Environmental Engineering Reference
In-Depth Information
Figure 1
Main sources of atmospheric dust and
estimates of the amounts transported.
the idea is oversimplified and not an accurate picture of the way desertification works.
The process of desertification is much more complex and is more likely to involve
vegetational degradation on the desert fringe. Maps have been prepared to show the
location of areas affected by desertification, or the risk of desertification, but they have
been strongly criticized.
CAUSES OF DESERTIFICATION
The development of vegetation degradation through inappropriate land use is rarely
investigated by long-term scientific monitoring; most comments appear to be based on
subjective judgement. We can identify three main factors which, it is argued, are likely to
give rise to desertification: overgrazing, overcultivation and deforestation. Salinization of
irrigated cropland is often viewed as an additional factor in some areas. We will examine
these potential causes in turn.
Overgrazing
. Excessive damage to vegetation caused by too many animals being
allowed to graze an area is considered by many to be the main factor behind
desertification. Edible and more nutritious species are removed, leading to an invasion of
coarser vegetation or even bare ground. Trampling, especially around sources of water,
can compound the problem by damaging soil structure. A lower soil porosity can reduce
the ability of the soil to retain moisture and support plant growth. Both soil and
