Hudson Briefing Paper
May 1996 Number 190
(The following is the text from Hudson Briefing Paper, #190. The full paper
is supposed to be accessible through the Worldwide Web at
http://www.hudson.org/hudson, or can be ordered for $1.00 per copy from
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Farming to Sustain the Environment
by Dennis Avery and Alex Avery
Humanity has worried about the sustainability of its farming ever since the
first Middle Eastern farmer found out -- the hard way -- that farming without
fertilizers depletes soil nutrients. The sustainability concern was
reinforced when the famous Hanging Gardens of Babylon were ruined by
salinization, and as the soils of the Mediterranean Basin were seriously
degraded by poor farming methods and overgrazing in ancient times.
Recently, sustainability concerns have taken on a new urgency as population
growth has forced the world to look farther into the future and evaluate
sustainability on a larger scale and over a much longer time frame.
Sustainability has thus become the new mantra in farm policy circles. It is
the latest buzzword, the focus of entire conferences. It has become
ubiquitous in agricultural research grants.
Environmentalists have discovered that the specter of “unsustainability” is
a powerful weapon in their attacks on mainstream farming practices.
But what exactly is “sustainability?” What are its measures? How far from
sustainability are we? If current farming practices are not sustainable,
what needs changing for agriculture to become more or fully sustainable?
Without a clear definition of this concept, constructive debate and
comparisons will be impossible -- and positive change may be impossible as
Most of us can agree on a broad definition of agricultural sustainability:
Sustainable farming is the ability to produce adequate food from farming
practices that can be continued well into the future without compromising the
underlying resource base.
Beyond this loose definition, however, there is considerable debate as to
what comprises sustainable agricultural practice and policy.
This paper will explore several commonly held views of sustainable
agriculture and their associated policy agendas in a global perspective. It
will try to define what is essential for long-term farming sustainability
without extraneous societal goals.
This paper will also emphasize that the large increase in world food needs
over the next 50 years will amplify the consequences of any policies and
practices which lower farm productivity and thus should be carefully
considered when evaluating even moderate-sounding “sustainable agriculture”
Finally, it will conclude that we are very close to a truly sustainable
agriculture in much of the world today, and rapidly getting closer through
What Are the Main Sustainability Issues?
The single greatest challenge for global agricultural sustainability is to
save the world’s remaining wildlands and natural areas from being plowed for
food. The world depends on the integrity of local ecosystems, climates, and
water cycles. Crucial in maintaining that integrity is the global
conservation of forests and other wildlands, as well as their wild plant and
animal species. Most of this conservation responsibility falls on
agriculture’s shoulders, since agriculture dominates world land use
The second biggest challenge is to ensure adequate funding for agricultural
research at this critical moment of world population growth and rising
affluence. We must be able to triple the productivity of the world’s
agriculture over the short span of fifty years to meet the needs of a larger
and richer world population. Current levels of productivity and knowledge
cannot sustainably do the job.
The third major sustainability issue is soil erosion. The ancient enemy,
erosion is still a significant problem in key parts of the globe, especially
the tropics. Getting the knowledge and capital that’s needed to implement
established solutions more broadly, and developing new techniques and
practices for regions where current solutions won’t work, must be a global
concern. The current solutions include no-till, mulch cropping and other
soil conservation practices, along with farming the best and safest farmland
to its fullest potential -- wherever it occurs.
Monocropping, pesticide use, and finite resource depletion dominate much of
the sustainablity debate. We will look carefully at the rationality and
long-term sustainability of these practices.
Environmental quality issues, such as salinization, soil compaction,
depletion of soil organic matter, surface water nitrification, and many
others follow behind these major concerns. Some of these problems pose
direct threats to future production; others affect future production only
indirectly or slightly.
Finally, beyond these physical issues, we will discuss the ancillary
societal and institutional concerns including relative farm size, rural
depopulation, government market intervention, etc.
