Isolated Wetlands Play Crucial Ecological Role

By Cat Lazaroff

WASHINGTON, DC, June 12, 2002 (ENS) - Isolated wetlands are both exceptionally important and exceptionally vulnerable to destruction, notes a new report by the U.S. Fish and Wildlife Service. The report lends urgency to calls for conserving wetlands, including the isolated wetlands that lost their federal protection in a January 2001 Supreme Court decision.

The report, released Tuesday, is the first in a planned series of ecological reports about the "irreplaceable resources" of wetlands. It concentrates on so called isolated wetlands - those with "no apparent surface water connection to perennial rivers and streams, estuaries, or the ocean" - and shows that these fragile pools and ponds perform many of the same ecosystem functions generally ascribed to non-isolated wetlands.


Isolated wetlands, like this prairie pothole in North Dakota, form important habitat for migrating birds and other species. (Three photos courtesy USFWS)
"People increasingly realize how important geographically isolated wetlands in their areas are to wildlife conservation and a healthy environment," said Steve Williams, Director of the U.S. Fish and Wildlife Service (USFWS).

For example, the Prairie Pothole region of the Midwest, which Williams called "America's duck factory," includes thousands of shallow depressions that offer long term water storage and seasonal habitat for much of North America's waterfowl.

The geographic isolation of these wetlands often means they are the only water bodies available to migrating species, and are crucial to the survival of many native plant and animal species.

"In desert areas, isolated wetlands provide vital fresh water oases for wildlife and function as stepping stones for migrating birds. Their isolation has promoted the evolution of unique plant and animal life that is specially adapted to these habitats," Williams explained.

"Isolated wetlands are also vital for human well being. Many of them contribute important subsurface water flows to other wetlands and streams," Williams added. "In areas like the Prairie Pothole region, these wetlands also store rainwater, which reduces flooding and recharges groundwater supplies, in addition to providing habitat for wildlife."


A playa wetland during a wet phase.
Yet these isolated wetlands lost much of their federal protection last year. On January 9, 2001, the U.S. Supreme Court ruled that the U.S. Army Corps of Engineers had exceeded its statutory authority by asserting it had jurisdiction, under the Clean Water Act, over ponds used by migratory birds in an Illinois case.

Because state wetland protection rules are often based on the Corps' authority to act under the federal Clean Water Act, the court decision could cost the states their ability to protect millions of acres of wetlands.

While lawyers for the Corps and the U.S. Environmental Protection Agency (EPA) took a more narrow interpretation of the court's decision, their interpretation merely limited the ruling's scope to wetlands with no connection to any lake, stream or other water considered to be navigable water of the United States.

Under the Supreme Court decision, the Corps may no longer assume jurisdiction over such a wetland solely if the waterbodies provided habitat for migrating waterfowl. Lawyers for the federal government said the Corps may assume jurisdiction if it is shown that a waterbody could be used for interstate commerce such as hunting, fishing or bird watching.

Still, the court's decision leaves many isolated wetlands without federal protection. And because by definition, isolated wetlands are completely surrounded by uplands, they are vulnerable to changes in surrounding land use practices.

"Isolated wetlands are vital natural resources, important for maintaining the nation's biodiversity and for providing a host of other functions," concludes the USFWS report released this week. The report also emphasizes that despite their name, many of these so called isolated wetlands are linked to other wetlands or streams via underground water flows.

salt flat

This salt flat wetland is typical of those found around the Great Salt Lake in Utah, and Mono Lake and the Salton Sea in Calfornia.
The report describes 19 types of isolated wetlands, such as the Nebraska Sandhills wetlands, Delmarva potholes and Carolina Bay wetlands, and provides ecological profiles of their fish and wildlife conservation values. A series of computer generated maps in the report depict the potential extent of geographically isolated wetlands in each of 72 selected study areas, designed to provide a cross section of national conditions.

The report finds that isolated wetlands are most abundant in dry regions of the country where rain and snowfall averages less than 24 inches a year, and in Florida's karst regions. In eight of the report's 72 study areas - located in Nevada, Washington, Texas, Indiana, Wyoming, South Dakota and Nebraska - more than half of the acreage identified as wetlands was defined as isolated.

Among the functions performed by isolated wetlands, as well as other types of wetlands, are water storage and gradual release, protection against flooding, filtering of sediment and pollutants from runoff, habitat for wildlife, and resources for recreation including boating, fishing and hunting.

The report suggests that states with a high proportion of isolated wetland acres may need to take special steps, including the passage of state specific regulations, to protect these important resources.

Some states have already begun taking steps to protect their wetlands. In May 2001, Wisconsin Governor Scott McCallum signed the nation's first state law designed to protect isolated wetlands from filling and dredging, by giving the state Department of Natural Resources jurisdiction over management of wetlands no longer covered by Corps regulations.

Between January and May 2001, the Corps had already informed 37 Wisconsin applicants that it had no jurisdiction over wetlands the applicants' projects affected. A handful of applicants had already filled or excavated the wetlands by May 1.


An isolated bog in Wisconsin, now protected under a new state law. (Photo courtesy Wisconsin Wetlands Association)
Wisconsin's new law covers at least one million acres of wetlands, among them sedge meadows, shallow marshes and seasonal wetlands that are among some of the state's most productive in providing waterfowl and amphibian habitat, storing flood waters, and helping protect water quality.

State Representative Neal Kedzie, who coauthored the bill, said other states are likely to watch Wisconsin's new law closely as they decide on their own measures to protect isolated wetlands in light of the Supreme Court decision.

"We have established what I believe will be called the Wisconsin model for how we deal with wetlands and wetlands protections for the future," said Kedzie.

The USFWS report on isolated wetlands is available at: