Look At This
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AFRICA
The severe Sahelian drought that extended from through l969 focused the world's attention on the human aspects of land
degradation and led to the convening of the 1977 United Nations Conference on Desertification. Drought, however, is not the
cause of desertification; man is. The drought served only to place additional stress on the biological resources of the Sahel. If
resource management has been good, little, if any, permanent damage is done by droughts. However, if resource management
has been unwise, a drought accentuates the adverse impact of that management and accelerates land degradation (Weaver and
Albertson, 1940). The latter is what has occurred widely in the Sahel and elsewhere.
All of the usual forms of desertification are present in the arid regions of the African continent and are manifested as serious local
or regional problems (Figure 2). Overgrazing has reduced range productivity virtually everywhere outside the tsetse fly regions, in
north, west, east, and south Africa. Wind and water erosion have devastated landscapes in the cultivated regions and in much of
the rangelands (Rapp, 1974). Shortened fallow periods in the shifting cultivation system south of the Sahara have led to severe
depletion of plant nutrients. Salinization and waterlogging of irrigated land is worst in the Nile Valley and North Africa but also
occurs elsewhere. Mining has left surface scars wherever it is practiced. The environmental degradation continues and shows no
sign of slowing down.
Desertification Characteristics
A number of factors have increased land degradation and the vulnerability of the African arid regions to desertification. Most of
them have had similar effects in Asia and Latin America. They can be grouped in three categories: (1) increased human and
animal population, (2) improved health services, and (3) injudicious use of technology.
Due to the increased sedentary population, pressures on cultivated land led to a shortening of the fallow period in the shifting
cultivation cycle and the extension of cropping into the more precarious drier regions. Crop harvests became less reliable and
more variable as the desert edge was approached. Concurrently, nomadic pastoralists were deprived of some of their best
grazing lands as the cultivators moved in (Delwaulle, 1977). At the same time the rangeland area was contracting, populations of
pastoralists and their livestock were increasing and the provision of improved veterinary services and the lack of a viable
marketing system helped assure that animal numbers would grow rapidly (Widstrand, 1975). The result was inevitable:
overgrazing and accelerated desertification.
Overgrazing inadvertently was made worse, particularly in the Sahel, by the drilling of additional wells that provided drinking water
for livestock throughout the year. Without the rest period that intermittent water supplies previously assured, forage conditions
deteriorated around the wells where water was no longer a limiting factor in livestock survival. Local authorities did not or could
not impose a control system that would allow forage plants to recover from heavy grazing.
A crude estimate of the amount of crop yield reduction that could be attributed to salinization and waterlogging in the Nile Valley
indicates it to be at least 17 percent on 80 to 90 percent of the old irrigated land. In the newly irrigated lands east and west of the
delta, the figure is likely to be a minimum of 25 percent yield reduction. Both problems are serious ones that can become even
more serious in the future if remedial measures are not taken. The situation in Algeria and Tunisia is similar to that in Egypt with
respect to yield reductions.
Solutions to desertification problems in Africa are known-- and in general--can be implemented readily if resources are available
to do so. An exploding population in the developing countries, however, means that land pressures will continue to build.
Reducing livestock numbers in the grazing lands until forage productivity can be improved is very difficult, at best, and introducing
range use controls on communal land is not easy. There is little likelihood that marginal dryfarm lands will be returned to pastoral
use unless production on the better lands is increased enough to offset the loss of cultivated land. While the latter can be done,
progress in that direction is very slow.
Destruction of woody vegetation has been hastened by the ever-increasing need for firewood to meet the demands of the larger
population. The destruction is especially noticeable around the rapidly growing urban centers, where the circle of deforested
lands gets larger every year (Delwaulle, 1973).
While desertification was a long-standing problem even in the absence of droughts, the gradually increasing vulnerability of the
land made the impact of the inevitable droughts worse than ever (Dahl and Hjort, 1979). The factors responsible for that
vulnerability are still operating, desertification continues, and future droughts will have ever-greater damaging effects.
Salt-affected soils are common in Tunisia and Algeria where both surface and well irrigation waters frequently are saline.
Salinization is important in other irrigated areas but on a small scale.
Magnitude of Desertification
About 18 percent of the arid region of Africa is severely desertified, and most of that represented by grazing lands and rain-fed
cropping lands on the south side of the Sahara (Table 3). The other large area that is severely affected is the mountain slopes
and the plains of North Africa. Moderate to high salinity affects about 30 percent of the irrigated land in Egypt (Aboukhaled et al.,
1975).
Wind erosion is dominant in the drier regions and water erosion on the wetter sloping lands. Ethiopia, Kenya, and the Maghreb
countries of Algeria, Morocco, and Tunisia have been subjected to especially serious water erosion, whereas wind erosion has
been most damaging in sub-Saharan West Africa. While good data on the effect of land degradation on crop and livestock yields
are not available, it seems likely that soil fertility losses, alone, have reduced dryland crop yields by 25 to 50 percent in the
severely desertified areas. Animal productivity may well have declined by at least 50 percent nearly everywhere that domestic
livestock are raised. In many areas south of the Sahara, rangeland forage production probably is less than 25 percent of the
potential.
