Desrtification

Desertification

Desertification is the expansion of dry lands due to poor agricultural practices (e.g. overgrazing, degradation of soil fertility and structure), improper soil moisture management, salinization and erosion, forest removal, and climate change. Two common misconceptions prevail about desertification, that it spreads from a desert core and drought is responsible. Desertification spreads outward from anywhere excessive abuse of the land occurs and far from any climatic desert. Droughts do increase the possibility of desertification if the carrying capacity of non-irrigated land is exceeded. Well-managed land can recover from the effects of drought. Combining drought with land abuse sets the stage for desertification.

Desertification became well known in the 1930's, when parts of the Great Plains in the United States turned into the "Dust Bowl" as a result of drought and poor practices in farming, although the term itself was not used until almost 1950. During the dust bowl period, millions of people were forced to abandon their farms and livelihoods. Greatly improved methods of agriculture and land and water management in the Great Plains have prevented that disaster from recurring, but desertification presently affects millions of people in almost every continent. Increased population and livestock pressure on marginal lands has accelerated desertification. In some areas, nomads moving to less arid areas disrupt the local ecosystem and increase the rate of erosion of the land. Nomads are trying to escape the desert, but because of their land-use practices, they are bringing the desert with them.

It is a misconception that droughts cause desertification. Droughts are common in arid and semiarid lands. Well-managed lands can recover from drought when the rains return. Continued land abuse during droughts, however, increases land degradation. By 1973, the drought that began in 1968 in the Sahel of West Africa and the land-use practices there had caused the deaths of more than 100,000 people and 12 million cattle, as well as the disruption of social organizations from villages to the national level.

Overgrazing has several effects. It:

* Causes a decline in pasture vegetation and palatable grass species.

* Replaces perennials with short-lived annual species that do not hold soil against erosion.

* Compacts soil under trampling hoofs.

* Destabilizes dunes when crest vegetation is eaten.

Forest cutting for fuel wood has deforested large tracks of land in Africa and Asia encouraging desertification.

The United Nations Conference on Desertification ranks desertification hazard on the basis of a drop in agricultural productivity:

None - less than 10%

Moderate - 10%