Environmental Engineering Reference
In-Depth Information
grown up during the years of plenty—quickly
stripped the available vegetation, and exposed
the land to soil erosion. The water holes, and
eventually even the rivers, dried up, and those
animals that had not died of starvation died of
thirst. When the nomads tried to move they
found that it was no longer as easy as it had
once been. The farmers who had formerly
welcomed the pastoralists for the meat and milk
they supplied and for the natural fertilizer from
their animals, no longer wanted herds trampling
fields which, with the aid of irrigation, were
being cropped all year round. Furthermore,
growing peanuts and cotton, and only a little
food for their own use, they had no excess left
for the starving nomads. Eventually, as the
drought continued, the farmers suffered also.
There was insufficient water for the irrigation
systems, the artificial fertilizers that had
replaced the animal product was less effective at
low moisture levels, and yields were reduced
dramatically. In a desperate attempt to maintain
their livelihood, they seeded poorer land, which
was soon destroyed by soil erosion in much the
same way as the overgrazed soil of the north
had been.
The net result of such developments was the
death of millions of animals—probably 5 million
cattle alone—and several hundred thousand
people. The latter numbers would have been
higher, but for the outside aid which provided
for 7 million people at the peak of the drought in
the Sahel between 1968 and 1973 (Glantz 1977).
Similar numbers were involved in Ethiopia
between 1983 and 1985, although accurate
figures are difficult to obtain because of civil war
in the area (Cross 1985b). Drought and locusts
destroyed crops in the northern Ethiopian
provinces of Tigray and Eritrea again in 1987,
and the UN World Food Program estimated that
as many as 3 million inhabitants were put at risk
of starvation and death (Mackenzie 1987a).
Elsewhere—in Kenya, Uganda, Sudan,
Zimbabwe and Mozambique—severe drought
continued into the 1990s. Even in the Sahel,
which had experienced some improvement in the
late 1970s, increasing aridity after 1980 was the
precursor of the more intense drought affecting
the area once again. The death of the animals,
the destruction of the soil and indeed the
destruction of society has meant that all of sub-
Saharan Africa—from Senegal to Somalia—
remains an impoverished region, dependent upon
outside aid and overshadowed by the ever present
potential for disaster the next time the rains fail,
as fail they will.
DROUGHT ON THE GREAT PLAINS
Since all of the nations stricken by drought in
sub-Saharan Africa are under-developed, it might
be considered that lack of economic and
technological development contributed to the
problem. To some extent it did, but it is also quite
clear that economic and technological
advancement is no guarantee against drought.
The net effects may be lessened, but the
environmental processes act in essentially the
same way, whatever the stage of development.
This is well illustrated in the problems faced
by farmers on the Great Plains that make up the
interior of North America (see Figure 3.10).
Stretching from western Texas in the south,
along the flanks of the Rocky Mountains to the
Canadian prairie provinces in the north, they
form an extensive area of temperate grassland
with a semi-arid climate. They owe their aridity
in part to low rainfall, but the situation is
aggravated by the timing of the precipitation,
which falls mainly in the summer months, when
high temperatures cause it to be rapidly
evaporated (see Figure 3.11). Contingent
drought, brought about by the variable and
unpredictable nature of the rainfall, is
characteristic of the area—consecutive years
may have precipitation 50 per cent above
normal or 50 per cent below normal—and this
has had a major effect on the settlement of the
plains. Averages have little real meaning under
such conditions, and agricultural planning is
next to impossible. The tendency for wet or dry
years to run in series introduces further
complexity. Strings of dry years during the
exploration of the western plains in the
