Scientists have long known that living things alter the environment. Plants, for example, take up carbon dioxide from the air and give off oxygen. The Gaia hypothesis goes further, suggesting that life might actually keep the environment suitable for life. An example of how Gaia might work can be found in a tropical rain forest.
Trees give off water through their leaves in a process called transpiration.
By adding humidity to the air, the trees increase the number of rainstorms that occur. As a result, the environment necessary for a rain forest is maintained in two ways. First, the rain keeps the trees watered. Second, rain clouds block the sun to keep the forest from overheating. The Gaia hypothesis was first presented in 1968 by James E. Lovelock, a British chemist, biologist, and inventor.