Environmental Engineering Reference
In-Depth Information
proposed a budget of $450 billion over 20 years
(Pearce 1992f).
Although obscured by the current controversy
and lost in the complexity of the attempts to
define the issue of desertification more accurately,
two questions remain of supreme importance to
the areas suffering land degradation. Can
desertification be prevented? Can the
desertification which has already happened be
reversed? In the past, the answer to both has
always been a qualified yes (see Table 3.3) and
seems likely to remain so, although some
researchers take a more pessimistic view (e.g.
Nelson 1990). In theory, society could work with
the environment by developing a good
understanding of environmental relationships in
the threatened areas or by assessing the capability
of the land to support certain activities, and by
working within the constraints that these would
provide. In practice, non-environmental
elements—such as politics and economics—may
prevent the most ecologically appropriate use of
the land. A typical response to the variable
precipitation, in areas prone to desertification,
is to consider the good years as normal and to
extend production into marginal areas at that
time (Riefler 1978). The stage is then set for
progressive desertification when the bad years
return. Experience in the United States has shown
that this can be prevented by good land-use
planning, which includes not only consideration
of the best use of the land, but also the carrying
capacity of that land under a particular use
(Sanders 1986). To be effective in an area such
as Africa, this would involve restrictions on
grazing and cultivation in many regions, but not
only that. Estimates of the carrying capacity of
the land would have to be based on conditions
in the worst years rather than in the good or even
normal years (Kellogg and Schneider 1977;
Mackenzie 1987b). Such actions would
undoubtedly bring some improvement to the
situation, but the transition between the old and
new systems might well be highly traumatic for
the inhabitants of the area. Stewart and Tiessen
(1990), for example, point out that in the Sahel
cattle are a form of crop insurance. When the
crops fail, farmers plan to survive by selling some
of their cattle. Any attempt to limit herds, and
prevent overgrazing, must therefore be
accompanied by a suitable replacement for this
traditional safety net. Without it the pastoralists
would lose the advantages of larger flocks and
herds in the good years. Some of the cultivators
might have to allow arable land to revert to
pasture—or reduce cash-cropping and return to
subsistence agriculture—and members of both
groups might have to give up their rural life-style
and become urbanized.
As with the other elements associated with
land degradation, the widely accepted
relationship that linked growing numbers of
livestock to overgrazing and the eventual onset
of desertification, has been questioned (Nelson
1990). This in turn has led to a reassessment of
the methods by which desertification in pastoral
areas can be prevented. Traditional herding
techniques involving nomadism and the
acceptance of fluctuating herd sizes seem
particularly suited to the unpredictable
environment of an area such as the Sahel. The
nomadic herdsmen of that region may in fact be
better managers of the land than the farmers in
the wetter areas to the south (Warren and Agnew
1988; Pearce 1992f). They may also know more
about dealing with pastoral land-use problems
than they are given credit for by scientists from
the developed nations. Pearce (1992f) has
concluded that there is no evidence that nomadic
herdsmen in places like the Sahel actually destroy
their pastures. They represent the best way to
use land in an area where there is no natural
ecological equilibrium, only constant flux. That
situation may apply only as long as the flux
remains within certain established limits. Too
much change in one direction, as occurs during
major drought episodes, without concomitant
change in herding methods could still encourage
desertification. Although the links between herd
size, overgrazing and land degradation are
considered less firm than was once thought, they
have not yet been disproved, and it does not
follow that they are entirely absent. In attempts
to deal with desertification in pastoral areas, such
