more global and many foods being marketed internationally.
3 Increased consumption of animal products is driving strong growth in
demand for feed. China is a country with a very large population undergoing a rapid rise in incomes, and a dramatic increase in meat
consumption has resulted. Consumption of fish, pork, poultry and beef
has more than tripled on a per capita basis since 1970. Human and animal feed are competing uses for crops. It takes more than 4kg of grain
to make a kilogram of poultry and around 20kg to make a kilogram of
beef. Meat consumption globally is expected to double by 2050
(Roberts, 2008). Changes in food preferences may see a reduction in
rice consumption and a strong growth in the consumption of meat, eggs
and fish in Asia (Von Braun, 2007).
A major ongoing issue is the extent of geographical mismatches between
supply and demand. Food transport consumes significant energy. Efforts to
better match food production to local demand have potential to make a significant contribution towards satisfying the growing demands on agriculture.
The concept of food miles has emerged as a measure of the distance food
has been transported and promoted as a way consumers can support the
consumption of local produce with less environmental impact due to the
energy costs of long-distance transport. This concept is only valid if the food
is produced efficiently. Two examples of the problem are the risk of using
large amounts of energy to grow tropical plants in a cold climate closer to
markets, or the displacement of biodiversity to produce crops at lower yield
in a less favourable environment closer to the consumer. We need to be able
to define food labelling options that also allow for these factors and provide
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Figure 2.4 World population growth
reliable guidance to consumers in choosing food that will reduce their environmental footprint. A measure of the total energy consumed, or better the
total greenhouse gas generated in their production, is a measure that incorporates many of these environmental considerations.
The growth in human population (Rosenberg, 2008) is depicted in
Figure 2.4. The rate of growth of human population is beginning to slow.
Ongoing population growth is driven partially by the age structure of the
population. A stable population requires that each adult has an average of
slightly more than one offspring to allow for the impact of premature deaths
(e.g. accidental deaths before reaching reproductive age). Many developing
countries with a large proportion of young people will experience continued
strong population growth even if family sizes are restricted as the young
reach reproductive age. Developed countries such as many in Europe are
expecting significant population declines as the population ages.
The consumption of food per capita is also a major cause of growth in
food consumption globally. The contribution of growth in numbers and
growth in consumption per capita varies greatly in different parts of the
world. However, these two factors are probably of about equal importance
currently at the global level. While population growth continues, its rate of
growth is slowing as societies become more affluent. Economic development
is also associated with major changes in dietary habits (WHO, 2008). The
recent rapid growth in per capita food consumption in many countries has
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Food consumption (WHO, 2008, – accessed 7
October 2008)
Figure 2.5 Global food consumption by industrialized and developing countries
seen them begin to catch up with consumption patterns in the developed
world (see Figures 2.5, 2.6 and 2.7).
This phase of increased consumption may slow as more of the world
population reaches high levels of food intake. These changes in dietary
habits are not all positive and many people in the world now consume too
much food. The inequalities in food supply globally result in large numbers
continuing to face food deficits, while probably equally large numbers consume excess food. Obesity is a major concern in developed countries, with
a wide range of diseases increasing in frequency as food intakes become
excessive. It has been suggested that life expectancies may begin to decline
if this problem is not addressed. The number of people that are obese may
exceed 2 billion by 2012 (Biospectrum Asia, 2008). This has resulted in considerable private efforts to produce drugs that will treat this problem.
Greater public efforts to promote healthy dietary habits are needed. This
suggests that we need to focus on the production of plants that will support
healthy eating habits and are attractive to consumers if we want to change
food consumption patterns to support healthy human populations.
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Food consumption (WHO, 2008, – accessed 7
October 2008)
Figure 2.6 Global food consumption by region
Food consumption (WHO, 2008, – accessed 7
October 2008)
Figure 2.7 Global food consumption – world
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Food versus non-food uses of plants
Human demand for plants for non-food uses also continues to grow – plants
are used for a wide range of non-food uses. The use of plants for fibre and
construction does not usually compete with food uses as woody plants or the
woody parts of plants are not usually edible. Some uses of plants for food
and fuel may compete and these are the focus of considerable attention
because of the conflicts they may create. For example, the use of the starch
from maize, potatoes or cassava for fuel production may compete directly
with human food use and maize, and sorghum use may compete with animal feed uses that indirectly contribute to human food. This will be
discussed in more detail in Chapter 6. Grain production to feed animals does
more often compete with grain production for direct use as human food.
Competition in the use of land or water is possible for many uses of plants.
A major use occupying a substantial area of land is production of wood
products in forests. Global forest production estimates for 2004 are as follows (FAO, 2007):
Round Wood
Fuel Wood
Charcoal Wood
Sawn Wood
Paper (including cardboard)
1646 million m3
1772 million m3
44 million tonnes
416 million m3
354 million tonnes
Forest products supply energy (fire wood and charcoal) for cooking and
heating, timber for construction, and fibres for paper and cardboard.
Electronic communications may reduce demand for newsprint but the use
of printer paper remains widespread. Construction from wood may be favoured
as a mechanism of carbon storage or capture, especially when compared with
the carbon emissions associated with alternative construction materials.
Composition of plants for food and non-food uses
Plants are composed of water, some inorganic salts and a wide range of
organic molecules, ranging from very simple compounds to large macromolecules. Plants also contain essential vitamins.
Carbohydrates are the major component of plants and are a key nutrient
in staple foods such as cereals, providing the bulk of the calories in human
diets. These carbohydrates include simple sugars and more complex carbohydrates often in the form of starch (a polymer of glucose). The most
common sugar in plants is the disaccharide sucrose (the sugar of sugarcane or
sugar beet) used widely as a sweetener in human foods. Humans and animals
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are well equipped to use sugars and starch as a source of energy. Human saliva
contains the enzyme alpha-amylase that begins the digestion of starch in the
mouth. This demonstrates the way in which humans and animals are adapted
to consume foods rich in plant starches.
Proteins are also an important part of plants from a food value perspective. Plants synthesize amino acids (constituents of proteins) that are not able
to be produced by the metabolism of humans or animals. These ‘essential’
amino acids must be obtained in the diet. A balanced human diet needs to
include plant or animal components that provide the amino acids needed to
produce proteins essential to normal cellular function. Animals with proteins
closer in amino acid composition to human proteins are often a better balanced source of amino acids for human diets than plants.
Fats sourced from plants are generally desirable in human diets. A range
of crops are grown for their oil content: soybean, canola, sunflower, peanut,
castor, olive, safflower, coconut and oil palm.
A unique feature of plants is the presence of a cell wall that provides a
rigid structure for the plant. Plant cell walls contain lignin and a range of polysaccharides (carbohydrates). Cellulose is a cell wall polysaccharide that forms
microfibrils that are an important structural component of the cell wall. These
cellulose fibres are surrounded by non-cellulosic polysaccharides of differing
composition in different plant species. Some of these cell wall polysaccharides
have an important role in human diets as dietary fibre and are food for bacteria in the digestive systems of animals. This is most developed in the
ruminants such as cows that are able survive on a diet high in these structural
carbohydrates. Even humans have large numbers of bacteria in the large
intestine and bowel that are able to partially digest these polymers. An average healthy human adult probably has more than 1kg of bacteria in their gut
active in the digestion of food. Plants with a high sugar, starch or protein content are likely to be good food plants, while plants or parts of plants with a
high cell wall or lignin content, as in the woody parts of plants, are generally
not edible but may be useful for other purposes such as timber or paper. The
targeting of plants to uses based upon their composition is an important consideration when competition for end use becomes an issue. The composition
of plants in relation to their suitability for energy use will be described in more
detail when we consider energy uses of plants in Chapter 5.
Genetic resources for food crops
(conservation and utilization)
The genetic resources available to support the sustainable production of
food and for other traditional uses are the primary, secondary and tertiary
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Figure 2.8 The concept of the gene pool
gene pools of the key species (Figure 2.8). The primary gene pool includes
those individuals with which the plant can freely inter-breed. The secondary
gene pool includes plants that are less closely related and would not normally
inter-breed in nature, but that can be used in plant breeding. The tertiary
gene pool extends to species that may often only be used in plant breeding
by using advanced or novel breeding strategies and technologies, including
gene transfer (genetic modification) techniques. We may consider cultivated
plants to have both a domesticated and a wild gene pool. The wild gene
pools of crop species are often referred to as wild crop relatives. These plants
in the wider gene pool provide a reservoir of genetic variation that may be
called upon to ensure continued production of essential crops in the face of
threats from new diseases or environmental change.
Wild crop relatives are an important group of plants that deserve greater
efforts directed at in situ (where they are in wild populations) conservation
and ex situ (in seed banks, living collections and DNA banks). Wild populations of crop species are threatened by all the factors that threaten other
species, but may also be subject to the risk of being genetically impacted by
gene flow from domesticated crops. The cultivation of large genetically uniform domesticated crops close to small populations of wild individuals of the
same species risks the wild populations being genetically overwhelmed by
pollen flow from the domesticated plants, with the resulting potential loss of
wild genes. This is a possible problem with Macadamia in Australia, with
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Figure 2.9 Wild grape and rice relatives
large clonal plantations being grown within the range of the native species
which are rare in the wild. A Macadamia conservation trust has recently been
formed to support conservation of the wild genetic resources of these
species. Examples of wild relatives of crop species are shown in Figure 2.9.
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These members of the tertiary gene pool of grape and rice provide knowledge and possibly genes that might allow these crop species to be adapted to
environments outside the current range of the crop species.
A distant relative of the grape, Cissus antarctica, is found in the sub-tropical rainforests of Australia (upper panel). DNA analysis shows that this
species and three other species from the same regions are much closer to the
grape genus Vitis than other Cissus. Cultivated grapes are very susceptible to
fungal diseases when grown in these warm and wet environments. A wild rice
relative, Potamophila parviflora, grows in the rivers of central Eastern
Australia, extending inland to grow in cool winter temperatures in the upper
reaches of these river systems (lower panel). DNA evidence indicates that this
species’ closest relative is the North American wild rice (Zizania species).
Two examples of the importance of wild crop relatives are described
below – rice and sorghum. Rice is a major food crop and the security of its
supply is very important for many human populations. Wild crop relatives
have a central role in providing a source of genetic variation that can be used
to maintain production in response to biotic (e.g. new diseases) or abiotic
(e.g. climate change) challenges. Sorghum is also an important human food
crop, but in its current form is not as highly valued as rice. The wild relatives of sorghum offer not only a resource for ensuring security of supply,
but also a source of new variation that might be used to make sorghum more
attractive as a human food.
Wild relatives of rice and potential for
use in rice improvement
Rice is one of 22 species in the Oryza genus (Table 2.3). This genus is one
of 12 in the Oryzeae tribe (Table 2.4). Oryza sativa and other closely related
species that can be readily cross-pollinated with rice (designated A genome
species) represent the primary gene pool of rice. Genes in other species in the
genus may be accessed for rice improvement and represent a secondary gene
pool. The wider genus may be considered a tertiary gene pool for rice from
which genes could only be accessed with much greater difficulty. Use of genes
from these wild relatives of rice requires an understanding of the relationships
between the rice species (Kovach and McCouch, 2008). The wider gene pool
of rice as represented in the wild relatives is an important target for conservation of biodiversity to support global food security. This gene pool remains
relatively poorly characterized and under-utilized to date. This would also be
the case for most important food crop species. The Oryza sativa complex
includes those closely-related species that can be directly inter-bred with rice.
These and other species in the genus are currently being characterized by
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Table 2.3 Rice genus
Oryza sativa complex
O. sativa L.
O. nivara Sharma et Shastry
O. rufipogon Griff.
O. glaberrima Steud
O. barthii A. Chev.
O. longistaminata Chev. Et Roehr.
O. mederionalis Ng.
Oryza officinalis complex
O. officinalis Wall ex Watt
O. minuta Pesl. Et Presl.
O. rhizomatis Vaughan
O. eichingeri Peter
O. punctata Kotchy ex Steud
O. latifolia Desv.
O. alta Swallen
O. grandiglumis (Doell) Prod.
O. australiensis Domin
O. brachyantha Chev. Et Roehr.
O. schlechteri Pigler
O. ridleyi Hook. F.
O. longiglumis Janse
Oryza meyeriana complex
O. meyeriana (Zoll. Et Mor. Ex Steud.) Baill.
genome sequencing and analysis, with the closest relatives being given the
greatest attention. The more diverse species within the tribe provide options
for more radical and probably longer-term genetic improvement of the cultivated plant species.
Table 2.4 Rice tribe
China, Japan
South Asia
Europe, Asia, North
North and South America
North and South America
South America
Tropical and Southern Africa
Southern Africa
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Wild relatives of sorghum and their potential for
use in crop improvement
Wild relatives of some crop species represent a very valuable resource that
can be used to expand the gene pool of the domesticated plant. Cultivated
sorghum originated in Africa and was probably domesticated 5000–6000
years ago. The sorghum genus includes 25 species and those species that
have not been domesticated have many characteristics that would be of
value in a crop plant. They are tolerant of extreme heat and drought and
grow with limited nutrients. Hybrids between cultivated sorghum and some
of these wild species have been recently produced. The availability of a
completed sequence of the sorghum genome (Paterson et al, 2009) provides
access to tools that would allow molecular-assisted breeding (the use of
DNA analysis to support plant selection). Sorghum genetic improvement is
just beginning to benefit from these new tools and insights into genetic relationships between domesticated sorghum and wild relatives (Dillon et al,
2007). Wild species that have been shown to be the closest relatives of cultivated sorghum have been successfully cross-pollinated with sorghum,
confirming the DNA evidence of a close relationship. This is a good example of how DNA analysis of plant relationships can guide conventional
breeding to successfully explore more options for accessing novel genetic
Genetic resources for crops species and their wild relatives need to be
conserved in the wild (in situ) when possible. However, this is often not
possible and seedbanks of the major species hold significant numbers of cultivars and other genotypes (Table 2.5) in ex situ (not in the wild)
collections. Seed life can usually be extended by keeping the seeds dry and
cool. Cool storage using refrigeration depends upon a constant energy supply that may be disrupted by major disasters. Long-term conservation of
large collections of seeds is being ensured by storage in the arctic permafrost. The seeds of many species (e.g. many from rainforests) do not
survive drying and storage, and they must be conserved ex situ as living
specimens. Ex situ plant conservation options for plants in general (not just
relatives of cultivated food crops) are discussed in more detail in Chapter
7. For cultivated plants, farmers fields remain a very important location for
the conservation of diversity as farmers’ continue to grow traditional varieties and retain the seed from previous crops. These crops will often retain
diversity that may be lost in the more intense genetic selection of elite varieties in plant breeding.
DNA banks are a new option to support the more efficient use of the
living collection or seedbank. DNA in these collections can be analysed to
identify genotypes that contain useful genes or genetic characteristics. These
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Plant Resources for Food, Fuel and Conservation
Table 2.5 Seedbanks for major crop germplasm resources
Number of accession in collections
Sweet potato
Faba bean
Pigeon pea
Source: Henry, 2005a
( accessed 16 February 2009)
can then be sourced from the seedbanks and used in agricultural production
or in plant breeding. International seedbanks make seed available to plant
breeders worldwide for use in developing new varieties.
Technologies and strategies for the improvement
of agricultural species
Humans have continuous genetically ‘improved’ domesticated crop plants by
processes of both conscious and unconscious selection and breeding. This
genetic change has targeted the growth characteristics of the plant (higher
yields), and especially the attractiveness of the food to human taste and
the convenience of harvest and processing. Selection by screening of large
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Plant Resources for Food and Fibre
Box 2.5 DNA banks for conservation and support of plant improvement
DNA banks (De Vicente and Andersson, 2006) represent a new type of ex
situ conservation that does not attempt to provide for continued propagation of the plants, but stores DNA for analysis in plant identification,
genetic diversity studies, population genetics and evolutionary analysis. The
DNA banks allow research aimed at gene discovery in support of plant
improvement. Such banks that mirror seed banks or other living collections
can be used as primary tools for screening and selection of germplasm in
plant breeding applications. The Australian Plant DNA Bank includes DNA
of important food species such as wheat, barley and rice that are derived
from seed samples held in international seed banks.
DNA Bank
South Africa
populations of wild material, much in the way this selection was imposed during domestication, continues to be a major strategy for identifying improved
plant cultivars for specific environments and uses. Plant breeding by cross
pollination of plants became a widespread approach to developing superior
crop plants over the last 100 years. Mutation breeding has also been important in many species as a mechanism for the introduction of a new genetic
variation for traits of commercial importance. The discovery of the chemical
basis of heredity with the determination of the structure of DNA more than
50 years ago has led to development of techniques for selecting plants for
desirable traits by direct analysis of the DNA. The recent advances of DNA
analysis technology has resulted in the complete genetic code of crop species
being determined. The science of genomics (the analysis of all the genes in
an organism) has begun to impact on agriculture and food production
(Henry, 2009). Genomics reverses the previous paradigm in which the analysis traditionally targeted the discovery of genes to match a single specific trait.
Now we can discover all the genes first and then ask what they do without
necessarily having a specific objective or target. This has dramatically accelerated the rate of growth in genetic knowledge, providing a basis for more
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rapid and radical genetic improvement in crop species. Very recently recombinant DNA technology has become an option for introduction of novel
traits. However, the major impact of DNA technology has been the more precise conventional selection of superior plants that DNA analysis allows. DNA
sequencing techniques (the methods used to determine the genetic code of a
plant or other organism) have been dramatically improved in the last few
years. This technology is continuing to be improved in efficiency and effectiveness, and the full impact of its widespread application to plants is only
likely to become apparent over the next couple of decades. Hybrid plants
offer the potential for further improvements in plant productivity, and the
rate of development and quality of hybrids may be greatly enhanced using the
tools of genomics. Hybrid plants with higher yields due to the ‘hybrid vigour’
that comes from crossing two individuals that are genetically diverse may be
Box 2.6 The Green Revolution
The Green Revolution produced new cultivars of the major crops, increasing world food production to keep pace with the growth in world
population in the period since the 1950s. Critics of the Green Revolution
have charged that the new cultivars made farmers more dependent on
high-cost inputs of fertilizer. While the full advantages of the new cultivars
did require more nutrient input to deliver the full benefit, the new cultivars performed much better than the cultivars they replaced even in the
absence of greater inputs. The simple laws of mass balance require that the
removal of much greater amounts of crop as grain requires greater inputs
to satisfy the need for replacement of soil nutrients. Norman Borlaug won
the Nobel Peace Prize in 1970 for his contribution to saving the lives of
millions with these advances in cereal breeding. A major achievement of
the Green Revolution repeated in several major species has been an
improvement in harvest index. Harvest index is the ratio of harvested crop
to total plant biomass. Increased harvest index results in more grain harvest for the same total amount of plant growth. Borlaug’s selection for a
single gene, the semi-dwarfing gene in wheat, increased the harvest index
of wheat, and is estimated to have provided the technology to allow the
production of food for an additional 1 billion humans from the same area
of land. Similar approaches have advanced the production of rice. Modern
cultivars have a harvest index that allows about half of the total mass of
the plant to be recovered as grain.
The implications of the Green Revolution for biodiversity will be discussed later in this book (Chapter 9).
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Plant Resources for Food and Fibre
considered the opposite of the poor performing individuals that result from
inbreeding between closely related individuals. This technology is still to be
perfected in many important food crops. These scientific advances may also
provide new tools to domesticate additional food crops, which will be discussed in Chapter 10.
The potential to domesticate new species to expand the diversity and
improve the security of food supply is generally viewed as being very limited.
Diamond (2005a) has argued strongly that humans have domesticated most
species with potential. Three types of exception to this may be found in:
1 species that are found in regions that had very few species that were
suitable for domestication. A critical mass of species may be necessary
to justify the transition to an agricultural lifestyle in any region;
2 species with new non-traditional uses and for which there was previously no reason for domestication (energy crops for biofuels may be a
good example of this category); and
3 species that have barriers to domestication that can only be overcome
with new technology that was not available in the past. Examples might
include toxic plants that can now be screened for lower levels of toxin
with modern analytical chemistry approaches.
Food from plants in the future
Humans have been very successful in domesticating plants for food and other
uses. Plants have been subjected to genetic selection and deliberate cross
breeding over a period of more than 10,000 years, resulting in highly domesticated plants adapted to human use. The challenge of the future will be to
ensure that the full diversity of both the domesticated and wild gene pools is
retained (especially for the major food crop species) to support food security
by coping with the impact of the climate change (explored in the next chapter), and expansion of agricultural production to keep pace with the growth in
human demand. The Consultative Group on International Agricultural
Research (CGIAR) relevant to plant genetic resources (Table 2.6) plays a key
role, especially in ensuring as far as possible ongoing outcomes of plant breeding of the staple food species are delivered to the poor in many countries.
Improving the nutritional value of food plants
We need to produce more food to satisfy growing demand, but we also need
to produce food with an improved nutritional value – foods that improve
human health are required. Our knowledge of links between diet and health
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Table 2.6 Consultative Group on International Agricultural Research (CGIAR) Centres working
on plant genetic resources
Main location
International Centre for Wheat and Maize Improvement
International Rice Research Institute
International Centre for Agricultural Research in the Dry Areas
International Centre for Agricultural Research in the Semi-Arid Tropics
International Potato Centre
International Food Policy Research Institute
International Centre for Tropical Agriculture
International Institute of Tropical Agriculture
International Livestock Research Institute
Africa Rice Centre
Centre for International Forestry Research
World Agroforestry Centre
Bioversity International
Source: (CGIAR) Centres working with plant genetic resources:
continue to improve and a major challenge is how to develop new cultivars
of food crops to deliver health benefits. We can attempt to breed health into
attractive foods or we can attempt to make healthy food more attractive to
humans. The relative effectiveness of these approaches will be case-specific.
The food industry tends to add ingredients that add health or at least allow
food labelling that suggests a health advantage. However, plant breeders may
also have dramatic and effective success in making highly nutritious foods
more acceptable or attractive to human tastes or preferences.
In recent years there have been periods when the prices of foods have risen
strongly due to reduced stocks and apparent inability of growth in supply to
keep up with growth in demand. Ongoing underlying factors contributing to
lower production and upward pressure on food prices include:
growth in human population;
growth in per capita consumption, especially associated with changes in
diet (e.g. more meat) resulting from global economic growth;
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Plant Resources for Food and Fibre
Box 2.7 Improving the folate content of cereals
Humans require a range of essential nutrients in their diet. These include
substances that are essential for biochemical processes in the body but cannot be produced by human metabolism. Folate is an example of this type
of substance. Different forms of folate (tetrahydrofolate) and glutaminated
derivatives collectively provide the folate in human diets. These are water
soluble vitamins in the B group (folate is sometimes defined as vitamin B9).
Plants produce these molecules especially in green tissues. Vegetables
(especially green leafy vegetables) and fruits are good sources of folate.
Cereals and tubers are relatively poor sources of folate, but because of
their large contribution to the diets of many humans these provide a significant part of the folate in many human diets.
Deficiency in folate is common in human populations both in the developed and developing world. A lack of folate has many serious
consequences for humans – neural development and function are damaged
by a lack of folate. This can result in congenital deformities such as spina
bifida and anencephaly, and may contribute to dementia and Alzheimer’s
Folate biosynthesis in plants is a complex process involving metabolism
in several different sub-cellular compartments, the cytoplasm, chloroplast
and mitochondria. This complexity partially explains the lack of progress in
developing plants with increased folate content.
Recently the genes in the folate biosynthesis pathway in wheat were
characterized (McIntosh and Henry, 2008). This research indicated that
folate was produced at all stages of the life cycle of the wheat plant, confirming the essential role of folate in the cells of all higher organisms. Even
the dormant seed was able to produce folate. This knowledge has provided
new tools for use in selecting cereals with elevated folate content.
This approach offers the potential to target the development of foods
produced from plants with optimal nutrient content. Research has already
defined many new options for plant breeders to improve human nutrition.
We can expect science to deliver substantial further optimization of the
nutritional value of major food plants. This is largely required because of
likely continued failure of human populations to access a balanced diet by
consuming an appropriate range of foods. The reason for this lack of balance in human diets varies in different populations and communities. Food
preferences may be economic or cultural. However, improving the aesthetic value and the taste of nutritious foods remains very important. We
need high folate content in foods humans prefer to eat.
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Plant Resources for Food, Fuel and Conservation
continuing removal of agricultural land by conversion to nonagricultural use (e.g. roads or urbanization);
loss of land to desertification and increased salinity;
increasing difficulty in continuing to find more water as production
competition for land and water with growing areas of energy crops,
especially in the future as energy costs grow;
loss of productivity in some regions due to climate change, especially in
the future as impacts increase.
Despite obesity being a major world problem, food prices were historically high (probably for several complex reasons) and almost 1 billion people
were suffering severe food deficiencies in late-2008 (FAO, 2008). The
strong imperative to deal with these issues and ensure global food security
adds to the risks that an expanding agricultural production footprint may
have adverse impacts on biodiversity. There is an urgent need for a greater
focus on research to enable more sustainable agriculture, and the development and implementation of policies to support sustainable agriculture and
biodiversity conservation. These issues are made more urgent by the threat
of climate change. The potential impact of climate change on food production will be discussed in the next chapter.
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Impact of Climate Change on Food
and Fibre Production
What’s more, climate change is a breaking story. Just over thirty years
ago experts were at loggerheads about whether Earth was warming or
cooling – unable to decide whether an ice-house or a greenhouse future
was on the way. By 1975, however, the first sophisticated computer
models were suggesting that a doubling of carbon dioxide (CO2) in the
atmosphere would lead to an increase in global temperature of around
3ºC. Still, concern among both scientists and the community was not
significant. There was a brief period of optimism when some researchers
believed that the extra CO2 in the atmosphere would fertilise the
world’s croplands and produce a bonanza for farmers.
Tim Flannery, The Weather Makers
Global warming is now a widespread concern in the community. Climate
change threatens crop and food production by changing the environmental
conditions in traditional crop production areas. With supply and demand
finely balanced, even small changes in climate over a few years become critical, especially as the scale of crop production required to support human
populations increases. Climate change has been linked to increased levels of
greenhouse gases such as carbon dioxide (CO2) in the atmosphere. Recent
research is firming up the causative link between greenhouse gas increases,
warming and biological impacts (Rosenzweig et al, 2008). Climate change
or even short-term variations in climate may have serious consequences for
global food production when global food supply and demand are as evenly
balanced as has been the case in recent years. Regardless of cause, climate
variation is now a major risk to food security.
Carbon dioxide concentrations in the atmosphere
Historical analysis of atmospheric CO2 concentrations has been followed back
650,000 years by examining bubbles trapped in ice in Antarctica, confirming
a strong correlation between CO2 and temperature (Luthi et al, 2008). CO2
levels have been monitored for some time and show a steady increase from
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Plant Resources for Food, Fuel and Conservation
Keeling and Whorf, 2005
Figure 3.1 Carbon dioxide concentrations in the atmosphere
320ppm in 1960 to almost 380ppm in 2004 (Figure 3.1). The concentration
of CO2 in the atmosphere is currently rising at around 2ppm per year.
The concentration decreases each year in the northern hemisphere
spring as trees grow new leaves, and increases again in the autumn as they
drop their leaves and return carbon dioxide to the atmosphere. The dominance of the northern hemisphere forests is illustrated by this distinct pattern
that can be detected worldwide. The underlying concentration increases
each year despite this annual cycle. The fixation of CO2 by plants also varies
dramatically throughout the day as the plants respond to the daily cycle of
light and dark, using the light energy to capture CO2 to produce carbohydrates (Darbyshire et al, 1979).
Other greenhouse gases
Nitrous oxide (N2O) is a potent greenhouse gas estimated to be 270 times
as effective as CO2, while methane is 21 times as effective. While these gases
are far less abundant (much lower concentrations in the atmosphere) they
can account for a significant part of the global warming impact because of
their much greater influence. Some of the more unpredictable aspects of climate change may be associated with greenhouse gases other than CO2. For
example, recent research has identified an unexpected burst of methane
from the tundra of Greenland at the point of freezing at the beginning of the
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Impact of Climate Change on Food and Fibre Production
Box 3.1 Scientific and popular views of climate change
The impact of human activities on climate and the association between
greenhouse gas levels and climate has been a major scientific and public controversy of the last couple of decades. The link between the increase in CO2
and global temperatures has not been so easy for some scientists and the
general community to accept. The acceptance of human-induced climate
change has dramatic consequences. Scientists, by their nature and training,
are sceptical of everything. The weather varies greatly and in the short term
provides no real evidence of a permanent change in climate. The steady and
continuing increase in greenhouse gases, especially CO2, has been more
convincing and is now widely accepted. CO2 can be measured easily and
objectively and the upward trend in concentration is indisputable. However,
convincing data showing historical evidence for a very close association
between CO2 and temperature suggest one of only two possibilities: either
CO2 increases cause global warming or global warming causes CO2 rises.
The later option leaves the cause of global warming unanswered.
Disturbingly the CO2 concentration in the atmosphere have recently been
rising more rapidly than that assumed in the models, providing some of the
more pessimistic predictions of global impact.
winter (Mastepanov et al, 2008). Many aspects of the cycling of these gases
remain to be discovered and explained.
