ENVIRONMENTAL DEGRADATION

A temporary or permanent decrease in the capability of the environment to support the resource demands of the organisms that inhabit it. Such a broad definition is necessary to encompass the various elements of the environment that may be affected by degradation and to stress that the impacts of degradation are normally expressed in terms of the environment as a resource base for a biological population, including humans.

In terms of the Earth’s surface, soil degradation and land degradation are the predominant forms. The former is expressed by a decrease in the productive capacity of the soil due to changes in the nutrient budget, erosion processes and chemical or biological attributes. The latter is a composite term to signify decreasing productivity of the land as a whole, thus implying a socio-economic dimension in parallel with environmental changes. soil erosion, salinisation and desertification are common causes of land degradation.

In terms of the hydrosphere, degradation primarily involves declining productivity potential of waterbodies, owing to pollution. acidification of lakes due to acid rain and metal pollution caused by contaminated runoff from waste heaps and derelict smelting works are two examples; both are known to cause long-term productivity decreases in both floral and faunal assemblages. In addition, the pollution of waterbodies used to provide drinking water (see potable water) is a form of degradation, because without specialist treatment, polluted water is incapable of sustaining its current usage.

Similarly, air pollution from a range of sources (including carbon dioxide and dust from the combustion of fossil fuels and carbon monoxide from vehicle exhaust emissions) has resulted in generally decreased air quality, which poses a threat to human health and causes productivity decline in the ecosystems of certain areas. The growing threat of global warming caused by an enhanced greenhouse effect also has the potential to degrade the environment on a global scale. The shifting of vegetation zones, sea-level change and modification of the hydrological and biogeochemicalcycles may locally change the suitability of the environment to particular purposes. Stronger zonal winds in response to steepened temperature gradients, for example, may cause accelerated soil erosion in susceptible areas such as the Chinese loess plateau, which would contribute markedly to soil and land degradation and cause a decrease in agricultural productivity.

[See alsodegradation, human impact on environment]