The Effect of Deforestation on the Climate and Environment
Uploaded by msnarayana on Sep 14, 2013
Deforestation is caused by the growing demand for forest products and the conversion of forest to agriculture as the human population continues to expand. In 1750 cropland and pastureland occupied 6-7% of the global land surface; by 1990 cropland and pastureland occupied 35-39% of the global land surface. It is estimated that the world is currently losing over 9 million hectares per year which is an area the size of Portugal. Deforestation not only affects the climate by increasing the atmospheric level of carbon dioxide but also affects the environment by inhibiting water recycling, triggering severe flooding, aquifer depletion, soil degradation and the extinction of plant and animal species.
Trees remove carbon dioxide from the atmosphere through photosynthesis (see my posting entitled The Carbon Cycle). Cutting down forests will cause a decline in photosynthetic activity which results in the atmosphere retaining higher levels of carbon dioxide. Forests also store an enormous amount of organic carbon which is released into the atmosphere as carbon dioxide when forests are cleared by burning. Clearly, deforestation contributes to global warming and ocean acidification (see my two postings entitled Solar Activity, Greenhouse Gas Levels and Climate Change on Our Earth and Atmospheric Carbon Dioxide Levels and Ocean Acidification).
Water recycling is the movement of rain from the forest to land masses further inland. When rain falls on forests the water is intercepted by the forest canopy. Some of this intercepted water is returned to the atmosphere by evaporation and transpiration (release of water vapor into the atmosphere through stomata on tree leaves) while the rest is returned to the ocean as river runoff. In a healthy forest about three fourth of the intercepted water is returned to the atmosphere as moisture laden air masses which move inland, cool and are converted to rain. Land cleared by deforestation returns only about one fourth of the rain water to the atmosphere. This air mass has less moisture and delivers less rain further inland. Deforestation inhibits water recycling and converts inland forest to dry land and potential waste land.
Severe flooding is a result of deforestation because removal of the forest leaves little vegetative cover to hold heavy rains. The inability of land void of forest to hold heavy rain water will also trigger mudslides like the ones that have occurred in recent years in California, China and other parts of the world. Severe flooding and mudslides are extremely costly because...