Our discussion will assume adequate rewards for farmers, since an
increasingly affluent world will surely spend what is required to acquire its
This paper will also assume realistic competition among farmers, with the
understanding that farming is an economic enterprise and as such will
structure itself for its fundamental purpose and realities within societies’
Sustaining and Sustainable
Any discussion of agricultural sustainability must begin with the needs that
agriculture must meet. To be sustainable, an agriculture must first be
sustaining. Agriculture’s fundamental purpose is supplying virtually all our
food and fiber. There is no visible, practicable substitute for production
agriculture in this role.
We must also realize the scale of agriculture needed to meet current and
future demand. Agriculture already uses a third of the earth’s land area.
Feeding and clothing a projected world peak population of 10 billion will
require a near tripling of the world’s agricultural output. (see World Food
Demand: 2050 of this paper)
This is the context for our discussion of agricultural sustainability.
Saving Wildlife and Wildlands
The leading threat to wildlife is the potential loss of habitat to low-yield
farming. Agriculture dominates the world’s land use; already, 1/3 of the
earth’s land surface is in agriculture and 1/3 is in forest as “left over”
from farming. Only by investing in sound, yield-increasing technology and
practices will we prevent the loss of the remaining wildlands and creatures.
Wildlife and wildlands have major importance in our lives. The overwhelming
reason for preserving them is for our quality of life. Hopefully there is no
debate that the wild places and creatures of this earth contribute enormously
to the condition of humanity. A world without natural places for
contemplation and perspective, without wild creatures to remind us of our
place on this earth and for pure aesthetic beauty would be sadly diminished.
Because we have the capability to save the wild habitat and animals, we also
have that responsibility. It would be arrogant and foolish to ignore it.
However, under a strict agricultural sustainability criteria there are two
other major reasons for preserving the world’s remaining wildlife and
-- First, forests and other non-agricultural areas are inextricably linked
to the existence and maintenance of global climate patterns essential to
current and future world food production.
-- Second, they are urgently needed as a reservoir of genes and biodiversity
for use in biotechnology -- necessary to enhance and ensure the
sustainability of our agricultural systems. A healthy, diverse and dynamic
pool of wild genes is essential for a truly sustainable agricultural system.
Our crop and livestock breeders must keep pace with the increasing pressures
on agricultural resources. As pests and disease organisms continue to adapt,
farmers will need new crop and livestock genetics to minimize the damage they
Wild genes are one of our biggest assets in meeting this challenge. They
have been made directly useful by the new tools of genetic engineering, the
most powerful crop and livestock improvement tools in history. Researchers
are no longer confined to the genes from an organism’s close relatives. The
entire spectrum of genes from all organisms now has the potential for crop
and livestock improvement and, therefore, real technological value. Without
a broad pool of natural genes to draw from, the benefits of these tools would
Fortunately, genetic engineering techniques will enhance our capacity to
continue the rising yield and productivity trends which have protected
wildlife habitats from conversion to agriculture over the past four decades.
The Organic Danger
Relying on seemingly “benign” organic and other lower yielding agricultural
practices has been the sustainability solution offered by many, especially by
environmental organizations. However, there is considerable reason to
question the sustainability of adopting these systems on any large scale.
It endangers the environment to let fears of pesticide and fertilizer
impacts push us toward lower yielding alternatives, which create a far
greater threat from the plow to the ecosystems and wild creatures. Despite
their claims of comparable yields, organic agriculture’s yields per acre are
sharply lower than mainstream yields when all of the extra acres needed in
organic production are included. Besides the acres involved directly in crop
production, organic systems need additional pasture acres for animal manure,
cropland acres for “green manure,” or cropland in non-yielding fallow
Because they need more land to produce a given amount of food, adopting
these systems globally would require converting large tracts of forests and
other “suitable” wildlands to agriculture. Estimates of the land area
necessary to meet demand in 2050 using strictly organic principles range as
high as 25-35 million square miles worldwide instead of the current 5.8
million square miles now in crop production.
