Deforestation is the removal or destruction of significant areas of forest.
Orbital photograph of human deforestation in progress in the Tierras Bajas project in eastern Bolivia. Photograph courtesy NASA.
Deforestation can result from long - term forest degradation for example, the sustained removal of trees without sufficient reforestation. It can be deliberate - as when land is cleared for slash and burn farming or human habitation - or unintentional, particularly where uncontrolled grazing prevents natural regrowth of young trees.
Deforestation has been practiced by humans for thousands of years. The earliest deforestation may have been the burning of the forest to create openings for wildlife and later, chiefly as a result of clearing land for growing crops, and developing pasture for grazing animals. While the earliest example of deforestation is unclear (there is some controversy over the origin of the Sahara Desert for example), examples such as that of Easter Island show clear evidence of the ecological impact of human activity.
Growing worldwide demand for wood to be used in construction, paper and furniture - as well as clearing land for commercial and industrial development ( including road construction) has combined with growing local populations and their demands for agricultural expansion and wood fuel to endanger ever larger forest areas.
The rate of clearance increased during the second half of the 19th century due to agricultural expansion in Europe. Deforestation rates peaked in the Great Lakes region of the United States in the late 19th century. Once those forest resources were depleted, timber demand shifted to tropical forests. Rates of tropical deforestation have increased substantially in to post-war period as logging operations became mechanised. Agricultural development schemes in Mexico, Brazil and Indonesia moved large populations into the rainforest zone, further increasing deforestation rates. One fifth of the tropical rainforest destroyed between 1960 and 1990. Estimates of deforestation of tropical forest for the 1990s range from ca. 55,630 km² to ca. 120,000 km² each year. At this rate, all tropical forests may be gone by the year 2090.
Deforestation is often cited as one of the major causes of the enhanced greenhouse effect. Trees and other plants 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 dioxide back in to the atmosphere.
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, carrying away topsoil and often causing flooding. In this environment, nutrients in the soil are leached off and the microorganisms that can replenish these nutrients are disturbed.
Some forests are rich in biological diversity. Deforestation can cause the destruction of the habitats that support this biological diversity - thus causing population shifts and extinctions
One answer to the problem of deforestation is to build houses out of non-wood materials, such as brick, stone, concrete, and fiberglass. These materials have the additional benefits of being fireproof, waterproof, and pest-proof. Paper can be made of hemp fiber instead of wood - although there are strong arguments stating that farming trees may create more forests than farming hemp.
Recycling paper reduces the number of trees cut down. E-mails and web pages reduce the amount of wood paper used as well. Some lumber companies are planting trees to replace the trees taken. Hay, dry weeds, trash, garbage, husks, and stalks can be burned for energy instead of wood, although this still causes air pollution. Non-polluting energy generation includes solar cells, windmills, and geothermal energy.
New methods are being developed to farm more food crops on less farm land, such as high-yield hybrid crops, greenhouses, autonomous building gardens, and hydroponics. The reduced farm land means less land is cleared for growing crops. In cyclical agriculture, cattle are grazed on farm land that is resting and rejuvenating. Cyclical agriculture prevents the soil from being overfarmed and stripped of its nutrients - reducing the need for slash-and-burn methods.
Grass is allowed to grow on the resting farm land. The cows eat the grass and leave behind their dung, which is also a source of fertilizer. This also reduces deforestation by using farmland to graze instead of using forest land.
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.
The Arbor Day Foundation 's Rain Forest Rescue program is a charity that helps to prevent deforestation. The charity uses donated money to buy up and preserve rainforest land before the lumber companies can buy it. The Arbor Day Foundation then protects the land from deforestation. This also preserves the way of life of the primitive tribes living on the forest land.