Deforestation is the logging and/or burning of trees in the forested area. There are several reasons for doing so: trees or derived charcoal can be sold as a commodity and used by humans, while cleared land is used as pasture, plantations of commodities and human settlement. The removal of trees without sufficient reforestation has resulted in damage to habitat, biodiversity loss and aridity. Deforested regions often degrade into wasteland.
Disregard or ignorance of intrinsic value, lack of ascribed value, lax forest management and deficient environmental law are some of the factors that allow deforestation to occur on a large scale. In many countries, deforestation is an ongoing issue that is causing extinction, changes to climatic conditions, desertification, and displacement of indigenous people.
However, among countries with a per capita GDP of at least $4,600, net deforestation rates have ceased to increase.[1][2]
sourcehttp://en.wikipedia.org/wiki/Deforestation
Saturday, June 6, 2009
Friday, June 5, 2009
CAUSES OF ANTHROPOGENIC DEFORESTATION
There are many root causes of deforestation, including corruption of government institutions,[3][4] the inequitable distribution of wealth and power,[5] population growth[6] and overpopulation,[7][8] and urbanization.[9] Globalization is often viewed as another root cause of deforestation,[10][11] though there are cases in which the impacts of globalization (new flows of labor, capital, commodities, and ideas) have promoted localized forest recovery.[12]
In 2000 the United Nations Food and Agriculture Organization (FAO) found that "the role of population dynamics in a local setting may vary from decisive to negligible," and that deforestation can result from "a combination of population pressure and stagnating economic, social and technological conditions."[6]
According to British environmentalist Norman Myers, 5% of deforestation is due to cattle ranching, 19% due to over-heavy logging, 22% due to the growing sector of palm oil plantations, and 54% due to slash-and-burn farming.[13]
The degradation of forest ecosystems has also been traced to economic incentives that make forest conversion appear more profitable than forest conservation.[14] Many important forest functions have no markets, and hence, no economic value that is readily apparent to the forests' owners or the communities that rely on forests for their well-being.[14] From the perspective of the developing world, the benefits of forest as carbon sinks or biodiversity reserves go primarily to richer developed nations and there is insufficient compensation for these services.
In 2000 the United Nations Food and Agriculture Organization (FAO) found that "the role of population dynamics in a local setting may vary from decisive to negligible," and that deforestation can result from "a combination of population pressure and stagnating economic, social and technological conditions."[6]
According to British environmentalist Norman Myers, 5% of deforestation is due to cattle ranching, 19% due to over-heavy logging, 22% due to the growing sector of palm oil plantations, and 54% due to slash-and-burn farming.[13]
The degradation of forest ecosystems has also been traced to economic incentives that make forest conversion appear more profitable than forest conservation.[14] Many important forest functions have no markets, and hence, no economic value that is readily apparent to the forests' owners or the communities that rely on forests for their well-being.[14] From the perspective of the developing world, the benefits of forest as carbon sinks or biodiversity reserves go primarily to richer developed nations and there is insufficient compensation for these services.
ATMOSPHERIC
Deforestation is ongoing and is shaping climate and geography.[19][20][21][22]
Deforestation is a contributor to global climate change,[23][24] and is often cited as one of the major causes of the enhanced greenhouse effect. Tropical deforestation is responsible for approximately 20% of world greenhouse gas emissions.[25] According to the Intergovernmental Panel on Climate Change deforestation, mainly in tropical areas, account for up to one-third of total anthropogenic carbon dioxide emissions.[26] Trees and other plants remove carbon (in the form of carbon dioxide) from the atmosphere during the process of photosynthesis and release it back into the atmosphere during normal respiration. Only when actively growing can a tree or forest remove carbon over an annual or longer timeframe. Both the decay and burning of wood releases much of this stored carbon back to the atmosphere. In order for forests to take up carbon, the wood must be harvested and turned into long-lived products and trees must be re-planted.[27] Deforestation may cause carbon stores held in soil to be released. Forests are stores of carbon and can be either sinks or sources depending upon environmental circumstances. Mature forests alternate between being net sinks and net sources of carbon dioxide (see carbon dioxide sink and carbon cycle).
