ABSTRACT
Desertification is a persistent reduction of land’s biological productivity of economic value—a terminal state of land degradation process. Land degradation and desertification (LDD) can occur anywhere, but the focus is on drylands, whose natural low productivity is water limited. LDD is a syndrome of interactive biophysical processes whose direct drivers are land resource overexploitation by land users. Underlying causes of LDD are economic, demographic, social, cultural, and political, operating across scales. About a quarter of global land is degraded, and active LDD is ongoing. LDD is of concern: it is believed to contribute to poverty, migrations, refugees, and conflicts; it undermines global food security and the emissions from degraded lands exacerbate global climate change, which is projected to increase the contribution of drought to LDD, and has already increased drying and a geographical expansion of some drylands. Some dryland communities demonstrate resilience to the underlying causes and take measures for avoiding LDD, and the United Nations Convention to Combat Desertification (UNCCD) is instrumental in assisting developing countries addressing their LDD.
