The Need for Sustainable Food Production Systems - Agroecology: The Ecology of Sustainable Food Systems - page 17

Neither is it possible to bring much more land under
cultivation through irrigation. In most drier regions, water
is already scarce and there is no surplus available for
increased agricultural use. Developing new supplies of
water, moreover, has increasingly severe environmental
consequences. In some areas that rely on groundwater for
irrigation, such as Saudi Arabia and parts of the U.S., the
amount of water available for irrigation will actually
decrease in the future because of overdrafting and increas-
ing nonagricultural demands.
There remain small but significant areas of land that
could be farmed but are now covered by natural vegeta-
tion. Some of this land is in the process of being converted
to agricultural use, but this way of increasing the amount
of cultivated land also has its limits. First, much of this
land is tropical rain forest, the soil of which cannot sup-
port continual agricultural production. Second, this land
is increasingly being recognized for its value to global
biological diversity, the carbon dioxide balance of the
atmosphere, and maintenance of the Earth's climatic pat-
terns. Because of this recognition and the efforts of envi-
ronmental groups, a large proportion of the planet's
remaining wild lands will be off-limits to agricultural
conversion.
Exacerbating the problem of limited arable land is a
trend toward meat-intensive diets worldwide. In the 30
years between 1973 and 2003, the world's population
increased 61%, while at the same time worldwide meat
production increased by more than 133% (FAOSTAT,
2005). The amount of meat produced per person, which
has risen steadily since data on meat production began
being collected in 1961, surpassed the 40 kg/person level
in 2004.
Because the conversion of plant biomass into animal
protein is highly inefficient, a large amount of plant bio-
mass is needed to produce meat. For example, about 43
kg of plant biomass go into creating 1 kg of beef flesh
(Pimentel and Pimentel, 2003). This means that a diet rich
in meat requires much more land (and much larger expen-
ditures of fossil fuel energy) to support than a vegetarian
diet. Already, more corn and soybeans go to fattening
livestock worldwide than to feeding human beings (in the
U.S., seven times more grain is fed to livestock than is
consumed by humans). As people increase both the total
number of calories they consume, and the proportion of
these calories that come from meat, they place increasing
demands on the Earth's limited supply of arable land.

The first part of this challenge for the future defines
the subject of most of this topic; the latter part, touched
on in the final two chapters, will rely to a large extent
on the reconceptualizations of agriculture offered
herein.
Preserving the productivity of agricultural land over
the long term requires sustainable food production.
Sustainability is achieved through alternative agricultural
practices informed by in-depth knowledge of the
ecological processes occurring in farm fields and the
larger contexts of which they are a part. From this foun-
dation we can move towards the social and economic
changes that promote the sustainability of all sectors of
the food system.

W HAT I S S USTAINABILITY ?

Sustainability means different things to different people,
but there is general agreement that it has an ecological
basis. In the most general sense, sustainability is a version
of the concept of sustained yield — the condition of being
able to harvest biomass from a system in perpetuity
because the ability of the system to renew itself or be
renewed is not compromised.
Because “perpetuity” can never be demonstrated in
the present, the proof of sustainability always remains in
the future, out of reach. Thus it is impossible to know for
sure if a particular practice is in fact sustainable or if a
particular set of practices constitutes sustainability. How-
ever, it is possible to demonstrate that a practice is moving
away from sustainability.
Based on our present knowledge, we can suggest that
a sustainable agriculture would, at the very least:

• have minimal negative effects on the environ-

ment and release insignificant amounts of toxic
or damaging substances into the atmosphere,
surface water, or groundwater

• preserve and rebuild soil fertility, prevent soil

erosion, and maintain the soil's ecological
health

• use water in a way that allows aquifers to be

recharged and the water needs of the environ-
ment and people to be met

• rely mainly on resources within the agroecosys-

tem, including nearby communities, by replacing
external inputs with nutrient cycling, better con-
servation, and an expanded base of ecological
knowledge

THE PATH TOWARD SUSTAINABILITY

• work to value and conserve biological diversity,

both in the wild and in domesticated landscapes The only option we are left with is preserving the long-

term productivity of the world's agricultural land while
changing consumption and land use patterns to more
equitably benefit everyone, from farmers to consumers.

• guarantee equality of access to appropriate agri-

cultural practices, knowledge, and technologies
and enable local control of agricultural resources