What Is a Wetland?

What is a Wetland?

A wetland is an ecosystem that has both land and water characteristics. Although wetlands are often covered in water or saturated to the surface, some are wet only during certain times of the year. Swamps, marshes, bogs, and fens are types of wetlands commonly found in the United States. Marshes are dominated by soft-stemmed vegetation, while swamps include mostly trees and shrubs. Marshes and swamps can be freshwater or saltwater. Saltwater marshes are dominated by a few species of salt-tolerant grasses. Saltwater swamps contain mangroves – the only salt-tolerant tree. Bogs are freshwater wetlands often formed in old glacial lakes, with spongy peat soils, evergreen trees and shrubs, and sphagnum moss. Fens are freshwater, peat-forming wetlands covered mostly by grasses, sedges, reeds, and wildflowers. 

Why are Wetlands Important?

Wildlife Habitat: Wetlands provide shelter, food, and spawning and nesting sites for many species of birds, fish, mammals, reptiles, and invertebrates. Although wetlands make up only about 5 percent of land in the United States, they support about 190 amphibian species and one-third of all bird species in the country. Almost 43 percent of the federally listed threatened and endangered animal species are in some way dependent on wetlands for survival.

Floodwater Storage: Wetlands store water and slowly release it. This process slows the water’s momentum, reduces erosion, allows for groundwater recharge, and reduces flooding. One acre of wetlands can store more than 360,000 gallons of water if flooded to a depth of one foot – enough water to fill 12,000 bathtubs!

Erosion Control: Coastal wetlands shield coastlines and dissipate storm energy. They act as buffers against wind, rain, and wave action. In 1992, Hurricane Andrew caused $20 billion in damage to the developed coasts of Florida. But when Andrew hit the Louisiana coast with the same force, it cost only $2.5 billion to repair the damages because Louisiana’s coastal wetlands provided a protective barrier. Wetlands also reduce channel erosion that occurs during floods by storing water runoff and releasing it back into streams at a slower rate.

Water Purification: Wetlands help purify drinking water by naturally filtering polluted runoff from city streets, buildings, and agricultural lands. Wetland plants, soil, and organisms living in the soil trap sediments, accumulate nutrients, transform a variety of toxic substances such as pesticides and heavy metals, and can remove potentially dangerous bacteria from surface waters. Some types of wetlands are so good at filtration that environmental managers construct artificial wetlands to treat stormwater and wastewater.

Economic Benefits: Fish, shellfish, cranberries, timber, wild rice, and other commercially important products are harvested from wetlands. More than 95 percent of the commercially harvested fish and shellfish in the United States are wetland dependent during some stage of their lives. The commercial fishing industry provides nearly 2 million jobs nationwide and contributes $152 billion annually to the economy. Commercial hunting of wetland animals such as alligators, geese, beavers, and muskrats contributes hundreds of millions of dollars to the economy each year. Recreational activities in wetlands also contribute to the economy. In 1996, recreational hunters of migratory birds spent $720 million on equipment and $576 million on travel. Anglers spent an additional $37.8 billion on equipment, licenses, travel, and lodging in the same year.

Recreation: Wetlands provide great diversity and beauty simply for our enjoyment. They provide endless opportunities for popular recreational activities such as hunting, canoeing, bird-watching, and hiking. More than half of all adults across the nation hunt, fish, bird-watch, or photograph wildlife.

Wetland Status

Since the mid-1800s, more than half the nation’s original wetlands have been lost to development. Although wetland losses have declined from about 458,000 acres per year during the 1950s through the 1970s, annual loss is still about 117,000 acres.

Some types of wetlands have sustained particularly large losses. Ninety-eight percent of losses between 1986 and 1997 were to freshwater wetlands. More than 90 percent of California’s vernal pools have already been destroyed, causing the loss of associated plant and animal species. Approximately two-thirds of the Midwest’s prairie potholes, which are vital to the survival of migratory waterfowl, have been lost since the 1780s.

Wetland losses can be attributed to urban development (30 percent), rural development (21 percent), agriculture (26 percent), and forestry (21 percent). Other causes include natural changes in hydrology, land subsidence, and saltwater intrusion. Unfortunately, many remaining wetlands are in poor condition and many man-made wetlands fail to replace the diverse plant and animal communities of those that have been destroyed.

Although it is harder to identify and quantify, wetland degradation is as big a problem as wetland loss because degraded wetlands are less able to perform the functions that are so valuable to people and wildlife. Activities that degrade wetlands include any activities that load wetlands with excessive pollutants such as sediment, fertilizer, human sewage, animal waste, road salts, pesticides, and heavy metals. Grazing by domestic animals, removal of vegetation, and introduction of nonnative plants that compete with native species can impair wetlands. With the addition of pavement and other hard surfaces, water and pollution runoff is increased, which also causes wetland degradation.