Global temperature
Recent increases in global temperature are depicted in Figure 3.2. These values are relative to the mean temperatures in the period 1951–80 (Goddard
Institute for Space Studies, NASA, 2008). Projected global temperatures in
the future vary widely with the uncertainty of the likely changes in the atmosphere due to human activities and the difficulty of predicting the impact of
this on global climate. Complex interactions may produce a wide range of
different outcomes in specific locations. A more variable climate with a
greater frequency of extreme weather events is widely predicted.
Climate Change reported in 2007 that the increase in global temperature was expected to have a number of impacts:
altered weather patterns with more extreme events;
rising sea levels;
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Plant Resources for Food, Fuel and Conservation
Figure 3.2 Global temperature
changes in the biotic (living) environment (populations and distribution
of micro-organisms and insects). The changed environment will impact
on plant and animal disease incidence;
changes in the availability of fresh water;
loss of social and urban infrastructure (e.g. buildings, sewage and public service infrastructure).
Global temperature trends may also be impacted by other factors acting
on different timescales. Global temperature will be the net result of all factors: those that are associated with greenhouse gas levels and those that are
not. A recent analysis has modelled the temperature to the end of the century and predicted increases in temperature that would directly reduce crop
yields and global food production (Battisti and Naylor, 2009).
Coping with climate change in agricultural production
The causes of climate change or more specifically global warming do not alter
the risks to agriculture that is posed, but may influence the options available
to deal with the problem. Higher temperatures and less rainfall (predicted
impacts of climate trends in many areas) will reduce crop production potential. Relocating agricultural production to more favourable environments will
offer at best a very limited option to cope with this. Greater environmental
variation has also been predicted for many areas. This will increase the difficulty of managing agricultural production inputs to maximize productivity.
Plants are now growing in an atmosphere with a CO2 concentration much
higher than the one to which they are adapted. The concentration of CO2 in
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Impact of Climate Change on Food and Fibre Production
the atmosphere in 2007 averaged 383ppm (World Meteorological
Organization, 2008). The photosynthetic apparatus of plants evolved in an
atmosphere with a concentration of CO2 in the 200–300ppm range. It may
eventually be possible or necessary to re-engineer plants to perform better at
higher concentrations of CO2. The targets for these efforts will be defined by
our ability to stabilize CO2 concentrations at some reasonable level.
Plants have a diversity of photosynthetic pathways (Box 3.2). CO2 is captured in most plants in a reaction that produces a three-carbon compound as
the first product of photosynthesis. Some plants have evolved an additional
mechanism for concentrating CO2 inside the plant in high-light tropical environments that produce an initial four-carbon product. These C4 plants are
able to perform better in these high-light environments fixing carbon more
efficiently in hotter and drier environments. Rising concentrations of CO2 in
the atmosphere were originally thought to be likely to lead to a reduction in
the advantage of C4 plants. However, while the direct impact of higher CO2
concentrations is to reduce the advantage of C4 plants, the associated
increases in temperature and reductions in water supply in the environment
should ensure that C4 plants continue to perform better. Selection of C4
plants may become an important option in the adaptation of crops to climate
Box 3.2 Pathways of photosynthesis
All plants have the biochemistry to fix carbon by combining CO2 with a
five-carbon compound (ribulose 1,5-bisphosphate) to form two threecarbon molecules (3-phosphoglycerate). This is the essential feature of C3
Plants from warmer climates have developed an additional ability to first
fix CO2 by combining it with a three-carbon compound (phosphoenolpyruvate) to form a four-carbon compound (oxaloacetate). This is C4
photosynthesis. The passage of CO2 into the leaf is associated with loss of
water since CO2 and water are molecules of similar size. Specialized anatomy
in C4 plants allows these two processes to be separated. The four-carbon
intermediate is transported to specialized cells, where it is de-carboxylated
to produce bicarbonate that is then fixed in the normal C3 pathway. This
effectively allows CO2 to be concentrated in the leaf, allowing more efficient
photosynthesis at high temperatures and with less water loss.
There are several variations on the C4 pathway involving different intermediates (e.g. malate and aspartate) (Vermerris, 2008a).
Adaptation of food and energy production to climate change may require
the selection or breeding of more C4 plants.
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Impact of climate change on wild crop relatives
The selection or breeding of crops better adapted to altered climates will be
difficult at the speed that may be necessary to respond to this challenge.
Climate change also threatens the survival of wild crop relatives, key longterm resources for crop adaptation and food security.
Recent research has examined the influence of climate on genetic diversity in wild populations of the first domesticated plant, barley (Cronin et al,
2007). Genetic diversity was found to be greatest at the driest sites and lowest in the wet or more favourable environments. The more extreme
environments are probably the most variable and this may explain the
greater genetic diversity that has evolved in the populations from the extreme
environments to allow the plants to adapt to environmental stresses. Diseaseresistant genes in these populations were found to be most diverse,
suggesting that adaptation to dry environments may require adaptation to a
different spectrum of pests and diseases in these environments. This is likely
to be a key factor in adapting plants to climate change. The plant not only
needs to cope with hotter or drier conditions, but also a new and possibly
wider range of diseases. More details on this research on gene diversity in
relation to the climate are given in Box 3.3.
Box 3.3 Gene diversity in relation to climate
An example of research on variation in a gene in wild barley is described
here in relation to adapting food crops to climate change and in Box 8.1
in relation to biodiversity conservation. The variation in the sequence of
the Isa gene and other genes in wild barley has been explored in relation
to climatic variables. The research initially analysed the variation in the
DNA sequence of a gene that had been characterized for some time. The
original interest in this gene was because it encodes a protein (BASI) in the
seed that inhibits the amylase enzymes that breakdown starch in the seed
during germination. This was of great interest to wheat breeders attempting the breeding of wheat with resistance to pre-harvest sprouting
(germination). The level of this protein had the potential to moderate the
impact of rain damage on wheat bread-making quality. Rain causes premature germination of wheat in the field before harvest, resulting in the
production of amylase that degrades starch during dough mixing. The
sequence of the gene was analysed in the laboratory of Kihoharu Oono in
the National Institute of Agrobiological Resources in Japan in 1990 (Henry
and Oono, 1991). At this time the protein was thought to be found in the
endosperm (the main starchy part of the seed). Much later, the work of a
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Impact of Climate Change on Food and Fibre Production
PhD student, Agnelo Furtado, in collaboration with Ken Scott (University
of Queensland) (Furtado et al, 2003), revealed that the protein was unexpectedly in the outer parts of the seed (pericarp). This discovery suggested
that the protein had a role in defence of the seed against pests or diseases.
Collaboration with Eviatar Nevo, Institute of Evolution, Israel, allowed an
examination of the diversity of this gene in wild barley populations in relation to environmental variation (Cronin et al, 2007). More recently this
work has been extended to the study of other genes in these same populations. These have included abiotic stress-related genes such as betaine
aldehyde dehydrogenase and alcohol dehydrogenase, and biotic stress
resistance genes that have been associated with resistance to fungal diseases. Experiments to test the variation of these genes in wild populations
of other species followed. This research showed great variation in gene
diversity between populations that may be associated with adaptation to
climate in wild plant populations. Understanding these processes will be
important if we are to rapidly adapt crop plants to climate change.
Impact of climate change on food production
Climate change is likely to have a major impact on the production of crops.
The level and type of impact is expected to vary greatly in different locations. A regional or even local analysis is required to fully understand the
implications of climate change. Cline (2007) has estimated the impact of
global warming on a country and regional basis.
Much of Africa is already marginal for agriculture with high temperatures
and limited water supply. Drier conditions over much of Africa are likely
to result in more frequent crop failures. Agricultural output has been estimated to decline by 17–28 per cent by the 2080s. The availability of water
for irrigation will be critical. The supply of water from the Nile will be
essential to allow continued production in Egypt. Dryland agriculture in
Africa is expected to suffer substantial adverse impacts from climate
change. Climate change in Africa is likely to have overall strong negative
impacts on people that are probably among those less able to cope with
reductions in income or food supply. The likely impact and the need for
efforts to adapt to climate change in Africa have been analysed by Dinar
et al (2008).
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The rapid industrial and economic development of Asia makes this region a
major and growing contributor to greenhouse gas emission. Asia accounts
for more than 60 per cent of the world population and food production is
likely to be impacted by reduced availability of water in many areas. Output
has been estimated to decline by 7–19 per cent by the 2080s. India is projected to suffer significant losses of production ranging from 30–35 per cent
in the south to 60 per cent in the north.
Increased temperatures may improve crop yields in northern Europe, but
this is likely to be offset by negative impacts in southern Europe. Grain production could be enhanced in areas (e.g. Norway and Finland) that are
currently limited by low temperatures, but warmer parts of Europe, such as
Spain and Italy, are likely to suffer reduced capacity.
North America
Production in Canada may expand north but reductions in the midwest of
the US are likely due to reductions in rainfall. The overall situation in the
US is relatively balanced to slightly negative. Southern areas will face
reduced productivity because of excessive temperatures: Mexico is expected
to suffer the greatest losses in production.
South America
The impact of climate change in South America is strongly negative, with
greater losses in Brazil than in Argentina. Brazil is currently a major food
producer with potential for significant growth in agriculture if climate does
not deteriorate. Again, areas such as Brazil, that are already warmer, have
the most to lose as climates become too hot for agricultural production.
Australia is one of the developed countries with a significant potential for a
loss of around 16 per cent in agricultural productivity by the 2080s (Cline,
2007). Temperatures are already above the optimal level in many areas.
Water is in limited supply, preventing irrigation to cope with the increased
water needs of higher temperatures. Much of Australia has low and variable
rainfall. Southern Australia has a Mediterranean climate with rain mainly in
the winter and a hot dry summer. Northern Australia has more monsoonal
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Impact of Climate Change on Food and Fibre Production
Box 3.4 Case study – cereals (rice, wheat, barley and sorghum) in Australia
Australia is a country with a relatively dry climate under threat of further
reductions in rainfall associated with global warming. Rice has for many
years been grown in low rainfall inland areas of southern Australia under
irrigation. Rice production has been reduced dramatically in the last few
years as irrigation water has not been available due to prolonged drought.
Perennial crops such as grapes and tree crops have expanded and gain priority in access to irrigation water relative to rice where the decision to
plant can always be delayed another year. A return to the peak levels of
production in the Australian industry may not now be possible because of
competition from more permanent crops, and a probable loss of infrastructure and capability if low production persists. Rice production in
northern Australia under rain feed conditions might be an option for the
future, especially as a response to global warming. Rice crops were grown
on the east coast of Australia in 2008. A crop in northern New South
Wales was the first commercial scale crop of rice in this region.
Wheat and barley are grown as winter crops in Australia, predominantly
across southern Australia in Mediterranean climates. Australia produces
only a modest amount of wheat, but is a major exporter because of low
population and resulting low domestic demand. Australia is a major
exporter of barley and with Canada accounts for most of the traded barley in the world. Exports of both wheat and barley were greatly reduced
in 2007/08 because of low production due to dry conditions across southern Australia. Barley is more tolerant of drought stress than wheat and
frequent dry seasons could increase the proportion of barley planted. The
current reductions in production are expected to be short term, reflecting seasonal conditions, but indicate the likely impact long term of climate
change. The low production of the past year may become more normal.
Sorghum production has increased greatly in recent years in the northern
Australian grain regions on the east coast. Sorghum is grown opportunistically on summer rainfall and as a result climate change may impact very
differently on this crop.
Overall cereal production in Australia may change in response to global
warming, with a reduction in total production but with the possibility of a
move of rice production to the north, an expansion of sorghum production and a reduction in barley, but probably more especially wheat
production in the main production areas in the south.
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Plant Resources for Food, Fuel and Conservation
rainfall mainly in the summer with warm dry winters. The variation in rainfall between seasons has been associated with climatic cycles over the Pacific
Ocean. The El Nino pattern associated with dry conditions in Australia has
become frequent recently. The main inland river system (Murray/Darling)
has had record low inflows in recent years.
Genetic strategies for adapting food production
to climate change
The above analysis of possible impacts on cereal production in Australia
assumes no change in the ability of these species to perform in more extreme
environments. As climate change impacts, great efforts will be made (and are
already being made) to adapt these key species to cope with their new environments. However, the potential to breed better adapted cultivars quickly
enough to cope with the pace of climate change is unlikely. Future needs
include many options that are likely to be longer-term outcomes of current
research activities. These include novel strategies for disease and drought
tolerance, nitrogen use efficiency and more efficient photosynthesis. Moving
production of each species to more suitable environments will be a key strategy in the shorter term. Changing species will be another main response.
The more stress-tolerant species such as barley and sorghum production
may increase at the expense of wheat and rice. Unfortunately wheat and rice
are more attractive human foods. Developing food technology and genetic
selection of better food cultivars for these more adaptable species should be
a high priority.
The magnitude of climate change that is now expected will be a major
challenge for plant breeders. Adaption of plants rapidly enough to maintain
current production levels of major food crops long term will probably
require significant research investment and probably represents an ambitious
target. The predicted growth in demand will not necessarily be met in this
scenario, but options to limit growth in demand are not easy to identify.
Agriculture needs to become part of the solution to climate change, not
just a victim. Research on how food production can contribute to reductions
in greenhouse gas production is an important area for investment (IFPRI,
2009). Innovations in agriculture to support mitigation of climate change
need support.
We will return to a discussion of the potential for future plant production to satisfy both food and energy demands in Chapter 6, but first we will
consider human energy needs (Chapter 4) and the potential contribution of
plants (Chapter 5).
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Energy Resources
Petroleum-based fuels and related materials are central to the economies
of developed and developing countries around the world. However, these
resources are finite and expected to enter a period of diminishing availability within the next several decades.
Ahmann and Dorgan (2007)
Human societies use energy in many different ways, in transportation, and in
industrial and domestic applications. Energy can be sourced from solar, wind,
wave, hydroelectric, geothermal and nuclear sources. Traditionally humans
have used plants as a direct source of biomass for heating and cooking.
However, more recently, fossil fuels (coal, gas and oil) have been used as
energy sources. These reservoirs of carbon compounds produced from CO2
by plants growing over long periods of time have been used extensively to produce electricity and liquid fuels for transportation. These resources are also
used as chemical feedstocks for the manufacture of a wide range of carbon
compounds from plastics to pharmaceuticals. The burning of fossil fuels
results in an increase in greenhouse gases, especially CO2 and the associated
threat of global warming. Human societies have a great dependence on oil and
for transportation. Oil stocks are declining and prices of products derived from
oil have been increasing sharply in recent years. It has been estimated that
humans have consumed around 875 billion barrels of oil since we started using
oil, that about 1.7 trillion barrels remain in established reserves and that we
might eventually find another 900 billion barrels (Ahmann and Dorgan,
2007). Two main factors encourage the search for alternative sources of
energy. Firstly, the growing cost of oil and in the long term the ultimately limited nature of the resource makes alternatives attractive. Secondly, the risks of
global warming associated with the consumption of fossil fuels provides further incentive to develop new technologies. Options that replace oil for high
volume uses such as transportation may also help conserve oil stocks for more
critical or less substitutable uses such as chemical feedstocks. Photosynthesis
by plants captures light energy by using it to combine CO2 to form carboncontaining compounds mainly in the form of carbohydrates. Simple
calculations indicate that the amount of energy captured by photosynthesis
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Plant Resources for Food, Fuel and Conservation
each day is far greater than the amount of energy used by human societies. In
2008, for the first time, the International Energy Agency (IEA, World Energy
Outlook, 2008) called for an urgent effort to move away from oil to a more
sustainable energy supply system to avoid catastrophic climate change.
Growth in human energy consumption
Human consumption of energy is growing at about 2 per cent per annum,
with almost twice this growth rate in Asia. Consumption grew by an estimated 2.4 per cent in 2007, with China accounting for half of this global
growth (BP Statistical Review, 2008). Natural gas consumption continues to
grow more rapidly than oil consumption. Coal consumption showed even
stronger growth at 4.5 per cent. Wind and solar power growth is rapid at
28.5 per cent and 37 per cent respectively for 2007. Nuclear power generation actually fell (due to an earthquake) and hydroelectric power generation
grew by 1.7 per cent in 2007. Around 80 per cent of the energy consumed
is currently from fossil fuels. Total energy traded in the world in 2007 was
around 11,000 million tonnes (oil equivalent). Growth in oil consumption is
depicted in Figures 4.1 and 4.2.
Oil consumption (BP Statistical Review of World Energy, 2008)
Figure 4.1 Oil consumption – regions
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Energy Resources 49
Oil consumption (BP Statistical Review of World Energy, 2008)
Figure 4.2 Oil consumption – world
Non-transport uses
Electricity generation is widely based upon the burning of fossil fuels such
as coal. Alternative options (Table 4.1) such as nuclear power are now being
considered more seriously because of concerns about greenhouse gas emissions. Methods of capturing CO2 in coal-powered power stations are being
investigated. The success or otherwise of this technology may determine the
future of electricity generation from fossil fuels.
Transport use
Common transport fuels include petroleum (gasoline or petrol and diesel)
for use in cars and trucks and specialty fuels for aeroplanes. Unless nonBox 4.1 Approximate conversions for units of energy
1 tonne of oil = 1.16 kilolitres of oil = 7.33 barrels of oil = 307 US gallons
of oil
1 tonne of oil = 10 kilocalories = 42 gigajoules = 40 million BTU (British
Thermal Units) = 1.5 tonnes of hard coal = 12 megawatt-hours of electricity
Source: BP Statistical Review of World Energy, 2008
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Plant Resources for Food, Fuel and Conservation
Table 4.1 Electricity generation from non-fossil fuel sources
Current capacity
Oceans (waves
and tides)
45,000 large dams globally
439 operational nuclear power plants
Capacity growing 25% per year (last 5 years)
Mostly used directly for cooking and heating.
Specially suited to liquid (biofuel) production
High-grade resources are rare
Only during daylight.
Limited by storage technology
Source: Schiermeier et al (2008). Electricity accounts for around 40 per cent of total energy
consumption by humans. The use of fossil fuels to produce electricity releases 10 gigatonnes of CO2
per year.
carbon-based fuels such as hydrogen are developed or electric cars are
adopted, carbon-based biofuel production will remain an important option
to replace fossil fuels for transport. A major advantage of carbon-based fuels
is that they are very energy dense (currently 10–100 times more dense) compared to energy stored in the most efficient batteries. Energy density (the
amount of energy per unit of weight) is a key characteristic for a fuel to be
used to power a mobile vehicle.
‘Renewable energy’
The use of renewable sources of energy is an attractive alternative to the consumption of fossil fuels. Solar and wind power are widely considered
renewable energy sources. They do depend on energy from the Sun which
is ultimately not renewable, but on the timescale of human lives these sources
of energy are effectively available forever. Geothermal energy may be harvested by circulating water underground to be heated and returning the
water and the energy captured to the surface. This energy is also not strictly
renewable, but may have major advantages in avoiding the release of greenhouse gases associated with fossil fuel consumption.
Plants capture energy directly from the Sun in photosynthesis. Fossil fuels
are derived from ancient plant material that has been accumulated in
deposits that can be mined. The problem with the use of fossil fuels is that
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Energy Resources 51
we are rapidly returning to the atmosphere large quantities of CO2 that have
been stored underground over very large periods of time. Bioenergy can be
produced by growing plants and using them directly in the generation of
electricity, production of fuels or chemical feedstocks. Biofuels is the term
now used most specifically for transport fuels (currently usually ethanol but
also biodiesel) produced from plants. This approach may reduce the greenhouse gas emission associated with the use of transport fuels. Carbon
dioxide captured by the plant as it is grown is released back into the atmosphere when the fuel is used. This recycling of carbon dioxide avoids a net
increase in CO2 due to the release of carbon trapped in fossil fuels into the
atmosphere. The extent to which this benefit is achieved depends upon the
efficiency with which the plant can be grown and converted to a biofuel.
Energy consumption and associated CO2 emissions during the whole cycle
of production need to be considered. For example, the energy used in
preparing the field, planting the crop, applying fertilizer, making the fertilizer, harvesting the crop, transporting the crop to a processing plant,
conversion to biofuel and transport of the biofuel to a retail outlet all need
to be determined to establish the relative energy and greenhouse gas impact
of this technology. Biofuels that generate more energy consumption than
they produce are possible and probably the easiest type of biofuels to
achieve in a technical sense. Biofuels with a more desirable environmental
impact are needed and much current research and development effort is
being devoted to making biofuels more energy efficient and environmentally
desirable. We are already seeing dramatic gains in efficiencies of commercial biofuel facilities.
Research needs for biofuel production from plants
The development of technology for the economic and environmentally
friendly biofuel production from plants requires significant research and
development. The risk for those making this substantial investment is that
another technology, for example, one that avoids the use of carbon fuels altogether (e.g. a very efficient technology producing hydrogen as a transport
fuel directly from the Sun), could be developed and make this technology
redundant. This is probably a scenario that is highly desirable from an environmental perspective; however, we cannot predict how long it might take
and so we are faced with an urgent need to improve current biofuel technologies at least for the short to medium term. The production of biofuels
from plants on a large scale has other risks associated with demanding more
of our agricultural production systems. Competition with food crop production may reduce food production and increase food prices. Expanded
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Plant Resources for Food, Fuel and Conservation
agricultural production may demand more land is cultivated, threatening
biodiversity and nature conservation. This issue will be addressed later in
this book, but before that we need to examine the use of plants for current
biofuel technologies and their limitations and promises of efficient second
and later generation biofuels that research and development might deliver.
This will be the topic of the next chapter.
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Plant Resources for Bio-energy and
Chemical Feedstock Uses
The cell walls of vascular plants account for much of the carbon fixed
during photosynthesis and make up much of their biomass.
Philip Harris (2005)
Biofuels from plants
Growing fresh plant biomass represents a source of carbon for energy and
feedstock production that is an alternative to the use of deposits of ancient
plant biomass (fossil fuels). Rather than return CO2 to the atmosphere as
we do when we burn fossil fuels we have the potential to recycle carbon,
fixing it in growing the plant and returning it to the atmosphere when the
biomass is consumed. Biofuels may be produced in a more carbon neutral
process, avoiding the addition of greenhouse gases to the atmosphere and
the associated risk of global warming. For example, life-cycle assessment
of ethanol production from switchgrass has produced an estimate of a
94 per cent reduction in greenhouse gas emissions compared with conventional fuel from oil (Schmer et al, 2008). Despite this potential the
current first-generation technologies for biofuel production (based upon
conversion of non-structural carbohydrates (sugars and starch) to ethanol
or plant oils to biodiesel) have been assessed as often having minimal
advantages, and may in fact have a net negative impact when all social,
environmental and economic factors are considered (Charles et al, 2007).
The efficiency of these first-generation processes is being rapidly
improved. However, current substantial investments in improvement of
technologies for biofuel production (US Department of Energy, 2008) are
essential to achieving the promised potential of plants to deliver significant
reductions in greenhouse gas emissions.
Electricity from plants
Plants may be combusted to generate electricity directly. This approach
has been adopted by the sugarcane industry with the widespread use of
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Plant Resources for Food, Fuel and Conservation
the fibre residue for electricity generation after extraction of the sugar.
Initially the objective of these processes was to generate enough electricity to power the sugar mills, but the technology has been developed to
allow electricity to be generated significantly in excess of these requirements and to be used for domestic and industrial applications. This may
be the best option for use of some types of biomass until more effective
technologies for biofuel production are developed. However, biofuels
could become a preferred use if efficient technologies can be perfected.
The first generation of biofuels has involved the production of ethanol
from corn or sugarcane and biodiesel from oilseeds. Current technology
developments aim to greatly increase the fuel value per hectare of crop
produced relative to these first generation technologies by developing the
technology needed to utilize the structural carbohydrates (cell walls) of
plants. The composition of the biomass and the available technologies
determines the suitability of biomass resources for these competing applications.
Composition of plants for energy production
Plants store carbon mainly in carbohydrates. The presence of structural
carbohydrates such as cellulose in the cell walls of plants, and nonstructural carbohydrates such as sugars and starch within the cell, was
introduced in Chapter 2. The potential of plants to replace oil in fuel and
chemical feedstocks relates directly to their carbohydrate content and our
ability to convert these carbohydrates efficiently into fuels and chemical
Non-structural carbohydrates in plants
Plant cells store carbohydrates as sugars. In green plants, the disaccharide
– sucrose – predominates, but the two monosaccharides that make up
sucrose – glucose and fructose – are usually also present. Fungi tend to
accumulate the disaccharide trehalose (two glucose units). All plants accumulate glucose, fructose and sucrose, but some plant groups also produce
other sugars. Plants from the family Rosaceae (apples, apricots, cherries,
peaches, pears and plums) accumulate a sugar alcohol – glucitol (the alcohol resulting from reduction of glucose) – often called sorbitol. Sorbitol is
the main sugar in a mature apple. The amount of sugar that plant cells
can accumulate is limited. The osmotic impact of very high sugar content
limits accumulation. To allow accumulation of more carbohydrates in the
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Plant Resources for Bio-energy and Chemical Feedstock Uses 55
cell plants polymerize simple sugars – polymers of glucose (starch) and
fructose (fructans) are most common. Almost all plants produce starch
which accumulates as starch granules. Starch is an effective carbon sink
in the cell, but carbon in these large structures may not be available for
immediate metabolic use. Many plants from cool or dry environments
have also evolved the ability to accumulate fructans (see Chapter 11 for
details of families of plants containing fructans). These soluble fructose
polymers can be readily polymerized and depolymerized in the plant to
allow physiological adaptation to cold or drought stress. Some plants
accumulate galactose polymers based upon sucrose (the raffinose series
oligosaccharides); in the human diet these are commonly encountered in
The non-structural carbohydrate content varies greatly in higher plants
and has enormous potential for modification to better suit the needs of biofuel production. Increased levels of sucrose or starch are important targets
for crops such as sugarcane and maize that are currently grown as sources
of these carbohydrates for biofuel production (Smith, 2008). Alteration in
the composition and properties of plant starch for a wide range of applications has been the subject of considerable commercial interest (Waters and
Henry, 2007).
Non-structural carbohydrates as a source of biofuel
These carbohydrates are very readily available for use in fermentation.
Biofuels generated by fermentation of plant non-structural carbohydrates
have been termed first-generation biofuels to distinguish them from those
produced from structural carbohydrates (second-generation biofuels).
Fermentation of plant carbohydrates to produce ethanol has been a technology long utilized by humans to produce alcoholic beverages. Beer and
wine production probably date back to the beginnings of plant domestication and agriculture. The question of whether beer or bread came first
illustrates the point. A mixture of ground cereal (flour) and water can
become bread or beer, and early agricultural communities probably produced both relying as they did on some of the same core technologies.
Adaption of these long-established ‘biotechnologies’ for the production of
fuel ethanol from the non-structural carbohydrates of plants has been a
relatively simple process, building upon the long human history of brewing, distilling and wine making. More recently bacteria have been
developed as an alternative to yeast in fermentation of sugars to produce
ethanol. Plants expressing starch-degrading enzymes would assist the conversion of starch to fuel. Maize expressing a heat stable amylase has been
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Plant Resources for Food, Fuel and Conservation
developed to facilitate efficient conversion of the starch to glucose during
Structural carbohydrates in plants
A defining feature of plants is the presence of a cell wall. The cell walls are
the ‘skeleton’ of the plant providing structural support to the plant. The
plant cell is much like an animal cell inside a rigid box (the cell wall). Plant
cell walls may be thought of as being like reinforced concrete with fibres of
cellulose (the metal rods) surrounded by non-cellulosic polysaccharides (the
concrete). This is further strengthened by the addition of lignin and phenolic cross links between the polysaccharides. Ester-linked ferulic acid,
p-coumaric acid and lignin provide cross linking. Plants contain a diversity
of non-cellulosic polysaccharides.
The cell walls of grasses contain polymers of glucose that are related in
structure to cellulose, but contain some glucose resides linked via carbon 3
rather than carbon 4 as in cellulose. This changes the properties of the polymer from a linear and rigid molecule likely to associate with others to form
long micro-fibrals (as in cellulose) to an irregular molecule that is not likely
to polymer in solution (the viscous beta-glucan solutions). Linear polymers
of xylose with arabinose resides attached (arabinoxylans) are also abundant
in these plant cell walls. The cell walls of the Commelinoid associate with
others, but to exist as a long group of families that includes the grass family (Poaceae) form a distinct group within the monocotyledonous plant
families (Henry and Harris, 1997) sharing common cell wall structures
(polysaccharide composition and the presence of the ferulic acid cross
links). These type II cell walls contain higher amounts of cellulose and very
little pectin or protein. These features distinguish this group of plants from
other higher plants (Figure 5.1). Other species of higher plants have type I
cell walls containing xyloglucan as the main non-cellulosic polysaccharide,
together with pectic polysaccharides. These polymers have often been
called hemicelluloses (half cellulose), but use of this term can lead to confusion because it has been variously used to include all non-cellulosic
polysaccharides and alternatively to include only neutral polysaccharides
and exclude pectin (polysaccharides containing acidic residues such as
galacturonic acid).
The diversity of cell wall structure and a growing understanding of cell
wall biosynthesis suggest that significant cell wall modification to suit biofuel
production may be possible (Pauly and Keegstra, 2008).
