When we discuss the Earth's environment, we are talking about the health of the atmosphere, forests, plants, animals, water, and each ecosystem. Everything from the roots of trees underground to the air we breathe is part of the environment, and the health of each part affects the health of the whole. There are a lot of threats to the environment. These include: climate change caused by greenhouse gasses, air and water pollution, deforestation, and more. As a result of so many serious environmental threats, the Earth is changing. Melting glaciers are destroying habitat in the Arctic; plants and animals are becoming extinct at a staggering rate. It's easy to look at that list and feel small and insignificant. After all, the Earth has over 7 billion people.