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Desertification

Desertification is the degradation of drylands which include arid, semi-arid and sub-humid areas. Drylands make up roughly 40 percent of the Earth’s land and are home to some two billion people, most of which live in developing countries. Dryland soil sustains a fragile ecosystem adapted to infrequent precipitation and dramatic temperature changes. Over-exploitation of dryland for cultivation and feedstock purposes renders the soil unproductive, forcing migration of communities in search of fertile land, leaving the unproductive land bare and vulnerable to erosive forces. A lack of food supply in many developing countries forces constant cultivation of land for short-term gain as well as deforestation to provide arable land.

Case studies

Desertification

Mouse over the map to read about the impact of desertification in different areas.

Downstream Effects

Soil affects the climate and biodiversity and often leads to irreversible desertification (see figure above). Roots increase the stability of soil and prevent erosion (Gyssels & Poesen, 2003). In addition, trees provide cover and protect nearby fauna and flora. In areas prone to soil erosion, this is especially important as rainfall tends to be rare but when it does occur, it is often very intense and easily leads to topsoil being washed away.

Roots are also important carbon sinks. Increasing root biomass is therefore very likely to improve the carbon budget of the plants we are seeding (Dr Alexandru Milcu, oral communication).

Image taken from the Millenium Ecosystems Assessment - Desertification synthesis [1].

References:

[1] Millenium Ecosystem Assessment (2005) Ecosystems and Human Well-being: Desertification Synthesis. World Resources Institute, Washington, DC.(Online) Available from: http://www.maweb.org/documents/document.355.aspx.pdf

[2] Pickup, G. (1998) Desertification and climate change - the Australian perspective. Climate Research 11, pp.51-63.

[3] UNCCD (2011) Desertification: a visual synthesis. (Online) Available from: http://www.unccd.int/knowledge/docs/Desertification-EN.pdf (Accessed on 12 August, 2011).

[4]Science Daily (2007). Severity Of Desertification On World Stage. (Online) Available from: http://www.sciencedaily.com/releases/2007/06/070619180431.htm.

[5] The Encyclopedia of the Earth (2010). Desertification. (Online) Available from: http://www.eoearth.org/article/Desertification?topic=49461