Desertification

The United Nations Convention to Combat Desertification defines desertification as land degradation in arid, semi-arid, and dry sub-humid areas arising from several factors, including climatic variations and human activities. The term describes a decline in the condition or productive capacity of land within drylands; it does not mean that the world's existing deserts are simply advancing across their borders. Dryland environments include grasslands, shrublands, croplands, and woodlands as well as deserts.

The causes differ from place to place and often interact. Extended drought and other rainfall or temperature variations can stress vegetation, while human pressures such as expanding cultivation and unsustainable land management can weaken the land's ability to recover. Overgrazing, clearing vegetation, or cultivating fragile soils may leave ground exposed; wind and water can then remove topsoil, and repeated disturbance can reduce soil fertility and plant cover. Climate change can intensify some risks, but the IPCC emphasizes that its contribution interacts with local land use and varies across regions and over time.

As soil and vegetation productivity fall, dryland communities may face lower crop or livestock output, reduced biodiversity, and less reliable supplies of useful land resources. Erosion and loss of plant cover can also increase dust and sediment movement, with effects that extend beyond the damaged site. The IPCC's assessment links desertification in some regions with lower agricultural productivity and incomes, biodiversity loss, and declining ecosystem services. The severity and combination of impacts depend on local ecological and social conditions.

A dry spell or a temporary decline in green vegetation does not by itself prove that desertification has occurred: plant growth in drylands can rise and fall with rainfall. Detecting persistent degradation therefore requires evidence over time and attention to local conditions. Satellite observations can reveal broad changes in vegetation, but NASA's account stresses the value of long records and field evidence when distinguishing persistent land change from rainfall-driven fluctuation. Responses are most effective when adapted to the site and its users. Measures supported in the IPCC assessment include maintaining plant cover, improving soil and water conservation, adjusting grazing and cropping practices, and combining scientific methods with relevant local and Indigenous knowledge.