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February 5, 2001


Population - Biodiversity Paradox


The Population/Biodiversity Paradox: Agricultural Efficiency to Save

Anthony J. Trewavas , Fellow of the Royal Society,

Institute of Cell and Molecular Biology, University of Edinburgh,
Edinburgh EH9 3JH, Scotland
'Plant Physiology', EDITOR'S CHOICE January 2001, Vol. 125, pp. 174-179

(See 'Plant Physiology' for many other interesting articles in this issue
including the history of plant gene cloning and memories on

"I know of no time which is lost more thoroughly than that devoted to
arguing on matters of fact with a disputant who has no facts but only very
strong convictions" (Simon, 1996). The comment aptly summarizes a common
experience (including my own) in dealing with technophobes. In one sense,
the genetic manipulation (GM) debate can only be conducted on a level in
which the participants are prepared to enlarge their knowledge and refine
their views accordingly. I consequently have tried in this article to
provide plenty of facts that can be used in discussion with reasonable
participants. My recommendation is to forget those who are not prepared to
modify in any way a prepared (i.e. ideological) position.

My own view of GM is that its primary use to mankind must come initially
in helping to solve fundamental problems that currently present
themselves. These outstanding problems concern population, global warming,
and biodiversity. In a longer version of this article I have tried also to
provide some critique of current trends toward placing ecological views
into agriculture in the hope of generating reasoned discussion. The full
version of this article is on my web site
(www.ed.ac.uk/~ebot40/main.html). All the information below can be
obtained from the referenced articles, although I have not always
indicated where.

Human Population Increase

The United Nations' median population assessments are for 8 billion human
beings by the year 2020 (United Nations, 1998; Pinstrup-Andersen et al.,
1999); these figures are considered the most likely population scenario.
The increase in the population in the next 20 years is expected to be
2 billion (35 the population of the UK; 8 the population of U.S.; 1.3%
per year) and common humanity requires us to ensure adequate nutrition for
these extra people where this is politically feasible. The largest
absolute population increase is estimated to be 1.1 billion in Asia, but
the highest percentage increase is expected in sub-Saharan Africa (80%).
By 2020 more than 50% of the developing world's population will be living
in urban areas instead of the 30% at present. Enormous problems in the
production, distribution, and stability of food products will be generated
and some of these problems require inputs from scientists
(Pinstrup-Andersen et al., 1999). India is a prime example of these likely
problems: 70% to 80% of the population currently farm traditionally and
simply eat all that they grow. By 2025, India will be the most densely
populated country in the world with 1.5 billion people and grossly swollen
cities. Radical changes in Indian agriculture, transport, and food
preservation would seem to be essential to avoid serious nutritional

An annual increase of 1.3% in food production is necessary at the present
time to feed the burgeoning human population, assuming present diets
remain invariant. However, richer populations eat more meat and a doubling
of cereal yields may instead be necessary (Smil, 2000). Annual increases
in cereal production, currently slightly below 1.3%, are predicted to
continue to decline with the most serious food shortages in sub-Saharan
Africa and the Middle East (Dyson, 2000). Most developing countries will
have to lean heavily on imported food as they do now. Approximately
120 out of 160 countries are net importers of food grain (Goklany, 1999).
In turn, a critical requirement is a genuine free trade in food, a
situation that has still not been achieved.

Cropland and population are not uniformly distributed (for example, China
has 7% of the world's arable land and 20%-25% of the world's population),
which will exacerbate future problems. However, predicted rises in crop
yields will not come about without policies that attach high priority to
agricultural research (Alexandratos, 2000; Johnson, 2000), particularly as
many developing countries desire self-sufficiency in food production.
Worldwide funding for agricultural research has declined substantially in
the last 20 years. These problems are exacerbated by diminishing cropland
area due to erosion (for alternative view, see Johnson, 2000); fewer
renewable resources, such as potassium and phosphate; less of, and
consequently more expensive, water (by 2050, it is estimated that one-half
the current worldwide rainfall on land will be used for industry and
agriculture); and a reduced population working the land (Kishore and
Shewmaker, 2000).

