|
Land degradation is the
reduction , or total loss, of the productivity of soils
caused by changes in their inorganic and organic
constituents and the natural balance between them. Land
degradation is a complex process involving several physical,
chemical and biological factors. Studies have shown that 15%
of the total land area in the world is degraded to varying
degrees. From this area, 55% has been degraded by water
erosion; 28% by wind erosion; and 12% by chemical factors
(salinization, water-logging, etc.). The main causes of this
land degradation are overgrazing, which accounts for 34% of
the degraded area; deforestation, 29%; agricultural
activities, 28%; over-exploitation, 7%; and other
activities, 1%.
Land degradation in arid and
semi-arid regions is known as “desertification”. It is
estimated that about 30% of irrigated land, 47 % of rainfed
cropland, and 73% of rangeland in these areas have been
affected by desertification to varying degrees.
Land
degradation causes many environmental, social and economic
problems. For example, migration from rural to urban areas,
incidence of famines in areas affected by recurrent
droughts, especially in African countries. In addition, land
degradation leads to the loss of stored carbon in the soil
system, with consequent rise in carbon dioxide emissions
into the atmosphere. In other words, there is a close
relationship between the problems of land degradation and
climate change. Furthermore, land degradation leads to
several negative impacts on biodiversity in the affected
areas.
In spite of the different national and
international efforts since the convening of the United
Nations Conference on Desertification in 1977, very modest
progress has been made in curbing land degradation.
AGENDA-21, adopted by the Earth Summit convened in 1992,
emphasized the importance of dealing with land degradation,
in order to achieve sustainable development. In 1994, a
United Nations Convention on Combating Desertification was
formulated. Since then over 140 countries ratified this
convention and started to formulate National Action
Programmes to deal with land degradation.
Egypt has
four main agro-ecological zones : the northern coastal
belts; the Nile Valley and the near-by reclaimed desert
areas; inland areas in the Eastern Desert and Sinai; and the
Western Desert, oases and southern agricultural extension
areas.
The main factors of land degradation in the
northern coastal belts are: degradation of rangelands due to
overgrazing, wind and water erosion, conversion of
rangelands in rainfed croplands; and inappropriate land and
water management and limitation of effective public
participation. In the Nile Valley and reclaimed desert
fringes the land degradation is due to : water-logging,
increase in salinity and alkalinity of soils; excavation of
top soil and urban expansion on cultivated lands, soil
pollution by agrochemicals and effluents from industries and
other sources; and adoption of inappropriate soil and water
practices. Lands in the Eastern Desert and Sinai are
degraded due to: water and wind erosion; inappropriate
management practices; and overgrazing. The main factors of
land degradation in the Western Desert and Oases are:
over-exploitation of soils and ground water resources
through inappropriate cropping patterns; sand encroachment
and movement of sand dunes; inappropriate management
practices of soil and water resources leading to increases
of salinity, alkalinity and pollution; social and economic
constraints.
Many efforts are under way to deal with
land degradation. Several of these efforts have been
supported by international and/or regional organizations.
Example of important major projects include : improvement of
soil properties; improvement of drainage in agricultural
areas; rational use of irrigation; planting salt-tolerant
varieties of crops and plants, etc. Most of these projects
are geared towards improved land use, to promote sustainable
development.
|
