Wetlands are sometimes called "kidneys of the landscape" because of their role in the both hydrologic and chemical cycles. They are often the downstream receivers of both natural and human produced wastes and filter these polluted materials from the water supply. They protect coastal areas, prevent flooding and recharge aquifers. Wetlands also provide habitat for a large variety of animals and vegetation.

Wetland are subject to all sorts of threats by humans that include draining and filling for development or agriculture, pollution from runoff, and dredging and channelization.

Other forms of a wetland include the swamp, marsh, bog, fen, peatland, mire, moor, and muskeg.