The composition of plant biomass can be used to estimate ethanol yields
in conventional conversion technologies (Table 5.1).
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Plant Resources for Bio-energy and Chemical Feedstock Uses 57
Box 5.1 Advances in technologies for the analysis of plant carbohydrates
The rate of progress in understanding the composition of plants and in
selecting appropriate cultivars better suited for specific food or other uses
has relied on the techniques we have for the analysis of the carbohydrate
composition of plants.
The approaches to these analyses were initially based upon the chemical approaches that had been used in the early determination of the
structure of carbohydrates and their chemical preparation and synthesis.
Determination of the monosaccharide (simple sugar) composition of a
polysaccharide (a polymer composed of many monosaccharide units (simple sugar residues) linked together with covalent chemical bonds) has
been based upon the breakdown of the polysaccharide into the monosaccharide units and their analysis, usually following separation of the
component sugars by some form of chromatography. A common
approach has been to use acid to break down the polysaccharide into
monosaccharides. The sugars in the resulting hydrolysate are complex to
analyse because each sugar (e.g. glucose) can exist in a range of chemical
confirmations and ring structures (e.g. alpha and beta). This complexity
has usually been minimized by chemically reducing these sugars (aldehydes) to alditols (sugar alcohols). In this process all forms of glucose
become a single open-chain molecule – glucitol. The resulting sugar alcohols can then be analysed. This has often been achieved by acetylating the
hydroxyl groups on the sugars to form volatile alditol acetates to allow
separation and analysis by gas chromatography. The protocols for these
analyses prior to around 1980 were very time consuming and used
approaches based upon preparatory organic chemistry.
The author was involved in a series of collaborations in the laboratory
of the late Professor Bruce Stone in the early 1980s, which developed a
series of methods to progress approaches that were based much more on
the strategies of analytical chemistry or biochemistry. These methods
were widely adopted because of the much larger numbers of samples that
could be routinely and quantitatively analysed, allowing the variation in
carbohydrate composition in biological samples to be more widely
explored. The first paper in a series published on these methods (Blakeney
et al, 1983) has been cited in more than 1000 publications. The same
approach was used to refine the techniques for methylation analysis of
polysaccharides (the method used to determine how (through which carbon atoms) the monosaccharide resides were linked together in the
polymer) (Harris et al, 1984). These methods have also been cited widely
in the scientific literature.
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Plant Resources for Food, Fuel and Conservation
These techniques are still relevant today, but can now be complemented
by the use of more advanced instrumental methods of analysis. Further
developments and the application of new tools to analysis of the carbohydrate composition of plant materials, especially complex aspects of
macromolecular structure, would facilitate the accelerated development of
plants as improved biomass for biofuel production.
Figure 5.1 Difference in biomass composition in flowering plants
Structural carbohydrates as a source of biofuels
Structural polysaccharide is abundant in plant material and as such an
attractive source of carbohydrate for conversion to fuels. This process is
much more challenging technically than the conversion of sugars and
starches. Cost-effective technologies for conversion of plant cell wall to biofuel are likely to be the key to the success of biofuels. Knowledge of the
structure of the cell walls in specific groups of plants is important in developing technologies for efficient conversion of this material to biofuel. For
example, the chemistry of the cell walls in grasses and related plants from
the Commelinoid group (as defined above) may dictate different processing
requirements compared to that required for other plant species.
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Plant Resources for Bio-energy and Chemical Feedstock Uses 59
Table 5.1 Examples of the composition of plant biomass and predicted ethanol yields
(baggase, fibre
residue after
sugar extraction)
Wheat (straw)
Rice (hulls)
Eucalyptus (E. saligna)
predicted yield (%)
Source: Chandel et al, 2007
Biochemical conversion
Biochemical conversion involves hydrolysis of polysaccharides using acid or
enzymes, followed by fermentation to produce fuel.
An important area of innovation in biochemical conversion technologies
is in the pre-treatment of the biomass to improve the efficiency of the carbohydrate hydrolysis. The aim of pre-treatments is to change the biomass
structure to make it more amenable to subsequent processing. Pre-treatments may include mechanical, thermal and chemical processes. Alkaline
and treatments may also be included. The key objective of most research is
to find a cost-effective pre-treatment method for the target biomass. Energy
and greenhouse gas efficiency of pre-treatments are also important.
Acid hydrolysis may be a multi-step process with options for different
acid concentrations and temperatures. Acid hydrolysis especially at high
temperature can cause degradation of the monosaccharides to furans that
may inhibit subsequent fermentation.
Enzymes that digest cell walls are known for microbial sources. Woodrotting fungi have long been studied as a source of these enzymes.
Micro-organisms from the gut of animals that derive energy from the cell
walls of grasses or wood (e.g. ruminant animals such as cows and sheep, and
insects such as termites) are another important source. These processes have
long been possible, but achieving a high level of conversion at low cost, as is
required for a commercial process, has proven more difficult. Combinations
of acid and enzymes may be used to digest cellulosic biomass to produce sugars for fermentation to fuel molecules. Research aiming to produce these
enzymes directly in the plant is in progress. This technology offers the potential to eliminate the cost of enzymes and to reduce the cost of mechanical and
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Plant Resources for Food, Fuel and Conservation
other processes required to allow access of the enzyme to carbohydrates
within the plant material. Research focuses on producing more efficient
enzymes at a lower cost and methods for pre-treatment of the plant material
to allow the enzymes better access to the polysaccharides. Conventional
micro-organisms used for fermentation cannot process both C6 and C5 sugars at the same time. The conversion of six carbon (C6) sugars such as
glucose and five carbon (C5) sugars such as xylose is being tackled in many
ways. The polysaccharide may be separated before hydrolysis to allow separate fermentation or organisms capable of simultaneous fermentation may be
engineered. In other strategies, enzymes may be used to convert these sugars
to forms better suited to simultaneous fermentation.
Thermochemical conversion
Thermochemical processes avoid some of the need to optimize the composition of biomass. The main disadvantage of these processes is that they generally
require high-energy inputs. The production of biodiesel from cellulosic biomass by thermochemical methods is a process that was developed long ago, but
is currently being re-examined and applied. Biomass can be heated in the
absence of oxygen (fast pyrolysis) to directly produce an oil, or heated in the
presence of a small amount of oxygen and steam (gasification) to produce a
gas (syngas) that can be burnt to generate heat energy (e.g. for the generation
of electricity) or subsequently converted to a liquid fuel (Fisher-Tropsch
process). The use of biomass to generate syngas can result in high levels of ash
which may damage turbines, indicating the need to develop sources of biomass
with a low ash content. The development of improved catalysts is an active area
of research and is likely to be a key factor in determining the success of thermochemical conversion. Pyrolysis oil may become ‘biocrude oil’, allowing the
concentration of energy in biomass before transport to centralized refineries.
Chemical conversion
Chemical- rather than fermentation-based approaches may have advantages
in being able to be readily scaled up. Recent novel strategies have been suggested for the production of high-value fuels from plants without
fermentation or the use of micro-organisms. For example, 2,5-dimethylfuran (DMF), a desirable fuel molecule, could be produced by converting
glucose to fructose with enzymes, acid-catalysed conversion of the fructose
to 5-hydroxymethylfurfural (HMF) and the use of metal catalysts and
hydrogen to produce the DMF (Schmidt and Dauenhauer, 2007).
Conversion technologies that combine one or more of these different
technologies are also being developed. For example, biochemical methods
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Plant Resources for Bio-energy and Chemical Feedstock Uses 61
may be used to convert the carbohydrates to sugars, while chemical methods
may be applied to the lignin component. Separation into a low lignin fraction
for pyrolysis and a high lignin component for gasification is another strategy.
Lignin is a major component of plant biomass. Lignin may be viewed as the
product of polymerization of three hydroxycinnamyl alcohol precursors,
resulting in p-hydroxyphenyl, guaiacyl and syringyl units in the lignin.
Biological degradation of lignin by enzymes and micro-organisms is difficult.
Plants with low lignin content are being selected for biofuel production
to overcome the problems associated with lignin degradation. The brown
midrib mutants of maize and sorghum have low lignin content and may
allow improved biofuel yields from biomass of these species (Li et al, 2008).
However, a high lignin is desirable in plant biomass that is combusted to produce heat energy or electricity. Recent reports also suggest that conversion
of lignin into high-value alkanes (C8 and C9) may be possible at high yield
using suitable catalysts. These developments might lead to an interest in
developing high lignin biomass.
Plant oils are a more direct source of fuel molecules. Plants have been widely
cultivated for their edible oils. Many of these can be used to produce fuel,
but fuel production can extend to the use of species that have not been suitable for human food use because of the presence of toxic compounds in the
oil. The yields of oil relative to biomass are generally very low, making the
use of plant oils a poor option compared to biomass production when the
required land, water and other resources are considered.
Types of biofuel that can be produced from plants
The type of biomass available influences the processes that are available to
convert it to fuel and the types of fuel molecule that can be produced.
Innovations in processing or conversion technology may allow more desirable fuels to be produced. This in turn may dictate different biomass
specifications. This iterative interaction between developments in the target
fuel, the conversion technology and the biomass is depicted in Figure 5.2
and Table 5.2. This has led to the use of terms such as first-, second- and
later-generation biofuel to signify different combinations of biomass source,
conversion technology and biofuel product.
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Plant Resources for Food, Fuel and Conservation
Figure 5.2 Interactions between biomass, conversion technology and fuel molecule
Table 5.2 Examples of different stages of development of biofuel technology
First generation
Second generation
Maize (starch)
Woody biomass
Thermochemical or biochemical
Higher alcohols/alkanes
Biofuels that are identical in chemical properties would be best to substitute for gasoline (C5-C12), jet fuel (C8-C16) and diesel (C10-C22). A wide
range of chemical and biochemical processes (Table 5.3) has been developed for conversion of plant biomass to fuels (Huber et al, 2006).
Ethanol has been widely produced and used as a biofuel and can be considered a first-generation biofuel product. Growth in ethanol production
Table 5.3 Biofuel technologies and products
Type of fuel produced
Fermentation from sugars/starch
Extraction from oil containing plants
Fermentation from plant cell walls
Thermo chemical (Fisher-Tropsch)
Chemical conversion of plant carbohydrates
Ethanol (butanol)
Ethanol (butanol)
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Plant Resources for Bio-energy and Chemical Feedstock Uses 63
BP Statistical Review of World Energy, 2008
Figure 5.3 Global ethanol production
worldwide is shown in Figure 5.3. Most production is in Brazil (from sugarcane) and the US (from maize). Ethanol from sugarcane is widely available
in Brazil (Figure 5.4). The current production is also all first-generation
technology being based upon the conversion of sugar and starch to ethanol
by fermentation.
Ethanol has long been produced by fermentation of sugars using
microorganisms in brewing and wine making, and these technologies have
been perfected by humans over many thousands of years. Most vehicles can
operate with the addition of a small amount of ethanol (5–10 per cent) to
the gasoline; vehicles can be readily produced, however, to operate on 100
per cent ethanol. Ethanol produced from cellulose rather than sugars or
starch is considered a second-generation biofuel in that it is produced using
a second-generation technology. The conversion of cellulose to fuel is much
more technically challenging than the processing of simpler sugars and soluble polysaccharides (Lynd et al, 2002). The efficiency of this process on an
industrial scale is the subject of considerable research efforts because of the
abundance and low cost of cellulosic biomass. Bacteria have recently been
engineered to produce more attractive fuel molecules such as 1-butanol, 2methyl-1-butanol, 3-methyl-1-butanol and 2-phenylethanol from glucose
(Atsumi et al, 2008).
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Plant Resources for Food, Fuel and Conservation
Figure 5.4 Ethanol produced from sugarcane on sale in Brazilia
Ethanol has several disadvantages as a biofuel:
much of the CO2 (two-thirds) contained in plant carbohydrates is
released into the atmosphere during fermentation;
ethanol does not contain as much energy as other potential biofuels;
ethanol is also hydroscopic and adsorbs water from the atmosphere
during storage and transport.
However, the addition of ethanol may improve the environmental
impact of petroleum use by reducing the emission of particulate matter and
carbon monoxide. Biofuels that do not require the development of new
infrastructure for distribution and storage are highly desirable. Higher alcohols such as butanol (C4) or even higher alcohols may be considered likely
second-generation biofuel products, have a higher energy value and are not
hydroscopic. Alkanes are still better options and may be the third-generation
biofuel products. Each of these stages offers real technical advantages, but is
difficult at present and requires more technical innovation. A further advantage of alkanes rather than molecules like ethanol is that alkanes are not water
soluble and separate to float on the top of an aqueous production vessel. A
large energy cost is associated with the separation of ethanol from water and
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Plant Resources for Bio-energy and Chemical Feedstock Uses 65
this may be avoided if alkane-producing bacteria of fungi can be developed
for biofuel production from plant biomass. However, ethanol as a firstgeneration biofuel product has a significant first-to-market advantage and
other fuels may find it hard to displace ethanol from the market despite their
technical superiority. The direct use of plant oils as biodiesel is another
example of a first-generation biofuel that can often be produced by simple
extraction of the oils from the plant, followed by a simple chemical conversion process to release fatty acid esters from the triglycerides. These fatty
acids are then trans-esterified to form methyl or ethyl esters. Non-fuel markets may derive other molecules directly from plants. For example,
fermentation may be designed to generate propanediol as a feedstock for
polyester production for use in products such as carpets, and plants can be
used to produce a range of chemical feedstocks that are currently sourced
from oil.
Plants as sources of chemical feedstocks
Rubber is an example of a polymer that has been produced from plants.
High oil prices will continue to make the traditional production of rubber
from plants attractive.
Plastic production globally now exceeds 100,000 million tonnes per
annum. The use of plants to replace oil for these applications is a key to
reducing the cost pressures on these products resulting from rising oil prices,
and ultimately making these products without consuming fossil fuels that
have an associated negative impact on global climate.
Two distinct options are available for using plants instead of oil to produce plastics. Firstly, plant biomass can be harvested and processed to
produce the required chemical feedstocks. The second option is to generate
the chemical feedstock molecules directly in the plant following appropriate
metabolic engineering.
An example of the first type (biomass conversion) is the production of
PLA. Polylactic acid (PLA) is produced from corn starch by hydrolysis to
glucose, fermentation of glucose to lactic acid, dimerization to produce lactide and then polymerized to produce PLA.
An example of the second type (production in the plant) is the production of PHA. Polyhydroxyalkanoate (PHA) production has been
demonstrated in switchgrass (Somleva et al, 2008) and sugarcane plants.
These renewable and biodegradable plastics may be produced as a co-product with fuel derived from the lignocellulosic biomass.
Other biopolymers that might be produced in plants include poly-amino
acids and fibrous proteins (Van Beilen and Poirier, 2008).
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The use of plants to generate multiple products is a key strategy to
ensure economic viability of plant production and processing. The concept
of biorefineries has emerged. A biorefinery processes plants to a range of end
products that may include energy (in various forms), chemical feedstocks
(e.g. plastic precursors), food ingredients and pharmaceutical compounds.
The total value of the products may make the process economically and
environmentally desirable even if each of the separate products is not viable.
Development of plants that can be processed in this way imposed complex
requirements on the plant breeder.
Plant species for bio-energy production
Many criteria may be devised to define the optimal plant species for use in
biofuel production:
high biomass accumulation;
high harvest index;
high fraction of biofuel in harvested biomass;
nutrients partition to non-harvested parts;
able to be grown on marginal lands;
harvested material able to be stored in the field;
high bulk density;
high water use efficiency;
high N use efficiency;
potential as a weed;
co-product potential;
biomass composition;
scale of potential production;
cost of harvest;
suitability for genetic improvement.
Most biofuels produced to date have utilized only a small number of species.
Sugarcane has been used in Brazil, maize in the US, canola (and sunflower)
in Europe and soybean in the US. A wide range of plant species are currently being developed or evaluated as bio-energy crops (Table 5.4). Several
of the most well-known options are now introduced.
All of the cereals are rich in starch and as such are potential sources of biofuels (Henry and Kettlewell, 1996). However, cereal such as rice and wheat are
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Plant Resources for Bio-energy and Chemical Feedstock Uses 67
Table 5.4 Examples of plants that have been considered as a source of biomass for biofuels
Giant cane
Saccharum X
Miscanthus sp
Panicum virgatum
Arundo donax
Current leading industrial crop
Relative of sugarcane
C4 dedicated energy crop
Large grass
Zea mays
Sorghum bicolor
Triticum aestivum
Oryza sativa
Hordeum vulgare
Feed/food crop (major current source of ethanol)
Feed/food (sweet sorghum possible energy crop)
Major food crop (straw available for biofuel)
Major food crop (straw available for biofuel)
Major food crop (straw available for biofuel)
Eucalyptus sp
Populus sp
Salix sp
Pinus sp
Casuarina sp
Allocasuarina sp
Pulp and timber species 700+ taxa
Major timber species (waste options)
Limited current uses
Oil crops
Oil palm
Soya bean
Castor oil
Diesel tree
Pongamia tree
Elaeis guineensis
Brassica napus
Helianthus annuus
Glycine max
Olea europea
Camelina sativa
Jatropha curcas
Ricinus communis
Carthamus titctorius
Simmondsia chinensis
Copaifera langsdorfii
Milletia pinnata
Food crop
Food crop
Food crop
Food crop
Food crop
Non-food crop
Other crops
Sugar beet
Beta vulgaris
Acacia sp
Cassia sp
Tropical cultivars under development
very attractive human foods and food end uses are likely to continue to dominate for these species. Maize is also important as a human food regionally
(e.g. in Africa and Meso-America), but on a global scale is less directly a
human food than wheat and rice being used predominantly as a feed for
domesticated animals that in turn supply food to humans. Maize was possibly
originally domesticated as a source of stalk sugar (Smalley and Blake, 2003)
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in the same way as sugarcane (a relative of maize) and was only later selected
for grain. Maize has recently been used to produce ethanol on a large scale,
mainly in North America. Maize is currently a major source of first-generation biofuel globally. Maize cultivars especially suited to fuel production are
being developed. First-generation biofuel varieties are developing the grain as
a source of fuel and second-generation varieties are targeting improvements in
the total plant biomass.
Sorghum is adapted to production in hot and dry environments that are not
generally suited to the production of major food crops, making it an attractive option for bio-energy. However, sorghum grain has become an important
animal feed in many areas, creating a potential for competition between animal feed and energy production in the utilization of sorghum as in the case
of maize. Sorghum cultivars are also being specially developed for fuel use.
Sugarcane (Saccharum X) is a major sugar and energy crop. World production is high and growing, especially in Brazil (Figure 5.5). This C4 plant
Figure 5.5 Sugarcane production
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Plant Resources for Bio-energy and Chemical Feedstock Uses 69
Sugarcane is the world’s leading industrial crop. Much more than 1,000,000,000 tonnes per year are
harvested worldwide.
Figure 5.6 Sugarcane
gives very high biomass yield in tropical environments (Figure 5.6).
Sugarcane has been selected for sugar production, while sugarcane for
energy – ‘energycane’ – does not require sugar (assuming efficient cellulosic
conversion technologies are available). Recent efforts in the selection of new
energycane genotypes for biofuel production as an alternative to the existing
sugarcane genotypes recognizes that selection for high sugar content in sugarcane has not been entirely consistent with obtaining the maximum biomass
as required for an energycane.
Ethanol production from sugarcane currently relies on processing the
sugar or other co-products but not the residual fibre. When the price of
sugar is high it is attractive to sell the purified sugar as sucrose rather than
convert it to ethanol. Co-products such as molasses (a sugar-rich residue
from sugar refining) may still be used for ethanol production in these
processes. Active research programmes are targeting the use of the fibre by
developing commercial-scale cellulosic conversion technologies specifically
targeting sugarcane. This use competes with the widespread use of the fibre
to generate electricity.
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Miscanthus is a close relative of sugarcane and it is being developed as a
dedicated energy crop. Hybrids between sugarcane and Miscanthus have
been produced as potential energy crops. One of the advantages of this
species is the potential to grow the crop for up to 15 years before replanting. The ability to harvest repeatedly without the need for replanting
greatly improves the performance of the system in life-cycle assessment
and reduces the energy and greenhouse gas impact of fuel production from
this type of crop. Miscanthus (Miscanthus X giganteus) has been shown to
have much higher yields than switchgrass (more than 20 tonnes per hectare
for Miscanthus compared to 10 tonnes per hectare for switchgrass) in
Europe and North America (Heaton et al, 2004). This high yield makes
Miscanthus a very strong candidate crop for use in biofuel production.
Switchgrass (Panicum virgatum) is a perennial grass that has been evaluated
as a bio-energy crop. Switchgrass is a C4 plant that is a native of North
America, being found from Mexico to Canada. The plant is polyploid, self
incompatible and highly heterozygous with great potential for further
improvement by current active plant breeding. A major advantage of switchgrass is that it can be produced on marginal farm land (Schmer et al, 2008).
Switchgrass is being bred for use in energy production.
Other grasses
Many other grass species are being evaluated as potential bio-energy crops in
different regions. Globally there are around 10,000 grass species. Many of these
have been evaluated as potential food crops or pasture species, but not as energy
crops. Grasses offer advantages in wide adaptation, allowing very large-scale
production. The mechanized harvesting of grasses is a well-established technology that provides an advantage relative to some other options such as trees
or shrubs. Systematic evaluation of the options for energy production from
grasses will require the establishment of the criteria that are required for selection of superior types. The domestication of new species for energy use
provides an opportunity to use many species that have not been domesticated
for food use. However, some of the same traits will be important. For example,
seed retention (non-shattering) will be required to allow harvest of seed for the
propagation of the crop. Traits such as seed size are more likely to conflict, large
seed has been a key to food use (of the seed), while larger seed may not be associated with the maximum biomass accumulation required for energy use.
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Plant Resources for Bio-energy and Chemical Feedstock Uses 71
Tree crops
Wood is an attractive biomass source for bio-energy production because it
has a relatively high bulk density. This makes it highly competitive with
other less dense biomass sources such as plant leaves (a major part of grass
biomass) because of the reduced costs of transport and handling. A key
issue for trees is how long the tree should be grown before harvest. Many
forest trees grown for timber (solid wood products) require 20 to 50 years
before harvest and these long crop cycles make economic production difficult. More frequent harvest of trees grown at higher density is an option
that has not been fully explored for many tree species. Ideally the tree can
be harvested and allowed to regrow for repeated harvesting without replanting. This approach to plant cultivation is not new, but has not been
optimized for most species being considered as energy crops. This depends
upon the biology of the tree and its ability to grow from the base following
harvest. The optimal harvest frequency could be as low as one or two years
for fast growing species than can be mechanically harvested if they are not
too large. The harvest frequency needs to be optimized to deliver the maximum sustainable yield of biomass per year. The costs of alternative
harvesting strategies and frequencies also need to be considered, together
with the impact of harvest frequency on biomass composition and resulting
suitability for biofuel production.
Hybrid poplars are potential energy crops in northern areas. The availability of the genome sequence makes this species a target for understanding the
genetic control of useful traits (including fuel traits) in tree species.
Willows (Salix species) have been suggested as energy crops especially in the
UK. They may represent a major woody biomass option in suitable environments, but have complex genetics that will make breeding challenging.
Harvest every 2–3 years should be possible, making this an attractive option
for biomass production in environments that suit willow species.
The Eucalypts are a group of 500–1000 species originating in Australia
and adapted to a wide range of climates, including many that are marginal
for use in agricultural production of food crops. Eucalypts are widely
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planted as a forest species and have been used as pulp for paper and as
solid wood for construction. They represent ideal candidates for development as bio-energy crops. The biomass yield from species such as
Eucalypts may be advanced in stages. Wild material can be screened to
identify genotypes that have high growth rates. The management of the
production system may then be adjusted to maximize biomass yield per
hectare per year. Eucalypts can regrow from a lignotuber, allowing coppicing and repeated harvests at a frequency designed to achieve the highest
possible sustainable biomass yield. Plant breeding could be used to produce genotypes that perform better under these management systems.
Eucalypts grown in a conventional rotation are shown in Figure 5.7 in
comparison with a related species harvested annually. Eucalypts have
become so widespread that they are considered a weed in many parts of
the world. This may result in some concern about their widespread use as
an energy crop.
The Casuarinaceae includes trees and shrubs that grow in areas with low soil
nutrients (e.g. Allocasuarina) and low or variable rainfall. These plants are
being evaluated in several countries because of their high nitrogen efficiency
due to associations with microbes in the soil.
Oil crops
Most oilseed crops that have been developed for other applications, especially food, have also been considered as options for bio-energy crops.
Soybean is an important example, with the protein component being a very
important co-product with the oil. Oil-producing plants, like other grains,
are probably not good options for biofuel production because of their relatively low fuel yield per hectare of land or unit of water consumed.
Camelina sativa is a member of the Brassica family (Brassicaceae) with a
seed containing around one-third polyunsaturated oil. Camelina is being
developed as a non-food oilseed crop suitable for more marginal production
environments. This may become a dedicated energy crop, but could also be
developed as a more traditional oil crop for other end uses.
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Plant Resources for Bio-energy and Chemical Feedstock Uses 73
Upper panel: Eucalypt plantation in South Africa. Eucalypts, members of the Myrtaceae family of plants,
are a major source of woody biomass worldwide but especially in warmer and dryer areas. These trees
are harvested after many years of growth. Lower panel: a Tea Tree Plantation in Australia. Tea Tree
(Melaleuca alternifolia), a woody plant from the Myrtaceae, has been adapted to annual harvest for the
production of oil from the leaves. Mechanized and repeated harvesting of this species is possible with
short growth cycles. This type of production system may suit other woody biomass crops for energy
production, allowing total above-ground biomass to be utilized.
Figure 5.7 Comparison of conventional cultivation of Eucalypts and growth of a
related Melaleuca for annual harvest
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Jatropha curcas is a weedy shrub from the Euphorpiaceae that can be grown
in marginal areas. The seeds are toxic, thus preventing their use in human
food. This species has received widespread publicity and interest. The seed
contains an oil that is suitable for use as a source of biodiesel. Oil crops such
as Jatropha are unlikely to be competitive long term with second-generation
biofuels produced from high biomass crops. Production is labour intensive,
with very low yields of seeds high in oil.
Palm oil
The oil palm (originally from Africa) has been widely cultivated for food oil.
Use as a fuel has been considered controversial because of the potential conflict with food use and the risk that sensitive tropical environments with high
biodiversity values might be used for increased oil palm production. Again,
this crop may allow production of biodiesel from the fruits and seeds, but is
unlikely to be a sustainable competitor with high biomass crops delivering
second-generation biofuels. A yield of around 10 tonnes per hectare of fruit
may be produced, but this represents only about 3 tonnes of oil per hectare.
More sustainable biofuel crops in these high rainfall environments could
potentially produce more than ten times this fuel yield per hectare. The environmental footprint of oil crops is generally excessive given the competition
for land and water with food and biodiversity conservation.
Castor oil
The castor bean (Ricinus communis) is native to the Caribbean and central
America. A product, Nylon-11, is manufactured from castor oil extracted from
castor beans and is used in powder coating (Ahmann and Dorgan, 2007).
Canola has been described in Chapter 2 as an important food crop.
Significant quantities of Canola are now being produced for biofuel production, especially in Canada and Germany.
Pongamia pinnata is a leguminous tree from the Indian subcontinent and
south-east Asia that is now grown widely in the tropics. The seed has 30–40
per cent oil and the trees can be grown on marginal land, suggesting that this
may be suitable as a biofuel crop (Scott et al, 2008).
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Both green algae and blue-green algae (cyanobacteria) can produce hydrogen
– a fuel that would allow the carbon cycle to be avoided. Developing this as a
commercial process will require substantial research and development. The
commercial-scale production of biofuels based upon the lipids from algae is
the subject of intense research effort. The biochemical pathways in these systems are now well known. More than 40,000 species have been described and
many more are known to exist. The production of protein co-products may
be an important contributor to the economics of algal biofuel production systems. Algae may have a use in the capture of CO2 released during
fermentation of carbohydrates from plants to produce biofuels. This could
provide a valuable carbon source for the growth of algae for biofuel production. A major limitation in the advancement of this technology has been the
observation that when algae are selected for higher oil content they are found
to grow more slowly. High oil strains are likely to be overgrown by lower oil
content strains in all but high input systems designed to exclude them. Energy
can either be used to produce oil or to support growth, but not both.
Algae production from salt water (sea water) is more attractive as it
avoids the issue of freshwater reserves. However, open production systems
suffer from evaporation leading to salt accumulation, and closed systems
designed to prevent water loss may suffer from poor light penetration.
Energy efficiency of bio-energy production
The energy efficiency of the production of different fuels from different plant
sources is an important basis for evaluating the value of specific production
systems. First-generation biofuel production has generally provided lowenergy returns, but this is now being improved in many existing facilities.
