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.

Present-day Drylands and Their Categories

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 ( ). 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.

Source: MA  Desertification Synthesis Report (2005), p.23

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Figure 1.1. Schematic Description of Development Pathways in Drylands

Figure 1.2. Land Uses in Drylands

Figure 2.1. Comparison of Infant Mortality and GNP per Person in Drylands and Other MA Systems in Asia

Figure 4.1. Key Desertification-related Findings of the MA Scenarios

Figure 6.1. Linkages and Feedback Loops among Desertification, Global Climate Change, and Biodiversity Loss

Appendix A: Present-day Drylands and Their Categories

Box 7.1Droughts in the Sahel Region: Lessons Learned and Knowledge Gaps

Figure 7.1. Overlap of Urban Areas with the Four Dryland Categories

Box 4.1. Millennium Ecosystem Assessment Scenarios

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