Saving the Tropical Forests
Tropical forests cover about 6 percent of the Earth's land area. It is difficult to be precise about the area, but in 2009 tropical forests of all types probably occupied approximately 7 million square miles (18 million km2). As well as rain forests, the Tropics support seasonal forest, dry forest, and mangrove forest, and all of these vary in structure and composition from one region to another. Tropical forests occur in at least 90 countries. The largest area is in Latin America and the Caribbean, which has about 52 percent of the total tropical forest, followed by Africa with 30 percent, and Asia and the Pacific Islands with 18 percent.
In some places, tropical forests occupy land that is in demand for food production, and in most regions where this is the case small-scale farmers and agricultural companies have converted substantial areas of forest to farmland. The forests also contain trees that yield highvalue hardwood timber, and in some areas illegal logging is clearing some forest and damaging more by opening tracks to gain access to selected trees. Roads driven through the forest encourage agricultural expansion by allowing farmers to penetrate the forest and clear land to the sides of the roads. Mangrove forests in Asia are being damaged by the expansion of shrimp farming in coastal waters.
News stories about areas of forest clearance, often accompanied by photographs showing forests devastated by machinery, have led many people to fear that the tropical forests are being subjected to such a ferocious attack that within a few decades they may disappear altogether. It is certain that the area of tropical forests has decreased substantially in the past, but it may be that the decline has been slowed and perhaps halted. There was no decrease, and possibly a small increase, in the area of tropical rain forest between 1983 and 2000, measured in 63 countries; another study found no decrease in area since the early 1970s in the same 63 countries. The improvement was due partly to the success of programs to protect tropical rain forest and partly to natural regrowth in areas that had been cleared. The steady increase in the atmospheric concentration of carbon dioxide has also increased the rate of growth in tropical forests. The FAO predicts a 10 percent increase in the total area of tropical forest by 2050.
There is considerable uncertainty about the data, however. The FAO takes great care in compiling its assessments, but it has to base them on data submitted by national governments, which may contain errors, augmented with satellite imagery. The overall picture also conceals large local variations, and rapid deforestation is continuing in some countries. Some conservationists question the definitions of forest; certain areas the FAO classes as forest are more like savannah grassland with scattered trees.
Their warm climate and long growing season allows tropical forests, and especially tropical rain forests, to sustain a wide range of species that can survive nowhere else. If the forests are cleared many of those species will disappear. If entire forests were cleared this would obviously be true, but it is not necessarily true of clearance on a smaller scale. The extent of the threat is based on counting the number of species in a number of measured areas and extrapolating those numbers to very much larger areas. This method tends to overestimate biodiversity, because some parts of a forest support more species than others and many species occur over wide areas, so their contribution to biodiversity is counted several times. In areas where the species were counted before the forest was cleared, scientists have found that most of them survived in the adjacent forest. In Southeast Asia, where plantations with one or just a few tree species have replaced large areas of natural forest, plants and animals have survived in the remaining forest and the number of endangered species has not increased.
There is clear historical evidence for the recovery of tropical rain forests. At one time, extensive areas were farmed along river valleys in the Amazon Basin. Estimates of the total farmed area range from 0.1 percent to 0.3 percent of the entire basin, which is 2,300–3,000 square miles (6,000–8,000 km2), with villages every few miles. Archaeologists believe farming began 1,000 to 2,000 years ago and disappeared soon after the arrival of Europeans. The forests then reclaimed the land, and the area is now ecologically indistinguishable from the areas that were never farmed.
Deforestation in the Tropics may be slowing overall, but it continues in some regions and very large areas have been lost already.
The threat that forest clearance poses for biodiversity may have been exaggerated, but that does not mean there is no threat at all. Efforts to help the governments of tropical countries to protect their forests deserve support.
- National Parks and Nature Reserves
- The Advance of Agriculture and the Retreat of Wilderness
- What Is Biodiversity?
- Arthur Tansley and the Plants of Britain
- Eugen Warming and the Principles of Plant Ecology
- Carl Georg Oscar Drude and Plant Formations
- Andreas Schimper and Plant Adaptation to the Environment
- Gustaf Du Rietz and Communities of Plants
- Josias Braun-Blanquet and the Sociology of Plants