This analysis needs to consider the energy input required to grow the plant
and convert it to fuel relative to the energy value remaining in the fuel. In
some situations energy balance may be less important than the impact the
overall process will have on greenhouse gas emissions. It may be that energyinefficient systems that avoid greenhouse gas production are of value in
reducing potential climate change. However, the cost of inefficient processes
may be prohibitive. The distance that the biomass needs to be transported for
processing is a key issue (Figure 5.8). The energy cost of transportation limits the distance that biomass can be moved – bulk density of the biomass is
important with low-density materials requiring too much energy to transport
long distances. The economies of scale of biofuel conversion are also important since the distance that biomass needs to be transported depends on the
capacity of the facility or the quantity of biomass required by a conversion
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facility for year-round operation. The amount of biomass that can be produced close to the facility depends very much on the yield per hectare. The
advantage of high-yielding crops can be considered in two different ways:
1 the distances required to source a given quantity of biomass will be
reduced; or
2 for the same transport distance, the capacity of the plant can be
increased to take advantage of economies of scale.
Box 5.2 Biomass transportation
Figure 5.8 Transportation of biomass for biofuel production
Transport of biomass consumes energy that reduces the net energy value
of the biofuel production process. Higher yielding crops allow more total
volume of biomass to be produced within a distance that justifies the
energy cost of the transport and allows a larger bio-refinery with greater
economies of scale to be built. Crops with a greater bulk density and with
a greater product yield per ton transported will also justify transportation
over greater distances.
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The movement of pyrolysis oil in pipelines to central facilities for further
processing is an example of the type of system being devised to cope with
these constraints.
The energy costs associated with the separation of fuel molecules (e.g.
the separation of ethanol and water) may be a very important aspect of the
energy efficiency of the process. Micro-organisms used for fermentation
produce ethanol only until the concentration of ethanol becomes toxic to the
organism. Distillation of ethanol from the dilute solutions that can be produced by fermentation may require significant energy. Use of renewable
energy such as solar energy as a source of heat for these processes is being
explored and alternative separation technologies are also an active area of
current research.
Thermochemical conversion technologies are conducted at high temperatures and this may require excessive energy inputs.
Carbon balance of bio-energy production
A key measure of the value of biofuel production in reducing greenhouse
gases is the assessment of the carbon balance of the whole life cycle of
production of the plant and the fuel. Each plant system will have different
An important innovation that may improve the carbon balance associated with biofuel production from biomass would be the capture and
sequestration of CO2 produced during biofuel production (fermentation).
Environmental impact of bio-energy production
Biofuel production may have a significant environmental impact. A narrow
analysis considers the energy and greenhouse gas impacts. However, a wide
range of environmental factors need to be considered when comparing biofuel production systems (Scharlemann and Laurance, 2008). The impact on
land that contributes to biodiversity conservation and contributes positive
environmental benefits is a key factor and will be considered in Chapter 9.
Some biofuel production systems contribute to undesirable emissions such
as nitrous oxide. Water consumption and impact on water in the environment is a key impact in some regions. The issues are essentially the same as
those facing all plant production for food or non-food uses.
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Future demand for plants as a resource for biofuels
Continuing developments in technologies for biomass to biofuel conversion
will impact on the demand for different types of biomass. Changing and
more ambitious target fuel molecules may also become more realistic for biofuel: this will define the targets for biomass crop development in terms of
biomass composition. The total relative environmental impact of different
biofuel crops will need to be evaluated. These constraints will ultimately
determine the demand (quantity and quality) for biofuel crops that might
emerge. The iterative interaction between fuel (molecule target), conversion
technology, biomass composition and biomass availability is likely to continue and generate several generations of biofuel technology.
The potential of plants to meet demand for biofuels
Total global biomass production greatly exceeds that required to replace all
human energy needs. However, competition for food production and the
need to conserve plants for environmental reasons limits the portion that
could realistically be used for energy. Transportation uses only a part of total
energy consumption; replacement of transportation fuels with fuels produced from plant biomass would be possible, but how we do it would
determine the impact on food production and the environment.
Global energy production in 2006 has been estimated at 11,741 million
tonnes of oil equivalence (International Energy Agency, 2008). Consumption
of energy was 8084 million tonnes of oil equivalent, with 43 per cent of this
(around 3500 million tonnes) being oil. This can be compared with the current world production of around 2000 million tonnes of cereals for human
food (FAO, 2007). Human energy needs represent a requirement for biomass that is similar in scale to that required for food. The important
difference is that food uses require plants with a very specific composition,
while ligno-cellulosic energy production is possible from a much larger proportion of available plant biomass.
Development of improved plants for
energy production
Many plants being used or considered as biofuel sources have been introduced above. However, it is likely that many other species that are better
suited to energy production could be identified by careful screening of the
large number of plant species. Systematic evaluation of plant species
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against carefully defined criteria is necessarily a time-consuming process
since growth rates need to be assessed in different environments and over
the entire growth cycle of the plant. The development of more suitable
plants for the production of biofuels will be built on our growing understanding of these organisms at the genome level (Rubin, 2008). The
technologies for the selection of superior genotypes are now possible using
DNA analysis methods that continue to improve (introduced in Chapter
2). The costs of analysis have been greatly reduced and the amounts of
data that can be collected have increased dramatically. The extraction of
DNA from plants and the analysis of the DNA can now be applied to
large plant populations using highly-automated laboratory analyses. These
methods have been developed with the improvement of crops for food uses
as a primary target. However, these advances will also allow the rapid
development of energy crop cultivars. Accelerated domestication with
current molecular technologies should allow the domestication of energy
crops in a few short generations much more rapidly than was achieved by
simple human selection in the domestication of most food crops over the
last 10,000 years or so. This option will be discussed in more detail in
Chapter 10.
The application of molecular genetics and genomics to plants is continuing to accelerate with technological developments (Henry, 2009a, b).
Dramatic recent improvements in DNA sequencing technology have greatly
increased our ability to analyse the genomes of plants. The development of
high-throughput genotyping technologies (Henry, 2008) and improved targeted mutagenesis methods (Cross et al, 2008) increases our chances of
developing the required genotypes for biofuel production.
The efficiency of biofuel production from plants may be improved by
the expression of enzymes that degrade the plants’ carbohydrates within the
plant. In first-generation biofuel crops, the expression of amylases to degrade
starch is an example of this approach. Second-generation crops may be engineered to express enzymes that can degrade the cell walls when required.
Expression of a cellulase (from poplar) in a rapid growing tropical legume,
Senagon (Paraserianthes falcataria), has been shown to result in increased
growth rates (Hartati et al, 2008). This species is an example of the potential to develop novel biofuel crops that could be used to deliver highly
efficient biomass production without the need for nitrogen inputs and with
accelerated potential for processing to fuel. A key to these strategies may be
the development of appropriate mechanisms to control the timing or location of enzyme expression in the plant.
The production of bio-energy from plants is an area in which there are
potentially many different combinations of plant species and conversion
technology. Significant scientific advances will be required to realize much
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Box 5.3 Nanotechnology provides greatly improved tools for analysis of plant genes
New technologies continue to expand our ability to analyse biological systems. Nanotechnology (processes that happen on a very small molecular
or atomic scale) has recently allowed the development of analytical platforms for the large-scale analysis of DNA sequences. This is currently
revolutionizing biology. The volumes of data that are being collected are
challenging modern computing technology. DNA sequencing with a single
instrument has moved rapidly from the daily collection of Kilobases (1990s)
of DNA sequence (one base = one letter of the genetic code) to
Megabases (early 2000s) to Gigabases (2008). Current DNA sequencing
instruments can generate terabytes of raw data in a day and petabytes of
data need to be stored. This trend is likely to continue (Doctorow, 2008).
These advances are providing new understandings of biological systems and
processes (Gravely, 2008). The technology is providing new insights into
the way plants develop and respond to their environment (Lister et al,
of this potential. For this reason it is essential that we pursue all the main
options in the hope of finding an effective solution. Exactly where the technical advances will come cannot be predicted – that is the nature of
innovation. We cannot afford the luxury of picking winners; we must follow
up on all serious options.
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Competition between Food
and Fuel Production
Biofuel output ‘crime against humanity’.
(Headline, Gulf News, Dubai, 15 April 2008)
The emergence of biofuel production from agricultural biomass has raised
concerns that biofuel production will compete with food production and
result in a reduction in food supply and higher food prices. The increases in
food prices in 2007–08, coinciding with the increased production of biofuels,
exacerbated this perception. This increase in food prices was associated with
a tightening of supply, but it was driven by many factors including increases
in demand with some hoarding of food, short-term seasonal production problems and probably also economic factors such as changes in exchange rates.
Oil prices also peaked in this period, increasing the costs of food production
and distribution. Defining the contribution of biofuels is difficult. However,
it is likely that the new end use of biofuels may result in a higher value being
placed on agricultural commodities generally and this may have a long-term
impact. The magnitude of these effects remains controversial with estimates
of the level of impact of biofuel production on food prices varying widely.
Food prices declined generally in 2008–09 together with oil prices.
Impact of biofuel production on food prices
The analysis of the influence of biofuel production of food prices is complex
and difficult to define even with the benefit of hindsight: prediction of future
impacts is very difficult. Recent reports have attributed widely differing components of food price rises to biofuel production, IFPRI estimating 25–30 per
cent while FAO estimated 10–15 per cent (McClung, 2008). These differences can be explained by differing assumptions in the analyses.
Agricultural commodity prices have been linked by the extent to which
they can substitute for one another. For example, a shortage of wheat may
result in increased wheat prices, but this may also push up the price of other
grains because demand for them will grow to substitute for wheat. This
interdependence of prices is especially relevant to the use of grains in animal
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feed where grains can be substituted depending on price to produce a feed
with the required nutritional composition. The price of energy commodities
has also been linked because of their potential substitution. The more recent
production of large quantities of fuels such as ethanol from agricultural commodities has introduced the prospect of food and energy prices becoming
Recent trends in sugar, maize and oil prices illustrate the challenge in
predicting the future relationships between energy and food prices. The
increased production of ethanol from sugarcane resulted in predictions of a
strong link between sugar and oil prices a year or so ago. Sugar prices have
remained low, however, despite spiking oil prices, largely because of
increased sugarcane production in Brazil, and they have recently risen while
oil prices were low. A link between maize and oil prices seemed to emerge
in early 2008 with both commodities rising strongly together. However, this
correlation in price is not likely to be strictly maintained.
Biofuel production may result in reductions in food costs if biofuels can
be produced at a lower cost than fuels from oil. Lower fuel prices may
reduce the cost of agricultural production and food distribution. This is most
likely to outweigh any increase in food costs associated with competition with
food if appropriate dedicated fuel crops or dual purpose crops are developed
(see Chapters 5, 10 and 12).
Land availability for crops
Estimates of the area available for the cultivation of energy crops vary
widely. Marginal lands not suited to conventional agriculture are considered
an important option for bio-energy production. Estimates of the area of such
land that could be used for energy production are from 100 million to 1 billion hectares (Worldwatch Institute, 2006). Agricultural land use changes in
response to market demands. Many areas that were previously used for
cropping are now underutilized because they have not been competitive with
other regions in a highly competitive global agricultural commodity market.
As prices improve more of this land could be introduced back into production. For example, examination of maize production in the US in recent
years shows a shift in production to more intensive and productive areas,
with a decline in production in some traditional regions. This indicates
that if demand was high enough, maize product could be expanded and reestablished on significant areas of land in the US that are not currently
Many areas of extensive agricultural production such as those used for
grazing of animals may be suitable for cropping to satisfy higher demand,
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Table 6.1 Examples of arable land estimates
Total area
Potential arable land
% in use
1000s ha
Asia & Pacific
North Africa
& Near East
North America
North Asia
East of Urals
South & Central
Source: FAO, 2008b
and may also be suitable for energy crops even if they are not ideal for food
crops. Land suitable for cropping is often called arable land, but just how do
we define arable land and how much do we have to use for all types of cropping? While many data (Table 6.1) can be found on areas of arable land in
different regions of the world (FAO, 2008b) the definition of arable land
probably needs to be redefined, especially when we consider the production
of crops for biofuels on land that is of a lesser suitability than that currently
used for food crops. Many countries have more than 100 per cent of designated arable land under cultivation by using irrigation. For example, it is
estimated that 144 per cent of arable land in North Africa and the near East
is under cultivation. Egypt and Saudi Arabia have significant agriculture but
would have almost no arable land without irrigation. In many other cases
data suggest that much of the arable land is not currently being used for agriculture. However, much if not most of the arable land that is not under
cultivation is not really available due to the presence of forests or reserves.
This makes analysis of the real situation with food security and the impact
of diversion of land to energy production very difficult to establish. New
technologies also have the potential to create more arable land. Finding ways
to deal with nutrient deficiencies in soils or to cope with hostile (toxic) soils
may make previously unusable land very productive.
Brazil is a major food exporting country with potential for continuing major
expansion of production (Figure 6.1).
Brazil is a large country with a very large agricultural production and
potential for expansion, and it includes diverse regions and environments.
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Box 6.1 Arable land in Western Australia
Areas of the south-western corner of Australia are used for the production
of cereal crops, mainly wheat. This area has a Mediterranean climate (wet
winters and hot dry summers) and generally sandy soils of very low fertility.
Many areas that had been considered unsuitable for cropping have become
productive by growing a legume (lupins) that greatly increases the yield of
wheat that can be obtained from these areas (wheat yields three times higher
have been achieved by using the legume in the rotation). This has made land
arable that was formerly not, by increasing nitrogen and providing crop
residues that improve soil carbon and key nutrient levels in the soil. Crop
rotation is an essential part of sustainable agriculture in many regions.
My first exposure to the cereal production system in Western Australia
was at a meeting at a plant breeding research station in Wongan Hills. The
sandy soils and relatively low crop biomass led me to comment to the scientists at the meeting that the poor crop may have been due to the poor
soils. My experiences had been with cereal crops in eastern Australia, especially the black clays of the Darling Downs in Queensland that produced
much higher yields. The extent of my faux pas became evident when they
later told me that not only was this equal to their best soil, but that crop
was also probably among the highest yielding crops in the region. This
example illustrates the complexity of defining arable land. The definition is
almost always a relative one and may differ greatly between regions. New
technology or the option of new crops can make previously non-arable
land arable. The amount of land available for food and energy use can really
only be established on a local basis after consideration of all of the cropping options that might work locally. All of this makes estimation of the
total food and bio-energy production potential of the Earth very difficult to
estimate objectively. New tools and processes are required to answer
these important global questions.
The Amazon rainforests are not a likely contributor of significant land for
agriculture as the biodiversity values are very high and the costs of land
clearing excessive given the short life of production on the resulting areas.
The major area that is likely to be used for expansion of sugarcane production is the Cerrado, an extensive area of savannah in the south of Brazil.
Significant areas of land with adequate rainfall are available for cropping
in this region without the need to clear native vegetation. Many of these
are degraded pastures that have already been cleared of the original native
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Source: Goldemberg, J. (2008) The Brazilian biofuels industry. Biotechnology for Biofuels 2008,
1:6doi:10.1186/1754-6834-1-6 at (
Figure 6.1 Brazil – land use
vegetation and used for extensive animal production. However, this expansion may still put pressure on biodiversity with many plant species endemic
to this region.
Mexico has significant areas that have not been used for food crops but may
suit energy crop species. The rainfall in many of these areas may be sufficient
but also highly variable. These areas that are marginal for the production of
food crops may be available and suitable for perennial energy crops.
Significant areas that have had the native vegetation removed for grazing
could be suitable for energy crop production. Rainfall is highly variable in
these areas requiring the careful selection of species.
Multi-purpose or specific purpose crops
The competition between food and fuel can be defined in relation to impact
on total crop production, the type of crops produced and the influence on
the market (supply levels and price). Plants that contain sugar and starch
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(non-structural carbohydrate) are used for first-generation biofuel production. These plants are also digestible by humans and other animals, making
them generally favoured as food species. In contrast, species that are rich in
cell wall carbohydrates such as cellulose (structural carbohydrate) are essentially not digestible by humans and are not major components of human
diets. Ruminant animals (e.g. cows and sheep) use micro-organisms in their
gut to digest these carbohydrates and can therefore use them as food.
Second-generation biofuels are produced from these less attractive human
food sources. Second-generation biofuel will not compete directly with
major human food crops, but will compete with ruminants for biomass. This
creates a potential for indirect competition between these animal-based
foods and biofuel production. Cellulosic biomass can often be produced in
more marginal areas not suitable to food crop production. Extensive pasture
areas used for grazing are among the most likely to be adopted for biofuel
production. However, these areas are relatively abundant and significant coexistence of biofuel and pasture production will be possible.
The potential for multipurpose crops needs to be explored for crops
with significant levels of both structural and non-structural carbohydrate
content. For example, grain crops could allow harvest of the seed (grain)
as a food (rich in non-structural carbohydrates of high nutritional value to
humans and animals) and the remaining parts of the plant as biomass
(straw containing most of the structural carbohydrates) for biofuel production. Breeding of grass cultivars to suit this dual purpose use may
optimize this option. However, the major gains in food production in the
last 50 years have been achieved by increasing the harvest index of cereals
(Chapter 2). The harvest index is the proportion of the plant biomass harvested as the edible part. The relatively high value of food relative to other
biomass suggests that it would not be attractive to reduce the harvest index
in dual purpose crops. The secondary or by-product role of the biomass
in these crops indicates that improvements in the composition of the residual biomass could be an important innovation. Crop residues remaining in
the field after harvest are important for soil properties and the sustainability of the farming system – removal of these crop residues may be highly
undesirable. Dedicated energy crops with high biomass potential, especially in areas not suited to efficient food crop production, will remain
attractive priorities.
Life cycle assessment of cropping systems
The environmental desirability of both food and energy crops needs to be
examined by analysis of the entire production system. Life cycle assessment
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(LCA) examines the environmental impact and economics of the entire
production system. Defining the limits of such systems appropriately is a
key to relevant analysis. For example, the environmental and economic
costs of producing nitrogen fertilizer used in crop production need to be
considered. However, the environmental costs of manufacture of the clothing worn by the workers in the nitrogen plant should be outside the analysis.
These costs to the environment would probably be incurred even if the
workers did not make fertilizer.
Direct and indirect land use changes
Direct land use competition may be avoided, but indirect competition may
apply. For example, use of land that has not previously been cultivated may
represent indirect competition. Displacement of animal production, or
increased reliance of animal production on grain or other feeds rather than
forage, represents another form of indirect competition.
Future competitive scenarios
Cline (2007) has analysed the situation comparing projections for 2085 with
2005. This illustrates the factors that need to be considered in predicting
how we might meet future demands for food and energy globally. These calculations are unlikely to predict the future. Factors that we cannot predict at
this time are likely to alter the absolute outcome of different scenarios. The
projected increase in demand or supply may not reflect what eventually happens over these extended periods of time. However, the comparison of
different options allows an evaluation of the relative value of alternative
directions and provides a basis for evaluating different policies or research
Growth in food demand
Population is predicted to grow to 10.5–14.7 billion by 2085. This represents a 1.63–2.28-fold increase in population. Per capita income is growing
and at a rate which would give a 1.63-fold increase in demand for food per
capita by 2085.
Taking these two factors together gives a 2.66–3.72-fold (1.63 × 1.63 –
2.28 × 1.63) increase in demand for food by 2085.
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Growth in supply of food
Diversion of land from food production to energy supply is estimated to alter
supply of food by a factor of 0.7 by 2085.
Increased yields derived from the application of improved technology
are estimated to give a 3.48-fold increase in food production by 2085.
These two factors give an overall growth in supply of 2.44-fold (0.7 ×
The growth in demand (2.66–3.72) exceeds the growth in supply in
these predictions.
These scenarios allow little room to cope with further losses in agricultural productivity due to global warming.
Several aspects of this scenario are worth analysis as we consider the
approaches we should take in trying to shape a workable future. The potential of technology to deliver increased agricultural productivity may be
considered optimistic if we consider recent trends. The rate of growth in
agricultural productivity has slowed in recent years as the influence of the
Green Revolution has worked through and better management practices
have been more widely adopted in agriculture. This trend may continue and
increases may slow further in the future.
Cline (2007) also points out that these projections may not fully account
for the impact of changes in diet towards the consumption of more meat.
This could add further significant increases in demand.
This approach allows the impact of different levels of diversion of land
for energy production to be considered. Table 6.2 details a range of future
scenarios based upon simple arithmetic adjustments to the numbers generated by Cline (2007). This approach (assuming all land is equal) is likely to
overestimate the impact of diversion of land to energy production if less
favourable land was used. However, the diversion of around 30 per cent of
current agricultural production (the intermediate option) would put great
pressure on food supplies.
The intermediate scenario clearly indicates that significant areas of land
not currently being used for cropping would also need to be used for energy
cropping to supplement the 30 per cent diverted from food production (the
impact of this on biodiversity will be considered in Chapter 9), and significant improvements in the technology are required to deliver the promise of
renewable fuels from plants. Advances in technology could make this scenario very realistic. The improvements in technology required to make this
scenario work will probably be delivered if we are able to perfect ligno-cellulosic conversion (as described in Chapter 5).
With current first-generation technology we currently produce only a
very small amount of biofuel – less than 1 per cent of transport fuels – from
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Table 6.2 Impact of different levels of biofuel production on food supply (assuming no
expansion in agricultural land)
Diversion of land
to Biofuels
(10.5 billion)
None (0%)
Intermediate (30%)
High (50%)
None (0%)
Intermediate (30%)
High (50%)
(14.7 billion)
Food supply
Food demand
+ 0.82
All values are times 2005 levels
a very small area of land – less than 1 per cent of arable land. Diversion of
all (100 per cent) of the current biomass produced in agriculture would
probably be required to replace all fuels used for transportation with current
technologies. However, new technologies will dramatically change this
and should allow production of all transport fuel from dedicated secondgeneration crops and technologies.
The above analysis is unlikely to predict the future, but provides a basis
for comparison of the impact of different policies in relation to agriculture
for food or energy production.
We also need to consider the impact these future scenarios might have
on global biodiversity. Chapter 9 will explore the competition between food
and energy production further in the context of the need for the conservation of biodiversity. We will now turn to consideration of the importance of
plants to the environment and biodiversity (Chapter 7) and the likely impact
of climate change (Chapter 8) on these roles of plants.
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Suddenly as rare things will, it vanished.
Robert Browning (as quoted by Leigh et al, 1984)
Plants are fundamental to life on Earth. They play a key role in determining
composition of the atmosphere and are the base of the food chain supporting other higher organisms. We have explored the key role of plants in food
and fibre production and their growing potential for direct use for energy
supply. Plant diversity provides food and habitat for a great diversity of
insects, fungi and animals. Conserving plant biodiversity is central to conserving biological diversity on earth. However, the expansion of human
populations has resulted in local and global reductions in biodiversity.
Species extinction on a large scale has followed human population growth.
Many more species are now endangered.
Plant diversity can be considered at many levels – most often we think
of it at the level of the species. However, diversity at both higher and lower
levels is important. At the higher level we need to consider questions such
as how different are the species we have and how are they related to one
another. At the lower level we need to consider how much variation exists
within the species. The extreme example in plants can be that no diversity exists within the species and all individuals are clones (vegetatively
propagated). In contrast, many plant species include highly divergent
Species diversity
The number of species of plants is not well defined. In some areas new
species are still being discovered frequently, yet many areas remain poorly
explored for plant diversity. Discovery rates sometimes reflect the amount of
analysis effort. For example, recent growth in commodity markets has
resulted in increased mining development in Western Australia and an
increase in the rate of discovery of new species as environmental impact
assessments are conducted on potential mine sites.
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Box 7.1 Case study – Queensland, new species
A report of the Queensland Herbarium for 2006–07 describes 55 new
species and three new genera (Queensland Herbarium, 2008). The total
flora of the state now includes more than 8300 vascular plant species. The
report also lists 52 new records for the state. These are native species not
previously recorded for Queensland.
The number of new taxa reflects the level of activity among taxonomists.
The list also includes new names that result from reclassification, resulting
in a total of 305 name changes, new reports and new species.
This analysis demonstrates that the number of species in a region is
not a good measure of the rate of loss of species or extinction since
many factors contribute to changes in species numbers over time. These
• naturalization of species from other regions (growth in numbers of
weed species);
• identification of an extended range from previously known species,
• discovery and naming of new species; and
• reclassification to create multiple species from a single species (splitting) or a combination of many species to form one (lumping).
None of these factors increase or decrease biodiversity, but they do
improve our knowledge and understanding of biodiversity.
New weeds
The movement of people distributes plants around the world, with species
being continually introduced into new areas and often becoming established as weeds.
Newly recorded species known from neighbouring regions are often
found to have a wider distribution and are reported as new records for
the flora of the region of interest. In the Queensland example above, 52
native species were recorded for the first time during the year. These
species had previously been known from outside the state but are now recognized as native to Queensland. In addition, five non-native species were
recorded during the year as completely new naturalizations because they
had not previously been recorded in the state. However, a further 13 nonnative species were also recorded as naturalized from species that have
previously been known from cultivation in the state or that had been
recorded as doubtfully naturalized. A further 16 non-native species joined
the list of doubtfully naturalized species during the year.
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New species
New species continue to be discovered, even in well-studied locations. In
the Queensland example, three new genera and 55 new species were
described. These are species new to science and were formally described
and published.
New species from old
New species may be defined by taxonomic revisions recognizing more than
one species within a single earlier species.
New names
Species can be renamed. This results from a reconsideration of relationships between species or from application of the rules of botanical
nomenclature to determine that a previously used name is not correct and
should be changed.
The current global status of plant diversity can be measured by the numbers of species listed as endangered. The IUCN Red List of threatened
species includes species defined as threatened internationally. More than
8000 species, or 3 per cent of described plant species, are listed as threatened in 2007.
IUCN Red List
The plants that are endangered or threatened are listed in the IUCN Red List.
This listing is published by the International Union for Conservation of
Nature and Natural Resources and is available online at
The list includes more than 12,000 species of plants. Classifications include
extinct, extinct in the wild, critically endangered, endangered, vulnerable and
data deficient. The list is far from complete and lists more species from
developed countries (e.g. US) than from other less well-documented locations. The list has only been available on-line since 2000 when the lists for
plants animals and other groups were combined and more details included.
This makes updating easier and improves access to this important
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Box 7.2 Coastal Fontainea – an example of a critically endangered plant species
Coastal Fontainea (Fontainea oraria) is a plant from a littoral rainforest of
eastern Australia and is known from only a single site. The ten adult plants
are found within a 6000m2 strip of private land that has been cleared of
native vegetation but where the littoral rainforest is regrowing. Rossetto
et al (2001) used DNA analysis to investigate the relationships between
individuals in this population and the relationships to other species.
The DNA analysis showed that most of the seedlings found at the site
were derived from a single adult tree, suggesting the need to actively
encourage the reproduction of the other individuals in the population to
ensure genetic diversity was retained in subsequent generations. The situation of this species is made more complex because individuals are of a
single sex. The species may be threatened by a limited number of female
or male trees.
The analysis indicated another population of the related species Fontinea
australis was genetically unique and in need of specific conservation.
This illustrates an approach that is useful for the analysis of any rare or
endangered population.
Classification of rare and endangered plant species
The definition of rare and endangered plant species is a relatively subjective but important task in defining targets for plant conservation efforts.
The following types of categories may be defined (Environment
Protection and Biodiversity and Conservation Act, 1999, Australia)
(Henry, 2005a):
• Extinct – no reasonable doubt that the last member of the species has
• Extinct in the wild – species exists only in cultivation.
• Critically endangered – extremely high risk of extinction in the
immediate future.
• Endangered – very high risk of extinction in the medium term.
• Vulnerable – high risk of extinction in the medium term.
• Conservation dependent – species is dependent on a specific conservation programme without which it could become vulnerable,
endangered or critically endangered within five years.
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Figure 7.1 Relationships between different groups of flowering plants
Higher level diversity
Diversity at higher levels above the species is also important. For example,
it may be more important to conserve ten species that are from divergent
families (a commonly used taxonomic grouping of related plants) than ten
species, all of which are members of the same family. DNA analysis is providing improved understanding of plant relationships at these higher levels
(Angiosperm Phylogeny Group, 2003, Figure 7.1).
DNA analysis has confirmed most of the relationships that were originally
deduced based upon the appearance (morphology) of the plant, especially the
flower in the case of flowering plants. However, important refinements of our
understanding of relationship have been provided by DNA analysis, resulting
in significant changes in the position of some groups in the ‘family tree’ of
plants. More details of the families of seed plants are provided in Chapter 11.
Diversity within species
Species of plants contrast in their diversity. Some vegetatively propagated
species are all genetically identical (clones), but most species reproduce sexually and vary to different extents. Morphological variation is apparent within
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many species, while others that show little apparent variation are highly divergent at the DNA sequence level. Diversity within species provides a reservoir
of genetic diversity that can be selected by the environment, allowing the
species to adapt and evolve. Many species show diversity that is structured on
a regional basis with populations at different locations having distinct characteristics. Other species display all of their variation within each population and
little if any divergence between geographically separated populations. Plant
population genetics defines these features of genetic variation and provides the
understanding necessary to manage the conservation of genetic diversity
within species. Knowledge that populations from different locations are distinct suggests that movement of plants between populations is undesirable if
the genetics of local populations is to be protected. This will have the practical implication of requiring seeds for plantings to be sourced from local
populations rather than elsewhere. Rare species may be genetically uniform or
may retain substantial diversity. Some species have little diversity because they
have been through genetic bottlenecks when the population has crashed due
to natural events or human activities. DNA analysis allows determination of
diversity in populations of rare or common plant species. Conservation of
diversity within species with large populations is also important.
