Desertification

Desertification means land degradation in arid, semi-arid and dry sub-humid areas regions, caused by climatic changes, human influence, or both. Land degradation means the reduction, or loss, in arid, semi-arid and dry sub-humid areas, of the biological or economic productivity and complexity of rainfed cropland, irrigated cropland or range, pasture, forest and woodlands, resulting from land uses or from a process or combination of processes, including processes arising from human activities and habitation patterns. Climatic factors include periods of temporary but severe drought and long-term climatic changes toward aridity. Human factors include the artificial alteration of the climate, such as degradation of the biological environment, which can be caused by removing vegetation (which can lead to unnaturally high erosion), excessive cultivation, and the exhaustion of surface-water or groundwater supplies for irrigation, industry, or domestic use.

Desertification drains a land of its life-supporting capabilities. A declining groundwater table, increasing erosion, and the disappearance of native vegetation characterise the process. Areas undergoing desertification may show all of these symptoms, but the existence of only one usually provides sufficient evidence that the process is taking place. Desertification typically begins in areas made susceptible by drought or overuse by human populations.

Public awareness of desertification increased during the severe drought in the Sahel in Africa (1968-73). In 1977 the world-wide consequences of desertification were the subject of a UN Conference on Desertification (UNCOD), held in Nairobi, Kenya. Given the importance of the interactions between climate and desertification, WMO has accorded a major priority to this area. Its action plan to combat desertification was first adopted in 1978 at the thirtieth session of the Executive Council of WMO, and has gone through several revisions since.

The Agricultural Meteorology Programme under the World Climate Programme (WCP) and the Hydrology and Water Resources Programme (both elements of WMO) have launched a number of activities in support of the combat against drought and desertification. WMO's strategy and activities in the field of desert therefore briefly include:

• Monitoring and assessment of drought and desertification;
• Application of meteorological and hydrological data;
• Research on the interactions between climate and desertification; and,
• Education and training upon the issue, including increasing public awareness of the problem.
  
  

Drought means the naturally occurring phenomenon that exists when rainfall has been significantly below normal recorded levels, causing serious hydrological (water) imbalances that negatively affect land resource production systems. It occurs when evaporation and transpiration (the movement of water in the soil through plants into the air) exceed precipitation for a considerable period. Drought is the most serious physical hazard to agriculture in nearly every part of the world. WMO has consistently been at the forefront of research into drought, its prediction, study, and prevention. The estimation, conservation and preservation of freshwater resources has also been of prime importance for the Organisation.