BACKGROUND
At the close of the twentieth century, there are approximately 3,500 million hectares of forests in the world, representing 27 per cent of land use. Of this total forest area, 2,000 million hectares are found in developing countries, mostly in the tropical and sub-tropical regions (FAO 1997). Although the original forest area is not known precisely, it is estimated that the world has lost approximately 40 per cent of the original forest area of 6,000 million hectares over the last 8,000 years (Bryant, 1997; Laarman and Sedjo, 1992). Most of the loss in forest area is a direct consequence of human intervention in the 20th century.
There are many different types of tropical forests, ranging from the rain forests of the Amazon to the dry woodlands of Southern Africa, from the coastal mangroves of Southeast Asia to the alpine forests in the Andean highlands of South America.
Deforestation is the permanent loss of forests to other land uses such as agriculture, grazing, new settlements, infrastructure, and dam reservoirs. Tropical deforestation is now widely recognized as one of the most critical environmental problems facing the world today, with serious long-term economic and social consequences. Largely overlooked by the developed countries and the urban dwellers of the developing countries until the 1980s, this deforestation has received much attention in recent years. Vivid images of burning trees in the Amazon have been seen by people around the world, and the effect of deforestation on biodiversity and climate change has been the subject of many newspaper articles and television documentaries.
The economic and environmental problems facing the developing world are staggering in their magnitude and their complexity. They are fueled by the vicious cycle of population growth and persistent poverty. Most countries face serious problems in the urban environment: overcrowding, unemployment, growing crime, lack of potable water, inadequate sewage disposal, increasing air pollution, and the inappropriate disposal of toxic wastes. In rural areas, the deterioration of natural resources not only destroys the environment, but also undermines the very foundation on which economic growth and long term prosperity depend. The catastrophic impact is seen in accelerating soil erosion which results in permanent loss in agricultural productivity, in advancing desertification accompanied by drought and famine, in declining coastal and inland fisheries with the associated threats to food security, in the misuse of agrochemicals that poison both people and the environment, in the alarming sedimentation of fragile coral reefs; and in the destruction of biodiversity-rich wetlands. None of these natural resource problems is more threatening, none more in need of immediate action, than the destruction of the tropical forests.
Deforestation is an enduring change of land use marked by forest loss (WCFSD, 1998). It is not within the scope of this paper to undertake a thorough examination of tropical forest degradation. Unlike deforestation, degradation does not involve a change in land use, but it is a serious problem in the tropics. Probably more than 10 million hectares are degraded each year by the action of loggers, firewood collectors, and livestock herders. Although the land remains under forest use, its composition and biological functions are compromised by human intervention. The chief cause of forest degradation is exploitative logging, with its selective removal of tree species, felling damage to the residual forest, soil damage from road construction and log skidding, and the displacement of bird and mammal species. Logging roads provide new access for farmers and ranchers who come to clear and burn the logged-over forests once the skidders and chainsaws have left. Forest degradation also occurs as a consequence of intensive fuelwood collection and overgrazing by livestock and wildlife. More research is required on the scale and impact of degradation on all types of forests.