The level of information required to effectively manage conservation of
diversity within plant species is significant. An examination of published scientific journal manuscripts (e.g. papers in Conservation Genetics) reporting
on the genetic structure of plant populations and the implications for conservation demonstrates the amount of effort required to define the needs of
a single species or population. These papers usually represent a substantial
amount of field and laboratory research and scholarship involving commitment of significant time (sometimes many years of work) and research
funds. However, they often report on a single species and sometimes only
on a single population of a single species. With more than 300,000 species
of higher plants, many distributed in large numbers of populations, the challenge of obtaining the knowledge to adequately conserve all plant diversity is
huge. Efficient tools are required for determination of genetic diversity
within and between populations (population genetics) and within and
between different species (phylogenetic analysis). Knowledge of genetic
selection and adaptation is also important in understanding the evolutionary
processes in progress, and especially in being able to predict the likely impact
of factors such as climate change on population genetics and the likelihood
of long-term survival of the population or species. New technologies for
DNA analysis and the more extensive use of DNA banks may facilitate the
more time- and cost-effective analysis of plant population structures
required to guide effective conservation efforts. However, this is just the first
step towards understanding plant diversity.
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Understanding plant diversity
We need to understand what we have if we are to effectively conserve it. The
conservation of plant diversity requires an understanding of genetics and the
evolutionary and environmental factors influencing the diversity of species
and plant communities (Henry, 2006). Evolutionary processes continue the
processes of speciation (the divergence or appearance of new species) and
extinction (loss of species), but are increasingly impacted dramatically by
human activity. The risks of extinction in small populations may be greater
than has previously been estimated (Melbourne and Hastings, 2008).
Understanding the reproductive biology of the species can be a very
important step towards understanding the diversity with the species, how
that is distributed in the population and the likely threats to conservation of
diversity in the species. For example, plants can be self-pollinating (pollination only within the flower or between flowers on the same plant) or
exclusively out-crossing (only pollinating another individual), or anywhere
in between (some combination of these possibilities). Knowledge of vectors
for pollen such as insects, birds or animals may provide important insights
into the distances over which pollination might be possible and the consequent extent of gene mixing over distance in the population. The mechanism
of seed dispersal is also a key contributor to population structure, defining
the extent to which populations are genetically distinct.
Box 7.3 What is a species?
In plants as in all other organisms this is not always an easy question to
answer. We usually consider a population of inter-breeding individuals to
be a species. This does not prevent the distinction of genetically different
groups within a species. Species are defined by taxonomists. Traditionally
this has been based upon morphology (the appearance) of the plant, with
a special emphasis on the flower as a distinguishing feature in the flowering plants. Increasingly we are using the evidence that comes from analysis
of the DNA. The sequence of genes (genetic code) provides evidence of
evolutionary relationships.
The Consortium for the Barcode of Life (CBOL,
is an international collaboration that is using DNA sequencing of agreed
genes to identify species of all types of organisms. Application of this barcoding approach to plants has proved more difficult than it was for animals.
A combination of the DNA sequence of more than one gene may be necessary to identify all plants to the species level. Sometimes this produces
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surprising or unexpected results. Species that we thought to be unrelated
on the basis of appearance turn out to be close relatives. In other cases,
plants that were classified as being related or even the same species are
shown to be very different. These are the exception, with most DNA
analysis supporting the classifications devised by taxonomists based upon
morphological observations. A recent example is our study of two ‘species’
of spotted gum (a type of Eucalypt) – Corymbia variegata and Corymbia
henryi – that grow in the same areas on the central east coast of Australia
(Ochieng et al, 2008). Genetic analysis (DNA analysis) shows that these
two ‘species’ are one inter-breeding population. The differences in size of
the leaves and fruits that were used to define the two species may be
explained by genetic variation within the population in only one or a few
The factors threatening the species or community also need to be well
understood so that they can be mitigated, or alternative options for conservation (e.g. ex situ conservation) can be implemented.
Defining threats to plant diversity
Factors causing loss of diversity or threatening extinction may be associated
with long-term evolutionary processes. However, most threats of loss of
diversity in the short term are due to human activities. Loss of habitat by
human displacement is a dominant cause of extinction. Other causes
introduction of new pests and diseases;
grazing by domesticated animals;
environmental pollutants;
competition from weeds;
altered water status of soil (drainage or construction of water storages);
removal of canopy to encourage pasture growth for grazing;
genetic impact of domesticated relatives.
The impact of successive colonizations of the Hawaiian Islands by humans
provides a useful example of the types of impact we have had and are having on plant biodiversity.
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The islands of Hawaii are unique in having a reasonable land area
(10,500km2) that is a long way from any other significant land area. These
volcanic islands now have around 1000 species of native plants (90 per cent
of which are endemic (found only in Hawaii)) competing with around 800
species (not including plants cultivated in gardens) of exotic naturalized
species that have been introduced since European contact, starting with the
visit of James Cook in 1778 (Sohmer and Gustafson, 1987). Since that time
at least 10 per cent of the plant species have become extinct and about 30
per cent of the remaining flora is endangered or threatened.
This was not the first human impact upon the flora of these islands. At
the time that Cook arrived, Hawaii had a population estimated at between
300,000 and 500,000. Polynesians arrived 1000 to 1500 years ago, bringing
at least 27 species of plants mostly with utility. Plants introduced by the
Polynesians included at least 12 food species. For example, the coconut
(Cocus nucifera) was introduced to Hawaii by Polynesians. This human invasion probably also resulted in a wave of plant species extinctions.
Weeds and biodiversity
Weeds may reduce biodiversity by displacing populations of more diverse
native species. Lantana (Lantana camara) is a serious weed in Australia and
Africa that was originally a native of tropical Central and South America.
The plant is relatively inconspicuous in the wild in Mexico except for the
attractive flowers. The plant was introduced into cultivation as an ornamental in Europe and from there garden cultivars were distributed around the
world, becoming naturalized as a very vigorous weed. In subtropical
Australia and in similar regions of South Africa, Lantana has become a dominant species, colonizing any cleared areas and forming a dense understorey
in Eucalypt forests and in gaps in rainforests. This example illustrates the
problems created when humans move plants from there native environments
and put them in new environments without the constraints to population
growth (e.g. predators, pests and diseases) that applied in the environment
in which the species evolved. Several insect pests of Lantana have been
introduced into Australia in attempts to control this weed that have met with
relatively little success.
Lantana is a serious weed in subtropical forests in Australia. This plant
has been a major weed for more than 100 years. Lantana, a native of
Mexico, was taken to Europe and developed as a garden plant before spreading to warmer climates worldwide, where it has become a major weed.
Lantana, as shown in Figure 7.2, is a major weed of subtropical cleared areas
(photographed in Australia) and (inset) has a wild relative growing in
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Figure 7.2 Comparison of a weed in a new environment and in its native habitat
Mexico. Plants that are not dominant in the landscape of their native habitat often become major weeds in a new environment, away from factors
controlling the population in the location in which they evolved.
Why conserve biodiversity?
We need to understand plant diversity and how to measure it, but we also
need improved understanding of why plant biodiversity is important (Henry,
2005b). Plants are an essential component of ecosystems that provide a wide
range of essential services on earth. These ecosystem services are outlined in
Box 7.4.
Plant diversity is a direct contributor to ecosystem productivity. The
greater the diversity of a biological system the greater the total biomass and
positive environmental contribution the ecosystem can deliver. Different
species co-existing together in a diverse plant community occupy different
parts of the environment in space and time, allowing the maximum biomass
to be supported and increasing the stability of the ecosystem. Diverse communities may be more robust and able to adapt to environmental change.
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Box 7.4 Ecosystem services
Ecosystems provide a wide range of services that are of value to humans.
Plants play a central role in many of these services.
Examples of the role of plants in ecosystem services include:
• Clean air: plants fix carbon dioxide and produce oxygen.
• Food: plants provide food directly.
• Waste decomposition and nutrient cycling: plants help create an environment for microorganisms that degrade organic matter.
• Climate: plants directly impact climate by transpiration, contributing to
the water cycle.
• Clean water: aquatic plants provide a habitat for surface organisms that
remove many solutes from water and can purify water for drinking.
Diversity of plants is also an essential resource for plant improvement in
the development of useful plants for agriculture and forestry. Economic
plants need to be continually genetically selected and improved to ensure
they remain productive in domestication, and can be adapted to changing
production environments or end-use requirements.
Biodiversity is very important to humans from an aesthetic perspective. Life is enriched by experiences or a wide range of diverse organisms.
In contrast, a life in which it was only possible to encounter a very small
number of other species would be less stimulating and desirable to many
Option available for conservation of plant diversity
Collections aiming to conserve plant biodiversity ex situ (in a location
other than the wild) include botanic gardens and seed banks. Private gardens are also an important site of ex situ plant conservation. Humans have
long been obsessed with plants as ornamentals. Private plant collections in
gardens remain an important contributor to the conservation of plant biodiversity. Plant collectors have not always made a positive contribution to
the conservation of rare species. Wild populations of rare plants, especially plants considered attractive by humans, such as orchids, have
suffered from over collection of wild populations. Indeed, any very rare
plant is threatened by the attractiveness of rareness itself with the determination of many plant collectors to have rare species in their collections.
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Figure 7.3 Biodiversity in cultivation – traditional village gardens
near Tsukuba, Japan
The locations of rare plant populations are often not revealed in public
databases to avoid the threats to the population that might result from
ready access to details of population locations if they can be located by a
search of the internet.
Domestication has created many new plant types that do not exist in the
wild. The diversity of cultivated plants has become a very important biological resource. Gardens are an important contributor to biodiversity in many
areas. A vegetable garden in a village in Japan is illustrated in Figure 7.3. The
conservation of diversity of domesticated crops by farmers managing the
genetic stocks that they cultivate is a major contributor to conservation of
crop diversity.
Options for the conservation of both wild and cultivated plants ex situ
include the use of living field collections (e.g. botanic gardens), seed banks,
and the storage of pollen and DNA.
These are key technologies as the potential for in situ conservation is
exhausted in specific regions (especially urban areas) due to human activities. The effectiveness of these approaches is critically dependent on
effective collection strategies to ensure the diversity of remnant wild populations as represented in the ex situ populations.
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Botanic gardens
Botanic gardens are key locations for conservation of plant diversity at local
and international level. Living collections in botanic gardens may be linked
to related collections in herbaria and to seed and DNA banks. Botanic gardens are widely distributed globally. Many have multiple roles in providing
public open space (as public parks) and struggle to contribute to their other
missions, including biodiversity conservation and community education.
Many focus on collecting the plants of the region or location in which they
are based. Others have attempted more extensive collections of plant diversity. Frequently these two objectives are combined. Increased levels of
collaboration between public and private gardens using improving internet
facilities may continue to enhance their potential to support plant biodiversity conservation on a global scale.
Box 7.5 Lismore Rainforest Botanic Gardens
This is an example of plant biodiversity conservation in a botanic garden
being established on a degraded site. I have served as a member of the
Lismore Rainforest Botanic Gardens Committee. This garden is being
established by the city of Lismore to represent the subtropical rainforests
of eastern Australia that were the original flora of the local area. The original rainforest, known locally as the ‘Big Scrub’, is now represented by very
small patches of remanent vegetation. The original forest was probably the
largest area of relatively continuous lowland subtropical rainforest. The
forest was cleared for timber (especially the local red cedar, Toona ciliata,
a member of the mahogany group (Meliaceae)) and then agriculture
(mostly dairying) more than 100 years ago. This is a long-term project
involving extensive community participation. The Australian Plants Society,
essentially an organization of private gardeners, formed to promote the
cultivation of Australian plants, has supported the project. The gardens are
being established on a degraded site that has been used for the disposal
of city waste as landfill. This provides an opportunity to demonstrate the
potential for ecological restoration of degraded areas. Community education and engagement in the process are key objectives. The outcome will
represent the plant biodiversity of the subtropical rainforests, delivering a
direct conservation outcome and providing for ongoing educational
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Seed banks
Seed banks mainly focus on plants of economic species, but have the potential to be expanded to also conserve wild species more generally. Many
collections extend to wild relatives of economic species (see Table 2.5), but
not to other species without current economic value. Seed banks are often
backed up by sharing of seed batches with other seed banks, often in another
country. The Global Seed Vault in Svalvard, Norway is a permanent backup system for seed banks. The location ensures that the seeds are maintained
at low temperatures with the requirements of energy (electricity) at most
other locations. This facility is supported by the Global Crop Diversity
Trust. An international treaty on Plant Genetic Resources for Food and
Agriculture has been established in harmony with the Convention of
Biodiversity. This treaty provides for multilateral agreements that guarantee
benefit sharing and the international exchange of essential plant genetic
resources for the most important food crops. This process of extensive sharing has been driven by the importance of these collections, especially for
species for which the conservation of wild or cultivated populations cannot
be assured. This makes it difficult to assess the numbers of distinct seed lots
(genetically distinct accessions or collections) in international collections.
Large numbers are replicates of those held in other collections so that the
total number of accessions in all seed banks internationally may seriously
overestimate the extent to which the wild or cultivated diversity of the
species has been sampled.
Seed banks generally rely on using low temperature and low moisture
content to preserve seeds for long periods. They are usually not an option
for seeds that do not survive desiccation (drying). This is a characteristic of
many plants from wet environments such as rainforests. Living collections
of the plant in a botanic garden or a dedicated field plot are the important
options for these species.
Pollen storage
Pollen storage techniques have mainly been perfected for species that are
the subject of active plant-breeding programmes. More widespread conservation of pollen would be an important aid to plant biodiversity
DNA banks
Management of in situ populations is refined by ongoing genetic research
that is now mainly at the molecular (DNA) level. Understanding the impact
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of habitat fragmentation on the long-term evolutionary potential of species
is essential to developing strategies for managing the islands of biodiversity
that are often created by human activities such as urban, industrial or agricultural developments.
Advances in genomics science are making much more data available to
researchers. These advances have been driven largely by medically focused
research, but promise to provide much more powerful tools for monitoring
and analysis of genetic diversity. The availability of DNA collections representing the diversity of plant populations will be a key factor limiting rapid
applications of this technology in plant conservation. Plant DNA banks are
only at the very early stage of development in most locations and require significant further investment to be able to fulfil their potential role in
biodiversity conservation. For example, the Australian Plant DNA bank aims
to hold DNA from every Australian plant species and to represent as far as
possible the diversity within each species. It is a very long-term goal to collect DNA from all 20,000 or more Australian species. For very rare species
it is possible to collect DNA from every known individual of the species,
while with species with large populations sampling to represent the diversity
becomes more challenging. A structured collection including all known distinct populations of the species, or covering the known geographic range of
distribution of the species, is often attempted. Plant DNA banks are a relatively new concept complementing the seed and germplasm banks that have
been established for much longer. An international network of plant DNA
banks with these objectives is starting to emerge. with recent initiatives in
Brazil and South Africa (see Box 2.5).
Novel techniques such as tissue culture of cryopreservation may be
required for the ex situ conservation of some plant materials.
Tissue culture
The growth of plants or plant parts in tissue culture is a technique that has
been developed for the commercial propagation of plants that are difficult to
reproduce from seed or by conventional vegetative methods (e.g. cuttings).
The conservation of specific rare genotypes or species may be greatly
assisted by mass propagation using tissue culture methods. These techniques
have been widely applied to high-value plants (e.g. ornamentals such as
orchids), but have had only limited application to conserving biodiversity in
other species, largely because of the cost. A major cost is the effort required
to develop an appropriate culture method tailored to the specific nutritional
requirements of each species or even genotype. Low-cost generic protocols
that could be applied to many species would be widely adopted and remain
a desirable research objective.
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The long-term storage of plants or plant parts by freezing may allow conservation of rare genotypes until new technologies for propagation are
developed, or more suitable environments are found for their establishment
in the wild. This technique has had limited application to date, mainly for
highly endangered material. The key limitation is that techniques for freezing and recovery of viable material have not been developed for many
In situ conservation
The availability of improved methods for the conservation of plants in environments created by humans (ex situ) should not be used as an excuse for
reduced efforts to conserve plants in their native environments (in situ).
The creation of nature reserves and their protection has been a primary
approach. These programmes need to be intensified in many areas. National
parks face increasing pressures from growing human use and climate
The conservation of plants on private lands and in disturbed areas is also
a very important strategy. Developing cooperation between landowners in a
local area is an important element of achieving conservation outcomes as
plants are not constrained within land boundaries imposed by humans. The
Australian Landcare movement has proven to be a very useful forum for discussion of conservation issues between neighbours. This scheme encourages
landholders in each area to join together, often on a catchment basis, to form
Landcare groups to mange their local environment. These groups have
become an important social network in many rural areas, possibly explaining their high participation rates and success. Landcare groups work on both
public and private land, and support the protection of endangered species
and coordinates forest regeneration efforts, especially the removal of weeds
as a community activity.
How do we measure progress in conservation
of biodiversity?
Unfortunately we currently have a lack of objective methods to measure our
success in conservation of biodiversity. This has been highlighted in a recent
study of progress in conserving areas of the state of Queensland
(McDonald-Madden et al, 2008). Land clearing and reservation of land to
conserve biodiversity are opposing activities and quantitative analysis of
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these competing factors is required to identify if progress is being made in
conservation efforts. We currently do not have enough data and careful
analysis to allow reliable assessment of biodiversity status and trends in most
parts of the world.
The emergence of the threat of climate change is a major factor with
potential to adversely impact upon biodiversity. This is the topic of the next
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Impact of Climate Change
on Biodiversity
Understanding the ecological importance of biodiversity for ecosystems
functioning and ecological services to mankind requires us to relate the
diversity of ecosystem properties to the diversity of species performances
in space, in time, in biotic interaction and under changing environmental conditions.
Beierkuhnlein and Jentsch, 2005
Climate change and the rate of loss of plant species
The implications of climate change for biodiversity conservation (Lovejoy,
2006) are central to management strategies used in conservation of plant
diversity. The importance of plant biodiversity to ecosystem functioning and
as a resource for human food, feed, fibre and energy has been well illustrated
in preceding chapters. The general acceptance of climate change as a major
issue facing human societies was outlined in Chapter 3. Climate change is
likely to accelerate the rate of species extinction in the immediate future
(next few decades). Rapid climate change has resulted in loss of species
diversity in the past. Many species are not able to adapt rapidly enough to
environmental changes and will be lost. Estimates of the likely rate of species
loss in the immediate future due to climate change vary widely. However, it
is likely that the current high rates of species loss due to human removal of
habitat are likely to increase with climate change. Very high levels of extinction of plants and animals are predicted by many models (Thomas et al,
2004). Food security long term may be threatened by loss of populations of
wild relatives of crop species due to climate change. This will reduce options
to continue to adapt crops to new climatic conditions.
Climate change and the rate of loss of
plant diversity within species
The loss of plant species may be relatively easy to monitor. However,
changes in climate will also result in some genotypes within the population
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being favoured. This loss of genetic diversity within species may not be easily detected even when serious loss of diversity has occurred.
Recent studies have examined the genetics of wild barley populations in
relation to differences in climate (Box 8.1; Cronin et al, 2007). This area
requires much more research. Advances to technologies for plant DNA
analysis promise to make this type of research more cost effective in the
future. This will hopefully allow more detailed analysis of diversity within
species, provide the tools required to monitor the impact of climate on diversity and the opportunity for more active management and conservation of
Box 8.1 Impact of climate on wild barley populations
Wild barley remains extensive today and represents the populations from
which our first crop plant was probably domesticated. Analysis of the DNA
from wild populations has been used to examine the links between gene
diversity and climate in different populations. This system was introduced
in Box 3.2 in relation to identification of genetic options for adapting food
crops to climate change. Wild barley extends over sites that vary in a wide
range of climatic variables – from rainfall and humidity to temperature
extremes and averages. The soil type may also be important in determining the amount of water retained in the soil and the resulting level of water
stress faced by the barley plants. The diversity in a gene associated with
expression of a protein in the seeds of the plant that apparently provides
defence against fungal pathogens (probably in the soil) varied with the environment in which the barley populations were found. Populations from dry
environments had greater diversity in this gene than populations from wetter environments. These observations can be explained by the presence of
more diversity in the populations of fungi in the soils of dry environments.
The wetter environments may favour fungal growth but the fungi present
are less diverse. More recent research has confirmed this finding for other
genes and identified different patterns of expression for genes with different functions in the plant.
Conserving plant species in situ
The preferred first option for the conservation of plant biodiversity is to
protect them in situ (where they are in nature). This will continue to be
the first option explored. As this becomes more difficult, a move to more
efforts in ex situ (in an artificial location – e.g. botanic garden, seed bank,
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Impact of Climate Change on Biodiversity
greenhouse) conservation will become essential. A future in which we can
only experience plants in a garden or an artificial environment is one in
which we concede defeat in the fight to protect wilderness areas (with all
their associated human emotional and aesthetic values), but realistically may
become the only option in many cases. Because it is the best way to conserve
entire ecosystems with all their diversity, in situ conservation must remain a
high priority. As already emphasized, we should not allow the development
of ex situ conservation technologies (e.g. cryopreservation or tissue culture),
no matter how effective they are, to become an excuse for reduced efforts at
in situ conservation.
A mixture of protected areas and strategies to conserve diversity outside these areas is required to conserve biodiversity for different types of
species. The designation of protected areas is a key strategy for conserving
plant biodiversity in situ. Many rare plant species are only found in very
small areas with unique habitats. Protection of these areas is probably the
only realistic option for conservation of these species, but significant climate change could lead to extinction of these species. Outside protected
area policies are required to encourage the management of landscapes to
allow a mosaic of nature conservation and agriculture. Areas of land
reserved for nature conservation within agricultural landscapes can
improve sustainability of agricultural production on the parts used for agriculture. They are also essential refuges for these animals, and corridors for
the movement of animals and even the dispersal of plants. Habitat is
required to support the insects’ need for crop pollination. Trees along field
margins may assist the sustainability of agricultural production by lowering the water table in the adjacent field. This can be critical when subsoils
have factors such as salt that threaten crop performance. These approaches
are key strategies for achieving environments better able to adapt to climate
Box 8.2 Climate change and Banksia conferta
Banksia conferta, the rare Banksia on the peak of Mount Tibrogargon in
Queensland (Figure 8.1), may be threatened by climate change that results
in more frequent fires. In recent years fires have swept across the mountain top in successive seasons. Many species including Banksia confera are
killed by fire, but regenerate readily from seed following a fire. Indeed, fire
is often necessary for long-term continuation of the species. Frequent fires,
however, may pose a significant threat. A fire that kills seedlings in successive years before the plants have reached an age at which they flower and
set seed will deplete the seed reserves in the soil. Widespread species can
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cope with this if the entire population is not burnt. However, on the small
mountain peak a fire can kill the entire population. Survival of the species
depends upon the seeds in the soil being able to grow to maturity and set
more seed before the next fire. The high frequency of fires may be a result
of a greater density of human settlement surrounding the mountain, but
may also be a consequence of climate change.
Figure 8.1 The rare Banksia conferta. This population is growing on the
peak of Mount Tibrogargon, Australia
Relocation of species
Some species may be able to adapt by moving to an environment to which
they are adapted. For example, species distributions may move to higher altitude as the temperature increases. In this way they may be able to exist in
an environment that has similar temperatures to the one they were adapted
to before the temperature rose. This has limitations as species have nowhere
to go when they reach the top of the mountains. Alternatively their distributions may move to higher latitudes to stay within the temperature range in
which they evolved. Unlike animals, individual plants cannot move.
However, movement of populations can take place over generations. Species
with a short generation time (rapid development to reproductive maturity)
and long-distance seed dispersal mechanisms are likely to relocate to
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favourable environments and cope better with rapid climate change than
long-lived (slow to reach reproductive maturity) species with a limited seed
dispersal range. Unfortunately these responses are now constrained in many
areas because of human development or land use. Many species are located
within limited reserves (sometimes created to protect the species) that have
become islands in an ocean of urban or agricultural development. Wildlife
corridors have been created largely to allow animal movements, but could
also be important for plant movement in these situations. Human intervention in the form of deliberate translocation will become increasingly
important to ensure the survival of many such plant species. Creation of new
reserves to cope with this problem will also become necessary. More research
on methods for effective plant translocation is required so that we have available technologies for the rescue of species. Many attempts at translocation
of rare plants, especially large trees, have been unsuccessful. Accelerated
movement with human assistance may create other environmental problems
and probably has a low chance of success (Hoegh-Guldberg et al, 2008).
Conserving plant biodiversity ex situ
The in situ conservation of many species will prove impossible despite our
best efforts and we will need to increase the scale of ex situ conservation
efforts. Technologies for ex situ conservation will need to continue to
improve to provide for the efficient achievement of ex situ conservation.
Rapid climate change may demand an acceleration of the development and
application of ex situ conservation measures. More extensive botanic gardens, seed banks and DNA banks may be required, and they may need to
be allocated significantly more resources to cope with increasing demand to
conserve genetic diversity of many plant populations.
Impact of the use of plants for energy
(fuel) on plant biodiversity
The production of biofuels from plants may be a response to climate
change, and a key approach to reducing the levels of greenhouse gas emission and reducing the risk of climate change to biodiversity. However,
biofuel production may itself become a threat to plant biodiversity. The
use of plants for biofuel production will require land and this may be at the
expense of areas that could be used for biodiversity conservation.
However, if this use makes a significant contribution to reduction in the
rate of greenhouse gas emissions, then it may have a net positive effect on
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biodiversity by limiting the rate of climate change and giving more species
a chance to survive. This should be a key criterion for deciding if use of
plants for biofuels is acceptable. The life-cycle assessment of the biofuel
production system should provide evidence of this net benefit. This issue
will be taken up in Chapter 9.
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Biodiversity Conservation
Moreover, had more environmentally fragile land been brought into
agricultural production, the impact on soil erosion, loss of forests, grasslands, and biodiversity, and extinction of wildlife species would have
been enormous.
Norman Borlaug (2004)
The competition between human needs for land for agriculture to meet our
requirements for food and our desire to live in a biologically diverse environment has been an issue that has often been avoided. We all need to eat
and we (mostly) appreciate the aesthetic value if not always the survival
value of biodiversity. The conflict between these two key human drivers is
not resolved unless we understand the competition between these worthy
objectives at the level of competition for space on a planet that is increasingly crowded by human activities. The emergence of energy as another
competitor in this space might help to focus us more on resolving the central issues of balancing the immediate day-to-day needs of humans and their
aspirations for long-term survival on earth. This chapter will examine the
competing needs of growing demand for agricultural products and the need
for biodiversity conservation. We can and do make active decisions to limit
our agriculture and to conserve areas for biodiversity. Japan provides an
important example of a large population in a developed country that has
retained a very high proportion of the country (more than 70 per cent) as
forest. This has been the result of long-term policies. The consequences for
the environment and biodiversity have been very positive, but Japan imports
much of its food.
Biodiversity implications of food or fuel production
Sufficient agricultural land may be found to produce food and fuel, and balancing these two requirements has been discussed in Chapter 6, but at what
cost to biodiversity conservation and the other essential functions of plants
in the environment? Plants are essential to the global carbon cycle and
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generation of oxygen in the atmosphere. However, these roles can also be
contributed to by crop plants. The essential role of non-crop (non-economic) plants is in biodiversity conservation generally. The replacement of
natural vegetation with crops producing biofuels may result in a large emission of greenhouse gases that is very much greater (17 to 420 times –
Fargione et al, 2008) than the annual reduction in greenhouse gas emissions
that would be contributed by the biofuel crop. Replacement of tropical
forests with biofuel crops is likely to be undesirable from both a climate and
biodiversity perspective (Danielsen et al, 2008). In contrast, the use of waste
or growth of perennial biofuel crops on degraded or abandoned agricultural
lands carries little carbon debt and may provide very significant benefits in
reduced greenhouse gas emissions.
A good example of the issues that need to be addressed is provided by
palm oil production. Palm oil is a source of food oil and also a potential
biodiesel crop. The production of palm oil has become controversial, with
opposition to the expansion of production in countries such as Malaysia,
Indonesia and New Guinea on the basis that areas of high biodiversity value
are being displaced for the planting of oil palm plantations.
A contrasting example may be provided by the opportunity to grow
perennial biofuel crops such as Miscanthus and Willow in environments
such as the UK. These crops are fast growing and because of their perennial nature the energy of greenhouse gas costs of production are low.
Displacement of annual crops with these species would represent a major
change in the rural landscape (Karp et al, 2009). The implications for biodiversity are not well understood but are probably positive.
Objective analysis of the economic, environmental and social implications of food or energy production is required to determine the merits of
different food or energy crops and their likely impact. This is best achieved
by LCA examining the total economic, energy, environmental or social
impact. The net energy balance and net greenhouse gas emission reduction
of biofuel production systems can be used to compare alternative options
(Hill et al, 2006).
Policies to promote desirable outcomes
Public policies include carbon trading, tax and mandating biofuel or renewable energy targets, and can be a key driver of change. Developing policies
that are sound from an economic, environmental and social perspective is
challenging. The wrong policies could easily deliver undesirable outcomes.
