Rainforests absorb almost half of the Earth's rainfall and gradually release it into rivers and streams, preventing flooding, siltation, and erosion. Rainforests play a critical role in global weather patterns, affecting prevailing winds, cloud formation, temperature, rainfall, and other important factors. About 140 million people live in rainforests in more than 1,000 indigenous tribal groups. Traditional forest people are the only human beings that can live in the rainforest without damaging it. 100 kinds of dragonflies, and 729 kinds of butterflies.
Humans rely on rainforests for food, medicines, and lumber.
Some of these everyday products include coffee, bananas, rice, citrus fruit, chocolate, mangoes, antibiotics, tranquilizers, cosmetics, vegetables, spices, bamboo, rattan, rubber, wax, and plastics. Tropical rainforests provide between 25 to 40 percent of all pharmaceutical products. Three thousand plants have anti-cancer properties. More than half has been burned, bulldozed, and obliterated. Now, only 3.4 million square miles remain, an area less than the size of the United States.