Summary for Decision-makers
Desertification is defined by the U.N. Convention to Combat Desertification as “land degradation in arid, semiarid and dry subhumid areas resulting from various factors, including climatic variations and human activities.” Land degradation is in turn defined as the reduction or loss of the biological or economic productivity of drylands. This report evaluates the condition of desertification in drylands, including hyper-arid areas, by asking pointed questions and providing answers based exclusively on the reports generated for the MA.
Desertification occurs on all continents except Antarctica and affects the livelihoods of millions of people, including a large proportion of the poor in drylands. Desertification takes place worldwide in drylands, and its effects are experienced locally, nationally, regionally, and globally. Drylands occupy 41% of Earth’s land area and are home to more than 2 billion people—a third of the human population in the year 2000. Drylands include all terrestrial regions where water scarcity limits the production of crops, forage, wood, and other ecosystem provisioning services. Formally, the MA definition encompasses all lands where the climate is classified as dry subhumid, semiarid, arid, or hyper-arid. Please see Appendix A for more details about their geography and demography.
Some 10–20% of drylands are already degraded (medium certainty). Based on these rough estimates, about 1–6% of the dryland people live in desertified areas, while a much larger number is under threat from further desertification. Scenarios of future development show that, if unchecked, desertification and degradation of ecosystem services in drylands will threaten future improvements in human well-being and possibly reverse gains in some regions. Therefore, desertification ranks among the greatest environmental challenges today and is a major impediment to meeting basic human needs in drylands.
Persistent, substantial reduction in the provision of ecosystem services as a result of water scarcity, intensive use of services, and climate change is a much greater threat in drylands than in non-dryland systems. In particular, the projected intensification of freshwater scarcity as a result of climate change will cause greater stresses in drylands. If left unmitigated, these stresses will further exacerbate desertification. The greatest vulnerability is ascribed to sub-Saharan and Central Asian drylands. For example, in three key regions of Africa—the Sahel, the Horn of Africa, and Southeast Africa—severe droughts occur on average once every 30 years. These droughts triple the number of people exposed to severe water scarcity at least once in every generation, leading to major food and health crises.
Desertification is a result of a long-term failure to balance demand for and supply of ecosystem services in drylands. The pressure is increasing on dryland ecosystems for providing services such as food, forage, fuel, building materials, and water for humans and livestock, for irrigation, and for sanitation. This increase is attributed to a combination of human factors and climatic factors. The former includes indirect factors like population pressure, socioeconomic and policy factors, and globalization phenomena like distortions to international food markets and direct factors like land use patterns and practices and climate-related processes. The climatic factors of concern include droughts and projected reduction in freshwater availability due to global warming. While the global and regional interplay of these factors is complex, it is possible to understand it at the local scale.