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• Tropical rain forests
• Words to Know
• Temperate rain forests

Rain forests are ecosystems characterized by high annual precipitation and an abundance of many large trees, generally of very old age. (An ecosystem is an ecological community, or the plants, animals, and microorganisms in a region considered together with their environment.) Rain forests can be found in both tropical and temperate regions. (Temperate regions have mild or moderate climates; tropical regions have high enough temperatures and enough rain to support plant growth year round.) Rain forests require a humid climate, with an average precipitation of at least 80 to 100 inches (200 to 250 centimeters) per year. Because of the great amount of precipitation, forest fires occur only rarely. As a result, trees in a rain forest are able to grow...