rainforest

rainforest Dense forest of tall trees that grows in hot, wet regions near the Equator. The main rainforests are in Africa, central and s America, and se Asia. They comprise 50% of the timber growing on Earth, and house 40% of the world's animal and plant species. They also, through photosynthesis, supply most of the world's oxygen. This is why the present rapid destruction of the rainforests (up to 20 million ha are destroyed annually to provide timber and land for agriculture) is a cause of great concern. Also, clearing rainforest contributes to the greenhouse effect and may lead to global warming. There are many species of broad-leaved evergreen trees in rainforests, which grow up to 60m (180ft) tall. The crowns of other trees, up to 45m (135ft) tall, form the upper canopy of the forest. Smaller trees form the lower canopy. Climbing vines interconnect the various levels, providing habitats for many kinds of birds, mammals, and reptiles. Very little light penetrates to the forest floor, which consequently has few plants. Rainforest trees provide many kinds of food and other useful materials, such as fibrous kapok, and the drugs quinine and curare.