More about Desertification.

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Vegetation

From Wikipedia, the free encyclopedia

Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants, and is, by far, the most
abundant biotic element of the biosphere. The term vegetation does not, by itself, imply anything regarding species composition,
life forms, structure, spatial extent, "naturalness", or any other specific botanical or geographic characteristics. It is broader than
the term flora which refers exclusively to species composition. Perhaps the closest synonym is plant community, but vegetation
can, and often does, refer to a wider range of spatial scales. Primeval redwood forests, coastal mangrove stands, sphagnum
bogs, desert soil crusts, roadside weed patches, wheat fields, cultivated gardens and lawns; all are encompassed by the term
vegetation.

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In ecology, an ecosystem is a combination of all the living and non-living
elements of an area. Ecosystems are the smallest level of organization in
nature that incorporates both living and nonliving factors. They can range in
scale from a wide geographical area such as the Sahara Desert to
something small as a puddle. The term microecosystem may be used to
describe a very small (often closed) ecosystem.

In general terms an ecological system can be thought of as an assemblage
of organisms (plant, animal and other living organisms—also referred to as
a biotic community or biocoenosis) living together with their environment (or
biotope), functioning as a loose unit. That is, a dynamic and complex whole,
interacting as an "ecological unit."

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Land Degradation.

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

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.