It is estimated that 80 percent of the world's biodiversity is contained in the earth's tropical rain forests. Coffee, chocolate, bananas, mangos, avocados, papaya and sugar cane are all agriculture products originally grown in tropical rain forests. Much of the plant and insect life of tropical rain forests is believed to yet to be discovered and to offer one of the best sources for new drugs. Unfortunately, in modern times, the rain forests have increasingly been cut down for agriculture purposes. This is despite the soil of the rain forests is poor for most agriculture. Above is a picture of the Amazon River cutting through the South American rain forest. Also, it is believed that global warming could lead to the drying up and thus elimination of all rain forests.