The world’s forest nowadays facing a serious problem which is deforestation, which is the clearance of indigenous forest and woodlands either permanently or temporarily for the sake of agriculture or other uses. Our forest are currently shrinking about 9 million hectares each year according to the world statistics on forest cover given by the UN Food and Agriculture Organisation(FAO).
Forests are natural climax vegetation of many parts of the world covering, until recent years, a third of the land surface. At one time, tropical forests cloaked regions that were, collectively, twice the size of Europe. For the thousand years or more, those forests endured in rich complexity, as the homes of an estimated 50 to 90 percent of all land-dwelling species. In less than four decades, human populations destroyed more than half of those ancient forests, and most of their spectacular arrays of species may be lost forever. With every passing year, another38 million acres is logged over. That is the equivalent of levelling thirty-four city blocks every minutes.
The destruction extends beyond the tropics. Today, highly mechanized logging operations are proceeding in the once-vast temperate forests of the United States, Canada, Europe, Siberia, and elsewhere. Why are people doing this? Paralleling to the rapid increase in the size of the human population are rapidly increasing demands for lumber or timber, fuel, and other forest products. More and more people compete for diminishing resources. They do so for economic profit, but also because alternative ways of life simply are not available to most individuals and families.
Recent and present deforestation affects mainly tropical rain forest. Why are tropical rain forest disappearing? In the Congo River basins of South American and Amazon, most of the remaining undisturbed tropical rain forest are being cleared and burned at a rate unprecedented in human history. Tropical rain forest also being destroyed at a rapid rate in Southern Asia, Indonesia, Central America and the Philippines.
Several studies show a strong relationship between population growth and deforestation. More people in turn more food needed, so they clear forest for agriculture expansion. However, population pressure is not the main reason that contribute to the deforestation of the tropical rain forest. The main reasons of deforestation is different from place to place, and a variety of economics, and government factors interact to cause deforestation. Government policies sometimes provide incentives which indirectly aid the deforestation. For instance, in the late 1950s the Brazilian government construct the Belem- Brasilia Highway, which cut through the Amazon Basin and opened the Amazonian frontier for the settlement.
Besides of the government policies issues, there are others reasons which are probably the most immediate causes of deforestation in the tropical rain forest. These are subsistence agriculture, commercial logging and cattle ranching. Other factors which contribute to the removal of forest also include the development of dam which generated by hydroelctric power, which inundates large area of the forest, mining and also plantation of the crops such as fruits and vegetables.
Subsistence agriculture, in which family produce enough food to feed themselves, accounts for perhaps 60% of tropical deforestation. In many developing countries where the tropical rain forest are located, most of the people do not own the land on where they work and live. Majority of the subsistence farmers have no place to go except into the forest, which the will clear then land plant their crops and grow their own food. Subsistence farmer usually follow loggers to access roads to find a suitable spot. They will cut down trees and allow the trees to dry, then they will burn the area and plant their crops. This is known as shift cultivation which also referred as slash-and-burn agriculture. Ashes form the burn will provide nutrient for the cultivation and at the same time will destroy the pest which might cause harm to their crops. The nutrient-rich ashes can sustain crops for one to several seasons. Yields from the first crops are usually quite high because the soil are still enriched with lots of nutrients. However, as the nutrients will become exhausted day by day the fertility of the soil will decline rapidly. This causes the soil become infertile hence the crops production will also drop. In a few years, famers must find a new area and move to a new part of the forest and repeat the process. When shifting cultivation is practiced on small, widely scattered plots, a forest ecosystem does not necessarily suffer extensive damage. The original plots then will take about 30-40 years to establish to a mature tropical rain forest canopy again.
About 20% of the tropical rain forest deforestation is the result of commercial logging, and vast tracts of tropical rain forests, particularly in the Southern Asia , timber are cut and to be exported abroad. Commercial logging is allowed in most of the tropical countries to proceed much faster than it is sustainable because it supplies them with high profits. In the final analysis, this practice does not benefits and contribute to the economic development; relatively it diminish and ruin the important natural resources of the country. Next, roughly 12% of the tropical rain forest is cleared to provide open pasture for cattle. After the removal of forest, cattle ranch on the land for as long asc20 years, after which time the soil fertility is deplete. When this occurs, shrubby plants, or scrub savanna, take over the range.
If forests are destroyed, environment will also facing destruction and people who depends on the forest will face dilemma. Deforestation increase soil erosion and also thus decrease soil fertility. Soil erosion is the depletion of soil layer. Deforestation causes the plant root system to be absence thus the soil structure become loose. The top layer of the soil will fall if heavy rain continues for a long period. This then contribute to landslides on hillslide. Soils erosion caused sendimentation of waterways, which harm downstream aquatic ecosystem by reducing light penetration, covering aquatic organism and filling up the waterways. Mudflows will occur especially on deforested slopes or hillside if soil erosion is not under controlled. By trapping and absorbing precipitation, forest on slopes and hillsides or mountain help to hold the soil at the same time protect lowlands from floods. When trees are cut down, the watershed cannot absorb and hold the water as well. The eroded soil is then carried by the water and flow in to bottom of the river. The total amount of surfave runoff flowing into the rivers and streams increase. Hence, lowland areas are at extreme risk of flash flood during rainy seasons. This will endanger human lives and properties such as houses and cars. Deforestation can also lead to the formation of deserts in drier areas.