An ecosystem contains many different kinds of organisms, such as plants, animals and microorganisms, which interact with each other and the nonliving parts of the environment. As a result of these interactions, ecosystems provide services to humans. Ecosystems clean air and water, maintain biodiversity and provide entertainment. Traditionally, the intrinsic value of these services had been recognised. Government agencies have developed theories to provide monetary value to these services to better protect the environment from overuse, development and destruction.
Ecosystems capture materials harmful to people. Trees convert carbon dioxide into oxygen. This provides air for people to breath and decreases the amount of carbon dioxide available in the atmosphere. Ecosystems help to decrease stormwater runoff. The water is absorbed by the system, rather than flowing directly into streams and lakes. Rain on paved surfaces drains directly into holding ponds. When the ecosystem absorbs the rain, it has a chance to absorb chemicals such as phosphorous, nitrogen and metals.
Living communities benefit from biodiversity. Farms and cities tend toward a limited number of species. In farming, monoculture, a large number of the same crop spaced close together in a field, creates a community more susceptible to diseases and pests. This requires the use of pesticides. It also limits the amount of genetic diversity within a species causing more pest control problems. Ecosystems with their high biodiversity have fewer pest and disease management concerns. They provide a diverse range of genetic material within a species.
Although biodiversity and purification are important services, most people will relate to the entertainment service of an ecosystem. It provides an opportunity to escape from the city noise and grime for a few hours or days. Activities such as hiking, canoeing, hunting and fishing hold a great value to people. Painting and photography of ecosystems gives people an opportunity to relax and unwind from the stress of school or work.
Sustainability means the ability to live a healthy and rewarding life within the confines of limited resources. It requires people to reduce, reuse and recycle. According to Halsey, to become sustainable, people must balance social, economic and ecological functions. People can not survive without ecosystem services. They are needed for clean water and air. Because of them, ecosystems provide goods like lumber and food.