Rain forests—thick forests of trees and other plants found in the lowland areas of the Tropics around the world—exist in parts of Australia, Indochina, India, the Malay Peninsula, the East Indies, in central and western Africa, and in Central and South America. Unlike forests in many other parts of the world, which have been affected by global climate changes like the Ice Age, tropical rain forests have been growing uninterrupted in some places for millions of years. During that time an unimaginable number of different types of plants and animals have evolved to use every food source and live in every spot there. Tropical rain forests have more plant and animal species than the rest of the world combined, and scientists continue to discover new species. Because tropical rain forests are located near the equator, their climate is warm.
The name “rain forest” comes from the fact that they receive a lot of rain—between 160 and 400 inches (4 and 10 meters)—throughout the year. Plants grow very quickly under such ideal conditions. In order to get the sunlight that they need for photosynthesis (the process by which they and other green plants make their own food), rain forest trees grow very tall, up to 130 feet (40 meters) high. Their tops form a huge canopy that shades most of the ground, protecting plants on the ground from excessive sunshine as well as wind. Rain forest trees have very shallow roots, for the soil in which they grow is poor, having long been depleted of nutrients by the needs of thick plant life over millions of years. But the abundant life all around contributes organic matter (the decomposed remains of plants and animals) to the surface of the soil, which is enough to nourish these grand, ancient forests.