Table 1. Degraded area and population distribution in dryland zones.
Dryland zones Size of the area (million km2)* Share of global area (%)* Degraded area (million km2)** Degraded area
(%) 		Population*** Population density (km2)
Dry sub-humid 12.96 8.7 2.5 19.5 909 972 000 70
Semi-arid 22.67 15.2 4.8 21.2 855 333 000 38
Arid 15.17 10.6 4.5 28.7 242 780 000 16
Total dryland 50.80 34.5 11.8 23.1 2 008 085 000 40
Sources:
* UN 2011. Global drylands: a UN system-wide response. Environment Management Group. 132 p.
    http://www.unccd.int/Lists/SiteDocumentLibrary/Publications/Global-Drylands-ENG.pdf.
** Zika and Erb 2009.
*** UNCCD 2011. Desertification: a visual synthesis. Bonn. 50 p.
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Fig. 1. Types of soil degradation (million km2) in dryland zones. (Data source: UNEP1997).

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Fig. 2. The extent of dryland disturbance and consequently degradation affects vegetation structural complexity. Dryland vegetation succession (→) and regression (― →).