Desertification

Desertification is land degradation in arid, semiarid, and dry subhumid regions caused by climatic variation and human activities. It reduces the land’s biological productivity and capacity to support livelihoods.

Soil erosion: The removal of soil by water, wind, ice, or gravity. Wind and runoff strip exposed soils after vegetation cover declines.
Sahel: A semiarid belt south of the Sahara spanning much of Africa from west to east. Rainfall variability and land-use pressures have made degradation a major concern across the region.
Agroforestry: A land-use system that combines trees with crops or livestock on the same land. Trees can shelter soil, improve water cycling, and diversify livelihoods in drylands.
Desert: A dry ecosystem defined by very low precipitation and sparse vegetation. A naturally arid desert is not, by itself, evidence of land degradation.
Soil salinity: The accumulation of soluble salts in soil to levels that impair plant growth. Irrigation without adequate drainage can leave salts behind and reduce productivity.
Dust Bowl: A period of severe dust storms and agricultural collapse in the Great Plains during the 1930s. It demonstrates how drought and intensive farming can combine to expose vast areas of soil.
Terrace (agriculture): A level or gently sloping platform cut into a hillside for cultivation. Terraces slow runoff and help retain soil and water on sloped land.
Aridification: A long-term shift toward drier climatic conditions in a region. It describes climatic drying, while desertification also includes degradation driven by land use.
Vegetation cover: The fraction of land surface covered by living plants. Its loss exposes soil to erosion and reduces water retention.
Aral Sea: A former inland sea in Central Asia, greatly diminished by river diversions for irrigation. Its exposed seabed became a source of salt- and pesticide-laden dust.

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