General Introduction - Integrated Assessment of Health and Sustainability of Agroecosystems - page 3

As most of the world's resources became engaged, the capacity for expansion of
agriculture diminished greatly. Attention shifted to intensification—with the aim of
maximizing productivity per unit of limiting resource. The result was yield-max-
imizing technologies based mainly on fossil energy and fossil-derived chemicals.
The increase in productivity has been so tremendous that Europe, North America,
and several other parts of the world are now confronted with the problem of surplus
production (Treitz and Narain, 1988). Owing to its high yield potential, this “high-
input agriculture” has been rapidly and widely adopted, replacing many traditional
agricultural practices.
Although the world now produces more food per capita than at any other time
in history (Waltner-Toews, 1996), agriculture has failed to satisfy the needs of a big
section of the world's population. The reasons for these are twofold. The first is that
agricultural productivity is highly heterogeneous, following patterns that widely dif-
fer from those of population density (Pimental and Hall, 1984). These differences
are becoming more pronounced since resource-poor regions also tend to have the
highest population growth rate. Second, today's agriculture requires heavy subsi-
dies (Pimental and Hall, 1984), implying that resource-poor regions cannot achieve
expected yields from technologies based on it.
Sub-Saharan Africa (SSA) is one region in the world where food demand is far
higher than the current production capacity (Lal, 1987; Okigbo, 1990; Brown and
Thomas, 1990). This has been attributed to many factors, including resource scarcity,
high population growth rate, and the inability to adopt fully high-input technology.
Three other important constraints are social disruption due to wars and urbaniza-
tion, climatic changes (Okigbo, 1990), and severe environmental degradation.
In SSA, decline in agricultural productivity and land degradation appear to be
locked in a vicious cycle driven by the spiraling population pressure. The high popu-
lation growth rate ensures that demand for agricultural produce remains high, while
more resources are required for purposes other than agriculture. Traditional prac-
tices (e.g., crop rotation, leaving land fallow), which for centuries have been used to
ensure natural resource preservation, have been disrupted (Okigbo, 1990; Yudelman,
1987). Increases in agricultural production have been achieved through increasing
the percentage of land under cultivation to include marginal areas, forest reserves,
and hill slopes. Millions of hectares of land have been cleared for food production, in
most cases without consideration of the ecological consequences. The result of this
process is frightening: land degradation, erosion, silting rivers (Treitz and Narain,
1988), poverty, hunger, and malnutrition.
These and similar outcomes in other parts of the world point to what are now
growing causes of concern: (1) Most of the resources on which today's agriculture
depends are nonrenewable, and (2) agricultural practices are major contributors to
environmental degradation. That many technological innovations—although hav-
ing high yield-maximizing potential—have only served to exacerbate environmental
degradation and carry unacceptable social costs is widely accepted. The most seri-
ous global concern during the twenty-first century will be to feed people without
destroying the natural resource base (Treitz and Narain, 1988). Focus has to turn to
agricultural practices with a potential for maintaining optimum productivity over
time (P.A. Allen and Van Dusen, 1988). Successful management of agricultural