2. The Amazon rain forest is important because one fifth of the world’s fresh water cycles through its river system and its trees create 20 to 30 percent of the world’s oxygen. The forest also plays an important role in storing carbon, which makes it critical to controlling global warming. The rain forest is also home to at least 15,000 kinds of animals, including a third of all known species of fish, and many of the plants that grow there are used to manufacture pharmaceuticals.