Hillel and Rosenzweig 2005

Hillel, D., and C. Rosenzweig, 2005: Desertification. In Encyclopedia of Soils in the Environment. D. Hillel, J.H. Hatfield, D.S. Powlson, C. Rosenzweig, K.M. Scow, M.J. Singer, and D.L. Sparks, Eds., vol. 1. Elsevier/Academic Press, pp. 382-389.

Ecosystems in semiarid and arid regions around the world appear to be undergoing various processes of degradation commonly described as 'desertification.' According to the United Nations Environmental Program (UNEP), all regions in which the ratio of total annual precipitation to potential evapotranspiration (P/ET) ranges from 0.05 to 0.65 should be considered vulnerable to desertification. Such regions constitute some 40% of the global terrestrial area. They include northern Africa, southwestern Africa, southwestern Asia, central Asia, northwestern India and Pakistan, southwestern USA and Mexico, western South America, and much of Australia, and are home to an estimated sixth of the world's population.

'Desertification' is a single word used to cover a wide variety of interactive phenomena — both natural and anthropogenic — affecting the actual and potential biological and agricultural productivity of ecosystems in semiarid and arid regions. It is an emotive term, conjuring up the specter of a tide of sand swallowing fertile farmland and pastures. Apparently with this somewhat simplistic image in mind, UNEP sponsored projects in the early 1980s to plant trees along the edge of the Sahara, with the aim of warding off the invading sands. While there are places where the edge of the desert can be seen encroaching on fertile land, the more pressing problem is the deterioration of the land due to human abuse in regions well outside the desert. The latter problem emanates not from the expansion of the desert per se but from the centers of population outside the desert, owing to human mismanagement of the land. A vicious cycle has begun in many areas: as the land degrades through misuse, it is worked or grazed ever more intensively, so its degradation is exacerbated; and as the returns from 'old' land diminish, 'new' land is brought under cultivation or under grazing in marginal or even submarginal areas.

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Hillel, D., and Rosenzweig, C.: Desertification, in: Encyclopedia of Soils in the Environment, edited by Hillel, D., Hatfield, J.H., Powlson, D.S., Rosenzweig, C., Scow, K.M., Singer, M.J., and Sparks, D.L., vol. 1, 382-389, Elsevier/Academic Press, Amsterdam et al., 2005.

Hillel, D., and C. Rosenzweig (2005), Desertification, in Encyclopedia of Soils in the Environment, vol. 1, edited by D. Hillel, J.H. Hatfield, D.S. Powlson, C. Rosenzweig, K.M. Scow, M.J. Singer, and D.L. Sparks, pp. 382-389, Elsevier/Academic Press, Amsterdam et al.

Hillel, D., and C. Rosenzweig, 2005: Desertification. In Encyclopedia of Soils in the Environment. D. Hillel, J.H. Hatfield, D.S. Powlson, C. Rosenzweig, K.M. Scow, M.J. Singer, and D.L. Sparks, Eds., vol. 1. Elsevier/Academic Press, pp. 382-389.

Hillel, D., & Rosenzweig, C. 2005, in Encyclopedia of Soils in the Environment, ed. Hillel, D., Hatfield, J.H., Powlson, D.S., Rosenzweig, C., Scow, K.M., Singer, M.J., & Sparks, D.L., vol. 1, 382 (Amsterdam et al.: Elsevier/Academic Press).

Hillel D, Rosenzweig C. Desertification. In: Hillel D, Hatfield JH, Powlson DS, Rosenzweig C, Scow KM, Singer MJ, Sparks DL, editors. Encyclopedia of Soils in the Environment, vol. 1, pp. 382-389. Amsterdam et al.: Elsevier/Academic Press; 2005.

D. Hillel, C. Rosenzweig, In Encyclopedia of Soils in the Environment, D. Hillel, J.H. Hatfield, D.S. Powlson, C. Rosenzweig, K.M. Scow, M.J. Singer, D.L. Sparks, Eds. (vol.1, Elsevier/Academic Press, Amsterdam et al., 2005), pp. 382-389.