Mandating a level of biofuel inclusion in transport fuels will probably result
in production of the target, but we may not be pleased if this is achieved at
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an undesirable social or environmental cost. In developing policies, we can
evaluate technologies as they exist today. However, there are great efforts
under way to invent a new future. The rate of technology advance and more
critically the directions that might take us in terms of the best options to
pursue is almost impossible to predict. This suggests that our approach
should be subject to constant review and updated rapidly to respond to
Policies need to ensure sustainable biofuel conversion technologies. For
example, the amount of water needs to be kept to a minimum by using water
recycling approaches. However, biofuel production may already be much
more water-efficient than gasoline production from oil. The greenhouse gas
balance is favourable even for first-generation biofuels when compared to
fossil fuels and will be dramatically improved by the development of secondgeneration biofuels (Hill et al, 2006).
Policies need to be set so as to encourage environmentally positive outcomes in any changes in agricultural production for food or energy. Factors
that need to be considered as policy targets include:
greenhouse gas balance;
energy costs;
nutrient run-off;
hydrological impact;
biodiversity impact (both within the crop and adjacent);
productivity (high yields reduce the land footprint of agriculture).
The role of food and energy prices
High food prices may encourage the clearing of more land to produce food
at the expense of biodiversity. Food prices have been historically low until
recently. Oil prices are likely to rise as supplies are exhausted. As technology
improves the cost of biofuels has been reduced. The cost of biofuels relative
to fossil fuel-derived fuels should continue to decline. Transport fuel costs
are likely to remain a significant component of food prices; indeed, some
recent rises in food prices are probably largely due to increases in oil prices.
Competition for land and water could put upward pressure on both food and
biofuel costs. This has become a focus of public concern. However, the alternative to continuing to use fossil fuels will probably be much more expensive
both for energy and for food (also with embedded energy costs). Many will
argue that this makes the case for pursuing other alternative energy options,
but these may not be technically feasible on the timescale needed to avoid
unacceptable global climate change. The total of energy and food costs
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together needs to be minimized to be politically acceptable. Food and energy
costs may need to rise relative to the prevailing levels of recent decades, but
this may be a necessary part of our adapting to the threats we now face.
Higher food and energy costs could have desirable impacts in affluent developed countries by providing an incentive to reduce consumption. The
problem is really one in developing countries, where it will be important to
protect the poor from shortages of affordable food that could result.
Addressing this issue globally is an important step in adapting to the future.
Crops as weeds (especially new biofuel crops)
impacting adversely on biodiversity
Weeds usually impact negatively on biodiversity. A weed by definition is a
plant that is not wanted in the place that it is found. A more important issue
is that it is has not evolved as part of the ecosystem in which it is now established. The usual consequence of a weed is the displacement of other species
native to the area, sometimes to the point of threatening endemic species
with extinction, but often at least contributing to a reduction in biodiversity
by displacing a diverse local biota with one dominated by large populations
of the weed species. One of the risks that needs to be managed is the potential for new energy crops to become major weeds. The desirable
characteristics of an energy crop, that allow rapid growth on marginal lands,
are those associated with species that have potential to become weeds.
Harvesting of weeds for biofuel production has been suggested as an economic way to control some woody weeds. The Camphor Laurel tree
(Cinnamomum camphor) from China has become a major weed in the high
rainfall areas on the coast in central eastern Australia. These areas were
mainly subtropical rainforest with a very high biodiversity that were cleared
for crops and then pastures, and have been colonized by the Camphor
Laurel trees to the exclusion of almost all other plant species in some areas.
Economic use of this species may support its harvesting, especially in areas
where it has become the main tree species, and this may allow regrowth of
a wide range of species contributing to enhanced biodiversity.
Extent of competition (for land water
and other resources)
The competition for land depends upon population growth and the resulting demands for food and fuel. The estimates of population growth and food
supply and demand discussed in Chapter 6 have been used to calculate some
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Table 9.1 Land requirements to satisfy food and fuel requirements by 2085 – relative to 2005
Diversion of land to biofuels
(10.5 billion)
None (0%)
Intermediate (30%)
High (50%)
None (0%)
Intermediate (30%)
High (50%)
(14.7 billion)
Extra land required
scenarios for the land use requirements for food and fuel production to 2085
(Table 9.1).
The high population option seems highly undesirable, especially if we
require a high portion of the land for biofuel production. In the lower population scenario, demand for land only becomes a significant issue if we have
a high proportion devoted to biofuels. Expansion of agricultural activity by
50 per cent is an outcome of high biofuel production at low population
growth and intermediate production at a higher population level. This is
probably the type of outcome we should consider in terms of likely impact
on biodiversity. However, we probably cannot afford to use 50 per cent
more land for agriculture globally. Some re-prioritization within the land
already used or assigned for agriculture will be necessary.
The expansion of sugarcane production in Brazil, as discussed in
Chapter 6, is a good example of the issue. Many people in the world are
aware of the rainforests of the Amazon and expect these forests to be a major
area of conflict between agricultural (food and feed) production and conservation. However, in this example, other parts of Brazil may present
examples of greater competition for land use. The rainforest is difficult to
clear and in some ways less threatened than other communities. The Atlantic
forests in Brazil are much more critically endangered because of population
pressures along the coast. The Cerrado is a large area of savannah (more
than 2 million km2) with more than 10,000 plant species, more than 40 per
cent of which are endemic. This is the area that is more likely to be used for
expanded sugarcane production to satisfy energy demand. The desired
approach in this area is to utilize land that has already been cleared for agriculture – mainly degraded pastures.
The latest analysis (2006 state of the environment report) of land use in
the state of New South Wales (Australia) indicated that 70 per cent of land
is used for grazing, less than 8 per cent is in protected areas, and a similar
amount, around 8 per cent, is used to grow crops. Forestry occupies less
than 4 per cent and urban and mining areas make up only 0.3 per cent of
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Table 9.2 Estimates of yields, conversion efficiencies and areas of land required to replace oil
with biofuel in a country consuming around 100GL/year fuel consumption
Proportion of biomass converted to biofuel
Land area
the state. This indicates the main area for reallocation to energy crops would
be from the very large area devoted to grazing. Similar conclusions may be
reached in many other regions.
Critical questions become just how much pasture can we convert to crop
production? What types of vegetation (and associated biodiversity) are currently found on the land that would need to be used for crops? This needs
to be assessed on a regional basis. The impact and the issues in Europe may
be very different to that in Africa or South America. Some changes in land
use could be positive for biodiversity if crops that provide a suitable habitat
for wildlife are planted in degraded environments. Integration of food and
energy production on farms could be based upon a greater diversity of crops
and a much greater standing biomass, especially if trees are included in the
plants farmed. The next chapter will explore our option for domesticating
new plants for these applications. The choice of species for biofuel production and the land footprint required depends upon the biomass yield per
hectare and the proportion of the biomass that can be converted to fuel. The
land requirements for replacement of oil use with biofuels in a country
around the size of Canada are outlined in Table 9.2.
This analysis indicates that combinations of large areas of low yielding
crops (or crop residues) and smaller areas of high yielding crops (dedicated
energy crops – e.g. trees or energy grasses) could be used. The cost of harvesting and transport will make the more intensive options with the smallest
land footprint more attractive. However, these options will probably require
the use of better land with more chance of competition with food production. While this needs to be avoided as much as possible, the small footprint
and the potential environmental benefits of replacing fossil fuel use may
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Table 9.3 Water use for electricity and biofuel production from different crops
Sugar beet
Water footprint
* Weighted average water footprint – volume of water required per unit of energy produced – data
from Gerbens-Leenes et al, 2008
justify this choice. Giving up a small area of land to reduce the risks of climate change may be a net benefit to food production.
The competition for land is not the only basis for competition. Plant
growth requires other inputs including water and a wide range of nutrients
from the soil. Water is probably the most critical of these, especially in the
context of potential reductions in rainfall in many regions due to global climate change.
Analysis of the water-use efficiency of food and energy crops can be
used to compare cropping options. Recent analysis of biofuel crops
(Gerbens-Leenes et al, 2008) has emphasized the wide differences in water
requirements of different production systems (Table 9.3). The production
of electricity is more efficient for these crops because it is based upon using
the entire biomass. Biofuel production efficiencies in Table 9.3 are based
upon first-generation production of ethanol from sugars and starch or diesel
from seed oils. The poor water-use efficiency of these processes, especially
the production of biodiesel, is emphasized by these estimates. Biodiesel production from Jatropha required almost ten times as much water per unit of
energy produced as bio-ethanol production from sugar beet. This analysis
demonstrates the importance of development of second-generation biofuel
crops that allow all of the biomass to be converted to fuel energy.
The relative importance of land and water use needs to be accessed on
a local or regional basis. For example, in a desert water use is critical, but
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land may be readily available and in a very high rainfall area water may not
be limiting, but conservation of land for diverse rainforest communities
might be very important. The growth of crops that are adapted to the local
environment is probably the key desirable objective to ensure optimal use of
land and water resources and to minimize competition with biodiversity.
Analysis of the land available for biofuel production in the UK has identified 3.1 mha of suitable land (Haughton et al, 2009). This area was
predicted to be environmentally acceptable. Planting of crops such as
Miscanthus and willow was likely to increase biodiversity in many areas relative to that associated with current food crop production.
Direct impact of the type of vegetation cover
(native vegetation or agriculture) on climate
The impact of agriculture on the albedo of the landscape may be an import
issue if land use patterns are altered over large areas of land. The albedo
is the diffuse reflectivity determining the percentage of incident solar radiation that is reflected from the land surface. A bright surface such as snow
reflects back much of the light, while a dark surface such as a forest or a
crop may not. Land use changes that influence albedo can contribute to
warming. Recently the development of crops that have a higher albedo
has been proposed as a strategy to combat climate change (Stephenson,
2009). For example, corn with a high level of surface waxes could be bred
to reflect more light and lower temperatures. The management of land
use to ensure the vegetation cover does not adversely impact in this way
needs to be balanced against the impact of the changes on greenhouse gas
The importance of new technology
Better tools for assessment of land use and biodiversity monitoring are
needed to allow better management. We cannot manage what we cannot or
do not measure.
Technology development is an essential requirement for coping with
demands for food and energy while conserving biodiversity. The competition between agriculture for food and energy and biodiversity will be greatly
reduced if second-generation biofuel crops are produced. More efficient
agriculture (higher production per unit area) is a key requirement to minimize the pressure for more land for agriculture. This will require the
continued advancement of all areas of agricultural and plant science.
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Competition between Agriculture and Biodiversity Conservation
Need for continued reservation of land for
nature conservation
Conservation of areas of high biodiversity remains critical. Rainforests of
eastern Australia are illustrated in Figure 9.1. The identification and protection of such areas will be an ongoing requirement, especially in the face of
competition from agriculture for land use. The most difficult areas to ensure
continuing protection are those remaining areas with unique biodiversity in
areas of high agricultural value.
Reserving specific areas for nature conservation and others for agriculture is an important mechanism for resolving the balance between these two
requirements, but some level of integrated agriculture and conservation in
Left panel: Subtropical rainforest (Nightcap Ranges, northern New South Wales). Right panel: Tropical
rainforest (near Kuranda, North Queensland). Both of these rainforests are protected as world heritage areas. These two well-separated areas (more than 1000km apart) contain related but distinct
species in some groups. For example, Hicksbeachia pinnatifolia (Figure 10.4) is found in the southern
sub-tropical rainforests, while the related Hicksbechia pilosa is found in the northern tropical rainforests.
Similarly, Davidsonia jerseyana is found in the subtropical regions and Davidsonia pruriens (Figure 10.5) in
the tropical areas. In both cases the differences are slight but significant enough to regard the plants
from these geographically well-separated forests as distinct species. Competition from agriculture
reduced the area of these forests more than 100 years ago. The remaining areas require ongoing conservation to ensure this biodiversity is not lost.
Figure 9.1 Rainforests
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the same landscape is required. Some of the advantages to agriculture of biodiversity in the landscape have already been discussed in the last chapter.
More innovative approaches to management of agricultural areas may be
required to promote biodiversity within the production environment
(Perfecto et al, 2009).
Recent analysis (Metzger and Hüttermann, 2008) suggests that sufficient
biomass to support human transport and other energy requirements could
be produced sustainably by the growth of trees on land that has been
degraded by human activity. This should be the priority to avoid competition with food production. Biodiversity conservation in these areas will be a
key constraint to manage. Degraded areas may have significant biodiversity
values if they support patches of remnant vegetation.
We currently use around 40 per cent of the land surface of the Earth for
the production of crops and pastures (Stokstad, 2009). Increasing efficiency
of agriculture (more food per unit of area) is an essential requirement if
we are to avoid expansion into areas that would compete with nature conservation and contribute to a significant loss of biodiversity. The efficiency
of agriculture has been improving rapidly in recent years, but we need to
continue this trend and do so sustainably if we are to meet the challenges of
future growth in food and energy demand.
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Domestication of New Species
But whether or not the selection of wild edible plants by ancient hikers
relied upon conscious or unconscious criteria, the resulting evolution of
wild plants into crops was at first an unconscious process. It followed
inevitably from our selecting among wild plant individuals, and from
competition among plant individuals in gardens favouring individuals
different from those favoured in the wild.
Jared Diamond (1997), Guns, Germs and Steel, p130
Domestication of new species has the potential to deliver outcomes that
meet the challenges of efficient food feed and energy supply in response to
growing human demands. However, the feasibility of domesticating new
species has been challenged and needs to be evaluated. The key issue is
whether science can define needs and opportunities that have been overlooked by the processes that have driven human domestication to date.
Most plants have been domesticated for food use and domestication was
introduced in Chapter 2. The emergence of new plant uses such as the provision of energy suggests the need to domesticate new species for these
purposes. The modification of plants to improve their suitability as energy
crops will require the selection of genotypes with novel traits that are not
necessarily optimal for survival of the plant in the wild. For example, an
improvement in accessibility to enzyme digestion of carbohydrates in plant
cell walls would facilitate conversion to sugars and use in fuel production.
This would potentially include steps to reduce the crystalline nature of the
cellulose and to reduce lignin content. Fears that this would lead to plants
that would be susceptible to pests and diseases have been expressed. While
these unintended consequences need to be considered and managed carefully, comparison with the domestication of food species suggests that these
concerns may not be impossible hurdles. Food plants have many characteristics that have been selected to suit humans and that would be
deleterious to the survival of the plant in a wild population. Plants grown
under domestication have human intervention to propagate them and to
remove competitors, provide nutrients and water, and protect against pests
and diseases.
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History of domestication and implications
for further domestication
The history of domestication of plant species to date should guide our
approaches to the domestication of new species for new applications. The
bottle gourd (Lagenaria siceraria) was domesticated very early as a storage
vessel in tropical Africa and was taken by humans to America. This plant
has a range of uses that suited the mobile hunter/gatherer.
Domestication of the major agricultural species has centred on a relatively small number of locations around the world where a critical number
of species, with characteristics that suit them to domestication, are found in
the same location. The best defined of these regions is the Fertile Crescent
at the eastern end of the Mediterranean (Figure 10.1).
Barley was probably the first major food crop domesticated around
12,000 years ago, with wheat, peas, chickpeas and domesticated animals also
originating in this area, all around 10,000 years ago. Evidence of early human
cultivation of cereals is abundant (Figure 10.2). Botanical archaeologists like
Dorian Fuller, University College London, are working to understand the
relationships between plants and early human societies, before, during and
after domestication (Fuller et al, 2007). Analysis of the genetics of early crops
can reveal knowledge of great value in attempts to continue the domestication process or to accelerate it to meet new or growing human needs. The
wild populations and landraces (traditionally cultivated cultivars) have many
characteristics that are important resources for ongoing genetic improvement
of modern cultivated crops. Domestication of genes from wild populations
continues. Berhane Lakew, a barley breeder from Ethiopia, has recently
defined genetic sources of drought tolerance in wild barley that have potential use in developing drought-tolerant crop cultivars. Abderrazek Jilal, a
barley breeder from Morocco, has also recently characterized the genetics and
human food qualities of wild populations and landraces as a basis for producing more food directly from barley crops. These important research
projects have been conducted in collaboration with the International Center
for Agricultural Research in the Dry Areas (ICARDA) in Allepo.
This is not a highly productive agricultural environment and many of the
more productive environments in the world do not seem to have produced
any domesticated plant or animal species. Diamond (2005a) offers many
possible reasons for the success of domestication in the Fertile Crescent:
Grasses with large seeds were abundant in this region (including the progenitors of wheat and barley) because the climate suited a species that
devoted a lot of energy to the production of large seeds that could survive the hot dry summer and grow during the wetter and cooler months.
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Domestication of New Species 127
Figure 10.1 Fertile Crescent – site of early domestication
Pulses (grain legumes), including pea, lentil and chickpea, were also
domesticated in this region. The combination of cereal and pulse provides both the carbohydrate and the protein for a balanced human diet.
Large mammals were also abundant in this region. The sheep, goat, pig
and cow were all domesticated in this region. They also lacked the
predatoriness of mammals in similar open grasslands of Africa, resulting in behavioural characteristics that made them better suited to
human interaction.
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Photographs provided by Dr James Helm (Field Crop Development Centre, Lacombe, Canada)
Figure 10.2 Ancient grain. Samples of barley (inset) collected in the 1950s by Dr
Robert Metzger in Turkey (fortress dating from around 2800 years ago)
Box 10.1 Did plants and animals domesticate humans?
The traditional human-centric way of considering domestication is to think
of humans domesticating plants. However, in an evolutionary or biological
sense it is also worth considering these developments from the perspectives of the plants and animals. Did barley plants evolve to become so
attractive to humans – the primate, Homo sapiens – that the humans
assisted the reproduction of the plant by collecting the seed and planting
it in the soil and even killing competing plants? In turn some of the plant
population was eaten by the humans. The evolution of the plant into a
domesticated form involved selection (by humans) for genes controlling
domestication traits that provided these barley plants with a key adaptive
advantage (under the conditions of human cultivation) over individuals in
the population without these traits.
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Domestication of New Species 129
This region is at the centre of the largest land mass on earth with great
potential for plants to be transferred east and west, allowing the spread
of agriculture. Plants generally do not perform well if they are moved
north or south because of sensitivity of growth and flowering to a day’s
Domestication may have been preceded by a period of pre-domestication
in which humans combined wild harvest and some limited cultivation. Early
harvest from cultivated grain may not have immediately met all food needs,
resulting in supplementation of this with grain harvested from wild stands.
This would be especially true in years of crop failure. The archaeological
records suggest that wheat and barley underwent a prolonged period of predomestication in which the grain size was increased by human selection,
before shattering was selected against, to give truly domesticated cereals
(Fuller, 2007). This contrast with rice in which loss of shattering is
observed at a similar time to or before an increase in grain size. The time
to domesticate has been estimated by experiments in which stands of grain
have been harvested to simulate wild harvest and the impact on domestication traits analysed. These experiments suggest short domestication periods
of the order of 100 years. The domestication of cereals may have taken
more like 1000 years. One explanation for this is the combination of wild
harvest with cultivation. If the seed from cultivated material and wild harvesting are combined the impact of genetic selection under cultivated
conditions is diluted, slowing down the genetic change in the population
and slowing domestication.
Box 10.2 Parallel domestication of plants and animals
The domestication of plants and animals may have proceeded together as
humans became less mobile and adopted a more sedentary lifestyle.
Despite their apparent great diversity, all domesticated dogs were apparently domesticated from the grey wolf in what was probably a single event
in the Fertile Crescent somewhere in the period 15,000 to 40,000 years
ago. Dogs may have coexisted with humans, travelling the same migratory
pathways following migratory food animals. This would have provided an
opportunity for long contact between dogs and humans to allow the
process of behavioural change necessary to transform a wild wolf into a
domesticated dog. Cats in contrast may have essentially domesticated
themselves. As humans built grain stores that attracted rodents, cats could
move in to feed on the new food source.
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The selection for seed size and shattering resistance in the cereals was
probably not a conscious process. However, the selection for size in fruit
probably was a very conscious process, explaining the very rapid increases
in fruit size that evidence from domestication suggests.
Some examples of domestication are listed in Table 10.1.
Table 10.1 Domestication of crop plants
Crop Cultivated
Hordeum vulgare
Zea mays
Oryza sativa
Oryza glaberrima
Triticum aestivum
Sorghum bicolor
Saccharum sp
Manihot esculenta
Lima bean
Solanum tuberosum
Olea europaea
Helianthus annuus
Cucurbita pepo
Vitis vinifera
Arachis hypogaea
Common bean
Phaseolus vulgarus
Progenitor species
(or modern relative
of progenitor)
Domestication site
Hordeum spontaneum
Zea mays ssp. parviglumis
Oryza rufipogon
Oryza barthii
Triticum monococum
Triticum. speltoides
Triticum tauschii
Fertile Crescent
Fertile Crescent
Saccharum officinarum
Saccharum spontaneum
Musa acuminata
Musa balbisiana
M. esculenta ssp
Solanum species
Phaseolus lunatus
New Guinea, South
East Asia
SE Asia
Near East
North America
North America
South America
South America
West Africa
Linum angustifolium
Near East
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Domestication of New Species 131
Box 10.3 The domestication of rice
Rice domestication involved the separate domestication of two species:
Oryza rufipogon to produce domesticated Orzya sativa in Asia; and Oryza
barthii to produce Oryza glaberrima in Africa. The history of domestication
of rice is complex (Sweeny and McCouch, 2007).
Asian rices have long been separated into Japonica and Indica types by
plant breeders and taxonomists, with Javonica being defined as a third
group. Molecular phylogenetic analysis provides further insights into these
major groups of rices. The following five groups can be defined:
Tropical Japonica (Jarvonica)
Temperate Japonica (Japonica)
The Indica and Aus groups are distinct from the other three which also
form a related group. The Indica group is more diverse than the Japonica
group. It is notable that the Basmati rices are related to the Japonica
rices, not the Indica rices, despite the Indica and Basmati rices sharing
long grain length. Exploring the origins of rice by analysis of wild populations in Asia is complicated by the likely extent of gene flow from
cultivated rice into wild populations. Gene transfer between divergent
rice germplasm is also suggested by genetic evidence (Kovach et al, 2007).
The case for single or multiple domestications of Asia rice has been
debated in the scientific literature. Recently, Duncan Vaughan and colleagues from the National Institute of Agrobiological Sciences in Japan
have suggested that a single domestication explains available evidence
(Vaughan et al, 2008).
Research on the pericarp colour trait (red in wild rice, white in cultivated rices) indicates that this probably arose in Japonica rice and was
transferred by out-crossing into Indica populations. Similarly, the long
grain trait may have arisen in Japonica types and transferred to Indica
Recent developments that illustrate the potential for domestication of
new rice types are the combination of the Asian (Oryza sativa) and
African rices (Oryza glaberrima) to produce new options. Sourcing of
genes from other non-domesticated Oryza species (see Chapter 2) is
also in progress.
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What happens to genetic diversity during
Domestication usually involves selection of genotypes that suit the intended
human use. This will normally result in the domesticated plant population
having only part of the variation that is to be found in wild populations.
Subsequent selection following initial domestication only continues this
trend to a narrower genetic variation (Figure 10.3). The domestication of
sunflower illustrates this process. The sunflower (Helianthus annuus) was
domesticated in the east central areas of North America. Molecular evidence
suggests a single domestication, with a chloroplast genotype representing
only 5 per cent of the wild populations in the region being the only one
found in the domesticated population. Domestication and genetic selection
following domestication each account for about half of the loss of diversity
between wild sunflowers and modern cultivated sunflowers (Burke, 2008).
Figure 10.3 Loss of genetic diversity in domestication
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Domestication of New Species 133
In many cases the wild and domesticated species have not been completely isolated, and genes have continued to flow between wild and
domesticated plants over a long period. The continuing interaction between
wild and cultivated barley gene pools in the Fertile Crescent has already been
mentioned in Chapter 2. The Azuki bean provides an excellent example of
this process. Duncan Vaughan, from the National Institute of Agrobiological
Sciences in Japan, conducts regular field trips to a site where a cultivated
Adzuki bean (Vigna angularis, the source of red bean paste) is growing near
populations of the wild plants. The cultivated beans are very distinct from
the much smaller wild beans. On the edges of the cultivation, plants with
seeds intermediate between the wild and cultivated forms can be found.
DNA analysis has been used to confirm the evidence for gene flow between
domesticated and wild plants at these sites.
In other cases the domesticated plants have become immediately reproductively isolated from their wild progenitors. Human removal of the plants
to a new environment with no wild populations is a common mechanism for
genetic isolation of domesticated plants. Plant domestication has also probably often involved human cultivation of genetic variants that suit human
uses well, but may have lost reproductive capacity. The cultivation of polyploids (plants with multiple copies of their chromosomes) that in some cases
have isolated themselves genetically from their diploid progenitors may be a
recurring process.
Can we regain diversity from wild relatives?
Wild crop relatives have been widely used as a source of genes for improvement of crop plants. This is an especially important strategy for plant
breeders when wild and domesticated populations have been genetically isolated by domestication events.
Knowledge of the relationships within plant groups provided by DNA
analysis can be a very useful guide in the identification of sources of accessible
wild genes for use in plant improvement. For example, the grape genus, Vitis,
is restricted to temperate climates, but other members of the Vitaceae family
are widespread in the tropics. DNA analysis has identified species currently
classified within the Cissus genus that appear to be much more closely related
to Vitis (Rossetto et al, 2002). Plants from these more tropical environments
contain genes that could be useful in adapting grapes to more tropical climates.
Can we re-domesticate species for new uses?
Lima beans are an example of a single species that has apparently been independently domesticated to produce two different domesticated crops. This
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example supports the view that we can consider the option of domesticating
species that have already been domesticated for food or other uses for new
applications, selecting for different attributes and generating a crop with very
different attributes. Lima beans have apparently been domesticated twice
from Phaseolus lunatus (Motta, 2008). This is one of five Phaseolus species
that have been domesticated. The lima beans, known as ‘Big Lima’, are of
Andean origin, and were domesticated from wild populations on the western side of the Andes (Ecuador and northern Peru) and have seeds 10–14g.
The small seeded (6–10g) ‘Sieva’ and ‘Potato’ lima beans were domesticated
from wild populations in Meso-America. The squash, Cucurbita pepo, is
another example of a species that has apparently been domesticated at least
twice; once in south central Mexico and once in eastern North America and
mid latitudes (Smith, 2006). These examples illustrate the potential to
domesticate species more than once and to produce different domesticated
Can we develop domesticated crops for new uses?
Flax (Linum usitatissimum) is a crop that was originally domesticated for oil
around 10,000 years ago, but was later adapted to use for fibre production
(Fu, 2008).
Options for domestication of new food crops
The potential to domesticate new food crops would be expected to be very
limited because of the long period of time over which plants have been evaluated by humans in most parts of the world.
Exceptions might include species worthy of domestication in their own
right that may have escaped domestication because there were not other
species in the region that were suitable for domestication. Change from a
hunting and gathering lifestyle to an agricultural one probably requires the
availability of several species to make the agricultural option attractive. A
good example may be found in the Macadamia. This Australian species was
domesticated only very recently. The domesticated plants are derived from
two wild species (Macadamia tetraphyla and Macadamia integrifolia) found
in subtropical rainforests of central eastern Australia. The wild population of
these species are now endangered. Wild trees were sent from Australia to
Hawaii in the late 19th century, and these trees were used to establish
Macadamia production there and were later re-imported to Australia to form
the basis of a new industry from the 1960s.
Another area in which new possibilities for domestication may be found
is when technology advances allow barriers to domestication to be overcome.
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Domestication of New Species 135
Figure 10.4 Domestication in the Proteaceae
The domestication of toxic plants as food crops by using modern genetics
and chemical analysis methods to develop non-toxic cultivars illustrates this
opportunity. The domestication of Canola from rapeseed may be considered
such an example. A relative of the Macadamia, Hicksbeachia pinnatifolia,
might prove to be another example (Figure 10.4). This species is a member
of the Proteaceae family like the Macadamia and is found in rainforests in
the southern parts of the range of the Macadamia species. The Hicksbeachia
was discovered in the late 19th century and was described as edible in the
records of early explorers. However, this now rare plant may not have been
eaten by many humans. The author’s experience of eating these fruits was
one that suggests that under some conditions the nuts could be poisonous.
Modern genetic and chemical analysis could be used to develop a more edible Hicksbeachia.
The Macadamia, originally a native of Australia, was largely domesticated in Hawaii. This cultivar, like most cultivated Macadamias, has a
parentage involving contributions from both of the edible wild species,
Macadamia integrifolia and Macadamia tetraphyla. Hicksbeachia pinnatifolia
is a relative of Macadamia that has not been domesticated. This species has
a range within the natural distribution of the two species of Macadamia
that are the source of the cultivated Macadamia. The Hicksbeachia pinnatifolia is less likely to be domesticated because the nuts are not as attractive
as a food and may also be toxic.
Many species are candidates for limited domestication. The Davidson’s
Plum – Davidsonia pruriens (Figure 10.5) – is found in the same areas as the
species from the Proteaceae described above. The Davidsonia now include
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Figure 10.5 Davidson’s Plum Davidsonia pruriens
three taxa; Davidsonia pruriens from northern rainforests; Davidsonia jerseyana from the subtropical rainforests; and Davidsonia johnsonii from the
same subtropical rainforests but without seeds. This later trait is of obvious
interest for a cultivated fruit. Complete domestication may involve hybrid
formation and exploitation of the seedless trait.
