Deforestation is the removal of trees, often as a result of human activities. Deforestation has been practiced by humans for thousands of years chiefly as a result of clearing land for commercial and industrial development, intensive collection of firewood, clearing of land for growing crops and to deveop passture for grazing animals. The rate of clearance increased during the second half of the ninenteenth century due to agricultural expansion in Europe and there has been massive increases since then. Currently major worries concern the loss of tropical rainforest, one fifth of which was destroyed between 1960 and 1990. 12 million hectares of tropical forest are lost each year, a land approximately the size of England.
Deforestation is often cited as one of the major causes of the enhanced greenhouse effect. Trees remove carbon (in the form of carbon dioxide) from the atmosphere during the process of photosynthesis. Both the rotting and burning of wood releases this stored carbon carbon dioxide back in to the atmosphere.
Pressure has been exerted on forests by the worldwide demand for wood and by local people who clear forests in their quests to establish an agrarian land base. Clearing of forests for the development of pasture for cattle has also resulted in deforestation as has the encroachment upon forests due to increasing human populations.
Deforestation promotes erosion of soil. Under normal circumstances trees and bushes and the forest floor act as a 'sponge' for rainfall, slowing its' overland and underground flow and releasing it back into the atmosphere through transpiration. Without the buffering effect of forest cover, rain impacting bare soil runs off, often causing flooding. In this environment, nutrients in the soil are leached off and the microorganisms which can replenish these nutrients are disturbed.
Forests are rich in biological diversity. Deforestation causes the destruction of the habitats that support biological diversity.
Some societies are making efforts to stop or slow deforestation. In China, where large scale destruction of forests has occurred, each citizen must plant at least 11 trees every year. In western countries, increasing consumer demand for wood products that have been produced and harvested in a sustainable manner are causing forest landowners and forest industries to become increasingly accountable for their forest management and timber harvesting practices.