Page 77 - Soil Degradation, Conservation and Remediation

2.6 Desertifi cation 63

Unsustainable agricultural practices including excessive use of chemicals (fertilizers,
pesticides, and herbicides), inappropriate technologies, wrong choice of crops,

inadequate and inefficient irrigation practices associated with salinity, and over

abstraction of groundwater have led to problems of desertification in vulnerable
2
regions. There are about 7.1 million km of land at low risk of human-induced
2
2
desertifi cation, 8.6 million km at moderate risk, 15.6 million km at high risk and
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11.9 km at very high risk (Eswaran et al. 2001 ).
2.6.2 Convention to Combat Desertifi cation

Following a severe drought in sub-Saharan Africa, a United Nations Conference on
Desertification was convened in 1977 in Nairobi, Kenya. This was probably the fi rst

global conference on land degradation. Although it was called a conference on

desertification, land degradation and its control was the sole subject. In 1990, at a
meeting in Nairobi called by the United Nations Environment Program, desertifi ca-
tion was formally defi ned as land degradation in the dry lands. At the 1992 United
Nations Conference on the Environment and Development, participating govern-
ments approved a resolution to establish an international agreement to combat
desertification. The title of the formal agreement is the United Nations Convention

to Combat Desertification in Those Countries Experiencing Serious Drought and/or

Desertification, Particularly Africa. The short title of the ratified agreement is the

Convention to Combat Desertification (CCD). However, much has not been achieved
regarding the reversing of desertifi cation situation.
2.6.3 Mechanism of Human-Induced Desertifi cation

Desertification caused by human influences has a long historical record; there is
evidence of such damage caused around the Tigris and Euphrates rivers in ancient
Mesopotamia. Human influences on desertification include loss of vegetation by

deforestation, shifting cultivation, overgrazing, depletion of groundwater, frequent

burning, and compaction of the soil. These factors affect desertification which is a
process of continuous and gradual ecosystem degradation, during which plants and
animals and other natural resources such as water and soil are stressed beyond their
ability to adjust to changing conditions. The physical characteristics of land under-
going desertification include progressive loss of mature, stabilizing vegetation from

the ecosystem, or loss of agricultural crop cover and a resulting loss of unconsoli-
dated topsoil.
Early human pastoralists living in semiarid regions moved their small groups of
domestic animals in response to food and water availability. Such regular stock
movement prevented overgrazing of the fragile plant cover. Settled human habita-
tion increased the risk of overgrazing by livestock around the settlements.