In the United Nations Convention to Combat Desertification (1994) the process has been defined as ‘land degradation in arid, semi-arid and dry-sub-humid areas resulting from various physical factors, climatic change and human activities.’ Desertification may be accentuated by reduction in average annual rainfall and increased evaporation, transpiration, especially in soils that have less humus content.
The sparsely populated arid and semi-arid lands cover about 34 per cent of the earth surface. The deserts and semi-desert areas are supporting about 700 million (8 per cent) of the total population of the world. The basic economic activity of the people of the deserts is nomadic herding. The worst affected areas are the Northern parts of Africa, South-West Asia, Central Asia, greater parts of Australia, Namibia, Atacama, Patagonia (South America), Mojave Desert, Arizona (USA), and Sonora Desert (Mexico). The spatial patterns of desertification show that the tropical and sub-tropical lands are more prone to desertification. According to an estimate made by the experts of United Nations, about 40 per cent of the African continent’s non-desert land is in danger of desertification. Nearly 33 per cent of Asia and 20 per cent of Latin America’s land are similarly endangered. It has been suggested that Mali may be the first country in the world rendered uninhabitable by environmental destruction (Fellmannet. al. 1990).
Soil is a complex mixture of rock particles, organic material, living organisms, air and water. Under natural conditions soil is constantly being formed by the physical and chemical decomposition of rock materials and by the decay of organic matter. It is simultaneously being eroded. The process of removing nutrients and organic matter from the soil is known as soil erosion. Soil erosion is a world-wide phenomenon. The rate of soil erosion depends on: (i) rainfall erosion capacity, (ii) volume of run-o, (iii) relief, (iv) slope and its length, (v ) wind velocity, (vi) shelter belts, (vii) population pressure, (viii) land use and type of agricultural practices, (ix) irrigation, and (x) soil management practices.
According to one estimate, all over the world, about 75,000 million tones of productive soil is eroded annually. In India, the problem of soil erosion is quite serious as about 6000 million tones of productive soil is being eroded annually.
Salinization is also an important factor of environmental degradation. At present, there is more use of chemical fertilizers in agriculture. The application of nitrate, phosphate and potassic fertilizers, especially after the Second World War have changed the soil chemistry. Although the production of cereal and non-cereal crops has gone up, these fertilizers are detrimental to the health of soil. The most significant adverse effect is the eutrophication of fresh water aquatic ecosystems that are in receipt of drainage from agricultural land. Consequently, many water-bodies and wetlands have suffered seriously. The ecosystems of Dal, Wular, Nageen, Anchar, Manasbal lakes in the Valley of Kashmir have been impaired to the extent that the very survival of these lakes has become a point of great concern for the people, planners and policy makers.
Disposal of Urban Waste Material
Industrialization, urbanization and modern lifestyle lead to huge quantities of domestic, industrial and nuclear wastes. The high energy consumption, large size of population and high population densities of the urban societies give rise to large quantities of waste-water and sewage as well as domestic garbage. The disposal of domestic rubbish needs landfill sites in the vicinity of urban ecosystems. The landfills result into obnoxious odors. Such landfills generate methane and hydrogen sulphide which are injurious to health. They contaminate surface and underground water. The contaminated water supplies cause epidemics and water borne diseases like typhoid, cholera, gastroentitis, dysentery, and diarrheoa. The industrial waste consists of chemicals, detergents, metals and synthetic compounds besides the solid wastes and garbage. The heavy metal chemicals pollute the water system which may be a threat to aquatic ecosystems and human health. It has been reported that mercury poisoning impair sensory, visual, auditory functions especially in unborn fetuses. There are several examples of methyl mercury poisoning that have proved fatal on a relatively large scale.
The increased nuclear waste is also an important cause of environmental degradation. There are more than four hundred nuclear plants generating nuclear energy. Most of these nuclear plants are in the developed countries. The nuclear waste contains radio-active isotopes which generate large quantities of heat. The radioactive elements remain active for many hundred years. The disposal of nuclear waste is therefore a serious danger to the biosphere in general and for the human health in particular. The nuclear proliferation after the Tohoku Earthquake (Japan) on 11th March, 2011, was alarming. The nuclear radioactive caesium leaked was about 168 atomic bombs of the size dropped on Hiroshima in 1945. In consequence, a series of hydrogen explosions took place at the Fukushima-Daiichi Nuclear Plants (Japan). The evacuation zone in the Honshu Island of Japan was extended about 20 km radius affecting about 160,000 people of the region.
The recent agricultural strategy and application of heavy doses of chemical fertilizers, insecticides, and pesticides in the market oriented monoculture has also substantially damaged the agricultural ecosystems. The intensification of agriculture in the developing countries is also depleting soil fertility at a faster pace. Remedial measures are imperative to enhance the resilience characteristics of the fragile agro-ecological systems of the world.