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Drylands

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Drylands

Drylands are defined by their scarcity of water. They are zones where precipitation is counterbalanced by evaporation from surfaces and transpiration by plants (evapotranspiration).[1] UNEP defines drylands as tropical and temperate areas with an aridity index of less than 0.65.[2] The drylands can be further classified into four sub-types: dry sub-humid lands, semi-arid lands, arid lands, and hyper-arid lands. Some authorities consider Hyper-arid lands as deserts (UNCCD) although a number of the world’s deserts include both hyper arid and arid climate zones. The UNCCD excludes hyper-arid zones from its definition of drylands.

Drylands cover 41.3% of the earth’s land surface, including 15% of Latin America, 66% of Africa, 40% of Asia and 24% of Europe. Worldwide there is a significantly greater proportion of drylands in developing countries (72%), and the proportion increases with aridity: almost 100% of all Hyper Arid lands are in the developing world. Nevertheless, the United States, Australia and several countries in Southern Europe also contain significant dryland areas.[3]

Drylands are complex, evolving structures whose characteristics and dynamic properties depend on many interrelated links between climate, soil, and vegetation.[4]

Dryland biodiversity

Dryland economies

See also

References

  1. ^ Middleton and Thomas, 1997. The World Atlas of Desertification Millennium Ecosystem Assessment (2005a). Climate Change. Chapter 13 in: Ecosystems and Human Wellbeing: Current State and Trends, Volume 1. Island Press.
  2. ^ Millennium Ecosystem Assessment, 2005. Drylands Systems. Chapter 22 in: Ecosystems and Human Wellbeing: Current State and Trends, Volume 1. Island Press.
  3. ^ Millennium Ecosystem Assessment, 2005. Drylands Systems. Chapter 22 in: Ecosystems and Human Wellbeing: Current State and Trends, Volume 1. Island Press.
  4. ^ Rodríguez-Iturbe, I. and A. Porporato 2004. Ecohydrology of Water-Controlled Ecosystems: Soil Moisture and Plant Dynamics. Cambridge University Press.
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