[PDF Notes] 4 important Causes of Desertification

In order to understand desertification processes in the Indian context, it is necessary to know the geomorphic processes under natural set-up and acceleration to the processes through human interventions.

1. Water Erosion

Soil erosion through fluvial processes affect large areas in the Saurashtra and Kutch uplands, and along the eastern margin of the Thar Desert where the average annual rainfall varies from 350 to 500 mm, but has very few occurrence to the west of 250 mm isohyets in the Thar.

The manifestations can be deciphered the pattern of sheet, rill and gully erosion features. Increased ploughing and destruction of vegetation cover for fuelwood, overgrazing and other destructive uses, must have accelerated the erosion in recent decades, but in the absence of specific data, it is difficult to suggest how much of the gulling activity is due to human activities alone and how much due to the natural processes. In Kutch region, a part of the problem is related to a slow natural uplift of the terrain over the centuries, which leads to a change in base level and increased erosion.

2. Wind Erosion/Deposition

The most vulnerable landforms to wind erosion/deposition are the sand dunes and other sandy landforms in the Thar. A closer look, however, indicates that the sandy landforms in the east are more stable than the similar landforms in the west. Rainfall gradient and wind strength are both responsible for the spatial variability in sand reactivation pattern.

The introduction of the tractor for deep ploughing, instead of the traditional animal-driven wooden plough, has increased the sand load manifold for the Aeolian processes in large parts of the desert, and accelerated the mobility of sand.

Increased destruction of the natural land cover in grazing lands for fuel and fodder and enlarging the frontiers of cultivation to less suitable sandy areas are also the responsible factors. In the foothills of the Aravali hill ranges along the wetter eastern part of the desert, such activities are also leading to accelerated water erosion, as manifested through the formation of rills and gullies.

The farmers are aware of headword progress of the gullies in the east, but do not believe that their agricultural activities hasten the process, unless tractors are used to loosen the soil. Many of them believe that the agricultural crop residues which they leave in the field are good sand binders and whatever land is being lost through gully erosion is a slow natural phenomenon. In other parts of the desert, farmers agree that deep ploughing with tractors, cultivation along dune slopes, or non-practising of long fallow systems and other traditional farming systems lead to accelerated sand movement and land degradation, but they have very few choices, as population pressure and economic consideration override environment consideration.

3. Mining

In western Rajasthan, about twenty major minerals and nine minor minerals are being mined. More than 90 per cent of the mine owners have open cast mining. The rest are underground mines. The area occupied by the mines is increasing and by 2000 AD 0.05 per cent of Jaisalmer district and 1.15 per cent of Jhunjhunu district are reportedly under mining activities.

The surface mining activity causes immediate degradation of land. The mining sites are abandoned after the excavation work is over, without adopting any reclamation measure. Mining on agricultural land, either surface or underground, reduces the productivity of land by way of excavation, disposal of debris and tailing. Mineral processing like grinding of limestone for cement industry, calcite and soapstone for ceramic industry, have three-fold adverse effects.

The fine dust, generated and released in the atmosphere, leads to surface scaling of the adjacent land after it settles down, consequently the infiltration rate is reduced and the run-off increases.

Mining activity restricts the sub-surface movement of water. With the removal of vegetation, the rate of evapotranspiration is reduced and as a result, there is a change in the hydrological balance in the area.

Due to this change, the perched water table rises and causes salinity. When the mining debris of minerals like ball clay, china clay, Fuller’s earth, bentonite and gypsum are dumped on the sandy plain, a semi-impermeable surface layer is developed. These areas get flooded during the monsoon and gradually develop salinity. Sodium salt mining activity increases the surface salt concentration, causing total loss of vegetation.

4. Vegetation Degradation

One of the first casualties of desertification is natural vegetation. Degradation of natural vegetation is also one of its major causes. With increasing pressure on land vegetation, degradation is increasing at an alarming rate.

The common grazing lands around the villages are now some of the very severely degraded sites, as these are highly exploited and most neglected. Many good grazing lands have also been encroached upon for agriculture.

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