The world's drylands supported about 850 million people in 1984, of whom 230 million were on lands affected by severe desertification. Worldwide it is estimated that millions of hectares are losing their biological diversity each year, as human and animal pressures have accelerated the removal of vegetation and consequent soil erosion. Two fifths of Africa's non-desert land risks being turned into desert, as does one-third of Asia's and one-fifth of Latin America's.

Disturbance of the ecological system has decreased the infiltration of rainwater, increased surface runoff, lowered ground-water levels, and caused the drying up of surface water and loss of topsoil and soil nutrients. Under these conditions, drought will more quickly reduce food output and lead to famine. However, political, economic and social factors are more important than low rainfall in the process of desertification. Besides rapid growth of human and animal populations and detrimental land use practices, the cultivation of cash crops on unsuitable  rangelands  has  forced  herders  and  their  cattle  onto marginal lands, thus accelerating soil degradation and outright desertification.

Declines in soil fertility or even total losses of land to agriculture are common in many parts of the world. Soil erosion by wind and water is serious in the arid parts of North Africa and the Middle East, parts of South Asia and South America. The problem is caused in great measure by inappropriate land use and cropping patterns. Substitution of traditional mixed cropping (which includes plants or shrubs along with food crops) by monoculture, and poor management of land and water have caused significant soil erosion and other types of degradation. Salinization affects extensive land areas in many countries in North Africa, the Middle East, and Asia. About half the land under irrigation is affected by secondary salinization and/or alkalinization in varying degrees. Some 40 million hectares of irrigated land are either waterlogged or suffer from excessive salinity or both. Salinization may be removing as much land from production as is added by irrigation. Irrigation has greatly improved farm productivity in areas of uncertain or inadequate rainfall and has been responsible for the adoption of high yielding varieties in many developing countries. Yet inappropriate irrigation has wasted water, polluted groundwater, and damaged the productivity of millions of hectares. Excessive extraction of groundwater for irrigation has depleted aquifers in Asia and Africa. Acidification of peat soils occurs when the groundwater table is lowered. It drastically reduces production of crops and fish (in ponds) as, for example, along extensive coastal areas in southeast Asia.