Deforestation（因果关系说明文）
Deforestation means the removal of a forest so that the land is converted for urban use or agriculture. The destruction of forests occurs for many reasons: trees are used as fuel or for construction, while cleared land is used as pasture for livestock and crop plantations. The main adverse effects of deforestation are aridity and damage to animal habitat, as well as climate change and erosion damage.
The main causes of deforestation are commercial agriculture by big business and subsistence farming by local people. In Indonesia, industrial logging is carried out to clear areas for the production of palm oil while in Brazil, large areas of the Amazon rainforest were cleared to grow soya and vegetable oil. Subsistence farmers clear an area big enough to graze cattle or grow crops by cutting down the trees and burning them. However, after two or three years, the land can no longer be used so the farmer moves to another piece of land. It takes around ten years for the piece of land to recover. However, in populated areas, the land cannot recover and this leads to heavy erosion because the layer of soil that protects the ground is removed during the crop-growing process. This can cause flooding problems in heavy rain.
One area affected by deforestation is the Amazon Basin in Brazil. The vast rainforests of the Amazon cover an area around 25 times the size of the UK and absorb an estimated 1.5 billion tonnes of carbon dioxide annually. They are thought to have helped keep global warming under control in recent years.
However, in areas where deforestation has taken place, the increased temperatures result in less rain because there are not enough trees to provide water for clouds to form. If tropical forests dry out, more trees will die and there will be more logging and more fi res. This will cause more emissions of carbon dioxide, making the rainforest contribute to global warming rather than help solve it.
Forest destruction is also having an effect on biodiversity. The growth in the world’s population is causing the loss of habitats and damage to land where plants and animal species live, reducing biodiversity and leading to the extinction of many species. A decrease in biodiversity threatens entire ecosystems and destroys future sources of food and medicine.
The damage caused by humans to the world’s forests leads to changes in the natural environment and causes global warming. Governments should act to protect forests from illegal logging and plant more trees to absorb carbon dioxide. Deforestation on such a large scale is sure to have disastrous eff ects for the environment.
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