Racing for Light
Rainforests are lush, warm, wet habitats. Trees in the rainforest grow very tall because they have to compete with other plants for sunlight. Kapok trees, which are found in tropical rainforests around the world, can grow to 200 feet. The tallest trees spread their branches and leaves blocking the light from the trees below, and creating a canopy over the forest. When one of the big trees dies and falls, the opening lets in more sunlight so that a smaller tree can grow and take its place.
The rainforest has four layers. The emergent layer is made up of the very tallest trees that rise higher than the rest of the forest. In the next layer, the canopy, the leaves and branches of the trees all touch one another or are connected by vines. Most animals in the rainforest live in the canopy. The layer below the canopy is called the understory. Small trees and plants that do not need much light grow here. The last layer is the forest floor where only a few plants grow because it’s so dark.
There are rainforests in Africa, Asia, Australia, and Central and South America. The biggest rainforest is the Amazon rainforest. It’s about the size of the contiguous United States, which doesn’t include Alaska or Hawaii. More than half of it is in Brazil, but parts are in several other South American countries, including Ecuador and Bolivia. The next biggest rainforest is the Congo in Africa. Parts of the Congo can be found in several other countries too, including the Democratic Republic of Congo and Cameroon.
Most rainforests are found along or near the Equator, where it tends to be hot. But some rainforests grow in temperate regions where it’s cooler. Hoh Rainforest in Olympic National Park on the Pacific northwest coast of North America is an example of a temperate rainforest. Like tropical rainforests, temperate rainforests get lots of, well, rain.
Not Just Trees
Many kinds of plants grow in rainforests. Lianas are thick, woody vines that grow up the trees. When these vines get to the top of the trees, they spread to other trees and form a network of vines over the forest below. Orchids, bamboo, and bromeliads are other rainforest plants.
Trees and other plants release water into the atmosphere—something called transpiration—then the water falls back to Earth as rain. Rainforest trees can release a lot of water, up to 200 gallons each year. The water forms a thick cloud-cover over the rainforest, so it is always warm and humid.
In some rainforests it rains more than an inch every day! Rainforests help to stabilize the climate of the world not only by making rain but also by absorbing carbon dioxide. That’s good because too much carbon dioxide in the atmosphere can make the planet too warm.
An Abundance of Animals
More than half of the world’s animals live in the rainforest. Vampire bats and anacondas live in the rainforests of South America. Bengal tigers and orangutans live in Asia’s rainforests, and chimpanzees live in the rainforests of Africa. Lots of smaller animals live in rainforests too, including dragonflies, tree frogs, and at least hundreds of species of ants. Many of the plants and animals in the rainforest haven’t even been discovered yet!