Desertification has been defined as land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variations and human activities.

Desertification directly affects over 250 million people. It threatens the lives of some 1.2 billion people in 110 countries who are among the world’s poorest and who depend on land for most of their needs.

A third of the Earth’s land surface, or over 4 billion hectares, is threatened by desertification.

Each year, desertification and drought cause an estimated US$ 42 billion in lost agricultural production worldwide. The annual cost of fighting land degradation is estimated at US$ 2.4 billion.

The consequences of desertification include:

• diminished food production, reduced soil productivity and a decrease in the land’s natural resilience;
• increased downstream flooding, reduced water quality, sedimentation in rivers and lakes, and the siltation of reservoirs and navigation channels;
• aggravated health problems due to wind-blown dust, including eye infections, respiratory illnesses, allergies, and mental stress;
• loss of livelihoods forcing affected people to migrate.

In the developing world, the total land area affected by desertification is estimated at between 6 and 12 million km2 (for comparison, the countries of Brazil, Canada and China are all between 8 and 10 million km2).

Desertification is found to some degree on 30% of irrigated lands, 47% of rain-fed agricultural lands, and 73% of rangelands. Annually, an estimated 1.5 to 2.5 million hectares of irrigated land, 3.5 to 4 million hectares of rainfed agricultural land, and about 35 million hectares of rangeland lose all or part of their productivity due to land degradation.

In Africa alone, 36 countries are affected by desertification or by land degradation, and an estimated 75% of the continent’s farmland is rapidly losing the basic nutrients needed to grow crops.

Information from:
the United Nations Statistics Division Environmental Glossary
from the UNEP’s ‘Facts About Deserts and Desertification’ [PDF format – 36 KB]
from the UNESCO Courier on Desertification (June, 2006)
the International Year of Deserts and Desertification (2006) website

Source: UNESCO Water Portal, June 2006