Desertification is a kind of land degradation in which deserts expand as a result of natural (cyclic changes in climate) and anthropogenic (wood cutting, overgrazing) causes. Desertification is indicated by deterioration of 50% of natural soil and plant cover. This is a major problem in the arid regions of the world.

The United Nations Convention to Combat Desertification (UNCCD) Article I (a): signed in October 1994, defines desertification in common terms as "land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climactic variations and human activities." Despite the fact that a world conference has been held on the subject, there is no generally accepted definition of desertification. For most people, the word probably evokes a mental picture of a barren, forbidding landscape. Fortunately, that grim picture does not apply to most of the land that has undergone desertification in Russia.

The desertification process is a consequence of the combined effect of various factors. The most important are climate, soils, vegetation, and land use, and of these, climate and land use are of primary significance. Other factors are secondary. Climate changes can trigger the desertification process, but human activities frequently are the proximate cause. Excessive cultivation and overgrazing are the major land use factors causing desertification. The extent of desertification processes in Russia is defined through various data from the CD-ROM.

Desertification data

To distinguish desertification we use the following data:
· Climate parameters
· Average annual precipitation
· Average annual temperature
· Average evapotranspiration (Penman-Monteith method)

Land use
· Cultivation
· Overgrazing

Soil factors
· Soil erosion
· Secondary salinization
· Soil characteristics
· Soil divisions (National soil classification)
· Plant available water
· Ground water table
· Topsoil texture

Vegetation
· Mean annual albedo of land cover
· Bio-climatic zones
· Total phytomass density of natural vegetation communities (dry matter)
· Grasses and shrubs vegetation

Method

A map overlay method has been applied. The intersection of numerous coverages results in the output desertification map. The model operates as follows:
Every locus at vector format, with coordinates X, Y receives a desertification attribute as:
D=f {A, B, C, …}
where A, B, C, … are attributes defined by the first, second, third …overlays, and f is a desertification function that has yet to be defined. Table 1 presents these attributes for 1993.

For the raster coverages, the same method is acceptable but with consideration of each coverage as a matrix of values. Thus calculation of the desertification attributes can be expressed as a matrix algebra operation:

Table 1. Desertification extent in Russia (for 1993).

The analysis shows that the extent of desertification in Russia is about 36 million ha, which is in line with previous studies (Stolbovoi and Fischer, 1999). According to the latest estimates, the area affected by desertification is currently about 100 million ha. The evidences of desertification are found in the Astrakhan, Volgograd, and Rostov oblasts; the Altai Krai, and the Republics of Tuva and Dagestan. Small areas of Krasnodar and Stavropol Krais have also been affected. Territories under the threat of desertification include land in the southern part of the steppe zone in the Voronezh, Saratov, Orenburg, Omsk, Chelyabinsk, and Chita regions, and in the Republics of Khakasia and Buryatia. However the most alarming situation is found in Kalmyk Republic, which is the most arid region of the European part of Russia. More than 80% of the territory is now in the grip of desertification, with almost half of it being either severely or very severely affected. Desertification of the unique pastures of the Black Lands of Kalmykia has led to the first man-made desert in Europe, with areas of open and blown sand. Satellite imageries confirm that large amounts of sand are blown out of this area during dust storms, reaching the borders of European countries beyond Russia. Man-made desert in Europe has expanded by about 1 million ha. The crisis resulted from intensive land degradation and a shortage of water, together with the increasing human load on the natural environment over the last few decades and extreme natural conditions, which caused a decline in the health of the population and falls in both life expectancy and the quality of life.

One instrument to be employed in implementing the Convention is the national Action Program, which, following the declaration of a state of emergency, defines the strategy to be used to combat desertification and to moderate the consequences of drought.

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