Global Warming May Be Global Warning We have stretched current ecosystem
stability to the limit by the destruction of wilderness and fixed carbon
in forests (Tilman, 2000). Continued combustion of coal and oil has
ensured a steady increase in global-warming carbon dioxide levels.
1998 was the warmest year in the last millennium (Crowley, 2000).
Predictions suggest average global temperatures will rise by 2C to 3C by
2100 with, more menacingly, increasing fluctuations in extreme weather
conditions. The world climate is a complex hierarchical system and
analysis and prediction lean heavily on the properties of nonlinearity,
chaos, emergence, feedback, attractors, and self-organization (Stanley,
2000, and references therein). The properties of such systems are often
strongly counterintuitive and at the best can only be based on
probabilities of outcome (Trewavas, 1986). Simple solutions; banner
waving; and using this form of agriculture and not that, which are
proposed by elevating the importance of one factor without reference to
the whole, are likely to produce dangerous or destabilizing results if
acted on fully. Similar nonlinear difficulties attend attempts to
construct world population and food production futures.

Arctic ice core analyses indicate the world climate can cross thresholds
and jump to new stable temperature states in fractions of a decade
(Stanley, 2000). One prediction, with a respectable probability, suggests
cessation of the Gulf Stream with some worrying indications already
reported in the salinity of the deep ocean (Edwards, 1999). The Gulf
Stream maintains average temperatures 5 higher for parts of Europe.
Cessation could be disastrous for those countries affected (including my
own) and would require an agricultural revolution to be instituted in a
few years. Most climate models predict a steady rise in temperature, but
the accuracy of prediction is constrained by lack of detailed information.

Climate change can radically alter rainfall patterns and necessitate
large-scale population movement and primary changes in agriculture. Such
dramatic climate changes are known to have occurred in the past in the
Mediterranean region (for example, abandonment of Troy and Petra) and in
parts of Meso-America in the 6th century A.D.

None of us will be immune to climate-change effects. Elevated ocean levels
resulting from polar ice cap melting will ensure that substantial portions
of land will disappear in low-lying areas, such as Bangladesh and Florida.
Because many large cities are ports, and thus at sea level, increased
flooding from weather extremes are more probable. Increased storm
activity, floods, and long-term droughts (currently three years in Sahel,
Ethiopia) will stretch agricultural resources and threaten local food
production. Such situations may lead to wars. Two to 3 years of breakdown
in monsoon patterns could, for example, cause nuclear exchange in Asia in
arguments over limited food resources. Excessive heat frequently kills
susceptible people and exacerbates respiratory problems. Tropical diseases
such as malaria, the West Nile virus (which visited New York recently),
dengue, and others may move outwards from the tropics as temperatures
climb (Epstein, 2000). All this against a backdrop of variable volcanic
activity known to alter climate patterns, sometimes drastically, with
100 volcanoes around the world capable of doing real damage (Crowley,
2000). Are the present fluctuations in climate the first rumblings of a
breakdown in the feedback circuitry that controls global climate?

Atmospheric carbon dioxide has been increasing for over 100 years. How
much of the increase of this global-warming gas is the direct result of
human activities is still argued, but most have now concluded that it may
be primary. Plowing up yet more wilderness, cutting down forests, or
increasing the area of land under agriculture, thereby increasing the loss
of fixed carbon, is no longer a viable option to solve population food
problems. Furthermore, methane and nitrous oxide are far more damaging to
global warming than carbon dioxide on a mole-for-mole basis. The primary
land-based origin of these gases is anaerobic breakdown of organic
material (particularly in rice paddies), bacterial activities in the
digestive systems of cows, and microbial degradation of agricultural
manure. The U.S. alone generates an estimated 1.3 billion tons of manure
per year (Nagle, 1998). Some rethinking about the drive to organic farming
with its heavy dependence on manure is urgently required.

The Kyoto 1997 Agreement is designed to control worldwide carbon
emissions, although there is skepticism over whether such an agreement can
be policed and achieved. This is not a good time for anyone to consider
abandoning new agricultural technologies such as GM or to turn the clock
back to organic kinds of agriculture.

