degradation

Natural degradation hazards

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The major natural hazards in the region, environmental conditions which act as predisposing factors for land degradation, are:

For water erosion:

• monsoonal rains of high intensity;
• steep slopes of the mountain and hill lands;
• soils with low resistance to water erosion (e.g. silty soils, vertisols).

For wind erosion:

• semi-arid to aria climates;
• high rainfall variability, with liability to drought spells;
• soils with low resistance to wind erosion (e.g. sandy soils).
• an open cover of natural vegetation.

For soil fertility decline:

• strong leaching in humid climates;
• soils which are strongly acid, and/or with low natural fertility.

For waterlogging:

• alluvial plains or interior basins which restrict outward drainage of groundwater.

For salinization:

• semi-arid to aria climates with low leaching intensity;
• plains and interior basins which restrict outward drainage of groundwater;
• soils which are naturally slightly saline.

For lowering of the water table:

• semi-arid to aria climates with low rates of groundwater recharge.

In some cases, these natural hazards are of sufficient intensity to give rise to unproductive land without human interference. Examples are the naturally saline soils which occur in some interior basins of dry regions, or areas of natural gullying (‘badlands’). Such conditions have been referred to as problem soils. Percentages of land covered by problem soils are given in Dent (1990).

With respect to land degradation, the key feature is that land shortage in the region has led to the widespread agricultural use of areas with natural hazards. These are the passive, or predisposing, conditions for land degradation. Problem soils require special care in management, and failure to give such care leads to land degradation.