Considering the possible changes to local, regional, and global climates and
the inevitable decrease in biodiversity, the sustainability of these
approaches is seriously in doubt. Even their rationality is highly
The Best and Safest Acres: An Environmental Priority
There is another reason related to wildlife and biodiversity for containing
our agriculture to the land it now occupies. The best agricultural land also
tends to have the least biodiversity. Michael Huston, an ecologist at the
Oakridge National Laboratory and author of Biological Diversity, reports that
with few exceptions, biodiversity decreases as soil fertility increases.
The harsher lands have fewer resources and competition among species is
higher, leading to increased diversity. Figure 1. illustrates that America’s
midwest and other areas with high soil fertility have relatively low numbers
of exclusive plant species (one measure of biodiversity), with many states
having none (Kansas, Iowa, Indiana, Ohio). States with larger areas of poor
soils and/ or low precipitation have the highest number of unique and
exclusive plant species (i.e. California - 1517, Texas - 379, and Florida -
What this really means is that there very little direct conflict between
feeding the world and keeping the remaining wildlife as we triple world food
output -- IF we continue to raise yields as we have for the past half century
and thus contain our farming to the land currently in production.
Show figure from Huston, page 305
and soil fertility/biodiversity curve.
Another factor often overlooked in preserving wildlife is the higher
productivity of the best and best-serviced farmland (i.e. serviced by
efficient infrastructure). The difference in yields between good,
well-serviced farmland and marginal farmland can be 10 fold or better. (Corn
yields in West Africa currently average 0.7 tons per hectare, while the U.S.
average is over 8 tons and rising, even though both sets of farmers have
access to high-yielding hybrid seeds.) Bottom line: it takes many more
low-yielding acres to match the output of one good acre.
North America has a significant share of the world’s good farmland and a
relatively sparse population. Asia is densely populated and short of
additional cropland for expansion. By the middle of the next century, Asia
will have 50 percent of the world’s population, yet only 31 percent of the
world’s arable land and 23 percent of its pasture. China will be even worse
off, with 25 percent of the world’s population and only 7 percent of the
world’s arable land.
Liberalizing the international farm trade rules would allow the world’s best
farmland to produce the crops its climate and soils are most suited for,
maximizing yields and minimizing the environmental impacts of food
production. Asia could concentrate on developing its lucrative manufacturing
and industrial sectors to earn foreign exchange, making up for its lack of
productive land resources with purchases on the world market just as the
Japanese currently do. This does not mean wasting Asia’s good cropland or
driving any of its farmers out of business. It is rather a question of where
we invest to expand world food output. The alternative is to convert forests
to marginal agricultural land, with a very limited return on the capital
Unfortunately, the world’s current farm trade rules still favor local
politics over comparative advantage and sustainability. In fact, The General
Agreement on Tariffs and Trade (GATT), the world’s most far-reaching free
trade agreement, mandates that comparative advantage be allowed to work in
every sector except agriculture. (Agricultural products are almost entirely
excluded from the GATT’s open-trade rules.)
Utilizing the world’s most productive farmland to its fullest extent,
wherever it occurs, should be a global environmental priority. Hardly any
more low-yielding acres should be brought into production.
Sustaining with Agricultural Research
Agricultural research is the most important sustainability component under
humanity’s direct control. Without the yield gains from agricultural
research, we would not have been able to more than double the output of our
farms over the last fifty years while farming the same amount of land.
Instead, we would have had to more than double the land area plowed to keep
pace with population growth and lower yields from the poorer land brought
into production. Virtually all of the world’s good farmland is already being
farmed. Thus, almost any new land brought under the plow will be of marginal
agricultural quality and crop yields will be lower as well. Ten million
square miles of wildlife habitat is a reasonable estimate of what would be
lost if we returned to 1960 yields.
Adequate research funding is urgent now for two reasons: 1) it can take
years or even decades to develop new research thrusts and bring research
findings into practice, and 2) the next half-century is the most critical
period -- when the wildlife will be saved or lost to food production.
