Drylands

Authored by: Lindsay C. Stringer , Andrew J. Dougill

Routledge Handbook of Ecosystem Services

Print publication date:  January  2016
Online publication date:  January  2016

Print ISBN: 9781138025080
eBook ISBN: 9781315775302
Adobe ISBN:

10.4324/9781315775302-34

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Abstract

Drylands are divided into arid, semi-arid and dry sub-humid sub-types, and cover approximately 6 billion hectares, or 40%, of the world’s terrestrial surface. Nearly 75% of the world’s drylands are located in developing countries. Estimates suggest that globally, more than 2 billion people live in the drylands, while billions of others depend upon goods and services from these systems (UNDP-UNCCD, 2011). Water is the key factor that limits dryland primary productivity. For an area to be classed as a dryland, it must have an aridity index of ≤0.65, where annual mean potential evapotranspiration is at least 1.5 times greater than annual mean precipitation (Middleton and Thomas, 1994). The combination of low rainfall and high evaporation leads to low soil moisture. Together with slow processes of nutrient cycling, this has an important influence on the types of land use that can be sustained, as well the nature and distribution (both temporally and spatially) of the ecosystem services from these environments. Across the arid, semi-arid and dry sub-humid dryland subtypes, land uses include rangelands, dry forests, arable cropland and urban areas. Some uses also encompass areas protected for conservation or used for mining.

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