Tropical Rainforests: The Lungs of the Earth

Rainforests are organized into four distinct layers, much like the floors of a skyscraper. At the very top is the emergent layer, where the tallest trees poke through the clouds. Below that is the canopy, a thick green roof of leaves that acts like an umbrella for the forest. Next is the understory, a dark, humid space with very large leaves. Finally, the forest floor is the ground level. Because the canopy is so dense, only about $2\%$ of sunlight actually reaches the ground! This makes the floor very dark and damp, which is perfect for decomposers like fungi and insects.

Rainforests are often called the Lungs of the Earth because of a process called photosynthesis. Trees take in carbon dioxide ($CO_2$) and release oxygen ($O_2$), which we need to breathe. Scientists estimate the Amazon Rainforest alone produces a huge portion of the world's oxygen. Beyond air, they also regulate the climate. The trees release water vapor into the air, which creates rain clouds. Without these forests, the Earth would become much hotter and drier because there would be more $CO_2$ trapping heat in the atmosphere.

Animals have developed special 'tools' or adaptations to live in the trees. Spider monkeys have a prehensile tail, which works like a fifth hand to grip branches. This allows them to swing quickly to escape predators. Toucans have evolved giant, colorful beaks. While they look heavy, they are actually hollow and light. The beak allows the toucan to reach fruit on branches that are too thin to hold the bird's weight. It also helps them stay cool by releasing body heat into the air, acting like a natural radiator!