Droughts - Extreme Events: A Physical Reconstruction and Risk Assessment - page 21

vegetation cover. The deep ploughing of drought tolerant native grasses in the
region and replacement with agricultural plants that were not drought tolerant
resulted in the exposure of soils to aeolian erosion (Abbott, 1999). The dust
storms were sufficiently severe to cause dust particles to be lifted to altitudes
where they were incorporated into the jet stream resulting in dust being carried
as far as Europe (Robinson, 1993). The drought also caused the failure of crops
and abandonment of thousands of farms.
The Sahel region of Africa has also experienced several periods of prolonged
drought in recent years (Robinson, 1993). The Sahel region occurs at the south-
ern margin of the Sahara desert where, collectively, approximately 25 million
people live as farmers in the south and nomadic herders in the north. The 1968
drought was a result of a change in the position of the intertropical convergence
zone, or the Equatorial Low, causing a 50% reduction in the average annual rain-
fall. At this time the ITCZ moved two degrees further south than normal, and
exposed the Sahel region to drying winds as the precipitation that would have
normally occurred here was released further south. The 1968--1973 drought was
thefirst drought in the area to receive international attention. Between 50 000
and 250 000 people died, and more than 3.5 million cows perished. Hardest
affected, however, were the children. Many were permanently retarded by dis-
ease, and cases of brain damage were related to malnutrition (Robinson, 1993).
Like the Great Plains drought, the Sahel drought was also exacerbated by
human agricultural practises as natural vegetation was removed. Native shrubs
and trees were cut down for fuel as people switched from kerosene to wood
as their principal source of fuel. Agricultural practices also led to reduced soil
structural integrity and increased surface crusting resulted in increased run-off
and decreased rainfall infiltration to the soil. The environmental impacts of the
drought were as severe as the humanitarian impacts. Expansion of the desert
(desertification) occurred along the grasslands bordering the Sahara desert caus-
ing it to expand about 150 kilometres further south. Similar impacts were also
experienced in a subsequent drought which began in 1983. At this time agri-
cultural practices were still unsustainable and there had been a further 30--40%
increase in population, resulting in even greater environmental strain (Bryant,
1991).
Droughts also affect water and air quality, animals and fish. Air quality is
reduced as dust particles in the air increase. The productivity of ecosystems is
severely reduced due to a lack of water which in turn results in the concentra-
tion of salts and an increase in salinity. Wildfires are also more likely during
such times. All of these result in a loss of aquatic and terrestrial faunal popula-
tions and habitat due to increased vulnerability to disease and pest infestations
(Chapman, 1999).