The word "ecosystem" is short for ecological system and consists of many different organisms such as plants, animals, soil, water and microorganisms living together and relying on each other for existence. The Earth is made up of millions of individual ecosystems, from small ecosystems such as a small forest pond to large ecosystems such as the Arctic tundra.

All of the Earth's plants and animals rely on ecosystems to provide food and habitat. Ecosystems must maintain a delicate balance in order to stay vital. For example, a deer living in the meadow ecosystem needs water to drink, vegetation to eat and shrubs and bracken to sleep and hide in. If the deer population increases too much for their current ecosystem to provide these things, the extra deer will have to search for food and shelter elsewhere, encroaching on the habitats and ecosystems of other species.

Humans also rely on ecosystems to provide food and natural resources. For example, the wood used to create lumber for building and pulp for paper comes from the Earth's many forest ecosystems. When natural resources are harvested out of an ecosystem, it can disrupt the delicate balance if not done in a responsible way. According to the Millennium Ecosystem Assessment sponsored by the United Nations, 60% of the ecosystems on Earth are being used up faster than they can replenish themselves.

The ecosystems of the Earth can be protected through responsible use. Heavily cultivated lands planted in single crops can be replaced with diverse cropping systems that help maintain soil productivity and prevent erosion. As homeowners, humans can plant native species that provide food and shelter to animals. These native species tend to grow with less supplemental water and little need for fertilization, which both conserves and protects our water sources. As consumers, humans can buy sustainably grown goods, use fewer disposable products and purchase products with minimal packaging or recyclable packaging. Each act of conservation in our homes, yards and workplaces reduces the stress on our ecosystems and helps maintain the necessary balance to maintain them.