World Food Demand: 2050
The world has 5.8 billion people right now. The peak world population will
be near 10 billion people, reached at or before 2050, with world population
slowly declining thereafter. The world population peak is unlikely to rise
to the 15-20 billion predicted by some doomsayers, mainly because of
affluence and urbanization. Affluent city families tend to have fewer
children than poor rural ones. Populations in most high-income countries
average only 1.7 births per woman (BPW), well below the replacement level of
2.1 BPW. More important, the Third World has come three-quarters of the way
to stability since 1960, dropping from an average of 6.3 BPW to 3.2 BPW
today. The global long-term trend is likely to be a slow population decline
as most countries stabilize at about 1.7 BPW.
Even as affluence cuts birth rates, however, it is raising farm resource
demands. Trade is rapidly spreading affluence throughout the Third World
today, encouraged by the First World’s open trade commitments, such as the
GATT and special trade exemptions for poor countries like America’s
Generalized System of Preferences. As a result of the increased
emerging-country trade opportunities, Asia’s gross domestic product (GDP) has
grown at nearly 10 percent annually for the last decade, and the trend seems
to be spreading to Latin America, Eastern Europe and other regions.
As their economies have boomed, Third World personal incomes have increased,
and a substantial part of the extra income has gone to improve diets. Diet
improvement, especially for high-quality protein foods such as cooking oil,
meat and dairy products, is and will be a major factor in increasing demands
on farm resources. These high-quality diets require more farm resources
(feeds, water, etc.) per calorie to produce than cereals. It takes twice as
many resources for a calorie of cooking oil and three to five times as many
farm resources for a calorie of meat.
Historically, we must remember that the world has never had any voluntarily
vegetarian countries or cultures. Even countries which have been near
vegetarian in the past have rapidly increased their consumption of animal
protein in recent decades. India is currently trying to increase dairy
production by an additional 2 million tons per year, partly by stealing
fodder from its forests and valuable crop residues from its fields. China’s
meat consumption has been rising by at least 10 percent per year for half a
decade and continues to increase by 4 million tons per year. These are
realities which the world must face when considering a sustaining and
Agricultural economists agree that in 2050 the world will have to supply two
and a half to three times as much food and fiber each year as we currently
do. Thus, sustainable farming systems which are 50 percent as productive as
current mainstream practices might ultimately require more than six times the
current land area to meet that expected need due to the declining quality of
the additional land being brought into production. With such a large
impending increase in food demand, any productivity compromise translates
into a major expansion of agricultural lands at the expense of wildlands.
We are not certain that high-yield agriculture can feed everyone and save
all the wildlife habitat. We are certain that low-yield agriculture cannot.
The real myth endangering the world’s environment -- especially its
wildlands -- is that low-yield farming is environmentally sustaining.
Since the world’s agricultural output must nearly triple in the years ahead,
no farming system can protect the environment and wildlife unless it achieves
far higher yields than today’s farms. To the extent we fall short of raising
yields to meet human demands, we will lose more wildlife habitat and wild
species to the plow.
Soil erosion has always been the Achilles heel of agriculture. For 10,000
years, humans have controlled weeds by fallow and tillage: letting the weeds
sprout in unplanted fields so they can be destroyed mechanically, or by
plowing weed seeds too far under the soil for them to sprout. Otherwise, the
weeds compete for nutrients and water and sharply reduce yields. The problem
is that plowing and fallow expose the soil to wind and water erosion. Until
now, the price we had to pay for weed control was gradual loss of our soil
resource, and a very real long-term sustainability problem.
In relative terms, though, we’ve been doing pretty well against soil erosion
for the last 50 years. We’ve doubled total world farm output by tripling the
yields on the best land. When we triple the yields on an acre of land, we
can get the same food tonnage even though we open only one-third as much soil
to wind and water. In that sense, fertilizer should be considered a powerful
soil conservation weapon.
What are some of the other strategies for addressing this sustainability
problem? The most basic soil-conserving strategies are contour plowing and
strip cropping. In contour plowing, the farmer plows his field along the
contour of the slope so that the furrows act like mini-terraces, slowing the
water and, to a certain extent, catching the soil before it leaves the field.
Strip cropping involves planting two or more different crops in “strips.”