SOURCEhttp://en.wikipedia.org/wiki/Deforestation
Deforestation is a contributor to global climate change,[23][24] and is often cited as one of the major causes of the enhanced greenhouse effect. Tropical deforestation is responsible for approximately 20% of world greenhouse gas emissions.[25] According to the Intergovernmental Panel on Climate Change deforestation, mainly in tropical areas, account for up to one-third of total anthropogenic carbon dioxide emissions.[26] Trees and other plants remove carbon (in the form of carbon dioxide) from the atmosphere during the process of photosynthesis and release it back into the atmosphere during normal respiration. Only when actively growing can a tree or forest remove carbon over an annual or longer timeframe. Both the decay and burning of wood releases much of this stored carbon back to the atmosphere. In order for forests to take up carbon, the wood must be harvested and turned into long-lived products and trees must be re-planted.[27] Deforestation may cause carbon stores held in soil to be released. Forests are stores of carbon and can be either sinks or sources depending upon environmental circumstances. Mature forests alternate between being net sinks and net sources of carbon dioxide (see carbon dioxide sink and carbon cycle).
SOURCEhttp://en.wikipedia.org/wiki/Deforestation
HYDROLOGICAL
The water cycle is also affected by deforestation. Trees extract groundwater through their roots and release it into the atmosphere. When part of a forest is removed, the trees no longer evaporate away this water, resulting in a much drier climate. Deforestation reduces the content of water in the soil and groundwater as well as atmospheric moisture.[32] Deforestation reduces soil cohesion, so that erosion, flooding and landslides ensue.[33][34] Forests enhance the recharge of aquifers in some locales, however, forests are a major source of aquifer depletion on most locales.[35]
Shrinking forest cover lessens the landscape's capacity to intercept, retain and transpire precipitation. Instead of trapping precipitation, which then percolates to groundwater systems, deforested areas become sources of surface water runoff, which moves much faster than subsurface flows. That quicker transport of surface water can translate into flash flooding and more localized floods than would occur with the forest cover. Deforestation also contributes to decreased evapotranspiration, which lessens atmospheric moisture which in some cases affects precipitation levels down wind from the deforested area, as water is not recycled to downwind forests
SOURCEThe water cycle is also affected by deforestation. Trees extract groundwater through their roots and release it into the atmosphere. When part of a forest is removed, the trees no longer evaporate away this water, resulting in a much drier climate. Deforestation reduces the content of water in the soil and groundwater as well as atmospheric moisture.[32] Deforestation reduces soil cohesion, so that erosion, flooding and landslides ensue.[33][34] Forests enhance the recharge of aquifers in some locales, however, forests are a major source of aquifer depletion on most locales.[35]
Shrinking forest cover lessens the landscape's capacity to intercept, retain and transpire precipitation. Instead of trapping precipitation, which then percolates to groundwater systems, deforested areas become sources of surface water runoff, which moves much faster than subsurface flows. That quicker transport of surface water can translate into flash flooding and more localized floods than would occur with the forest cover. Deforestation also contributes to decreased evapotranspiration, which lessens atmospheric moisture which in some cases affects precipitation levels down wind from the deforested area, as water is not recycled to downwind fores
SOURCEhttp://en.wikipedia.org/wiki/Deforestation
Shrinking forest cover lessens the landscape's capacity to intercept, retain and transpire precipitation. Instead of trapping precipitation, which then percolates to groundwater systems, deforested areas become sources of surface water runoff, which moves much faster than subsurface flows. That quicker transport of surface water can translate into flash flooding and more localized floods than would occur with the forest cover. Deforestation also contributes to decreased evapotranspiration, which lessens atmospheric moisture which in some cases affects precipitation levels down wind from the deforested area, as water is not recycled to downwind forests
SOURCEThe water cycle is also affected by deforestation. Trees extract groundwater through their roots and release it into the atmosphere. When part of a forest is removed, the trees no longer evaporate away this water, resulting in a much drier climate. Deforestation reduces the content of water in the soil and groundwater as well as atmospheric moisture.[32] Deforestation reduces soil cohesion, so that erosion, flooding and landslides ensue.[33][34] Forests enhance the recharge of aquifers in some locales, however, forests are a major source of aquifer depletion on most locales.[35]
