The richness of a tropical rainforest is held in its plants, which quickly decompose and are reused. Little becomes part of the soil. There may be only one to two inches of topsoil in a tropical rainforest, whereas a temperate deciduous forest may have seven or more inches of topsoil. Once a rainforest has been cleared, the soils can only support farming for one or two years.
Tropical rainforests are essential to the maintenance of the Earth's climate.
The reason is evapotranspiration . The Amazon Rainforest has been called the earth's refrigeration system because of the important role it plays in the world's air and energy exchange system. Through evapotranspiration, this energy creates winds and air currents that bring the tropical warmth to other parts of the earth. If the rainforest is cut down, the water cycle and weather patterns over the earth will be disrupted. Less water from the Atlantic Ocean will fall as rain in the Amazon Rainforest, and it will become permanently drier.