As one crop is harvested, the other crop is still growing and the slope is
never totally bare. The steeper the slope, the narrower the strips need to
be. If possible, the strips are situated along the slope contour.
These strategies, however, only mitigate the soil erosion problems which
Mulch crops and cover crops are strategies for limiting soil losses in
fields. As their name implies, a crop is planted which acts as a mulch or
cover for the soil when there isn’t another crop growing, protecting it from
wind and water erosion. (Cover crops are especially effective when combined
with no-till farming systems) There are many benefits to using cover crops.
In addition to the soil savings, many cover crops are legumes which add
nitrogen to the soil. Soil organic matter is increased from the increase in
plant residues. The cover also suppresses weeds, reducing weed control
costs. The residues can insulate the soil and the young plants of the next
crop from cold snaps. Some cover crops can actually yield a grain harvest
before the next crop is planted. For the southern U.S., where half of the
rainfall and a good portion of the solar radiation occurs in the cool season,
cover crops can be very effective.
There are some drawbacks to using cover crops. Cover and mulch crops are
viable only where there is sufficient moisture for both the cover crop and
the primary crop. Planting primary crops into the still-dying cover crop can
subject the new seedlings to disease. The cover also shades the soil, so it
can take longer for the soil to warm in the spring and therefore shortens the
Cover crops have been used for many years, but their use has increased
significantly in recent years, in large part because of the development of
herbicides which allow farmers to fully kill the cover crop so that it won’t
compete with the primary crop. Herbicides have also made possible no-till
and conservation tillage systems.
Tillage means plowing or cultivating the soil. Conservation tillage is
formally defined as any tillage system which leaves at least thirty percent
of the soil covered by crop residue. Conservation tillage controls weeds
with a combination of limited tillage and herbicides. No-till also leaves at
least a 30 percent residue cover on the soil, but goes further than
conservation tillage. No-till disturbs less than ten percent of the surface
area in planting, there is no plowing, disking or cultivating, and no-till
keeps a grass cover on the soil in the winter. No-till relies completely on
herbicides to control weeds.
Conservation tillage and no-till cut soil erosion an additional 65-95% over
traditional tillage practices. Using these appropriate strategies, farmers
should now be able to create soil faster than it is lost through erosion on
the best land, and thus be truly sustainable for this precious resource.
However, the benefits of these tillage systems go far beyond reduced soil
-- Pesticide and fertilizer runoff is greatly reduced (these often enter
surface waters by piggybacking on soil particles).
-- Soil organic matter content is radically increased.
-- Increased soil nutrients, water infiltration and holding capacity are due
to increased organic matter with no-till.
-- Earthworm populations grow significantly. Increases of 100 fold have been
documented. Worms contribute large benefits in soil structure, water
uptake, and water retention. Worm populations can be reduced by as much as
90% by deep and frequent tillage operations.
-- Diversity and abundance of soil organisms is increased, and insect
problems are decreased due to higher numbers of predatory arthropods such as
ground beetles and centipedes.
-- More snow is captured over the winter and evaporation losses are reduced
by plant residues, thus increasing the total soil water available.
-- Disease pressures are actually reduced in some systems, even though the
increased crop residues provide potential overwintering sites for foliar
-- Less soil compaction results from fewer passes with farm machinery and
improved soil structure which is better able to resist compaction forces.
-- Higher average yields are achieved.
-- Fuel use is reduced.
We’re now using conservation tillage on more than 100 million acres in
America -- including most of our higher-risk acres. This revolution is
spreading to Western Europe, Brazil, Australia and even Zimbabwe.
