Desertification: Its Features and Scope

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Highlights

  • In the Convention to Combat Desertification (1995), desertification is defined as ‘land degradation in arid, semi-arid and dry-sub-humid areas resulting from various factors including climatic variations and human activities.’

  • The wetter parts of the arid zone and the semi-arid areas are more prone to water erosion. The counter crusting of soil and its subsequent erosion

Desertification

The term desertification was coined by the French forester Aubreville in 1949 to describe land degradation. Since then there have been over 100 published definitions of this controversial term which gained prominence after the 1977 UN Conference on Desertification. The term has been confused with drought in some circles, and its social impacts have sometimes been
associated with famine that may in fact have non-environmental causes.

In the Convention to Combat Desertification (1995), desertification is defined as ‘land degradation in arid, semi-arid and dry-sub-humid areas resulting from various factors including climatic variations and human activities.’ The problem is therefore confined to the susceptible
dry-lands, with land degradation regarded as soil erosion, internal soil changes, depletion of ground water reserves and irreversible changes to vegetation communities. In many respects, desertification is no different than land degradation occurring world-wide, except that it specifically refers to its occurrence within dry areas.

In environmental terms, the soil degradation component of desertification comprises water and wind erosion, and physical and chemical changes within the soil. These factors reduce the potential productivity of the affected land. Desertification is a serious global problem, affecting 16 per cent of the total population, about 34 per cent of the land area and 70 per cent of all dry-lands of the world. Though the Convention to Combat Desertification (CCD) definition includes possible multiple causes for desertification, it is undoubtedly the case that the principal agent of degradation is human actions. Though desertification has often been viewed as a particular problem of the

Twentieth Century, the ability of humans to detrimentally alter dry-lands is not new. Salinization in Mesopotamia around 2500 BC has been attributed to agriculture, while in central Mexico, prehistoric societies caused severe soil erosion. In the Twentieth Century it is the
growth and changing distribution of human population in dry-lands, and the spread of technological advances, that have increased the propensity for dry-land degradation. Several issues make the dry-lands especially susceptible to degradation by humans.

Desertification involves four processes that have an extensive impact on the biological productivity of desert land. They are : (i) degradation of vegetation cover, (ii) soil erosion, (iii) salinization, and (iv) water-logging including soil compaction. Thus desertification is a serious threat to the socio-economic fabric all over the world. Environmentally, it contributes to climate change, water air and soil pollution, desertification and soil loss. Some of the glaring aftermath effects of environmental degradation are:

1.loss of global biological diversity, (2) loss of biomass and bio-productivity, (3) exhaustion of humus reserve, (4) disrupting normal global bio-geochemical turnover and (4) reduction on the global carbon-dioxide sink, (5) desertification contributes to climatic changes by increasing potential and decreasing actual evapo-transpiration rate, (6) changing ground-surface-energy budget and adjoining air temperature, and (7) adding dust and carbon-dioxide to atmosphere. Drought and Desrtification: Land in many parts of the world has been degrading into desert like conditions because of drought. Consequently, drought is threatening more people than ever before. Worth noting is the fact that drought is a temporary problem and desertification is not that temporary, and is creating a more serious problem than drought. Man can do little to prevent drought, but he can halt desertification. Drought is temporary, cyclical and can be
expected in all climates, whereas desertification is insidious, unexpected and permanent. In fact, drought is considered as an engine of desertification.

Drought and desertification are closely linked. Water shortages and high rainfall variabilities make desertification more acute. This, in turn, promotes drought and intensifies its effect. Ecological degradation processes are set in through excessive destruction of natural vegetation.
It is only during prolonged periods of drought that the above mentioned processes lead desertification. Ecological consequences of long-term rainfall deficits are: (i) elimination of grass cover, (ii)elimination of some bush vegetation, (iii) drop in ground water- table near the
surface, (iv) an increase in shifting sands and reactivation of some old sand dunes, (v) more wind erosion of fine soil components, and (vi) increased evaporation, with drying out of soils cracking on clay soils.

Desertification Control: Regardless of the challenges involved, desertification control and
restoration of degraded lands is a win-win strategy. It needs to be done.

Before taking up desertification control on any dry-land or area, it is necessary to assess and monitor the type and the severity of the land degradation. The causes of land degradation are also to be ascertained. Based on degradation, the selection and application of appropriate
actions, will have to be taken. Whatever steps or actions are taken to combat desertification, they should aim at achieving sustainable development of the area, which can be possible with the management and conservation of the resource-base, the land, so as to meet the present and future needs of the people habitating that area or region. The sustainable development of arid, semi-arid and dry-sub-humid zones usually confronts three challenges: (i) using preventive measures, to check or to prevent desertification of land slightly or not yet degraded; (ii) to regenerate, through corrective measures, the productivity of the moderately degraded land, and (iii) to restore the productivity of seriously degraded land, using rehabilitation and repair measures.

