Global extent of soil degradation types

The GLASOD map covers the earth surface between 72 degree North and 57 degree South. Summation of the surface area of all GLASOD units leads to a total land area of 13,103 million hectare. Th GLASOD map ad accompanying statistics do not allow assessment of soil degradation on a country by country basis. However, statistics are provided for seven continental regions. Human induced soil degradation worldwide has affected 1966 million hectare or 15% of the total land area.

These percentages range from 5% in North America, 12% in Oceania, 14% in South America, 17% in Africa, 18% in Asia, 21% in Central America to 23% in Europe.

Water erosion

Water erosion is by far the most important type of soil degradation, affecting about 1100 million hectare land worldwide. The most widespread  form of water erosion is the loss of topsoil (920 mha), whereas terrain deformation occur on 175 mha land. Water erosion occurs on all continents and under all climatic conditions, although somewhat more in humid climates. Almost 80% of the terrain affected by water erosion has a light to moderate degree of degradation. This implies that around 225 mha are degraded by water erosion to such extent that they are no longer suitable for agricultural land use.

Wind erosion

Wind erosion is a widespread phenomenon in arid and semiarid zones, usually on coarse textured soils with limited vegetation cover. The global extent of soils affected by wind is around 550 mha. Loss of topsoil by wind forces is by the most important type of wind erosion, whereas terrain deformation and overblowing are relatively less important in extent, although these types of wind erosion may have very serious effects on human activities. The degree of wind erosion in mainly light to moderate. Wind erosion is mainly caused by overgrazing and exploitation of the vegetative cover for domestic use.

In my next post I will discuss about chemical and physical degradation.