Maintenance of Biodiversity Technological progress driven by the forces of
technological change, economic growth, and trade is a prime cause of the
problems facing biodiversity. The demands of an increasing human
population are responsible for diversion of water, wilderness destruction,
water quality problems, and accumulations of pesticide residues.
Fragmentation of habitat and loss in turn places major burdens on the
world's forests and terrestrial carbon stores and sinks (Goklany, 1998).
Many species have been placed under stress and there is possibly a higher
rate of species extinction now than previously, although this is
contentious (Simon and Wildavsky, 1984). However, species extinction is
not a necessary adjunct of large human populations. Relatively small
numbers of human beings apparently eliminated mammoths, mastodons, the moa
in New Zealand, the dodo, some 100 species (10%) of plants in Hawaii
(Raven, 1993), and others some 25,000 years ago. Biodiversity has direct
economic value. Pimentel et al. (1997) estimate that biodiversity
contributes $100 billion to the U.S. economy each year.


To conserve the present ecosystems, increased food production must be
limited to the cropland currently in use. Goklany and Sprague (1991) argue
that conserving forests, habitats, and biodiversity by increasing the
efficiency and productivity of land utilization represents a sensible
alternative to sustainable development. This view is powerfully echoed by
Avery (1999), who argues that recourse to less efficient forms of
agriculture, for supposed environmental reasons, will result in plowing up
of yet more wilderness and cutting down forest to feed the increasing
population. However, the best land is almost certainly in agricultural
production; what is left is usually of poor quality and likely to produce
poor yields.

Smil (2000) has indicated that to feed the increase in population expected
by the year 2050 with traditional agriculture (relying as it does for the
basic mineral resources on limited recycling, rain, and biological
nitrogen fixation) would require a 3-fold increase in land put down to
crops. Tropical forests, much of the remaining temperate forests, and most
remaining wilderness consequently would be eliminated with disastrous
effects on atmospheric carbon dioxide. In contrast, feeding the increase
in population could result in extreme damage to ecosystems unless farms
are increasingly seen as small ecosystems with efficient recycling of
minerals and water (Tilman, 2000). Use of renewable micro-energy sources
would be beneficial. However, the Haber-Bosch process of chemical nitrogen
fixation is completely sustainable if solar sources of energy are used.

Although increasing efficiency as a conscious strategy to reduce
environmental impacts is virtually an article of faith for the energy and
materials sector, it has received short shrift for agriculture, forestry,
and other land-based human activities. Many institutions (e.g. green
organizations) and strategies that would conserve species and biodiversity
are conspicuously silent on the need to increase the efficiency of
farmland use (Goklany, 1999). Either they do not understand the policy, or
improving efficiency contradicts their desire to impose some
less-efficient, supposedly ecological solution on agriculture. However,
the consequence of less-efficient agriculture will be the elimination of
wilderness that by any measure of biodiversity far exceeds that of any
kind of farming system. It is the fundamental contradiction in current
environmental arguments (Huber, 1999).

Broad technological progress is also necessary to ensure that affluence is
not synonymous with environmental degradation by helping to create the
technologies and financial resources needed to reduce pollution and
natural resource inputs of consumption across the board. Readier
availability of the necessary technology and fiscal resources will also
help translate the probably universal desire for a cleaner environment
into the political will for public measures.

How Have Technological Improvements in the Past Helped to Preserve
Wilderness? From 1700 to 1993 there was an 11-fold increase in human
population but only a 5.5-fold increase in cropland area (Table I). The
recent improvements in agricultural efficiency brought about by technology
can be seen when comparing the figures from 1961 to 1993 (Table II). An
approximate doubling of the world population has been gained without
massive starvation and with a barely detectable increase in cropland. The
agricultural yield has been a per capita increase, over and above the
increase in population and this must remain as one of the major
technological achievements of the last century.

The total estimated land in use as farmland in 1993 was 4,810 Mha. Much of
this land is rough grazing and of poor soil quality with toxic levels of
aluminum toxicity or low pH. But in total, 36% of the land surface
(excluding polar caps) of the globe is farmed. Farming is the largest land
management system on earth.

