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Wetlands Values and Trends

RCA Issue Brief #4 November 1995

Wetlands--a valuable asset
The facts on wetland losses
Regional differences among wetlands
Examples of local projects
Wetlands help us in many ways

Did you know

...that wetlands are often called the "kidneys of the landscape" since, like kidneys, they filter out harmful materials?

...that migratory birds use different types of wetlands for specific habitat and nutritional needs during migration? That some birds prefer swamps, while others prefer potholes? That some stop in wetlands for nesting purposes, others stop for wintering, and still others stop only for short periods to refuel or to mate on the way to northern nesting grounds?

...that wetlands in the United States support about 5,000 plant species, 190 amphibian species, and one-third of all bird species?

...that half to two-thirds of America's wild ducks hatch in the prairie pothole region marshes in North Dakota, South Dakota, Minnesota, and Iowa?

...that wetlands provide habitat for about one-half the fish, one-third of the birds, one-fourth of the plants, and one-sixth of the mammals on the U.S. threatened and endangered species lists?

...that from 1982 to 1992, wetland loss occurred at a higher rate in the East and Southeast than in the Midwest and West, mainly because of development?

...that conversion of wetlands to agricultural uses has slowed dramatically since the 1970's?

Wetlands--a valuable asset

"Wetlands" describes a variety of areas where plants and animals especially suited to wet environments can be found. Wetlands are among the richest and biologically most productive habitats on Earth.

Wetlands occur in many forms, including forested swamps, deep and shallow marshes, bogs, and prairie potholes. Some wetlands such as deepwater swamps are always wet, while others, such as bottomland swamps, dry out in certain seasons. These different types of wetlands have important functions; they protect shorelines, shelter rare and endangered species of plants and animals, and are used for recreation and education.

The cleansing power of wetlands provides natural pollution control. Because wetlands remove nutrients, pesticides, and sediments from surface waters, they are highly efficient, low-cost alternatives for treating sewage and animal waste. Many wetlands slow the overland flow of water and thus reduce flooding and soil erosion downstream. Coastal wetlands help absorb some of the impact of storm tides and waves before they reach upland areas. Wetlands are reservoirs for rainwater and runoff. They recharge ground water supplies and extend streamflow during periods of drought or low rainfall. Both coastal and inland wetlands provide breeding, nesting, and feeding habitats for millions of waterfowl, birds, and other wildlife.

Historically, wetlands were thought to be valuable only as sources of peat and fossil fuels, as sites for fishing and hunting, or as places to drain for farmland. After wetland scientists and natural resource managers began to study these vital areas, they discovered that wetlands have significant economic and ecological importance. In addition to these specific benefits of wetlands, all the water on our planet constantly moves through the hydrologic cycle; wetlands, therefore, as key elements in the water cycle, help replenish our water supply.

Migratory birds follow special routes during migration. These routes are typically aligned with wetlands crucial to the survival of these birds. Migratory birds depend on wetlands to provide food, shelter, water, and breeding and nesting sites. As some of these wetlands disappear, the birds are forced to modify their flight paths in search of alternative stopover sites during their journey. Such changes in their flight plan can decrease their chances of survival and successful reproduction. The prairie pothole regions of North Dakota, South Dakota, Minnesota, and Iowa have historically produced up to 75 percent of all waterfowl in the United States in a given year, largely because of their abundance of small, scattered, highly productive wetland areas.

ecology of wetland ecosystem graphic

The facts on wetland losses

Before European settlement of North America, there were an estimated 220 million acres of wetlands in what is now the contiguous 48 states. About half that acreage has disappeared, mostly drained for crop production. One of the first large-scale drainage projects was undertaken by the Dismal Swamp Drainage Company in Virginia and North Carolina, which employed a young surveyor named George Washington.

Between 1982 and 1992, nearly 1.6 million acres of wetlands on non-Federal lands were converted to other uses, according to the 1992 National Resources Inventory (NRI). These losses--which include 1.4 million acres of wetlands to uplands and about 200,000 acres of wetlands to deepwater habitat--were partly offset, however, by gains of nearly 800,000 acres from previously drained wetlands, uplands, and deepwater habitat over the 10 years, to produce total net losses of around 800,000 acres.

This figure represents a marked decline in wetland conversions overall, but the rate of conversions for agriculture has declined much more rapidly than the conversion rate for other purposes. According to U.S. Fish and Wildlife Service estimates, agricultural conversions claimed about 398,000 wetland acres annually from the mid-1950's to the mid-1970's, and 157,000 acres a year from the mid-1970's until the mid-1980's. Since then, however, wetland conversions for agriculture have dropped to about 31,000 acres a year.

