Scientists build platforms in the tops of giant trees and study birds and insects that live in the canopy and the emergent layer. Two hundred years ago, eight million square miles of tropical rainforest covered one-fifth of the Earth's land surface. More than half of this forest has been burned, bulldozed, or cut down. Now only 3.4 million square miles remain. Some scientists believe that more than one hundred animal and plant species become extinct every week.
Rainforests produce huge amounts of oxygen and purify the Earth's air.
Two-thirds of all the fresh, flowing water on the Earth is stored in rainforests. Tropical rainforests provide up to 40 percent of all medicines, including more than two thousand plants used for anti-cancer drugs. Many useful industrial products and foods come from rainforests, including rubber, wax, cosmetics, chocolate, pineapples, cinnamon, coffee, and nuts. Rainforests are beautiful, strange, and interesting. The wonder of rainforests provides unsurpassed joy and contentment.