If we had frozen technology at 1961 levels, to feed the 6 billion in
2000 we would need to increase the cropland area by 80% (910 Mha), thus
converting 3,550 Mha (an additional 27% of the land surface) to
agricultural uses (Goklany, 1998). This calculation assumes that new lands
would be as productive as present cropland, which is unlikely. The effect
on atmospheric carbon dioxide levels would be disastrous. This putatively
additional farmland exceeds net global loss of forest since 1961 (143 Mha)
and matches the increase in cropland since 1850 (910 Mha). Ausebel (1996)
estimated that wilderness the size of the Amazon basin has been saved by
technological improvements since 1960. Technological improvements in U.S.
agriculture in the last decades have ensured that 80 Mha of farmland has
been returned to wilderness in the U.S. (Huber, 1999). If U.S. agriculture
had instead been frozen at 1910 levels (part organic technology) then it
would need to harvest at least an extra 495 Mha to produce present levels:
more than the present cropland and forest combined.

Many technological developments have given rise to this huge improvement
in yield and thus the saving of wilderness. Without pesticides, 70% of the
world food crop would be lost; even with pesticide use, 42% is destroyed
by insects and fungal damage (Pimentel, 1997). Dispensing with pesticides
would require at least 90% more cropland to maintain present yields.
Yields from irrigated fields are three times those from nonirrigated crops
(Goklany, 1998). In 1960, 139 Mha were irrigated and in 1993 this amount
had increased to 253 Mha. Without irrigation, 220 Mha of extra cropland
would be required to feed the current population. Because application of
fertilizer can increase yields by anywhere from 1.5- to 2-fold, dispensing
with fertilizer would require at least an extra 400 to 600 Mha of cropland
(Smil, 2000). Without these technologies, current food production would
only have been achieved by plowing up an extra 2,000 Mha!

The Downside of Technological Progress: Problems to Be Solved Water has
been diverted for irrigation and industry, but often used wastefully
(Evans, 1998). On average only 45% of irrigation water reaches crops
(Goklany, 1999). In 1997 the Yellow River (China) ran dry for 200 d as a
result of low rainfall and extraction for industry and agriculture. The
Colorado River has not reached the sea for many decades. Eutrophication
and oxygen depletion caused by nitrogen and phosphate leaching from
agricultural lands has resulted from the profligate use of manures and
fertilizers (Smil, 1997). Stable pesticide residues are now much lower
than 30 years ago because the chemical industry ensures that new
pesticides are biologically unstable. Pesticide residues are detected
rarely now in vegetables but it is more common that one or a few residues
can be detected in about one-half of supermarket fruits at levels 100- to
1000-fold below safe recommended limits. However, current procedures for
application are wasteful; only 1% of pesticides is thought to land on

Technological progress to solve the above problems is now necessary to
help ensure that a growing human population does not squeeze out the rest
of nature in the process. Abandoning technology is not the answer;
improving technology to remove the hazards ensures continued benefit to
both mankind and the environment. Integrated crop management systems
(Chrispeels and Sadava, 1994) that optimize the use of pesticides,
minerals, and water offer the best potential for future conventional
agriculture to achieve yield increase without waste.

The vital basics of life are warmth, food security, freedom from disease,
and long life. These basics require a high standard of living and people
are prepared to ignore the environmental impacts of industrialization
until the basics are achieved. Figure 1 indicates the development through
various simple designations of either economic or agricultural structure
from agrarian, industrial, and knowledge-based/service economies now
prevalent in the west. Most damaging environmental effects are associated
with the dominance of heavy industry and large-scale, intensive
agriculture necessary to feed large numbers of people. No form of
agriculture is really environmentally friendly because wilderness is
eliminated and diversity is largely replaced by crop monocultures.