These low-till farming systems are dependent on herbicides -- chemical weed
killers -- for their weed control. Without the chemicals, you would not be
able to see the crop plants in a no-till field; they’d be completely
drowned out by weeds. Some argue that the negative environmental impacts of
herbicide use outweigh the benefits. Although herbicides do appear as
environmental pollutants, mostly in ground and surface waters, the low levels
of contamination do not appear to pose any significant human or ecological
Innovative solutions such as no-till are only the most recent developments
of a constantly changing body of research and technology which enhance the
sustainability of our agriculture. We should encourage the spread and
further development of these established technologies, and assist in the
creation of new systems which can be used more broadly or address unique
The sustainability charge against monocropping is that planting large tracts
of relatively identical plants makes us more vulnerable to catastrophic
disease outbreaks and to overall disease spread and damage. This is a valid
concern. In 1970 there was a devastating outbreak of a fungal disease in
corn due to an overdependence on a single cell line for hybrid corn seed
production. This cell line eliminated the need to remove the corn pollen
tassels (time-consuming hand work which kept many high school kids employed
in the summers, but increased the cost of seed production). Almost 80% of
hybrid corn was produced using this cell line because of the cost savings.
Many growers lost 100% of their crop to the disease and the country paid a
heavy price for the overdependence on a narrow genetic line. Estimates of
crop losses totaled more than $1 billion. But farmers, breeders and seed
companies learned a hard and valuable lesson on the dangers of genetic
uniformity and have applied that knowledge. As an example, in today’s corn
breeding, careful and deliberate shuffling of the genetic base, multiple
pollen sterility factors, and hand detasseling are all used to maintain
genetic diversity and reduce the chance of another catastrophe. Competition
between the seed companies also plays a real part in maintaining genetic
So far, the benefits of using the best seeds and varieties have justified
their intensive use. Any losses incurred because of uniformity have been far
outweighed by higher yields. And the benefits in land not plowed are even
greater. We can maintain adequate genetic breadth in our crops without
turning our fields into low-yield gene museums.
Nor should we forget one of the biggest culprits in continuous monocropping
-- the Federal Government. The structure of the federal farm subsidy
programs has done more to limit crop rotation and cropping diversity than any
other single factor. The Federal Government subsidy programs have required
farmers to maintain a base level of production every year in the commodity
which they grow in order to continue to receive subsidy payments. Production
of crops without attractive price supports has been severely discouraged.
Farmers have had a direct disincentive to crop rotation and diversification
because of the need to maintain their payment base in a commodity. If the
government switched to a policy that did not shackle the farmer to specific
crops, the amount of diversity in the fields would increase dramatically. In
addition to rotating more mainstream crops, farmers would also grow more of
such immediately-available and highly useful alternative crops as canola,
sunflower, meadowfoam, and kenaf. (Farmers would still be limited to whatever
crops grow best in their regions.)
Agricultural Myth -- Newer Crop Varieties Are More Fragile Than Older
Many people both in an out of agriculture have accepted the conventional
perception that newer, higher yielding varieties of crops are more fragile
and less competitive than their older counterparts. The myth is that the
higher yields of the newer varieties are the result of only the fertilizers
and pesticides which protect them. Because of this, some claim we should
return to the older varieties in the interest of sustainability.
However, researchers at the University of Guelph have recently shown that
this is only a myth. They found that the newer varieties were less fragile
and were hardier than their older counterparts -- exactly the opposite of
They conducted a range of studies under field and controlled environment
conditions comparing the yields of nine corn hybrids released between 1959
The 1988 variety averaged 80% higher yields than the 1959 variety. The yield
differences were smallest when growing conditions were best. Yield
differences became much larger when the two varieties were grown under
stressful conditions such as high plant density, low soil moisture, and low
soil nitrogen. The researchers state that “most of the yield improvement
[from 1959 to 1988] in corn appears to be the result of increased stress
tolerance in the new hybrids.” In other words, it is the increased
competitiveness of the newer hybrids which give them their advantage, not the
fertilizers and pesticides. The newer hybrid had higher yields under all
conditions, and vastly higher yields when the plants were stressed.
The use of agricultural pesticides has long been one of the most hotly
debated issues in environmental and agricultural circles. The claim is that
they are unsustainable due to their impact on the environment, wildlife, and
human health, and the development of resistance in the pests. But a careful
and thorough look at these issues fails to support the claims.
In fact, there is tremendous evidence that the chemicals greatly enhance