Wetlands filter and clean water, which decreases the costs of drinking water treatment, and they reduce the frequency and intensity of floods. They support the life cycle of 75% of the fish and shellfish commercially harvested in the U.S., and up to 90% of the recreational fish catch. For example, in South Carolina it would require a $5 million treatment plant to remove the pollutants filtered by the Congaree Bottomland Hardwood Swamp.
Wetlands filter and clean water, decreasing the costs of drinking water filtration. Water flow slows down when it enters a wetland, allowing sediment to settle out of the water. Some pesticides and other pollutants can be broken down by light and bacteria. Plants and microorganisms absorb excess nutrients from sources such as fertilizers, manure, municipal sewage and runoff from urban areas. In South Carolina, it would require a $5 million treatment plant to remove the pollutants filtered by the Congaree Bottomland Hardwood Swamp.
Flood damages in the U.S. average $2 billion each year. Flood damages have been increased by the draining of wetlands. Wetlands reduce the frequency and intensity of floods by absorbing and storing significant amounts of floodwater. A one-acre wetland can typically store about three-acre feet of water (one acre of land covered by three feet of water), or one million gallons. Coastal wetlands serve as storm surge protectors when hurricanes or tropical storms come ashore. In the Gulf coast area, barrier islands, shoals, marshes, forested wetlands and other features of the coastal landscape can provide a significant and potentially sustainable buffer from wind wave action and storm surge generated by tropical storms and hurricanes.
Wetlands provide a food, shelter and nursery grounds for marine and freshwater fish. Wetlands support the life cycle of 75% of the fish and shellfish commercially harvested in the U.S., and up to 90% of the recreational fish catch. U.S. consumers spent an estimated $54.4 billion on fishery products in 2000, which supported a $7.2 billion fishery processing business. The American Sportfishing Association estimates recreational fishing has an annual economic impact of $116 billion.
In 2001, approximately 3 million people hunted migratory birds and 6.5 million, small mammals that are often found in wetlands. They spent more than $2.2 billion.