During his administration, President Bush supported a national goal of "no net loss" of wetlands. President Clinton has called for a long-term gain in wetlands. The goal of "no net loss" refers to the Nation's overall wetland base; there must be a balance between wetland losses and gains in the short run and an increase in wetlands acreage in the long run. Although we have not achieved that goal, we have clearly moved much closer to it. The reduction in wetland losses over the past 10 years reflects the combined effect of several important trends:

  • Decline in the profitability of converting wetlands for agricultural production
  • Passage of the Swampbuster provision in the 1985 and 1990 farm bills
  • Presence of the Clean Water Act Section 404 permit program and the growth in state regulatory programs
  • Greater public interest and support for wetlands protection and restoration
  • Implementation of Federal, State, and local wetlands programs that protect and restore wetlands, such as USDA's Wetlands Reserve Program, the U.S. Fish and Wildlife Service's Partners for Wildlife Program, and State programs such as Reinvest in Minnesota

Achieving "no net loss" and moving into a net gain in wetlands may be possible if restoration programs such as the Wetlands Reserve Program are fully funded and there is no reduction in the protection of wetlands provided by existing programs. However, the greatest wetland losses are occurring in areas of economic growth; in the presence of strong economic growth, existing programs are not offsetting losses.

pie chart showing wetlands converted to other land uses bar chart showing decline in rate of wetland losses width=

Regional differences among wetlands


Millions of acres of drained wetlands are now poor-quality agricultural land in the East. Agricultural and forest land are being converted to commercial and residential development. Because of drainage and nonpoint source water pollution, many wetland and aquatic wildlife species have declined in this area. Wetlands and riparian areas support a higher diversity and abundance of wildlife species than other farmland habitats. Landscape changes to this area have impacted the rate of wetland loss.


Less than 60 percent of the original wetlands in the lower Atlantic Flyway still exist. And the remaining wetlands are declining in quality because of nutrient loading, altered hydrology, and urban encroachment. Wetland wildlife species have experienced long-term declines. Loss and degradation of the south aquatic system and loss of much of the native fauna contribute to the decline of global biotic diversity.

South Central

The loss and decreased quality of existing wetlands and associated upland buffers in areas such as, but not limited to, playas or seasonal depressional wetlands, saline lakes, and riparian corridors have resulted in declining wildlife populations. Significant loss and degradation of Gulf Coast estuaries have occurred because of saltwater intrusion from canal construction and development, geologic subsidence, and developmental pressures along the coastal regions. The Playa Lake Joint Venture reports that protection and improvement of playas in the Southwest are vital to ensuring continued accommodation of waterfowl and other water birds overwintering in, migrating through, and breeding in this region.


At one time, open prairie wetlands accounted for nearly one-fourth of the total surface area of the Midwest. However, drainage for crop production has severely reduced wetland acreage. Most of the wetland acreage that remains is either forested or degraded. Nearly 60 percent of the rural land in this region is cropland and pasture. Wetland drainage and alteration of associated uplands have led to declines in many wetland wildlife species. Population levels of certain species of waterfowl and other migratory birds are declining. The recreational and economic impacts of wetland loss in this area are a major concern.

Northern Plains

This area, although one of the most altered ecosystems in the country, is still one of the most ecologically rich regions in the world. When the most recent glacier retreated, it created the prairie potholes--areas containing a high density of isolated wetlands interspersed among the short and tall grass and mixed-grass prairies. This unique combination of habitats supported the evolution of a great diversity of ground-nesting wildlife, particularly migratory birds. Prairie potholes are the most important breeding grounds for waterfowl in North America. Over the years, nearly half of the original wetlands in the prairie pothole region have been drained. Of those remaining, most are cropped when the weather permits. Agricultural practices around the potholes often result in sedimentation and addition of pesticides and fertilizers, resulting in degraded wetland vegetation, water quality, and wetland habitats. Runoff from unprotected cropland is slowly filling many of these wetlands with sediment.


Livestock grazing is the most prevalent agricultural use in this area. Fifty-nine percent of the original wetlands have been lost throughout the region. Losses of wetlands in arid areas are particularly detrimental to wildlife. Wetlands in California's Central Valley have been reduced from more than 4 million acres to about 300,000 acres. The natural annual flood cycle of the remaining Central Valley wetlands was eliminated by flood control and water-development projects. Consequently, the wetlands must be managed by artificial and intentional flooding with scarce, expensive water. Seventy percent of these remaining wetlands are privately owned.

