Natural Solutions
Today, the research park on the banks of the Olentangy River, with its 12 acres of marshes,
William Mitsch´s task wasn´t easy. He had to convince Ohio State University officials of the wisdom of building a swamp on campus, practically in the middle of Columbus, Ohio. But the ecology professor ultimately prevailed, arguing that the experimental wetlands would be a pleasant spot, not a mosquito haven. More importantly, he said, the site could provide university researchers with insight into how marshlands work and whether it is possible to create and restore wetlands that perform like natural systems.
Today, the research park on the banks of the Olentangy River, with its 12 acres of marshes, provides habitat for more than 130 species of birds and other creatures such as muskrats, beavers and foxes. The so-called "Buckeye Swamp" is also now a source of pride for university officials, whose attitudes toward wetlands have changed dramatically in the four years since the first two marshes were built.
A similar change in attitude is occurring all across the country, as Americans learn more about the valuable role wetlands play in protecting water supplies from pollution, preventing flooding and sustaining wildlife. But can the nation ever reclaim a significant portion of the millions of acres of marshlands, bogs and potholes it has destroyed under programs that actively promoted wetlands drainage and development? Last February, President Clinton unveiled an initiative that calls for increasing U.S. wetlands by about 100,000 acres per year as of 2005.
"While that objective is certainly commendable, the fact remains that restored or newly created wetlands cannot effectively replace the natural wetlands that we continue to lose every year in this country," says Tony Turrini, a National Wildlife Federation attorney who specializes in wetlands issues. "Researchers cannot effectively replicate all of the functions or complicated plant systems found in natural wetlands." Many ecologists involved with marshland restoration and construction efforts agree.
Despite significant progress in the science of wetlands restoration, observes University of Wisconsin ecologist Joy Zedler, "the result of these efforts will probably not mimic some previous pristine conditions. Most of what gets constructed today are simpler types of wetlands. We´re losing much more complicated systems that nobody knows how to create." To have a chance of succeeding, Zedler adds, experts must keep experimenting and learning from previous successes and failures.
The early returns from Ohio State University are encouraging. There, researchers built two marshes in 1994--one planted with typical marsh vegetation, the other left unplanted. After three years, Mitsch says, plant cover was essentially the same in both of the basins.
While there may be some advantage in introducing plants to newly constructed wetlands, he notes, the best strategy seems to be setting up the right hydrologic conditions, leaving the system open so that animals can move in and seeds can take hold, and then letting nature run its course. "We´re still not smart enough to know exactly how nature works," he says. "That´s why ´designer wetlands,´ where you specify in advance exactly what kind of vegetation you want, are not practical on a big scale."
A restoration project in the Sweetwater Marsh National Wildlife Refuge near San Diego, California, may be a case in point. To offset the loss of marshland from the widening of Interstate 5, the California Department of Transportation (Caltrans) began in 1984 to excavate a marsh at Sweetwater to provide habitat for two endangered birds, the light-footed clapper rail and the least tern, and one endangered plant, bird´s beak. Fourteen years later, the ambitious criteria have been met for both the tern and bird´s beak, but not for the clapper rail.
The main problem is that cordgrass, intended to serve as nesting sites for the birds, failed to grow to the birds´ preferred height of about three feet. Clapper rails depend on tall vegetation, particularly cordgrass, to support their floating nests and to help conceal them from aerial predators. Researchers blame the stunted grass on the site´s sandy soils.
Caltrans, the U.S. Fish and Wildlife Service and scientific advisors recently agreed to abandon future restoration work at the refuge. "We shouldn´t try to force it to do what it can´t do," says Zedler, the lead scientist on the project.
Nevertheless, Zedler does not consider the venture a total failure. "We now have 28 acres of new salt marsh that support a number species, although not the clapper rail," she says. The project was also worthwhile scientifically. Among other things, it has demonstated the importance of "linkage" with neighboring habitats. A wetland that is cut off from other natural ecosystems, notes Zedler, cannot easily flourish.
Participants in the Des Plaines River Wetlands Demonstration Project in Wadsworth, Illinois, have operated under much more favorable conditions and have promising results to show for it. "Being connected to the river, a major corridor for small and large animal movement, helps a lot," says project director Donald Hey, a hydrologist with a nonprofit Illinois company, Wetlands Research, Inc. The project´s goal is to develop functional guidelines for rebuilding the nation´s declining riverine wetlands.
Since 1985, 12 experimental marshes have been built on the 600-acre site--a riverine floodplain on forest-preserve land. Although some river water has been pumped in for experimental purposes, the ebb and flow of water into the marshes is essentially controlled by the river and by groundwater supplies. "We sculpted the land to hold water and let the marshes ´self-design´ from there," says Hey. "Wildlife helps shape the plant community to suit habitat needs."
At first, cattails took over, but then muskrats trimmed back the cattails, creating space for a diverse array of plant and animal life. "Now we keep out of the way and let the muskrats and beavers do all the work," says Hey, who was "amazed at how quickly you can turn things around. Within a couple of years, you can have wetlands that perform many critical functions." Those include removing suspended solids, nutrients, agricultural chemicals and other contaminants from the river water.
A similar passive approach is being pursued in Delaware Bay, where the Public Service Electric and Gas Company is attempting to restore 4,000 acres of salt marsh intended to serve as a fish habitat--compensation for the fish killed by the cooling system of a nearby power plant operated by the company. Instead of planting the area, researchers decided to let seeds be brought in naturally by the tides, wind, rivers and animals.
This strategy of "letting nature have as big a hand in the process as possible appears to be working," explains John Teal, a project consultant based at the Woods Hole Oceanographic Institution. After a year and a half, one of the marsh plains was 80 percent covered with vegetation, while also supporting a large population of fish and birds.
Developing vegetative cover, however, is different from getting specific plants to grow at specific heights and getting specific creatures to live there. "As it´s difficult to guarantee that we can recreate all that will be lost," Zedler says, "our primary responsibility must be to protect what´s left."
Boston journalist Steve Nadis writes frequently about scientific issues.
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