Environmental Engineering Reference
In-Depth Information
Figure 3.3
Variability of precipitation at selected stations in Africa
Source:
Compiled from data in Landsberg (1986)
felt beyond the areas directly affected. Drought
is expected in such areas, but elsewhere it is highly
irregular and, as a result, all the more serious.
Such was the case in 1976 when the normally
humid UK was sufficiently dry that the
government felt it necessary to appoint a Minister
of Drought.
Drought may also have played a significant
role in the historical development of society
through its impact on past civilizations. For
example, changes in wind circulation and
increased aridity in what is now northern Syria
from about 2200 BC are thought to have
destroyed the agricultural base of the
Mesopotamian Subir civilization (Weiss
et al.
1993), and the decay of the Harrapan civilization
in the Indus valley has been linked to the
desiccation of that region after 1800 BC (Calder
1974). In Europe, some 3000 years ago, the
flourishing Mycenaean civilization of southern
Greece went into irreversible decline. The rapidity
and extent of the decline was such that it was
commonly attributed to the invasion of Mycenae
by Greeks from the regions to the north. In 1968,
however, Rhys Carpenter reassessed the available
evidence, and suggested that no invasion had
taken place. Instead, he postulated that drought
followed by starvation, social unrest and
migration led to the downfall of the Mycenaeans.
Climatologists at the University of Wisconsin-
Madison developed Carpenter's theory further,
and concluded that drought was a major
contributory factor in the decay of the civilization
(Bryson
et al.
1974; Bryson and Murray 1977).
As in many cases where a climatic explanation is
invoked to account for major societal changes in
the distant past, the link between the decline of
the Mycenaean civilization and drought is not
considered convincing by some researchers (see
e.g. Parry 1978). The absence of adequate and
appropriate data prevents such hypotheses from
being developed much beyond the speculative
stage.
Modern views of drought vary with time and
place and with the nature of the event itself. It
may be seen as a technological problem, an