ASIA
Desertification in the arid regions of Asia is characterized by overgrazing of the rangelands of the Middle East and Central Asia,
water erosion of cultivated lands from eastern China to the Mediterranean Sea, and salinization and waterlogging on a large
scale in Iraq, Pakistan, China, and the Soviet Union. Mining (including oil and gas production) has caused severe land damage
wherever it is carried on.
Overgrazing, soil erosion, and salt damage to irrigated land are long-standing problems in the Middle East and Central Asia, as
is water erosion on the rain-fed cultivated lands of India, Pakistan, and the loessial plateau of China. Waterlogging and
salinization are problems centuries old in the lower plain of the Yellow River in China, but are of relatively recent origin in the
Indus Basin of Pakistan and India. Ameliorative measures to reduce land degradation have been undertaken in every country
affected, with varying degrees of success. The problem is an immense one in terms of the area involved and the amount of
degradation that has occurred.
Desertification Characteristics
Man first placed his imprint on the landscapes of Asia thousands of years ago. Historical records make it clear that the
destructive impact of man was already apparent two or three thousand years ago in China and the Middle East. It was then that
the first period of accelerated, man-made erosion began (Dregne, in press). Woodcutting and cultivation of sloping lands were
responsible for most of the land degradation that occurred in the uplands of China and around the Fertile Crescent.
Sedimentation of canals, waterlogging, and salinization combined to raise havoc in the Tigris and Euphrates valleys of
Mesopotamia (Jacobsen and Adams, 1958).
Grazing pressure seems to have become a much greater problem in the past two or three decades than it was before. There has
been an explosion of human and livestock population recently from India (Office of Environmental Planning and Coordination,
1977) to the Middle East (Pearse, 1971). Cultivation has been extended into pastoral lands, wells have been constructed to make
pastures usable throughout the year, and improved transportation facilities have made formerly remote areas accessible to
livestock. As a consequence, cropping has become a high-risk land use in the climatically marginal areas that formerly were the
best grazing lands. At the same time, overgrazing of the remaining range lands is accelerated by the increased concentration of
livestock on drier lands. Destruction of vegetative cover on sandy lands has led to widespread wind erosion, depletion of soil
fertility, and the undertaking of expensive erosion control projects in China, Iran, Saudi Arabia, and elsewhere.
Magnitude of Desertification
Asia has large areas where desertification is so severe that it borders on being classed as very severe desertification, but about
half of the land is only slightly desertified (Table 4). Water erosion is spectacular in the loessial plateau in the middle reaches of
the Yellow River. The eroded silt is sometimes so thick in the river that at Shanhsien, east of Xian, the sediment load has been
measured at 46 percent. The river annually carries 1.3 billion tons of sediment, enough to cover 1,800 square kilometers of land
30 centimeters deep (de Crespigny, 1971). Virtually all of that represents loess eroded from 300,000 square kilometers of
highlands. Efforts are being made to reduce erosion but the problem is so huge that progress is slow. Only the great thickness of
the aeolian deposits has allowed cultivation to be continued on the eroding slopes.
Water erosion also approaches the spectacular on the slopes of the dryland farming areas of western India and northern
Pakistan. Fortunately, the soils there are more resistant to displacement than in loessial material. Nevertheless, the damage--in
the form of reduced yields--is serious nearly everywhere, and it is getting worse.
Salinization and waterlogging are as bad--and as difficult to control--in the irrigated region of southern Iraq as they are anywhere
in the world. Deep fine-textured soils and almost flat topography make it hard to provide drainage that is adequate to maintain a
deep water table and prevent salt accumulation. Techniques of soil and water management that are suitable for conditions in Iraq
have been developed and tested successfully, but the technical problems are less difficult to resolve than the social ones
(Dougrameji and Clor, 1977). Land reclamation is much easier on the more permeable soils of the Indus Valley and Central Asia.
Range productivity over most of the Middle East and western Pakistan is among the lowest in the arid world. A small beginning
has been made in bringing the pastoral lands up to their potential productivity. Much remains to be done, however, because
range management is only a young science in Asia. Recent emphasis on sand dune stabilization has led to a number of
successful efforts to find effective methods and to identify adapted plants. Accomplishments have been outstanding, under very
difficult circumstances.
A rapidly growing population and limited land resources mean that combating desertification will be difficult for the developing
nations of Asia and very difficult for the poor countries. Land pressures must somehow be relieved, and that can only be
accomplished by raising productivity and yields per unit area. A start can be made with presently available knowledge, but
research and training will be needed to broaden the knowledge base and to provide guidance to the pastoralists and cultivators.
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