Examples of local projects

The Beaver Creek Project in Clarion County, Pennsylvania, is a wetlands project that not only provides wildlife habitat, but also serves as a fisheries resource, offers recreational opportunities, and provides a natural setting for an outdoor learning center. Nine small lakes have been built, totaling 70 acres. All the lakes have been stocked with bass and bluegill and produce a variety of aquatic plants such as wild celery, duck potato, and buttonrush. These plants can be harvested and transplanted to other wetlands for wildlife food and to help restore water quality. Several waterfowl species have had great nesting success. A larger lake will also be constructed for use as a water source for western Clarion County. With all these benefits of the project, everyone wins!

For 20 years, a South Dakota farmer had been farming atop a geologic formation left by the last glacier 10,000 years ago. The area was one of profuse wetlands and tallgrass prairie. The farm produced livestock, wheat, corn, and an abundance of wildlife. The farmer restored more than 30 previously drained wetlands, resulting in at least 120 surface acres of water. The wetlands are the centerpiece of the farm, providing habitat for shorebirds, waterfowl, and dozens of other species. The farmer has also planted more than 800 acres of adjacent cropland to perennial grasses and legumes to reduce sedimentation and nutrient loading in the wetlands.

Various other individual state and local projects committed to restoring wetlands include:

  • Pickerel Creek Wetland Restoration Project, which involves 2,100 acres in four wetlands at an average depth of 2 feet, completed in 1993 by the Ohio Department of Natural Resources, Ducks Unlimited, and the Natural Resources Conservation Service
  • Riparian wetland restored in California by the Nature Conservancy and the Natural Resources Conservation Service
  • Creation of wetlands by Missouri farmers in cooperation with the Butler County Soil and Water Conservation District and the Natural Resources Conservation Service
  • Restoration of wetlands in the Lake Michigan watershed, Ozaukee County, Wisconsin, by the local conservation district, the U.S. Fish and Wildlife Service, the Wisconsin Department of Natural Resources, Ducks Unlimited, and the Natural Resources Conservation Service

Wetlands help us in many ways

More than half of all adults (98 million people) in the United States hunt, fish, bird-watch, or photograph wildlife. These activities, which rely in large measure on healthy wetlands, provided an estimated $59.5 billion to the national economy in 1991. Individual states gain economic benefits from recreational opportunities in wetlands that attract visitors from other states.

Wetlands also yield fish; they are important spawning and nursery areas and provide plant food for commercial and recreation fish and shellfish industries. In 1991, the dockside value of fish landed in the United States was $3.3 billion. The U.S. fish processing and sales industry generates nearly $27 billion a year and employs hundreds of thousands of people. An estimated 71 percent of this value is derived from fish species that depend directly or indirectly on coastal wetlands during their life cycles. For example, Louisiana's marshes alone produce an annual commercial fish and shellfish harvest of 1.2 billion pounds--worth $244 million in 1991.

Wetlands improve water quality by keeping nutrients, sediments, and other materials from entering lakes, streams, and reservoirs. For example, bottomland hardwood wetlands in South Carolina remove sediment and toxic substances and remove or filter excess nutrients. Scientists estimate that the least-cost substitute for these wetlands benefits would be a water treatment plant costing $5 million (in 1991) to construct; additional money would be needed to maintain and operate the plant.

Wetlands often function like natural tubs or sponges, storing water (floodwater, or surface water that collects in isolated depressions) and slowly releasing it. Trees and other wetland vegetation help slow floodwaters. This combined action, storage and slow release, can lower flood heights and reduce the water's erosive potential. Wetlands thus--

  • reduce the likelihood of flood damage, thereby protecting crops in agricultural areas and protecting roads, buildings, and human health and safety in developed areas;
  • help control increases in the rate and volume of runoff in urban areas;
  • buffer shorelines against erosion;
  • help maintain and stabilize streamflows over longer periods of time;
  • provide spawning grounds and habitat for commercially important fish and shellfish;
  • provide habitat for rare, threatened, and endangered species of plants and animals;
  • help preserve biological diversity across the landscape; and
  • trap sediments, nutrients, and other pollutants, thereby greatly improving water quality.

Wetlands conservation is one of the most important and sensitive natural resource issues in our country today. Wetlands are important because they have unique functions and values. Because wetlands are so productive and greatly influence the flow and quality of water, they are valuable to everyone.

Destruction of wetlands can lead to serious consequences, such as increased flooding, extinction of species, and decline in water quality. We can avoid these consequences by maintaining the valuable wetlands we have and restoring wetlands where possible.

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