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Domestication of New Species 137
Davidsoniaceae is in limited cultivation for the edible fruits which are
large and numerous, but not generally attractive to human tastes without
the addition of significant amounts of sugar. The Davidsonia genus
includes three taxa, two of which are rare rainforest species. The species
are in limited domestication as a source of novel fruits. The reproductive
biology of these species is poorly known, with Davidsonia johnsonii not
known to have seeds.
The general conclusion that can be reached when looking at options for
new food crops is that domesticating a new major crop with the value of rice,
wheat, potato or maize is unlikely. However, regionally significant alternatives may be found and our reliance on such a small number of major food
crops makes diversification highly desirable.
Options for domestication of new energy crops
The key genetic change that was selected in the domestication of the cereals
was loss of shattering (as described in Chapter 2), so that the crop was not
dispersed as it matured but stayed on the plant until harvested by humans.
Domestication was also associated with strong selection for large seeds.
Energy crops in which the total biomass is to be utilized for energy production will not require large seeds. Smaller seeds could be an advantage in
production, allowing easier propagation of large populations of the crop.
Non-shattering types will still be preferred, in sexually reproducing species,
to allow for seed production. The genes determining both shattering and
seed size have been identified and characterized in rice, and this knowledge
should prove invaluable in rapidly modifying these traits in other plant
species. Efforts to demonstrate the accelerated domestication of a wild
Australian grass are in progress using targeted mutagenesis and a selection
of natural variation in these genes.
The novel requirements of plants for energy makes it likely that plants
better suited to this use have been overlooked by earlier domestication
focused on food production. However, the potential to domesticate additional food crop plants is less clear. The selection of plants that have a high
fibre or cell wall content for energy production will remove the potential for
conflict with food use, as this type of biomass is not likely to be very edible
or nutritious.
Domestication of new species starts with the selection of wild material,
development of an agricultural production system, and then ongoing refinement of the crop by plant breeding and optimization of the production
technology. Several examples of new energy cropping options will now be
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Energy cane
Energy cane could build on sugarcane domestication to deliver greatly
improved crops with energy and sugar as co-products. The utilization of
the plant for energy could be more economic if sugar is extracted first and
the remainder of the plant is used for energy. Sugarcane was domesticated
by human selection of a fast growing plant with a high sugar content.
Saccharum officinarum was domesticated (probably in New Guinea) as a
sweet form of the wild Saccharum robustum. Genetic selection was for
plants with a high sugar (sucrose) content in the stalk as a source of sweetness to satisfy human taste. Modern sugarcane cultivars have been
developed by subsequent hybridization of the domesticated S. officinarum
with wild S. spontaneum to improve growth rates without loss of sugar content. We may now wish to place more emphasis or total emphasis on the
growth of biomass in the development of an energy cane. Modern cultivated sugarcane is a highly polyploidy species (it has many copies (often
more than ten) of each chromosome). This high polyploidy makes breeding very difficult with the inheritance of many traits not behaving in the
simple way that they do in diploid (only two copies of each chromosome
as in humans) plants. In this extreme case the domestication of a plant that
was less complex genetically may be a worthy objective. This would allow
more rapid breeding. Sugarcane is propagated vegetatively (using cuttings)
and has gone through relatively few generations of sexual reproduction
since domestication. Modern cultivars are probably only a few sexual generations from wild plants. The related grass, Miscanthus, is being widely
evaluated as a potential energy crop. Crosses between Miscanthus and sugarcane have been produced as additional options for energy and sugar
Energy grain
Sorghum could be de-designed as a multipurpose food/feed and energy
crop. The entire plant could be utilized with the grain contributing either
starch to biofuel production and protein to feed uses or to novel food products, with the remainder of the plant being utilized as a source of energy.
Domestication of sorghum has focused on grain traits as this is the part of
the plant eaten by humans or animals. The vegetative growth of the plant
would become the primary target for breeding for use as a biomass source
for biofuels. Recent efforts have focused on sweet sorghum as an option that
allows first-generation biofuel production from the grain and vegetative parts
of the plant. The focus should shift to the potential of sorghum as secondgeneration biofuel crop. Total biomass production rather than grain or
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Domestication of New Species 139
sucrose content is the target for this research. Several species that have been
identified as close relatives of cultivated sorghum by DNA analysis can now
be included in the germplasm pool for use in sorghum breeding. These may
increase the range of traits that are available in sorghum.
Energy tuber
Tuber crops such as potato, sweet potato and cassava may contribute to
energy production. They have potential for current use, especially use of
waste components of these crops, in first-generation fuel production. The
role of these high-value food crops in second-generation biofuel production
is less clear.
Energy grass
New grass crops could be domesticated as dedicated energy crops. Total
biomass production with minimal inputs would be the main selection criteria. Biomass composition could also be optimized for specific biofuel
conversion technologies. Domestication of grasses as energy crops requires
some of the same steps as the domestication of the cereals as food crops. For
example, a reduction in shattering is still required to allow harvesting of the
seed for propagation of the crop rather than harvest of seed as food.
However, large seed size beyond that necessary to ensure good seedling
establishment may not be an advantage. Miscanthus species and switchgrass
(Panicum virgatum) are good examples of grasses being evaluated as new
energy crops (Vermerris, 2008b).
Energy wood
Novel woody biomass crops such as Eucalypts could be developed. Poplar
(Populus spp.), willow (Salix spp.) and pines (such as Pinus elliottii) are also
important options. Options to maximize the sustainable harvest of biomass
on an annual basis would require the determination of the optimal harvest
frequency (e.g. every year, two years or ten years) to minimize the costs of
harvesting and deliver the maximum yield of biomass per year. Breeding for
this production system would require the selection of species with a long life
between replanting combined with maximal growth rates. Novel changes in
biomass composition could be introduced to enhance the value of this biomass in biofuel production. A very large number of species adapted to a wide
range of environments are available to select as energy crops.
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Energy legume
A legume crop, or at least one that results in increased incorporation of nitrogen into the soil, may be an important option in many regions. These species
reduce the reliance on nitrogenous fertilizers produced using energy-intensive processes and including the use of fossil fuels. Pongamia is a legume that
has been developed as a first-generation, oil producing, energy crop. The
development of second-generation energy crops from legumes is now
needed. These species may have value as a crop in their own right. However,
their main use may be as a rotational crop delivering advantages in nutrition
to the crops that are planted following them in the same field. This is important for both food and energy production. A legume with food or energy uses
(or both) could rotate with a non-legume with either food or energy uses (or
both). The economics of the whole system need to be considered. Ideally,
the value of each crop is maximized in addition to considering the value of
each crop in the rotation.
Urgent application of these strategies is needed to generate the new
crops required to satisfy human energy requirements.
Novel tools for domestication
An improving understanding of the processes of domestication has come
from the availability of genetic analysis tools. Genetic relationships between
wild and domesticated populations have been used to define the processes
that resulted in domestication. The analysis of DNA sequences from
domesticated plants has defined some of the exact changes required to
adapt a plant to domesticated production. For example, the genes controlling shatter in cereals are being defined. Manipulation of these genes could
rapidly alter this key domestication trait. Similar approaches might be
employed to target other important domestication traits. New and emerging tools are greatly increasing our capacity to analyse large amounts of
DNA from large numbers of individuals in increasingly efficient and lowcost protocols. These scientific advances offer the potential to greatly accelerate our ability to domesticate new species. We can expect rapid growth in
our knowledge of domestication genes and processes in the next few years,
as these new technologies are more widely applied. The application of
genomic approaches is likely to further accelerate research in the accelerated domestication of new plant species. Genomics involves the study of
all (or most) of the genes in an organism as opposed to conventional
genetic approaches that consider the role of individual genes. The positive
impact of this technology on the breeding of food and energy crops has
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Domestication of New Species 141
been discussed in Chapters 2 and 5. Advances in DNA sequencing technology (see Chapter 5) since about 2005 have been very rapid, making this
technology much more widely available and feasible for this type of application. DNA banks are improving access to biodiversity for this type of
research. This technology is continuing to be applied widely to food and
forest species, and can now be used to accelerate the domestication of
energy and new food crops to rapidly catch up on much of the 10,000 years
or more that the traditional food crops have. Improvements in biomass
composition and specific traits will become increasingly feasible as the science improves. Major advances in total plant biomass yield may be slower
and require much more field evaluation and a greater understanding of the
performance of plants in each local target environment.
Figure 10.6 Relationships between higher plants
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Humans have domesticated many plants for food, but it remains difficult to identify a plant species that has yet been domesticated for energy.
Some plants may be considered to be currently in the early stages of
domestication as energy plants. Some of these may continue to full domestication. However, it is likely that new species not yet even under
consideration may be rapidly domesticated and become our dominant
energy crops. All of the plants should be considered options (Figure 10.6).
However, the angiosperms or flowering plants are the dominant large plant
group and represent the main option.
A systematic analysis of the families of angiosperm and gymnosperm
families and their food, energy, or other current or potential use, is provided
in Henry (2010).
Chapter 11 will look at options for the future use of plant resources for
food, fuel or conservation.
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As potentially environmentally sustainable commodities, the enthusiasm
for plant-derived products is understandable. In principle, a deeper
understanding of plants and other living systems could allow us to better manage the earth’s resources for both environmental and economic
ends. Demand for land, water and biomass resources is intensifying
with consequences that are being felt by all. If current developments are
anything to go by, the politics of plants will quickly become increasingly
Frow et al (2009)
The demands of human populations for food and possibly energy from agriculture are likely to be sustained, over the next few decades at least. This will
be driven by continued population growth and increased food consumption
associated with economic growth in developing countries, and increased use
of bioenergy as an alternative to fossil fuels in an attempt to minimize the
impact of climate change. Conserving biodiversity will continue to be a challenge, while pressure to commit more land to agriculture will remain an
enduring reality. The greatest uncertainty is probably the extent to which climate change will exacerbate these problems by reducing agricultural
productivity, as a result increasing the demand for land for agriculture; and
by directly driving species to extinction. This chapter will define the issues
and possible solutions. Key aspects of these challenges to be covered include
the need to focus on strategies to minimize food energy competition both at
the biomass and land-use levels. The areas in which science can contribute
need to be systematically evaluated.
Historically food production has increased to meet or exceed population growth and associated demand for food. In the second half of the
20th century this was achieved in the ‘Green Revolution’ that combined
new higher yielding genotypes with the use of increased inputs such as fertilizers, but with very little change in the area being cultivated. In the last
decade the view has emerged that this technology has reached its limits with
a slowing in the rate of growth of food production (Fedoroff and Brown,
2004). Some people argue that scientists are to blame for the growth in
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human populations because they developed more efficient agriculture that
has kept pace so far with the growth in populations. The alternative to not
developing the capacity to feed a growing population would be limiting
growth by starvation. Surely the ethics of scientists and the community at
large must be to support human life, while highlighting the strain population growth places on global sustainability? However, the ‘Green
Revolution’ has not been without significant problems. A consistent criticism is that the technology has made farmers in developing countries more
dependent on high cost nutrient inputs. The reality is that the new plant
cultivars tend to yield more regardless of fertilizer use, but do respond very
well when additional nutrients are used. Loss of biodiversity in agriculture
due to the dominance of high-yielding crop cultivars that encourage the
growth of monocultures is another continuing concern. Plant breeders are
now able to directly tackle this problem by deliberately introducing more
diverse material into their programmes. Modern DNA analysis tools assist
in maximizing diversity in cultivated plants by allowing deliberate selection
of new cultivars or parental lines for use in breeding that are as genetically
different as possible from other cultivars in cultivation. This needs to continue as a very active process to balance the relentless pressure on
agriculture to maximize performance by selecting the very best performing
genes or genotypes. These deficiencies do not detract from the key role
this technology has played in feeding the human population and protecting biodiversity by minimizing the footprint of agriculture, but they do
dictate a need for continued efforts to address the unintended problems that
Climate change and the costs and limits of fossil fuels have provided a
strong incentive to explore the potential for efficient energy crops.
However, competition for land with food crops and biodiversity conservation are potentially serious negative impacts of biofuel production. This
suggests the urgent need to focus biofuel crop production on species that
are highly efficient and do not compete directly with food crops for land or
water. The ideal species for these applications have not been identified for
most production environments worldwide. Time has probably been wasted
on attempts to adapt or use food crops rather than undertake the testing
required to reliably identify and in many cases domesticate new species as
biofuel crops from the many plant species available (see Chapter 11). The
long-term priority for biomass production will probably be to replace fossil
fuels in applications other than transport fuels. Biofuels provide a partial or
possibly a complete solution for transport in the short term (next few
decades). However, they will only make a net positive contribution if their
production and use is managed better than it is at present. New technologies will be needed to supply energy for transport in the long term.
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Scenarios for the future requiring differing degrees of success in these
areas can be defined. It is worth thinking about options over a period corresponding to the current life expectancy of someone born today in a
developed country. The lifespan of this person may depend on how the different scenarios play out, with the possibility of it being much longer (due
to advances in medical research) or much shorter (due to environmental
decline) than current expectations. The scenarios explored here are to the
2085 time point based upon the calculations of Cline (2007), as introduced
in Chapter 6. These estimates are based upon two population projections for
2085; a low population projection of 10.5 billion and a high (worst case)
projection of 14.7 billion.
These calculations suggest a 2.66-fold (low population) and a 3.72-fold
(high population) growth in food demand by 2085 compared with a starting point of 2005. Growth in food supply was estimated to be 2.44-fold in
these scenarios. This immediately suggests we should be using all our efforts
to aim for the lower population outcome. One complication is that an outcome of lowering population growth may be associated with a further boost
to per capita consumption (already as big a factor as population growth in
determining food demand). This would reduce the benefits of population
control. Affluence is generally associated with lower population growth rates,
as economic concerns rather than survival determine human reproductive
We can now consider the impact of our approach to biofuel production
on these scenarios in a low biofuels future and a high biofuels future.
Low biofuels future (next two decades)
This low biofuel option avoids tackling replacement of fossil fuels and has
a great risk of resulting in continued high levels of greenhouse gas accumulation and associated climate change, with serious implications for
ongoing food security and biodiversity conservation. The low biofuel option
only looks good for climate change mitigation if it is achieved by making
biofuels redundant, by developing new alternative energy technology that is
carbon neutral and can replace most uses of fossil fuels. This is relatively
unlikely in the next two decades but should remain a longer-term objective.
The benefits of this option may include reduced competition with food
production and the associated resulting lower pressure on biodiversity.
This needs to be balanced, however, against the high risks of climate
change, and a resulting loss of agricultural productivity and direct loss of
biodiversity. The high cost of fossil fuels may also drive up food production costs in this scenario.
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High biofuels future (next two decades)
Second- or later-generation biofuels (defined in Chapter 5) should allow a
reduction in greenhouse gases in the short to medium term, allowing time
for alternative technologies to be developed to replace carbon-based fuels in
the longer term. This option only looks good if we are able to develop highly
efficient second-generation fuel technology. Current first generation technology is too inefficient, resulting in a much larger environmental footprint
for biofuel production.
The attractiveness of this option relative to the low biofuels option suggests that we should place great emphasis on achieving efficient secondgeneration technology quickly. Despite the greatly improved efficiencies
promised by second-generation technologies, the potential for food and biofuel production to compete for land, water and other resources needs to be
managed carefully and actively, as does competition with land for biodiversity conservation.
The choice between these two options becomes one related to the relative difficulty and likelihood of success in developing these technologies
(new carbon neutral energy or second-generation biofuels). In reality we
need both technologies as soon as possible. The high biofuels option is only
a partial solution to our long-term energy needs. If we have sustainable cellulosic biofuel we will still need other technologies to satisfy our total energy
Scenarios for the future
Biofuel production is likely to be an essential component of delivering a sustainable future. We need to begin to reduce CO2 emissions. Large-scale
adoption of biomass-based biofuels has been estimated as being capable of
replacing 30 per cent of US oil production by 2030. This would require 1
billion tonnes of biomass and it has been suggested that this is feasible (US,
DOE, 2005). This could be combined with the replacement of another 20
per cent of oil consumption with solar and wind energy on the same
timescale. Many other countries have a much greater capacity to produce
biofuels relative to their energy use. This type of scenario would project the
possibility of CO2 emissions peaking by 2050 and make significant progress
towards an end to substantial use of fossil fuels by the end of the century
(Ahmann and Dorgan, 2007). While this is a relatively easy path to follow,
many suggest we need to act much more aggressively than this. Larger volumes of biofuel production to replace most or all of fossil fuel use on a
shorter timescale would require the production of dedicated biofuel crops.
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Lessons from the past
Can we learn from previous human experiences and avoid a disaster in the
supply of food and energy, but at the same time conserve biodiversity?
Diamond (2005b) has examined a number of examples of dramatic failures
of human societies in his book, Collapse. In a similar way climate change may
result in food supply failing to satisfy the needs of large human populations.
Box 11.1 The case of the Mayan society
The downfall of the Mayan society provides lessons that have many parallels with the current situation. The ruins of this society in Mexico (Figure
11.1), much still overgrown by forest, should be a reminder of what appears
to have happened when a society was unable to feed itself. The Mayan society collapsed rapidly around 1000 years ago. The society was highly
dependent on maize and had limited water storage facilities for crop irrigation. This region has a highly variable rainfall, making the society vulnerable
to a series of low rainfall years. Climate change – even short-term fluctuations in the climate – may have a catastrophic impact on a society that has
a large population with very limited amounts of stored food and is reliant
on a very limited number of crop plants for agricultural production. This
parallels human society today with our great dependence on a few crop
species, the products of which we have little of in storage at any time, with
a large and growing population facing the prospect of climate change.
Figure 11.1 Mayan ruins on the Yucatan Peninsula, Mexico. These
societies were based upon maize. The rock carvings (inset) depict maize
grains and maize leaves
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Was Ehrlich right?
Paul Ehrlich predicted that the world would face widespread starvation if
population was not controlled in his work The Population Bomb, published in
1971. This work and The Limits to Growth (Meadows et al, 1972), and its
follow-up volume The Limits to Growth: The 30-Year Update (Meadows et al,
2004), shaped the views of many and can be linked to the awakening of wider
environmental awareness of resource constraints in society. The predictions
of Ehrlich’s book proved inaccurate in so much as the impact of technology
allowing us to feed a growing population was underestimated. But effectively
we may have just delayed the inevitable. The alternative is to assume that
technological advances will continue to allow us to avoid disaster. It is important that if this is our assumption then we acknowledge that this is the basis
on which we go forward and consider the consequences of this strategy. If we
bet the future on technology advances we need to make sure we resource the
science and technology necessary to deliver these required outcomes. Public
policies generally fail to acknowledge this link and often support continued
expansion of human activities, while withdrawing or not supplying the
resources required to develop the technology to deal with the consequences.
Does new technology offer solutions?
The key areas of technology that are essential to our ability to sustainably produce food and energy for the human population are in plant production
(agriculture and forestry), in the processing of crops to food (food processing), and in producing energy from biomass (conversion technologies).
Crop production
The technology inputs in food crop production can be divided into the
genetic component and the management component. The genetic component is the contribution of the plant breeder to selecting and breeding a
cultivar with high yield, and with the desired functional and nutritional properties. The management component (agronomy and farming systems)
includes the entire process of where and how we cultivate the crop.
Relative contributions of plant breeding and better
crop production systems
Both genetics and management have been major components of the
improvements in crop productivity in the past, and both must be pursued
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aggressively if we are to continue to match food production to human
demand. The relative contributions of these inputs have varied in different
regions and for different crops, but are probably each responsible for about
half of the improvements we have made and are likely to continue to make.
Genetics and management have made synergistic contributions to achieving
our food production needs.
Plant breeders argue that the advantage of the genetic contribution is the
ease of adoption. A new cultivar can simply be supplied to a farmer as seed,
and all the benefits in performance and environmental adaption built into the
cultivar in the research and development are transferred to the end user.
Many technologies, including the production of hybrid cultivars, continue to
offer the potential to greatly increase the productivity of crop production systems. Wide hybrids (hybrids with genetically diverse parents) result in hybrid
vigour (heterosis) that gives much greater productivity in many plant systems.
Maize hybrids are probably the best known example of this technology, with
great advances in productivity being achieved in corn production using
hybrids. Hybrid Eucalypts with greatly improved performance have been
recently developed as ornamentals (Figure 11.2), but may also become a
major opportunity for energy crops. Hybrid tropical pines have been developed and successfully deployed for plantation forestry. For example, timber
for the frames of houses in Queensland has been largely sourced from
Figure 11.2 Hybrid Eucalypts – Hybrid vigour. This inter-specific Eucalypt hybrid
was produced as an ornamental, and shows growth and floral characteristics superior
to either of the two parental species
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plantations of tropical pine trees (Pinus), with the Slash pine (Pinus elliotii var.
elliotii) and the Caribbean pine (Pinus caribaea var. hondurensis) being grown
on different sites to satisfy this requirement. The Slash pine is better adapted
to lower, wetter areas and was favoured for planting in these environments.
Better drained areas were planted with Caribbean pine. A hybrid between the
two has been found to be broadly adapted and suited to planting across the
entire area of forest plantations, and has been replacing the pure species in
recent plantings. This is a good example of how breeding technology has
impacted to improve the management efficiency of forest tree production.
More widespread application of hybrid technology can be expected to continue to provide an important tool in meeting the critical demand for
improvement of the productivity of food, forest and energy crops.
Plant-breeding technologies, especially the efficiency and accuracy of
genetic screening, have been enhanced by the development of molecular
techniques for the selection of plants with desirable production traits.
Advances in genomics promise to greatly increase the effectiveness of this
technology in the future as we learn more about the genetic basis of many
key plant traits. Automation of these molecular screening techniques continues to advance, suggesting that the widespread and cost-effective application
of these technologies will play a central role in accelerating the genetic
improvement of plants for all end uses.
Box 11.2 Advances in DNA fingerprinting techniques for use in plant improvement
The future will see direct analysis of plant DNA for the traits of importance to humans, rather than the indirect approaches of recent decades
that have required analysis of DNA for genetic markers that are not always
perfectly linked to the trait of interest. DNA analysis in plants has had a
wide range of uses.
DNA-based plant identification has application in:
• the protection of intellectual property rights associated with plant cultivars;
• forensic applications in the analysis of crime scenes;
• determining the identity and purity of seed lots in commercial trade
and production;
• determining the cultivar of an agricultural species that is being traded
to ensure appropriate contract compliance;
• food processing to ensure the processing method is optimized for the
• analysis of the composition of competitors’ food products.
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These same DNA fingerprinting techniques are useful in selection
and breeding of new plant cultivars with desirable production traits
(see Chapters 2 and 5). The technology used has been generally
based upon the approaches used in the DNA fingerprinting of
humans, largely for health (genetic disease analysis), paternity and
criminal identification. The technologies used have evolved over the
last decades (Henry, 2001; Henry, 2008) to become more reliable,
automated and low cost. The technology has now advanced to the
stage that the largest component of the cost of most analyses is the
cost of collecting and handling the sample. The utility of this technology will be greatly enhanced by the increased knowledge of plant
gene sequence flowing from recent technology developments.
Advances in the genomics (study of all of the genes) in plant species (Box
11.3) have underpinned the rapid growth in understanding of gene function
necessary to apply selection at the DNA level in plant breeding. The analysis of the sequences of plant genomes is a great platform of information on
which this technology is now developing rapidly.
Box 11.3 Plant genomics
Plant genomics provides enabling technologies for developing the plants of
the future and for monitoring the status of plant biodiversity. New and
emerging technologies are accelerating the rate of discoveries in plant
Key developments include:
• rapidly increasing capacity to determine the DNA sequence (genetic
code) of any plant;
• growth in functional genomics (understanding how plant genes function);
• improved understanding of the genetic basis of nutritional and functional characteristics of foods;
• insights emerging into how plants may adapt or be adapted to climate
• greatly improved ability to efficiently select plants with desirable characteristics in plant breeding;
• related improvements in DNA fingerprinting for identification of plant
cultivars in production and food processing and distribution;
• emerging tools for objective DNA-based biodiversity assessment and
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• improved understanding of evolutionary and adaptive processes in
• tools for determining relationships between individuals in critically
endangered plants and managing populations for long-term survival and
Improved ways to grow the crop and manage the overall farming operation
may offer very large opportunities for improved productivity and sustainability, as well as biodiversity conservation. However, the impact of research
and development aiming to deliver these outcomes will depend upon the
extent to which new management practices are adopted by farmers. The
communication of the technology may be frustrated by the necessarily conservative nature of farming operations. Many farmers even in the developed
world tend to farm the way their parents did, resisting new approaches.
Demonstrations of the benefits of the new approaches on the farmer’s own
land or on the farm of a neighbour is a strategy that is often necessary to
convince farmers to change long-established practices.
We need both strategies (genetics and management) to be able to satisfy
future food and energy needs. New plant cultivars need to be produced using
new management strategies to allow the necessary increases in productivity
and sustainability. The synergies of these interdependent developments are
essential to satisfying demands for agricultural production.
Food processing
Significant gains in food supply may be achieved by improving the efficiency
of food processing. Increasing the yield of flour from wheat is a good example of this approach. Most wheat (in excess of 500 million tonnes per year)
is processed by milling to produce flour. The flour accounts for the bulk of
the grain, but significant amounts are separated as bran that despite a high
nutritional value is not consumed in large quantities by humans. Genetic
improvement of wheat to produce cultivars that yield more flour on milling,
or improvements of the milling process to recover more flour, are options
for increasing the supply of food from wheat. These processing advances
provide more food without the need for more land, water or other farming
inputs. Because of these advantages these approaches should be given high
priority. Protection of plants against post-harvest spoilage may also make a
significant contribution to food supply.
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Box 11.4 Research targeting better health and functionality in foods
Much research effort is being devoted to developing foods that have the
potential to contribute to improved human health and provide improvements in the yield and quality of processed foods. Two examples of
programmes aimed at delivering these outcomes are the Healthgrain programme in Europe and the Grain Foods Cooperative Research Centre in
Healthgrains ( is supported by the European Union
are with contributions from many food companies and research organizations in Europe. Grain quality attributes such as fibre content, important
for human health, are major targets of this research. The project
‘Improving health by exploiting bioactivity of European grains’, or
Healthgrains, aims to deliver whole grain products or grain fractions that
contribute to improved human health.
Grain Foods CRC
The Grain Foods Cooperative Research Centre (
is supported by the Australian government and food companies and research
agencies. Research aims to improve the efficiency of recovery of quality foods
from grain and to deliver products with health and processing advantages.
Examples of research outcomes include genetic discoveries that will allow the
production of grains with enhanced folate content and improved flavour.
Improvements in both the plant cultivars and the processing techniques are
combined to deliver these outcomes.
Another good example of the type of innovation in this area is the development of low-allergy peanuts (Chu et al, 2008). Peanuts are a high-value
food, in both developing and developed countries, that can nevertheless
cause a serious and fatal allergy in a small portion of the population.
Increasing understanding of the proteins in peanuts that are responsible for
the allergic reaction in humans has defined targets for research, aiming to
develop peanuts that will not be allergenic or at least will be low in allergens. The specific proteins in the peanut that cause the allergy are now
known and the genes expressing these proteins can become targets for
efforts to turn them off by genetic manipulation, or by mutation or even
selection within natural variation. More widespread application of this type
of approach may assist the diversification of human food sources by allowing food use of plants that are currently not considered edible because of
toxins or other health risks.
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Conversion to energy
Improved technologies for conversion of crop biomass to energy also have a
great contribution to make. Developing the ability to convert all of the carbon (or at least all of the carbohydrate, structural and non-structural) to
energy is an essential step in achieving the efficiencies required to make this
technology attractive from an economic and environmental perspective. This
advance would facilitate the application of strategies to manage the efficient
utilization of total biomass for food and energy production, and allow the
capture of all current waste streams from agricultural and forest production
and processing. Multipurpose crops might become a major option with the
whole plant being used for food and energy, as discussed in earlier chapters.
Genomics is promising new insights into how to improve crops based
upon identification of the genes controlling the composition of plant biomass. The structure of cellulose, non-cellulosic polysaccharides, lignin and
the linkages between these components are all targets for development of
novel plant biomass that facilitates efficient conversion to biofuel.
A significant example of the type of innovation that the future might
bring is provided by the recent report of new insights into the control of cell
wall formation in plants (Held et al, 2008). This research has identified
genetic mechanisms that influence the transition from primary to secondary
cell wall synthesis in plants. The primary cell wall is formed while the cell is
still enlarging. Mature cells may then form a secondary cell wall after cell
growth has been completed. The composition and extent of the secondary
cell-wall is very dependent upon the cell type. Small interfering RNAs have
been shown to influence the expression of the genes encoding the major
enzymes of cellulose and non-cellulosic glucan (glucose polymer) biosynthesis in barley. This research suggests options for manipulation of the
biomass value of grasses and possibly all other plants.
Even more novel organisms might be engineered in the future to facilitate conversion of biomass to biofuels, or even direct biofuel production.
