school energy&environment

Desertification

Desertification is a complex phenomenon that occurs in all those areas where temperature and humidity do not make it possible for vegetation to growth. Like for many other natural processes, men can have an influence on desertification, sometimes in very negative ways. Fires and the destruction of the savannah near tropical forests in order to create land for cereals and forage cultivation, are some of the worst examples of irreversible destruction of a delicate ecosystem that favours the desert moving forward. Millions of hectares of land are involved each year in new desertification processes.  Degraded lands can be hundreds of kilometres from the nearest desert, but they can expand and get closer one to another, by creating desert-like conditions.
What areas are at risk?
Most of the regions that risk to become dry areas are near the world five deserts:

• Sonora desert between Mexico and the United States;
• Atacama desert in South America;
• a wide desert area that stretches from the Atlantic Ocean to the east, including the Sahara desert, Iran and former Soviet Union deserts, the big Indian desert of Rajasthan and last Taklamakan and Gobi deserts, that are located in China and Mongolia;
• Kalahari desert in South Africa;
• most of Australia.

This does not mean that desertification does not threat milder areas (even though they are quite dry), like the south of Italy, or some wet areas like the Amazon Forest.
What are the causes? 
Mainly, the human causes for desertification are three:

• the over-exploitation of pasture areas and agricultural nearby areas, which provoke the disappearance of grass cover and reduce soil fertility;
• excessive presence of water, that in wet areas provokes a rise in aquifer levels, damaging crops from the root, while in dry areas it provokes salinization of the soil due to strong evaporation;
• deforestation, a phenomenon that, especially in wet regions, leaves the soil without vegetation, reduces water retention in the ground, and allows violent tropical rains to exercise a strong erosive action.