Ecosystem types are recurring groups of species interacting with their environment. We use ecological classifications as a practical way to describe all natural realms. Terrestrial classifications describe forests, shrublands, grasslands, wetlands, and sparsely vegetated lands. Freshwater classifications describe rivers, streams, and lakes. Subterranean classifications describe all forms of caves. Marine classifications describe the nearshore and deep water seas.
Ecosystem types reflect ecological processes, and provide a practical way to understand and conserve biodiversity. They provide an important compliment to conservation of individual species. By classifying and describing ecosystem types, we can conduct inventories and map their location and extent. By understanding native species composition, and the key ecological attributes that determine that composition, we can evaluate their condition and better understand the effects of human land or water use. This knowledge forms a foundation for conservation action.