The production of synthetic genomes has been proposed by Craig Venter as
a strategy for biofuel production and the process of synthetic genome construction has already been demonstrated (Gibson et al, 2008). This
technology creates complete micro-organisms to human designs by chemical synthesis of DNA sequences encoding the functions required in the
organism. This could be used to generate organisms that produce biofuel
molecules directly from carbon dioxide, using light from the Sun as a source
of energy. Alternatively, organisms could be engineered to convert carbon
capture by plants into biofuels.
Organisms that are found in extreme environments may provide some of
the solutions to biofuel production. These organisms are found in environments
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that are extreme in temperature or chemical composition. High-temperature
volcanic sites or soils that are very acid or alkaline may provide these unique
organisms. These organisms or enzymes isolated from these organisms may
have properties that allow their use in novel industrial processes.
The production of higher value fuels may be achieved by using organisms that are able to produce these molecules by fermentation. For example,
changing from ethanol to butanol may simply require the use of a different
micro-organism for fermentation.
New technologies for biodiesel production are also likely. The use of
supercritical fluid extraction may replace the use of organic solvents to provide more efficient and more environmentally desirable processes for oil
extraction from plants. More efficient methods for production of biodiesel
from cellulosic biomass are also required.
Integrated food and energy production systems
Multipurpose crops (in which part of the plant is eaten and part used for
energy), or crops that can be grown together in the same field to address different end uses, are important options. Increasingly, food processors are
examining all waste streams as options for use in energy production. It is
likely that these options will be among the first to be exploited because the
cost of harvest and transport of the biomass to a central location has already
been invested.
Contribution of plants to carbon storage
The use of plants to capture carbon may also become important. Changing
land use towards the production of large plants such as trees may increase
the amount of biomass in plants at any one time. This will increase the
amount of carbon in the standing biomass. Crop residues contribute carbon
to the soil, which has an important role in retaining soil nutrient status and
allowing sustainable production. Some of the carbon from crop residues is
in forms that may persist for long periods in the soil. This allows carbon to
be stored or sequestered and may assist in reduction of the amount of CO2
in the atmosphere. Small amounts of carbon may be trapped inside cells –
phytoliths – with walls rich in silica that protect the contents long term. The
burning of plant residues may generate biochar that also has a relatively long
life in the soil. The selection of crops may be influenced by these environmental values. Plant breeding may be used to develop crops with greater
potential to contribute to carbon storage in these ways.
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What type of future are we creating?
If we agree that humans can continue to expand their population indefinitely
using technology to deal with the problems as they arise, then we need to
understand that that is our strategy and accept its consequences for the type
of future world we are creating. We cannot argue that all humans are not
entitled to the same environmental footprint. However, we need to be aware
of the huge impact of the world population moving to the level of resource
consumption of those in developed countries.
Human evolution is increasingly locking us into a future environment
that is of human creation. As we occupy more of the space on Earth and
continue to reduce the numbers of other species and their contribution to
the biosphere, we become more reliant on our science and technology for
our survival. The ultimate step is probably for the human species to
develop the capability to survive beyond this planet. This may become
more than an option, rather a necessity, if we continue to overrun the biological systems on Earth. In some ways continuing on Earth may become
almost the same option if we need to create an artificial environment on
Earth for survival. This is a dangerous path, especially if followed at the
rate we are at present. Can we be sure we can continue to find the technical fixes in time as we exhaust the capacity of the Earth to support our
needs for food, energy and a survivable environment? A slower rate of
advancing down this path would help. Slowing these processes down to
give the human species a better chance of surviving the future implies
greater efforts to retain the biological resources of Earth as long as possible. Some actions we can take to contribute to a more sustainable future
are listed in the next section.
The development of the Internet has undoubtedly been a major advance
in human communication. The rapid exchange of information creates the
potential for a much more global approach to our problems and much
greater international understanding and cooperation. Humans are also
becoming more disconnected from the biological systems on which they
depend. We are already spending less time relating to nature as access
declines and more to systems created by humans such as the Internet.
Environmental education needs to adjust to this reality and aim to ensure we
do not lose sight of our origins.
Conscious selection of the future
Growth of human populations has largely driven our expansion and the consequences of this growth have been dealt with as they arise. Should we just
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let events decide themselves? Humans need to consider the balance they
want in their future. Emphasis to date has been on the quantity of food and
energy consumed per person as measures of our quality of life. Energy
allows travel, thus enriching human lives by exposure to diversity of human
cultures and to biodiversity. However, travel and communication is also
accelerating the development of a more homogeneous world, as well as contributing to climate change, and we face the prospect of a continuing loss of
biodiversity. An alternative emphasis would preserve more of the diversity of
biological experiences available to humans. Quality of life can also be derived
from the diversity of life forms we have the opportunity to interact with and
the diversity of foods (based upon biodiversity) that we have to eat.
A future in which we have the greatest possible diversity of life forms
seems to be more attractive than one in which we simply have enough food
and energy to survive.
We will now consider the implications of these two contrasting futures.
Low biodiversity future
The extension of many current trends will see a low biodiversity future. In
this scenario species extinctions will continue, probably at an accelerating
pace. The outcome will be that human life will be dependent on a narrower
biodiversity base. This will carry significant risks. It will directly limit our
ability to adapt food production to environmental change. It will mean we
rely on fewer species to maintain the biological cycles that are essential to
maintaining air, water and soil, indispensable to a life based upon biological
inputs. The science and technology required to continue life without these
resources is likely to take a very long time to develop if it proves possible.
We are on a path that will increasingly lock us into a future that anticipates
such dramatic and potentially unattainable developments.
High biodiversity future
A high biodiversity future is a much safer option. It gives us more time to
develop the science and technology required to cope with our future. It provides a reservoir of biological resources to support adaptation to a changing
environment. It will ensure evolutionary processes can flourish, delivering
the biological resilience to ensure life continues on Earth long term. This
outcome requires that we focus on the issues of sustainability discussed in
this book. Recommended actions that will contribute to ensuring this are
given in the following section.
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Regional or local solutions
The outcomes of efforts to balance the competing needs for food, energy
and conservation of biodiversity at a global level will be the sum of all local
or regional outcomes. The environment differs from place to place in many
ways that influence the choices that are available. Local analysis is required
to identify the best local solution. Agriculture in any given region has
developed in response to the experiences of local farmers in working with
the soil and local climate to deliver crops that are profitable. Subtle differences in day length, temperature and rainfall (total amount and
distribution over the year) are among very many environmental variables
that determine the choice of crop species and cultivar, the planting time
and other management requirements. Over time sustainability becomes
more important as farmers seek to continue repeating their crop success
each year by adopting more sustainable techniques. Many agricultural scientists report that their experience of working with farmers in many
different regions has been that they are interested in the sustainability of
their businesses. For them environmental sustainability is economic sustainability. The converse is also true; without economic sustainability they
cannot afford to consider environmental sustainability. The difference is
only in the timescale, especially in variable environments when the production of a good year needs to cover potential losses in less favourable
years in the cycle. The global balance is also important to ensure we meet
the needs of the planet at a higher level. Unless this is monitored and
actively managed we run the risk that outcomes at a global level will not be
balanced. We need to continue to work at both a local and global level.
Agricultural research and development has declined in developing countries in recent years. Increased investment in this area is essential if we are
to maintain food security and improve sustainability (Von Braun, 2008).
The future of human life on Earth depends on a globally sustainable
environment that remains suitable for human survival. The management of
the future will require complex decisions and actions. More biologically
diverse futures will be more stable and more biologically secure. The quality of human life will also be enriched if we can retain significant biodiversity.
A scientifically literate society is the base on which this future depends. If we
fail to provide rigorous scientific training to large numbers of people we will
lose the capacity to respond to future needs. Indeed, this may be the greatest threat to a sustainable future. We need many technologies and many
solutions both local and global, and to achieve this we need many active
minds seeking sustainable options.
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Options for the Future
Recommended actions
The discussion in this book has directly or indirectly defined actions that can
be taken to improve or diversify future options. Twenty-five key technical
and policy objectives (not in priority order) in support of a sustainable food,
energy and biodiversity future for humans on earth are:
1 Increase efforts to conserve genetic resources of the major food crop species
on which we all depend for food (especially those such as wheat, rice, potato
and maize)
The critical dependence of humans on these few species for food requires
that genetic resources are available to allow adaptation to changes in climate and the outbreak of new strains of major plant diseases. The loss of
any one of the major species would put great pressure on food supplies.
Although the collections of germplasm for these species seem large,
much of the store material is redundant (many copies of the same genotype stored), and as our major sources of food they require continued
efforts to conserve all available diversity. Conservation of diversity of
these species needs to be balanced against the need to diversify support
for food crop species to the many minor food crops. However, the overwhelming importance of the major species in global food supply cannot
be ignored.
2 Identify and protect more areas with high biodiversity value in national
parks and reserves
National parks and reserves with resources to ensure they are protected will be very important in the conservation of biodiversity on an
increasingly crowded planet. The conservation of plant biodiversity
outside protected areas needs to also be addressed. However, the conservation of plants in protected areas is essential because many species
are found in very restricted habitats that require special protection to
give these species any chance of survival.
3 Improve the palatability of more stress-tolerant food crops (e.g. barley and
sorghum) that are better able to cope with climate change and develop food
technology so that these species can contribute new options to meet the
demands of food supply
Diversification of the species used as staple crops will expand the
range of environments that are able to make a major contribution to
human food needs. Making productive species more palatable as foods
needs to complement the more common strategy of increasing the productivity of attractive foods. Barley and sorghum are especially
important targets as they are well adapted to marginal environments
and close to being acceptable as human foods. Most other species are
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either not suitable for very widespread production or a long way from
being highly palatable to humans.
Develop technologies to achieve maximum recovery of food from harvested
crops and reduce post-harvest losses of foods in transport and storage
Improvements in the recovery of food from harvested crops make an
especially valuable contribution since the water and land resources
required have already been consumed in the production of the crop.
Most other options for producing more food will put more pressure
on these resources.
Develop new second-generation energy crops by adapting current crop
species (especially grasses and trees that can deliver high biomass quantities
from less favourable environments (e.g. disturbed areas or disused agricultural areas of low biodiversity))
Energy production that has a minimal potential to compete with food
production or biodiversity conservation is the outcome this will support.
Perfect ligno-cellulosic (second-generation) conversion technologies so that
they are efficient and environmentally sound
This will provide the maximum potential energy and greenhouse gas
reductions that biofuels offer.
Ensure public policies on agriculture, food and energy production encourage
sustainable technologies that are compatible with outcomes that include biodiversity conservation as a key objective
Biodiversity is often not considered in the rush to satisfy food and
energy needs.
Focus on improving the composition of biomass for the replacement of oil in
specific chemical feedstocks
This will ensure that biomass can replace oil for non-transport applications.
Where possible, use waste or co-products from food or forest production as
a source of biomass for biofuels
These waste products probably have the lowest environmental footprint of any source of biomass.
Promote the development of alternative energy systems (not based upon
carbon-based fuels) for transportation in the longer term
This strategy will ensure that in the long term we move to the most
environmentally desirable sources of energy and eliminate competition
with food and biodiversity.
Document biodiversity by establishing information technology systems and
develop repositories of DNA and DNA sequence data (collected using emerging technologies)
This technology will enhance the management of biodiversity and
genetic resources for agricultural species.
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Options for the Future
12 Develop second generation biofuel molecules (beyond ethanol)
This technology will improve the energy efficiency of vehicle operation and reduce the quantity of fuel required.
13 Identify new biofuel species and domesticate these new species for energy
(and other uses) using accelerated molecular assisted selection
This will allow efficient biofuel production in a wider range of environments. The species being targeted for biofuel production at present
are probably not optimal. Most were originally domesticated for food
or other uses. The full range of plant genetic resources needs to be
14 Research co-products to improve the viability of bioenergy production from
This research will improve the economics of biofuel production.
15 Encourage discussion and policy development on sustainable population
Population control and reduced environmental footprint per person
remains a key objective to improve our chances of a sustainable future.
16 Ensure the features of the local or regional environment are understood and
considered in finding and applying solutions for a sustainable future
Global solutions will not always work locally. Local or indigenous
knowledge needs to be recorded and communicated. The idea that
there is only one approach needs to be resisted with support for the
identification of locally relevant solutions to sustainability.
17 Conduct global agricultural research and development to support food security
We need to support the technology required to achieve a sustainable
future. More resources are required to support plant genetic resource
characterization and conservation. Plant breeding at all levels (from
molecular tool development and application to field assessment) needs
more public support. Genetic solutions to greater nutrient and water
efficiency need to be complemented with continued investment in
management techniques and decision-making tools. The underlying
scientific skills required for this effort seem to be in decline internationally and need to be maintained and expanded.
18 Support ex situ (not in the wild) collections of plant diversity at a regional,
national and international level
Plant genetic resources stored in this way assist in ensuring food security and biodiversity conservation.
19 Actively manage populations of rare or threatened plants
They will not always survive without intervention.
20 Encourage responsible human diets
Consumption of too much food and the wrong food is a major and
growing problem, resulting in growing obesity in human populations.
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Reduced food consumption per capita in societies with very high consumption rates would greatly ease pressure on land, water and other
resources, and improve human health.
Research and encourage adoption of sustainable agricultural production
Knowledge of approaches to increased sustainability need to be communicated to rural communities worldwide. For example, technologies
to sustain soil nutritional status and water supply and quality, while
continuing to maintain agricultural productivity, need to continue to
be refined and adopted.
Research and promote techniques to support on-farm conservation of
On-farm strategies to support biodiversity with cultivated fields and in
the adjoining areas need to be identified and communicated worldwide. These strategies may include the reservation of some parts of
farms for nature conservation, creating refuges for plants and animals
with potential benefits to productivity within the crop.
Look for genetic or biological rather than chemical solutions to pests and
These approaches will deliver better environmental outcomes, reduce
costs of production and deliver more sustainable high crop yields.
Domesticate a wider range of species for use in food production
Diversified food production will contribute to food security and provide a wider range of options better adapted to specific local
Reduce greenhouse gas emissions
Climate change threatens food supply and biodiversity, both directly
and indirectly through increased demand for land for food.
Page 163
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The following list includes publications cited in this book and others that
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Acacia 67
adzuki beans 12, 133
affordable food 118
Africa 43
Africa Rice Centre 34
agricultural research 161
albedo 122
alcohol 54
alfalfa 12
algae 75
alkanes 61, 64
allergy 153
Allocasuarina 72
Amazon 84, 119
amino acids 24
ancient grain 128
angiosperm 141, 142
Angiosperm Phylogeny Group 95
animal feed 5
anti-nutritional factors 12
apple 8, 30, 54
apricots 54
aquatic plants 101
arabinoxylans 56
arable land 2, 83
Arachis hypogaea 130
archaeological records 129
aroma 17
arrowroot 8
Asia 44
asparagus 8
aubergine 8
Aus 131
Australia 44, 85
Avena sativa 10
avocado 8
bagels 11
balady 11
bamboo 8
banana 8, 12, 130
Banksia conferta 111
barabari 11
barley 8, 9, 10, 30, 45, 67, 121, 126,
130, 159
basmati 17, 131
bay leaves 8
beans 8
beans (green) 12
beef 7, 19
beer 5, 13
beta-glucan 56
beverages 5, 13
biochemial conversion 59
biodiesel 54, 62
biodiversity 100, 157, 162
biodiversity in cultivation 102
bioenergy 50
biofuel 53, 145
biofuel production 51
biomass transportation 76
biorefinery 66, 76
Bioversity International 34
black gram 12
borlotti bean 12
botanic gardens 102, 103
bottle gourd 126
Brazil 83, 85, 119
breads 11
breakfast foods 11
broad bean 12
Bryophytes 141
bulk density 66, 75
1-butanol 63
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butanol 62, 64
cabbage 8
calorie intake 10
camelina 67, 72
Camelina sativa 72
camphor laurel 118
Canada 45
canola 24, 66, 67, 74
capsicum 30
carbohydrate 11, 23, 24, 54
carbon balance 77
carbon dioxide 37, 38
carbon storage 155
carbon trading 116
cardamom 8
caribbean pine 150
carob 12
carpets 65
carrot 8, 30
cashew 8
cassava 8, 13, 30, 121, 130, 139
Cassia 67
castor oil 24, 67, 74
casuarina 67, 72
cats 129
cauliflower 8
celery 8
cell wall 24
cellulose 24, 56
cellulosic biomass 86
Centre for International Forestry
Research 34
cereal 5, 9, 45, 55
cereal breeding 32
Cerrado 84, 119
CGIAR 33, 34
chapatti 11
charcoal wood 23
chemical conversion 60
chemical feedstocks 51, 53
cherry 8, 54
chestnut 8
chickpea 12, 30, 127
chicory 8
Chikusichloa 28
China 2, 19
Cinnamomum camphor 118
cinnamon 8
CIP 34
Cissus 133
Cissus antarctica 27
citrus 12
climate change 37, 40, 109
clover 8
cloves 8
clubmosses 141
CO2 37
coal 47
coastal fontainea 94
coconut 8, 24, 99
Cocus nucifera 99
coffee 5, 8
common bean 130
competition for land 121
competition from weeds 98
composition of plants 23
Conifers 141
conservation genetics 96
Consortium for the Barcode of Life 97
Consultative Group on International
Agricultural Research 33, 34
cooking requirements 17
copra 8
co-product 66
Corymbia variegata 98
cosmetics 5
cotton 5, 130
cowpea 30
cows 13, 86, 127
critically endangered 94
croissant 11
crop residues 86, 120
crumpets 11
cryopreservation 106
cucumber 8
Cucurbita pepo 130
currants 8
custard apple 8
cut flowers 5
Page 177
Cycads 141
danish 11
dates 8
Davidsonia 135
Davidsonia jerseyana 136
Davidsonia johnsonii 136
desertification 36
diesel 62
Diesel tree 67
dietary fibre 24
dill 8
2, 5-dimethylfuran 60
dimethylfuran 62
Dioscorea 13
Dioscorea rotundata 130
diversity within species 95
DMF 60
DNA analysis 29, 96
DNA banks 25, 29, 31, 96, 103, 104
DNA fingerprinting 151
DNA sequencing 80, 141
DNA sequencing technology 79
DNA technology 32
dogs 129
domestication 125, 132, 140
ecosystem services 101
eggs 9, 14
El Nino 46
elderberry 8
electricity 5, 53
electricity generation 50
Eluesine corocana 10
endangered 94
energy crops 160
energy resources 47
energycane 69
English muffin 11
environmental pollutants 98
environmental sustainability 158
enzymes 59
erucic acid 12
ethanol 5, 62, 63
eucalypt 67, 71, 73, 149
eucalyptus 59
eudicots 95
Europe 44
evolutionary processes 97
ex situ 25
extinct 94
extinct in the wild 94
Faba bean 12, 30
fast pyrolysis 60
fats 24
fatty acids 65
fennel 8
fermentation 62
ferns 141
Fertile Crescent 1, 15, 126, 127
fertilizer 51
ferulic acid 56
fibre 5
fig 8
fires 112
firewood 5
first generation 68, 75
first generation technology 63
fish 14, 19
Fisher-Tropsch 62
flax 130, 134
flowering plants 7, 95, 141
fodder 5
folate 35
Fontainea oraria 94
food 5
food and energy prices 117
food chain 91
food consumption 21, 22
food crops 159
food deficiencies 36
food demand 87, 89
food from animals 13
food ingredients 66
food labelling 19
food miles 19
food prices 34, 81
food processing 150, 152
food production 7
food security 161
food supply 89
forestry 119
fossil fuels 47
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fragrance 17
fructans 55
fruit 5, 8, 9, 12
fuel 5
fuel wood 23
garden plants 5
garlic 8
gas 47
gasification 60
gasoline 62
gene pool 25
genetic code 80
genetic resources 24
genomics 31, 154
geothermal 50
geothermal energy 50
germplasm 30
Giant cane 67
ginger 8
Ginkgo 141
Global Crop Diversity Trust 104
Global Seed Vault 104
global temperature 39, 40
glucose 23, 63
glucosinolates 12
Gnetales 141
goat 13, 127
gooseberries 8
Gossypium 130
Gossypium arboretum 130
Gossypium barbadense 130
Gossypium herbaceum 130
Gossypium hirsutum 130
grain legumes 11
grape 8, 12, 13, 27, 30, 130
grazing 98
green revolution 32, 88, 143
greenhouse 110
greenhouse gas balance 117
greenhouse gas emissions 53, 162
greenhouse gases 5, 38
gymnosperm 142
haricot beans 12
harvest index 32, 66
Hawaii 99
heat stable amylase 55
Helianthus annuus 130, 132
hemp 5
herbaria 103
heterosis 149
Hicksbeachia pinnatifolia 135
higher level diversity 95
Higher plants 141
HMF 60
hops 8
Hordeum spontaneum 15, 130
Hordeum vulgare 10, 130
hornworts 141
Horsetails 141
human diets 9, 161
human energy consumption 48
human food preferences 14
human population 19, 34
hybrid plants 32
hybrid poplars 71
hybrid vigour 149
hybrids 29
hydro 50
hydrogen 51
hydrological impact 117
5-hydroxymethylfurfural 60
Hygroryza 28
ICARDA 34, 126
in situ 25
in situ conservation 106
India 2, 19
Indica 131
International Center for Agricultural
Research in the Dry Areas 34, 126
International Centre for Agricultural
Research in the Semi-Arid Dry
Tropics 34
International Centre for Tropical
Agriculture 34
International Centre for Wheat and
Maize Improvement 34
International Food Policy Research
Institute 34
Page 179
International Potato Research Centre 34
International Rice Research Institute 34
International Union for Conservation of
Nature and Natural Resources 93
Internet 156
IUCN Red List 93
Japan 115
Japonica 131
Jarvonica 131
jatropha 67, 74, 121
Jatropha curcas 74
Jerusalem artichoke 8
jet fuel 62
Jojoba 67
kava 8
kidney beans 12
Lagenaria siceraria 126
land availability 82
land clearing 106
land use 119
lantana 99
Lantana camara 99
LCA 116
leek 8
Leersia 28
lemon 8
lentil 12, 30, 127
lettuce 8
life cycle assessment 86
lignin 24, 56, 61
lillipilly 8
Lima bean 130, 133, 134
lime 8
Linum angustifolium 130
Linum usitatissimum 130, 134
liverworts 141
living collections 25, 103
living standards 2
loss of plant diversity 109
lucerne 8
lupin 12, 30
Luziola 28
lychee 8
Lycophytes 141
macadamia 8, 25, 26
Macadamia integrifolia 134
Macadamia tetraphyla 134
magnolids 95
mahogany 103
maize 8, 9, 10, 14, 16, 30, 62, 66, 67,
121, 130, 159
Maltebrunia 28
mango 8
Manihot esculenta 130
maple sugar 8
Mayan society 147
meat 3, 9, 34
mechanized harvesting 70
medicine 5
melaleuca 73
melon 8
Meso-America 16
2-methyl-1-butanol 63
3-methyl-1-butanol 63
Mexico 85, 99
milk 9
millet 8, 10, 30
Miscanthus 67, 70, 116, 139
Miscanthus X giganteus 70
modern cultivars 132
molasses 69
monocotyledons 58, 95
mosses 141
mulberries 8
multi-purpose crops 85, 155
mung bean 12
Musa 130
Musa acuminata 130
Musa balbisiana 130
mustard 8
mutation breeding 31
N use efficiency 66
N2O 38
naan 11
nanotechnology 80
natural gas 48
nature conservation 123
new technology 122
Page 180
Plant Resources for Food, Fuel and Conservation
newspaper 59
nitrogen fixation 11
nitrous oxide 38
non food uses 23
non structural carbohydrates 54, 55
non-cellulosic polysaccharides 24
noodles 11
North America 44
nuclear power 48
nutmeg 8
nutrient run-off 117
nutritional value 33
oat 10, 30
obesity 21, 36
oceans (waves and tides) 50
oil 11, 47, 61
oil consumption 48, 49
oil palm 12, 24, 67
oil prices 82, 117
oilcrops 72
oilseed rape 8
oilseeds 5, 9, 11, 12
Olea europaea 130
olive 8, 24, 67, 130
onion 8, 30
orange 8
orchids 105
ornamentals 105
Oryza 28
Oryza barthii 130
Oryza glaberrima 10, 130, 131
Oryza rufipogon 130, 131
Oryza sativa 10, 27, 130, 131
palm oil 8, 74
pan bread 11
Panicum virgatum 70
papaw 8
paper 5, 23
Paraserianthes falcataria 79
paratha 11
parsley 8
passionfruit 8
pasta 11
pasture 5, 8, 120
p-coumeric acid 56
pea 8, 12, 30, 127
peaches 54
peanut 12, 24, 30, 130, 153
peanut (groundnut) 8
pear 8, 54
pecan 8
Pennisetum glaucum 10
pepper 8
per capita consumption 34
perfumes 5
pests and diseases 98
PHA 65
Phaseolus 130
Phaseolus lunatus 130, 134
Phaseolus vulgaris 130
2-phenylethanol 63
photosynthesis 41, 47
pig 13, 127
pigeon pea 12, 30
pine 59, 67, 139
pineapple 8
pinto bean 12
Pinus caribaea 150
Pinus elliottii 139, 150
pipelines 77
pistachio 8
pita 11
pizza crust 11
PLA 65
plant breeders 46, 149
plant carbohydrates 57
plant collectors 101
plant diversity 97, 98, 101, 113
plant domestication 2
plant genomics 151
plastic 66
plum 8, 54
policies 116
pollen storage 104
Polyhydroxyalkanoate 65
Polylactic acid 65
polysaccharides 24
polyunsaturated oil 72
Pongamia 140
Pongamia pinnata 74
pongamia tree 67, 74
poori 11
Page 181
poplar 59, 67, 71, 139
population 2
population control 161
population growth 20, 118
pork 19
Porteresia 28
post harvest spoilage 152
Potamophila 28
Potamophila parviflora 27
potato 8, 13, 30, 121, 130, 139, 159
poultry 19
pre-treatments 59
pretzels 11
private plant collections 101
Prosphytochloa 28
protein 11, 12, 24
public parks 103
pulses 5, 9, 11, 12, 127
pumpkin 8
pyrolysis oil 60
rainforests 123, 104
raisin bread 11
rapeseed 121
rare plants 101
rare species 96, 101
raspberries 8
relocation of species 112
renewable energy 50
renewable energy targets 116
Rhynchoryza 28
rice 8, 9, 10, 27, 28, 30, 45, 59, 67, 121,
130, 159
Ricinus communis 74
rising sea levels 39
roots 9, 13
roti 11
round wood 23
rubber 65
ruminant animals 86
rye 10, 30, 121
Saccharum 130
Saccharum officinarum 130, 138
Saccharum robustum 138
Saccharum spontaneum 130
safflower 24, 67
saffron 8
sago 8
sake 13
salinity 36
Salix 71
sandwich buns 11
sarsaparilla 8
sawn wood 23
sea water 75
Secale cereale 10
second generation technology 63, 79
seed banks 25, 104
sheep 13, 86, 127
slash pine 150
small populations 97
soil nutrients 32
soils 83
Solanum species 130
Solanum tuberosum 130
solar power 48
sorghum 8, 9, 10, 27, 29, 30, 45, 67, 68,
121, 130, 159
Sorghum bicolor 10, 130
South America 44
soybean 8, 12, 24, 30, 67, 121
species diversity 91
squash 130
staple crops 159
starch 23, 55
steamed breads 11
strawberries 8
structural carbohydrates 56
sucrose 23, 55
sugar 5, 9, 13, 54, 59
sugar alcohols 57
sugar beet 23, 67, 121
sugarcane 8, 13, 23, 59, 64, 67, 68, 69,
119, 121, 130
sunflower 8, 12, 24, 66, 67, 130, 132
sweet potato 8, 30, 139
sweet sorghum 138
switchgrass 67, 70, 139
syngas 60
tamarind 12
targeted mutagenesis 79
taste 14
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Plant Resources for Food, Fuel and Conservation
tax 116
tea 5, 8
tea tree 73
thermochemical conversion 60
tissue culture 105
tomato 8, 30
tortillas 11
toxic plants 134
traditional village garden 102
transport 49
Tree crops 71
triglycerides 65
Triticale 30
Triticum aestivum 10, 130
Triticum durum 10
Triticum monococum 130
Triticum speltoides 130
Triticum tauschii 130
trypsin 12
tubers 8, 9, 13
tumeric 8
turf grass 5
udon noodles 11
urbanization 34
vanilla 8
vegetables 5, 8, 9, 12
vetches 12
Vigna angularis 133
vitamins 35
Vitis 133
Vitis vinifera 130
vulnerable 94
walnut 8
water use efficiency 66, 121
weeds 92, 99, 118
Western Australia 84
wheat 8, 9, 10, 18, 30, 45, 59, 67, 121,
126, 130, 159
white cinnamon 8
wild barley 15, 110
wild crop relatives 42
wild grape 26
wild populations 132
wild rice 27
wild wolf 129
wilderness 111
willow 59, 67, 71, 116, 139
wind 48
wind power 50
wine 5, 13
wood 71
World Agroforestry Centre 34
World Meteorological Organization 41
world population 20
xyloglucan 56
yam 8, 13, 30, 130
Zea mays 10, 130
Zea mays ssp. Parviglumis 130
Zizania 27, 28
Zizaniopsis 28
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