The Need for Sustainable Food Production Systems - Agroecology: The Ecology of Sustainable Food Systems - page 8

WHY CONVENTIONAL AGRICULTURE IS
NOT SUSTAINABLE

grains has trended downward since reaching a peak in
1984. This situation is the result of reduced annual yield
increases combined with continued logarithmic popula-
tion growth.
The ways in which conventional agriculture puts
future productivity at risk are many. Agricultural resources
such as soil, water, and genetic diversity are overdrawn
and degraded, global ecological processes on which
agriculture ultimately depends are altered, human health
suffers, and the social conditions conducive to resource
conservation are weakened and dismantled. In economic
terms, these adverse impacts are called externalized costs .
They are real and serious, but because their consequences
can be temporarily ignored or absorbed by society in gen-
eral, they are excluded from the cost-benefit calculus that
allows conventional agricultural operations to continue to
make economic “sense.”

The practices of conventional agriculture all tend to com-
promise future productivity in favor of high productivity
in the present. Therefore, signs that the conditions nec-
essary to sustain production are being eroded should be
increasingly apparent over time. Today, there is in fact
a growing body of evidence that this erosion is underway.
In the last 15 years, for example, all countries in which
Green Revolution practices were adopted at a large scale
have experienced declines in the annual growth rate of
the agricultural sector. Further, in many areas where
modern practices were instituted for growing grain in the
1960s (improved seeds, monoculture, and fertilizer
application), yields have begun to level off and have even
decreased following the initial spectacular improvements
in yield. Mexico, for example, has seen little change in wheat
yields since 1980, after climbing from about 0.9 tons/ha in
1950 to 4.4 tons in 1982 (Brown, 2001). For the world
as a whole, the rise in land productivity has slowed
markedly since about 1990. In the 40 years before 1990,
world grain yield per hectare rose an average of 2.1% a
year, but between 1900 and 2000, the annual gain was
only 1.1 percent (Brown, 2001). From 2000 to 2003,
global grain reserves shrank alarmingly every year, from
635 million tons (a 121-d supply), to 382 million tons
(a 71-d supply).
Figure 1.4 shows the world's annual per capita grain
production for each year from 1961 to 2004, as calculated
by the Food and Agriculture Organization (FAO) of the
United Nations. These data indicate that after trending
upward for many years, per capita production of cereal

S OIL D EGRADATION

Every year, according to the Food and Agriculture Orga-
nization of the United Nations, between 5 and 7 million
ha of valuable agricultural land are lost to soil degrada-
tion. Other estimates run as high as 10 million ha per
year (e.g., World Congress on Conservation Agriculture,
2001). Degradation of soil can involve salting, waterlog-
ging, compaction, contamination by pesticides, decline
in the quality of soil structure, loss of fertility, and ero-
sion by wind and water. Although all these forms of soil
degradation are severe problems, erosion is the most
widespread. Worldwide, 25,000 million tons of topsoil
are washed away annually (Loftas et al., 1995). Soil is lost
to wind and water erosion at the rate of 5 to 10 tons/ha

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1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001

FIGURE 1.4 Worldwide grain production per capita, 1961 to 2004. Data source : Food and Agricultural Organization, FAOSTAT
database; Worldwatch Institute.