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of extreme events such as droughts, an influx of immigrants and livestock from other
regions, and restricted access to former grazing lands. Not surprisingly, local percep-
tions and government perceptions did not always coincide, and sometimes they were
radically different (see also
Table 24.1
).
Williams and Balling (
1996
) provided a comprehensive account of the interactions
between desertification and climate, and the two UNEP Atlases of Desertification
included a number of useful case studies from across the desert world (UNEP
1992a
;
UNEP,
1997
). The direct consequences of desertification are now reasonably well-
known. However, in their early stages, they may be hard to discern, except by prescient
and experienced observers, as was the case with the Aral Sea (Glantz,
1999
). The
causes are far more complex and involve a web of interlinked social, economic and
environmental factors, as illustrated in
Figures 24.1
and
24.2
.
24.5 Interactions between biophysical, economic and social factors
Figure 24.1
represents a higher level of complexity than the simple biogeophysical or
albedo model reviewed in
Chapter 23
and illustrates some of the interactions at global
and regional scales between physical, chemical and biological processes involved in
land degradation in drylands. The importance of considering how feedback mech-
anisms operate in different ways at different spatial scales and institutional levels is
illustrated in
Figure 24.2
. One matter that has become increasingly evident over the
past few decades concerns failures of past attempts to control desertification through
a lack of attention to social and economic factors at local and regional scales. Bas-
sett and Crummey (
2003
) provide a wealth of examples from Africa that underline
the importance of taking into account and indeed being willing to learn from local
knowledge and experience. Many attempts to 'combat' desertification have failed
because they were imposed from above and took no notice of local customs and capa-
cities. One example concerns the restriction imposed by governments on traditional
grazing rights, which leads to overgrazing, for which the pastoral nomads are then
blamed. The creation of National Parks without consulting of those most affected -
the people who were previously living in the parks or were accustomed to moving
through themwith their herds - has in a number of instances led to anger and violence,
which is not a good recipe for long term land management (Western,
2002
). Con-
servation measures will seldom work until fundamental issues of poverty alleviation,
food security and health are also dealt with effectively. We return to this question in
the final chapter of this volume (
Chapter 26
).
24.6 Consequences of desertification
In a pioneering study of the global context of desertification in Australia, Mabbutt
(
1978
) defined desertification as 'a change to more desertic conditions', which of
