The United Nations Convention to Combat Desertification (CCD) defines desertification as:
"land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climate variation and human activities" (UNCCD 1995)
The term 'desertification' makes one think of barren, desertlike conditions. In addition to dry, sandy soils though it should be remembered that the CCD definition also includes other factors including biodiversity loss, ecological deterioration, disturbances of vital natural resources such as water supplies, poverty and the breakdown of human societies as a result.
'Land degradation' is is a complex concept with many dimensions. However the human suffering it causes is all too real. Here are a few major, well-known examples:
The USA 'Dust Bowl' during the 1930s dislocated and impoverished hundreds of thousands (famously captured in John Steinbeck's novel 'Grapes of Wrath').
The Soviet Union created land degradation on a large scale in the Central Asian drylands through mechanized over-farming (Holzel et al. 2002).
The diversion of water flowing into the Aral Sea for crop irrigation during the Soviet era triggered catastrophic desertification over a large area (Saiko and Zonn 2000).
The limited amount of farmland available in North Africa and West Asia are being pressured by overgrazing combined with extension of the cropped area (Abahussain et al. 2002), and by salinization caused by dam and irrigation systems, such as in the Nile Delta (Juo and Wilding 2001).
Dryland degradation is widely reported across Sub-Saharan Africa.
Northern China, Australia, northeastern Brazil, the Caribbean Islands, and many other dryland areas have experienced damage from deforestation and overgrazing.
Even Europe is not exempt; degradation is a significant issue across its driest, southern Mediterranean zone (Garcia Latorre et al. 2001; Yassoglou 2000).
As the major use of land in the dry areas, agricultural systems play a critical role in desertification and its frequent companion, drought. The poor in developing countries are especially hard-hit by these scourges, because they depend on agriculture for a bare living. In short, desertification, drought, poverty and agriculture are interdependent problems of enormous magnitude and worldwide extent.
What are the major causes of desertification?
Abahussain, A. A., Abdu, A. S., Al-Zubari, W. K., El-Deen, N. A., and Abdul- Raheem, M. 2002. Desertification in the Arab region: analysis of current status and trends. Journal of Arid Environments 51:521-545.
Holzel, N., Haub, C., Ingelfinger, M. P., Otte, A., and Pilipenko, V. N. 2002. The return of the steppe - large-scale restoration of degraded land in southern Russia during the post-Soviet era. Journal for Nature Conservation 10:75-85.
Garcia Latorre, J., Sanchez Picon, A. and Garcia Latorre, J. 2001. The man-made desert: effects of economic and demographic growth on the ecosystems of arid southeastern Spain. Environmental History 6:75-94.
Juo, A. S. R. and Wilding, L. P. 2001. Land and civilization: an historic perspective. Pp. 13-19 in Bridges, E. M., Hannam, I. D., Oldeman L. R., Penning de Vries, F. W. T., Scherr, S.J. and Sombatpanit, S. 2001. Response to Land Degradation. Enfield, New Hampshire, USA: Science Publishers.
Saiko, T. A. and Zonn, I. S. 2000. Irrigation expansion and dynamics of desertification in the Circum-Aral region of central Asia. Applied Geography 20:349-367.
UNCCD 1995. Down to Earth: A simplified guide to the Convention to Combat Desertification, why it is necessary and what is important and different about it. Bonn, Germany: Secretariat for the United Nations Convention to Combat Desertification. (see also Facts Sheet, FAQ and Explanatory Leaflet at http://www.unccd.int/knowledge/menu.php
Yassoglou, N. J. 2000. History of desertification in the European Mediterranean. Pp. 9-15 in Enne, G., D'Angelo, M. and Zanolla, C. (eds.) Indicators for Assessing Desertification in the Mediterranean. Proceedings of the International Seminar held in Porto Torres, Italy, 18-20 September, 1998. Sassari, Italy: University of Sassari Nucleo Ricerca Desertificazion.