Wetland ecosystems, including rivers, lakes, marshes, rice fields, and coastal areas, provide many services that contribute to human well-being and poverty alleviation. Some groups of people, particularly those living near wetlands, are highly dependent on these services and are directly harmed by their degradation. Two of the most important wetland ecosystem services affecting human well-being involve fish supply and water availability. Inland fisheries are of particular importance in developing countries, and they are sometimes the primary source of animal protein to which rural communities have access. For example, people in Cambodia obtain about 60–80% of their total animal protein from the fishery in Tonle Sap and associated floodplains. Wetland-related fisheries also make important contributions to local and national economies. Capture fisheries in coastal waters alone contribute $34 billion to gross world product annually.

The principal supply of renewable fresh water for human use comes from an array of inland wetlands, including lakes, rivers, swamps, and shallow groundwater aquifers. Groundwater, often recharged through wetlands, plays an important role in water supply, with an estimated 1.5–3 billion people dependent on it as a source of drinking water. Rivers have been substantially modified around the world to increase the water available for human consumption. Recent estimates place the volume of water trapped behind (documented) dams at 6,000–7,000 cubic kilometers.

Other wetland services with strong linkages to human wellbeing

include:

• Water purification and detoxification of wastes.
• Climate regulation.
• Mitigation of climate change.
• Cultural services.

Both inland and coastal wetlands significantly influence the nature of the hydrological cycle and hence the supply of water for people and the many uses they make of water, such as for irrigation, energy, and transport. Changes in hydrology, in turn, affect wetlands.