Drought is the result of a deficiency in precipitation. It constitutes a major risk and can have a serious impact in a number of ways:
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climatic (e.g. an increase in temperature, sun or wind);
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hydrological (e.g. a decrease in surface overflow, the drying up of rivers, lakes and springs, groundwater drawdown);
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agronomical (e.g. drying out or loss of crops, including dry-land crops);
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geological (e.g. drying out of soil and an increase in salinity levels).
Roughly speaking, desertification can be considered as a severe case of drought (both in intensity and in duration) which leads to conditions generating landscapes similar to that of a desert. Desertification encompasses a wide range of effects which degrade the vegetation cover and soil, for example:
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raised vegetation cover (tropical forest) is degraded to savanna;
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savanna evolves to a steppe landscape;
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the climate becomes excessively dry.
In order for desertification to occur, two factors appear to be crucial:
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natural physical conditions which are susceptible to desertification;
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intensive human activity exceeding acceptable thresholds.
PREPARED BY CRSTRA - The Centre for Scientific and Technical Research on Arid Regions, Biskra, Algeria & the Editorial Board.