Shrinking forest cover lessens the landscape's capacity to intercept, retain and transpire precipitation. Instead of trapping precipitation, which then percolates to groundwater systems, deforested areas become sources of surface water runoff, which moves much faster than subsurface flows. That quicker transport of surface water can translate into flash flooding and more localized floods than would occur with the forest cover. Deforestation also contributes to decreased evapotranspiration, which lessens atmospheric moisture which in some cases affects precipitation levels down wind from the deforested area, as water is not recycled to downwind fores
SOURCEhttp://en.wikipedia.org/wiki/Deforestation
SOIL
Undisturbed forest has very low rates of soil loss, approximately 2 metric tons per square kilometre (6 short tons per square mile).[citation needed] Deforestation generally increases rates of soil erosion, by increasing the amount of runoff and reducing the protection of the soil from tree litter. This can be an advantage in excessively leached tropical rain forest soils. Forestry operations themselves also increase erosion through the development of roads and the use of mechanized equipment.
China's Loess Plateau was cleared of forest millennia ago. Since then it has been eroding, creating dramatic incised valleys, and providing the sediment that gives the Yellow River its yellow color and that causes the flooding of the river in the lower reaches (hence the river's nickname 'China's sorrow'
SOURCEhttp://en.wikipedia.org/wiki/Deforestation
China's Loess Plateau was cleared of forest millennia ago. Since then it has been eroding, creating dramatic incised valleys, and providing the sediment that gives the Yellow River its yellow color and that causes the flooding of the river in the lower reaches (hence the river's nickname 'China's sorrow'
SOURCEhttp://en.wikipedia.org/wiki/Deforestation
ECOLOGICAL REASONS
Deforestation results in declines in biodiversity.[38] The removal or destruction of areas of forest cover has resulted in a degraded environment with reduced biodiversity.[39] Forests support biodiversity, providing habitat for wildlife;[40] moreover, forests foster medicinal conservation.[41] With forest biotopes being irreplaceable source of new drugs (such as taxol), deforestation can destroy genetic variations (such as crop resistance) irretrievably.[42]
Since the tropical rainforests are the most diverse ecosystems on Earth[43][44] and about 80% of the world's known biodiversity could be found in tropical rainforests,[45][46] removal or destruction of significant areas of forest cover has resulted in a degraded[47] environment with reduced biodiversity.[48]
Scientific understanding of the process of extinction is insufficient to accurately make predictions about the impact of deforestation on biodiversity.[49] Most predictions of forestry related biodiversity loss are based on species-area models, with an underlying assumption that as forest are declines species diversity will decline similarly.[50] However, many such models have been proven to be wrong and loss of habitat does not necessarily lead to large scale loss of species.[51] Species-area models are known to overpredict the number of species known to be threatened in areas where actual deforestation is ongoing, and greatly overpredict the number of threatened species that are widespread.[52]SOURCEhttp://en.wikipedia.org/wiki/Deforestation
Since the tropical rainforests are the most diverse ecosystems on Earth[43][44] and about 80% of the world's known biodiversity could be found in tropical rainforests,[45][46] removal or destruction of significant areas of forest cover has resulted in a degraded[47] environment with reduced biodiversity.[48]
Scientific understanding of the process of extinction is insufficient to accurately make predictions about the impact of deforestation on biodiversity.[49] Most predictions of forestry related biodiversity loss are based on species-area models, with an underlying assumption that as forest are declines species diversity will decline similarly.[50] However, many such models have been proven to be wrong and loss of habitat does not necessarily lead to large scale loss of species.[51] Species-area models are known to overpredict the number of species known to be threatened in areas where actual deforestation is ongoing, and greatly overpredict the number of threatened species that are widespread.[52]SOURCEhttp://en.wikipedia.org/wiki/Deforestation
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