Desertification Control in Arid Lands of India: Desertification is a serious problem in the arid dry-lands in India. It is more severe in the north-western plains of the country, especially in the desert tracts of Rajasthan, Gujarat, Haryana and Punjab. Wind erosion is a major problem in part of theThar desert. Higher average wind speeds, dominantly sand terrain, sparse vegetation cover and high human activities on the sand-dunes and sandy-plains lead to an accentuation of sand-blowing. It also leads to erosion of top soil, containing nutrients and precious little organic matter as also moisture, thereby reducing soil quality required for sustainable agricultural production. Standing crop-plants are damaged and good agricultural lands and infrastructure are buried as a result of wind erosion. The major activities of wind-erosion control are sand-dune stabilization and shelter belt plantation. The following steps can go a long way in controlling the process of desertification:

1.Sand-Dune Stabilization: The sand-dunes are generally categorized into the old and the new sand-dunes. Old sand-dunes, usually higher than 10 m, are naturally stabilized with potential to support copious natural vegetation. These dunes have extremely low rates of movement unless their ecology is disturbed by human action. The new dunes are mostly smaller than 10 m. They are bare of vegetation and have a high rate of movement.

Most programmes of sand-dune stabilization have been directed towards old dunes, to restore production potential. The activities mainly consist of: (i) protection of the area from human and livestock encroachment; (ii) creation of micro-wind breaks on the dune slopes, (iii) direct seeding or transportation of indigenous or exotic species; (iv) plantation of grass-strips, and (v) management of vegetated sites.

2.Shelter-belt Plantation: Erection of shelter belts along the boundaries of crop fields helps reduce injuries to tender seedlings from sand blasting and hot desiccating winds. Wind velocity at the lee side of the shelter belt is reduced and also the losses by about 76 per cent.

3.Soil and Water Conservation Measures: The wetter parts of the arid zone and the semi-arid areas are more prone to water erosion. The counter crusting of soil and its subsequent erosion, a number of practices have been suggested, like contour bunding (low rainfall area) and contour tillage and contour sowing in the agricultural fields. Moreover, mixing of crop residue and organic matter with light-textured soils helps increase moisture and crop yield.

4.Management of Pastures: Permanent pastures are most degraded, as they do not have any basal plant-cover. The natural vegetation has been destroyed and the pastures have been converted into barren ground. These degraded pastures need to rehabilitated.

5.Management of Waterlogged and Salt Affected Tracts: Mismangement of water and over- irrigation have rendered many productive lands to waterlogged and salinity-alkalinity affected areas. The command area of the Indira Gandhi Canal (Rajasthan), and the command areas of small and medium irrigation tanks in the desert are some of the glaring examples. Lining of canals, judicious use of canal-water, soil management and scientific rotation of crops are necessary to arrest degradation.

6. Rehabilitation of Mine-Spoils: There is need to plant suitable tree bushes, shrubs and grass species to be planted in the areas of desertification. Development of micro-catchments with 5% slope to ensure run off to single row of plants, coupled with other soil conservation practices like ridge and furrow system.

7. Hilly area: In the hilly and rocky areas like the Aravallis planting acacia (Babul trees) helps in the combating of desert. In the saline and alkaline affected areas the application of gypsum and farmyard manure alongwith salt-tolerant plants can help appreciably in combating deserts.

8.Contour Farming: Contour farming and contour bunding, graded bunding, bench terracing on steep slopes, and run-off harvesting, storage and recycling are also important steps in combating deserts, especially in the sub-humid areas. Mixed grass and furl-wod tree species may be planted on denuded lands.

9. Ravine Lands Reclamation: Gully plugging is done to conserve soil moisture, control erosion and provide better growing conditions for natural as well as for planted grasses and forest species.

10. Rehabilitating Degraded Rural Commons: In the tropical deserts, Rural Common Property Resources, community pasture, forest, wasteland, watershed drainage etc. form an important asset in the desert of India. Rehabilitation of the community degraded lands and pastures should be done with new technology at the priority basis. The silvi- pastoral system, which not only provide fodder and fuel-wood but also improves the soil fertility.

If the above steps and methods are adopted in collaboration to each other, the problem of desertification can be solved to a great extent.

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