Land Degradation in the World's Arid Zones

Land degradation in the arid regions of the world is an enduring problem, the dimensions of which are a matter of conjecture. At the global scale, land degradation in the arid regions is primarily the result of four processes: vegetation degradation, water erosion, wind erosion, and salinization. The principal land uses in the drylands are grazing, rain-fed cropping, and irrigation. Four classes of severity, by land use, were used in the assessment: slight, moderate, severe, and very severe. A variety of information sources was used to make the productivity lossestimates. The criterion for rangeland productivity classes is range condition, which is commonly used by range scientists to evaluate productivity status. Reversing salinization can be costly. Fortunately, the cost/benefit ratio usually is favorable because of the generally high productivity of irrigated land. Vegetation degradation of rangelands and salinization of irrigated land are largely reversible.