This is part of the Millennium Ecosystem Assessment report Ecosystems and Human Well-Being: Desertification Synthisis.
Core Writing Team: Zafar Adeel, Uriel Safriel, David Niemeijer, and Robin White
Extended Writing Team: Grégoire de Kalbermatten, Michael Glantz, Boshra Salem, Bob Scholes, Maryam Niamir-Fuller, Simeon Ehui, and Valentine Yapi-Gnaore
Review Editors: José Sarukhán and Anne Whyte (co-chairs) and MA Board of Review Editors
Appendix A. Present-day Drylands and Their Categories
Drylands include all terrestrial regions where the production of crops, forage, wood and other ecosystem services are limited by water. Formally, the definition encompasses all lands where the climate is classified as dry subhumid, semiarid, arid or hyper-arid. This classification is based on Aridity Index values†.
† The long-term mean of the ratio of an area’s mean annual precipitation to its mean annual potential evapotranspiration is the Aridity Index (AI).
Notes: The map is based on data from UNEP Geo Data Portal (http://geodata.grid.unep.ch/). Global area based on Digital Chart of the World data (147,573,196.6 square km); Data presented in the graph are from the MA core database for the year 2000.
Disclaimer: This chapter is taken wholly from, or contains information that was originally written for the Millennium Ecosystem Assessment as published by the World Resources Institute. The content has not been modified by the Encyclopedia of Earth.
This is a chapter from Ecosystems and Human Well-being: Desertification Synthesis (full report).
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