 Drought, an insidious
slow-moving disaster, destroys food crops, kills
human beings and animals and has long-term effects on the
environment. Drought affects population groups in different
ways; understanding and monitoring these differences is
important for preventing famine. Drought may, for example,
result in unusual long-distance movement of herds in search
of grazing and bring them into contact with new diseases.
Irrigation systems may be affected, especially when the
rains fail over successive years. Crop yields are reduced
when irrigation water is lacking or becomes more saline.
Shallow wells, water-holes and small reservoirs dry up or
become contaminated, which affects human and animal health.
The land loses the protection of vegetation and becomes
vulnerable to erosion by wind and - when the rains
finally return - to erosion by water. Erosion in turn
results in loss of soil fertility, which reduces future crop
yields. Increased runoff from eroded soil can bring
flooding, silting up of dams and irrigation works and
further erosion.
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