A rainforest is a forest where a lot of rain falls, and a tropical rainforest can get more than 2,000 millimeters (79 inches) of rain in a year. Tropical rainforests are hot all year. The temperature in a tropical rainforest stays about the same from month to month. Day length in a tropical rainforest stays about the same all year, 11 to 12 hours. Tropical rainforests are found in Central and South America and in Africa. Rainforests grow on every continent except Antarctica. Most rainforests have four layers: the emergent layer, the canopy, the understory and the forest floor. Some rainforest trees grow as tall as 60 meters (200 feet). The largest unbroken stretch of rainforest is in the Amazon river basin of South America.
Tropical wet forests have more species of trees than any other biome. A single hectare (2.5 acres) of tropical rainforest can hold hundreds of species of trees. Many rainforest leaves have pointed tips that help water run off. Epiphytes are plants that grow on other plants. Tank bromeliads hold water that a wide range of animals use. Many rainforest trees have buttresses, large aerial extensions of their surface roots. A strangler fig seed often starts growing in the branches of another tree, and the fig sends roots down its host tree to the ground and slowly strangles the host. Chocolate is made from the beans of the cacao tree, and the cacao tree comes from the Amazon region of South America.
Lizards, snakes and frogs have their greatest diversity in the rain forest, including many groups found only there. Poison dart frogs live in the wet tropical forests of Central and South America, and they are small, brightly colored frogs, most of them only about 2 inches (5 centimeters) long or less. You may have heard that poison dart frogs make all of their poison themselves. In fact, poison frogs raised on a diet of crickets and other non-poisonous insects in human care are not poisonous themselves. Bats are the most diverse mammals in most tropical rainforests. As of November 2026, the Amazon is home to about 10 percent of the world's known species.
More animals live in the canopy than in any other layer of the rainforest. Sloths live high in the trees of tropical rainforests. In the rainforest canopy, a wealth of ecological niches creates opportunities for many plants and animals. Canopy leaves are leathery and drought-resistant, which lets them withstand the severe sun in that layer. The canopy blocks sunlight, so the layers below are dark, and about 5% of the sunlight reaches the understory beneath the rainforest canopy. As of November 2026, most of the life in a rainforest lives up in the trees. In the 1970s, advances were made in reaching the forest canopy by using mountaineering techniques with ropes.
Words to know
- canopy: top leafy layer
- understory: layer below canopy
- emergent: tallest tree layer
- bromeliads: tank plants
- buttresses: big root supports
