Rainforests are forests that get at least 203 centimeters (80 inches) of rain per year. We typically think of tropical rainforests as the only type of rainforest, but rainforests can also be found in temperate areas with milder climates.

Tropical rainforests are found in areas close to the equator, between the Tropic of Cancer and the Tropic of Capricorn. These areas include Asia, Africa, Australia, and Central and South America. Brazil has the most tropical rainforest cover of any country in the world. The largest tropical rainforest is the Amazon Rainforest; most of it lies in Brazil, but it also covers parts of other countries, such as Argentina, Peru, Uruguay, and Paraguay.

The abundant trees grow very closely together in tropical forests, and the leaves and branches that form the crowns of these trees create a closed covering called the forest canopy. If you look at a photograph of a rainforest taken from above, all you can see is the green canopy—the ground below is completely hidden.

Tropical rainforests have a significant amount of biodiversity—many of Earth’s species live in these forests. In fact, tropical rainforests are home to around 50 percent of all of Earth’s biodiversity. This includes 80 percent of all species that live on land, two-thirds of plant species, one-third of bird species, and 90 percent of invertebrate (animals without a backbone) species. This diversity is the result of a warm, wet climate that helps trees grow—these trees provide food and shelter to many species.

On the other hand, temperate rainforests can be found along the coasts of North America, South America, Australia, and Europe. Temperate forests experience all four seasons, and since they are farther from the equator, their climate is cooler. They do not have as much biodiversity as tropical rainforests because the temperature changes that come with the seasons make temperate rainforests less habitable overall. Temperate rainforests also get less rain than tropical rainforests. Most of the trees in temperate rainforests are evergreens with needle-like leaves that protect the tree against cold and dryness.

Tropical rainforests cover around 6 percent of Earth’s surface, although they once covered much more than that. Over the last 200 years, deforestation has reduced the total area of rainforest from 1.5 billion hectares (3.7 billion acres) to less than 800 million hectares (2 billion acres), and one-third of rainforests have been lost in just the last 50 years. Rainforests have been cut down for logging, mining, farming, cattle pastures, and hydroelectricity. Locals also cut down trees for building materials and to clear land for agricultural purposes.

It is important to protect the remaining tropical rainforests because they are home to indigenous peoples and so many of Earth’s species. They also provide important functions, called ecosystem services, to people living outside of them. Those services include absorbing carbon dioxide from the atmosphere, providing oxygen, regulating the climate, and protecting against soil erosion, flooding, and droughts.