Drought and desertification
Mechanisms of destruction
Lack of water affects health of crops, trees, livestock, humans:
land becomes subject to erosion and flooding; effects are gradual but if not
checked, crops and trees and livestock die, people lose livelihood, are forced
to move, and may starve if aid is not provided: then buildings and
infrastructure are abandoned and decay and cultural artifacts are lost.
Parameters of severity
Rainfall level, rainfall deficit (mm), period of drought; extent
of loss of soil cover, extent of desert climatic zone.
Drought mainly caused by short-term periodic fluctuations in
rainfall level; possibly by long-term climatic changes; desertification caused
by loss of vegetation and subsequent land erosion caused by combination of
drought, overgrazing and poor land management.
Hazard assessment and mapping techniques
Rainfall map indicating areas of desert and semi-desert climatic
conditions; mapping of erosion rates and desertification.
Potential for reducing hazard
Drought is uncontrollable; desertification can be reduced by
improved land management practices, forest management, infiltration dams,
irrigation and range management (control of land use and animal grazing
Onset and warning
Slow onset, period of years, many warnings by rainfall levels,
river, well and reservoir levels, human and animal health indicators. Onset of
severe drought, causes death of livestock, rise in infant mortality, migration.
Elements most at risk
Crops and forests; human and animal health, all economic
activities dependent on continuous water supply; entire human settlements if
drought is prolonged.
Main mitigation strategies
Water rationing; conserving or replacing failing water supply by
watershed management, construction of dams, pipelines or aqueducts; conserving
soil and reducing erosion rates by checking dams, levelling, planting, herd
management; reducing firewood cutting by improved fuel stoves, introduction of
flexible farming and cropping patterns; population control; education and
Construction of check dams, reservoirs, wells, water tanks,
planting and afforestation; changing cropping patterns; introducing water
conservation policies; changing livestock management practices; development of