96 ENVIRONMENTAL SCIENCE
vegetal cover brings about marked changes in the local climate of the area. In this way
deforestation and overgrazing etc. bring about changes in rainfall, temperature, wind velocity
etc. These lead to desertification of the area. Desertification often starts as patchy destruction
of productive land. In margins of the zones that are not humid, increased dust particles in
atmosphere lead to desertification and drought. In case droughts continue to occur over a
series of years, even the humid zones are in danger of getting progressively drier. As the
forest diminishes, there is steady rise in the atmospheric temperature and the threat of
desertification becomes imminent.
Causes of Desertification
(1) Man Made
Most of the vegetation in arid and semi-arid regions is threatened with man-made
desertification, a result of excessive, indiscriminate, and archaic land-use practices.
(2) Forest Grazing
Forest grazing is the most serious cause of desertification in arid and semi-arid areas.(3) Shifting cultivation
Shifting cultivation is likewise important in the humid tropics and N.E. Himalayas.(4) Increasing Population
Increasing population pressure has greatly accentuated the adverse impacts of the
above causes.
Position of Desertification
Desertification used to be an issue of considerable concern during the 1970s and 1980.
However, much credence is now not given to the theory of deserts advancing and swallowing
up adjacent savanna landscapes. According to UNEP (1984), in 1983 it was estimated that
17 per cent of the world’s arid, semi-arid and sub-humid regions had suffered some loss of
productivity land degradation resulting from removal of the vegetation cover is a serious
problem throughtout the world’s savannas. Loss of biodiversity is also a serious problem in
savannas. In areas of high domestic grazing pressure, loss of animal biodiversity is aggravated
by a reduction in the number of forage plants available for wildlife.
Concept of Desertification
Desertification is usually defined as an irreversible change in a land resource. Losses
are considered irreversible if recovery would take more than a decade. There forms of
desertification can be identified.
- Loss of economic potential to produce goods and services of direct human-use
value; - Loss of ecological functions necessary to maintain ecosystem processes;
- Loss of biodiversity at the ecosystem, species, or genetic level.
According to Nelson (1988): - A permanent national land monitoring systems is needed to identify emerging and
difficult-to-reverse forms of degradation.