The environmental transition is marked by reductions in emissions such as
sulfur dioxide (i.e. acid rain) from industry. There is also a change in
perception from Mother Earth, providing an abundance of resources, to
Spaceship Earth, with its limitations in provision. The "ultimate
resource," human ingenuity and creativity, is not limited but increases
with population numbers. The concept of Spaceship Earth is drawn from
ecology and may be completely invalid for many natural resources (Simon,

Detection of environmental problems requires advanced technology and
equally advanced technology and wealth to solve the problems. There will
always be problems until individual ambition is satisfied. Economic growth
is commonly blamed for much environmental degradation (Myers, 1997).
Economic growth is not synonymous with quality of life nor an end in
itself, but merely the means by which all individuals advance their
quality of life for themselves and their children. But until the majority
of nations pass through the environmental transition, the overall quality
of the planetary environment is unlikely to improve. No government is
going to agree to rules and conditions that keep their population poor. It
would certainly be hypocritical for rich nations to impose constraint on
others who have not yet achieved the fundamental basics of human
existence. To impose such views would be tantamount to yet another example
of western cultural domination. The misinformation about GM to third-world
countries by current activist groups is just such an example. It is
fortunate that many countries have decided to ignore the propaganda.

Living in harmony with nature, a theme of new-age groups, is a possibility
that disappeared some 5,000 to 10,000 years ago and is not sought by many
in poorer nations. One can, if he or she wishes, live in harmony, but one
will live in poverty if one lives at all. The present wealthy and complex
western societies require large numbers of people to carry out the
necessary highly diverse tasks.

feed all of humanity is over. In the 1970s and 1980s hundreds of millions
of people will starve to death in spite of any crash program embarked upon
now" (Ehrlich, 1968). Like Malthus before him, Ehrlich failed to
appreciate that technological advances negate predictions of gloom. This
time the green revolution intervened. Pressure from population increase,
economic necessity, and the mere statement of the problem usually throws
up solutions. It is notable that critical advances in agricultural
technology, such as agricultural engineering, recognition of mineral
requirements for plant growth, the Haber-Bosch process for ammonia
production, and the green revolution all occurred at times in which food
provision and population problems were pressing. Predictions could have
been made over 100 years ago that burgeoning populations and business in
London would result in the city being knee deep in horse manure (Huber,
1999). It is fortunate that the internal combustion engine intervened
preventing potentially dangerous levels of ammonia toxicity!

The impact of plant breeding improvements and the green revolution rice
and wheats are responsible for much of the recent increased yield (Table
I). Increased yields in India indicate the achievement. In 1950, India
produced 1,635 Kcal per day per person and in 1963 produced 2,069 Kcal per
day per person. The recommended minimum is 2,300 Kcal per day per person
and a recommended average is 2,700 Kcal per day per person to ensure that
virtually all have an adequate diet. In 1950, India produced 6 million
tons of wheat and in 1998 produced 72 million tons. The total land area of
India is 292 Mha and from 1961 to 1998 the population doubled to
1 billion. However, the per capita production from 1961 to 1998 actually
increased by 16% (green revolution crops) and the cropland increased only
from 161 to 170 Mha (Goklany, 1999).

If food production had been kept at 1951 levels (as argued by green
revolution critics such as Shiva [1991]), then the requirement for
cropland by 1998 would have exceeded India's land mass (thereby
eliminating all wilderness and forest) or massive starvation would have
been unnecessarily inflicted. In fact, Indian forest and woodland expanded
by 21% between 1963 and 1999 (Goklany, 1999). The claims by Shiva (1991)
that "the food supplies (in India) are today precariously perched on the
narrow and alien base of the semi-dwarf wheats" have been shown to be
merely polemic and have no scientific basis. The number of land races
dramatically increased with the green revolution; the resistance of green
revolution cereals to rust is much greater than previous varieties (Smale,

Those who constantly agitate for the worldwide introduction of primitive
and frankly "land-guzzling" forms of agriculture must answer this basic
question: How would their form of agriculture have fed the burgeoning
human population? Although recognizing that the world produces a slight
excess of food (about 8% over consumption), without the agricultural
efficiency of western agriculture (the main exporters), most countries of
the world would have experienced serious food shortages and the attendant
human illnesses that go with starvation. Sentiment is no substitute for a
full belly.

All technologies have problems because perfection is not in the human
condition. The answer is to improve technology once difficulties appear;
not, as some would wish, discard technology altogether. Remove the
problems but retain the benefits! The benefits of modern agricultural
technology are well understood; now is the time to reduce the undoubted
side effects from pesticides, soil erosion, nitrogen waste, and
salination. GM technology certainly offers some good solutions.

LITERATURE CITED (has been cut here..... Please visit

2001 American Society of Plant Physiologists