Desertification and Land Degradation

Abstract

Drylands may undergo relatively rapid changes in land cover, plant communities, erosion rates, and hydroclimatic conditions that result in losses of ecosystem services and livelihoods. These socio-environmental changes are often termed “desertification,” which literally means “transition to desert-like conditions.” Because deserts occur in different forms and shapes, desertification is a rather ambiguous term that does not uniquely point to a specific environmental process, final outcome, or underlying driver of environmental change in drylands. Indeed, desertification can lead to, among other outcomes, a loss of vegetation cover, accelerated soil erosion, bush encroachment in xeric grasslands, displacement of perennial native grasses by exotic annuals, and an increase in soil salinity or toxicity (e.g., Martinez-Beltrán and Manzur 2005; Rengasamy 2006; Schlesinger et al. 1990; Van Auken 2000). These changes are relatively irreversible at timescales spanning human generations. In other words, desertification is the environmental “deterioration” of drylands (Dregne 1977) that leads to a persistent and, in the most extreme case, an irreversible transition to desert-like conditions (MEA 2005; D’Odorico and Ravi 2016).