7.3.2. Ecosystems

• The region is characterized by arid and semi-arid lands, on which it depends for much of its economic activity (e.g., agriculture and livestock grazing in rangelands). These ecosystems are under extreme pressure from human activities and current climatic conditions (e.g., high temperatures and prolonged droughts). Because of the current marginality of soil-water and nutrient reserves, some ecosystems in semi-arid regions may be among the first to show the effects of climate change. However, a number of management options (e.g., better stock management, more-integrated agroecosystems) could improve land conditions.
• The relatively hospitable mountain regions are under particular pressure from human settlements and commercial cultivation, which have led to land degradation and adverse effects on water supply. Glacial melt is forecast to increase under climate change, which would lead to increased summer flows in some river systems for a few decades, followed by a reduction in flow as the glaciers disappear.
• A tenth of the world's known species of higher plants and animals occurs in this region. Some countries (particularly Turkey and Tajikistan) are centers of origin for many crop and fruit-tree species; as such, they are important sources of genes for the wild relatives. Few studies are available to assess the impact of climate change on the biodiversity of the region; given its importance, however, there is a need for such studies. Biodiversity is being lost in the region because of human activities, especially land degradation and the overuse of resources.

7.3.2.1. Grasslands, Rangelands, Woodlands, and Deserts

Half of the region (see Table 7-1) is classified as arid land, much of which is true desert (i.e., extremely arid, as defined in IPCC 1996, WG II, Chapter 3). Another tenth of the region is classified as semi-arid rangeland, dominated by grasslands or shrublands. About 10% of the arid and semi-arid land is classified as having some soil constraints, indicating either that it shows significant soil degradation or that it is desertified (see Table 7-1). The region's major deserts and some of their characteristics are listed in Table 7-2, along with their classification (i.e., semi-arid, arid, or extremely arid, as defined in IPCC 1996, WG II, Chapter 3). For comparative purposes, deserts in adjoining regions (e.g., the Gobi desert from the Temperate Asia region) are included. Deserts are classified as cold deserts (e.g., upland deserts of Middle Asia that are 1,200 m above sea level) or hot deserts (e.g., those in the Middle East). The seasonality of the deserts' rainfall varies; some receive predominantly winter rain, whereas others receive mostly summer rain. Deserts with very sporadic rain events are classified as aseasonal.

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