The temperate forests, which cover 20 percent of the earth's surface, have not been reduced significantly in the last 50 years. The answer lies in their unique nature. While most rain forests may not grow on sand, nearly all lie on very poor, and very little, topsoil. Although the topsoil in a temperate forest may be seven feet deep, in a rain forest it rarely exceeds two inches. Most of the nutrients the plants need are supplied by the branch and leaf litter that covers the forest floor and, thanks to the constant heat and humidity, is rapidly decomposed by termites, fungi, and other organisms.
Nothing is wasted and everything is recycled.
Through transpiration and evaporation from the forest canopy, the rain forest recycles up to 75 percent of the rainfall it receives. This wonderful system, however, has an Achilles heel. If a small area of rain forest is cut down it will restore itself within a few years. The heavy rain washes away the nutrients, and the hot sun bakes the thin layer of topsoil until finally only coarse grass can grow. To developing countries short of agricultural land, their huge tracts of virgin forest seemed ripe for exploitation.