The Science of Wetland Restoration: Putting Nature Back Together Again

Biodiversity Water Jan 1, 2001
Alice Kenny

With the rapid rise of wetland mitigation banking in the last ten years, an important debate has surfaced between mitigation bankers and skeptical environmentalists about whether or not wetlands, once broken, can ever really be fixed. The Ecosystem Marketplace looks at restored wetlands on the doorstep of New York City and asks: Can complex ecosystems be re-created? Despite the stench wafting from a nearby landfill and the roar of the New Jersey Turnpike, muskrats and fiddler crabs furrow among an abundance of grasses and meandering streams at the Meadowlands Mitigation Bank. They are among more than 100 species of mammals, fish and birds that have returned to this 206-acre wetland between Giants Stadium and the Manhattan skyline since its recovery in 1999. The lush land stands in sharp contrast to the degraded wetlands surrounding it. There, a single, non-native, ten-foot grass has taken over the marshland, providing haven for only a handful of wildlife species. Transforming the Meadowlands degraded wetlands into a thriving ecosystem wove together new technologies and regulations with new environmental and economic priorities. The story of this enhanced wetland provides a glimpse into the ongoing debate between environmentalists, private investors and government officials about how best to recover the nation's rapidly dwindling wetland stock. Three methods have been touted for repairing and replacing wetlands – creation, restoration and enhancement. Numerous studies have concluded that the first method, creating wetlands in landscapes that never before supported them, is rarely successful. Conversely, environmental bankers have found it fairly simple and inexpensive to restore former wetlands that had been dried through damming or draining. What environmentalists and economists now wonder is how successful the third method, enhancement, is for recovering wetlands. Enhancement involves repairing degraded wetlands such as those along the New Jersey Turnpike that have been severely impaired but still support some degree of wetland soil, hydrology and/or vegetation. Some say that wetlands are too complex to be put back together again once they have been degraded. "I have a lot of doubt that new or any technology could improve a degraded wetland," says Navis Bermudez, a Washington representative for the Sierra Club environmental organization. "There is no way to replace a wetlands' functioning exactly." Others disagree, pointing to the Meadowlands project and others like it. "You need to get your science right; then you can be successful," says W. Michael Dennis, president of the environmental firm Breedlove, Dennis, and Associates. His firm designed the Disney Wilderness Preserve, a 12,000-acre mitigation project considered a model for enhancing, restoring and preserving wetlands.

Banking on Getting the Science Right

Fewer than half the wetlands that covered the New World at the time of its discovery by Europeans remain. Yet wetlands serve vital functions providing flood protection, preventing shoreline erosion, filtering pollution and offering a home to endangered and migratory wildlife. Concerned about wetlands' rapid decline, the federal government passed the Clean Water Act in 1972. The Act mandated that builders create, restore or enhance an equal number of wetland acres — preferably in the same watershed — as those they destroyed. Yet wetlands continued disappearing. Over a million more acres of wetlands were destroyed or degraded between 1985 and 1995, according to a report by the U.S. Interior Department. Acknowledging regulatory defeat, the government agreed in the 1990s to give the private sector, specifically mitigation banking, a shot at helping with the cleanup. Wetland-mitigation banks such as the one in the Meadowlands pull private industry into the environmental-preservation business. The goal is to protect wetlands while minimizing the impact on economic sectors. Unlike financial banks built from bricks and mortar, mitigation banks are actual wetlands that have been created, restored or enhanced by private companies or government agencies. Developers can buy "credits" from these banks to replace marshes they destroy while constructing roads, subdivisions and shopping malls. Many environmentalists, however, remain skeptical when it comes to mixing environmental goals with economic incentives. "Banks have a profit motive," observes Robin Mann, chair of the Sierra Club's Wetlands Taskforce "and the fact is that a profit motive impacts the whole set up." But mitigation bankers and enforcement agencies including the U.S. Environmental Protection Agency and Army Corps of Engineers dismiss this concern. "Every environmental organization I know of supports rehabbing wetlands," says Craig Denisoff, president of the National Mitigation Banking Association and vice president of Wildlands Inc. "Now they say banks are a bad thing just because money is involved." Meanwhile, mitigation banks have thrived. Approximately 100 are in operation or proposed for construction in 34 states across the country, according to Environmental Protection Agency data. Successfully enhanced wetlands typically share a number of characteristics, says Joy Zedler, chair of Restoration Ecology at the University of Wisconsin. Zedler co-authored a study on wetland-mitigation banking in 2001 and found that wetlands ripe for successful enhancement are: usually surrounded by larger natural wetlands; have relatively intact topography and have not been severely contaminated. She also says it is important that some natural soil remain on the site and that the site be monitored through a long-term restoration mandate. The Meadowlands Mitigation Bank meets most of these criteria.

How a Vibrant Wetland Became a Putrid Swamp

The New Jersey Meadowlands, a former freshwater swamp wedged between the Hackensack River and the Hudson Bay, ripples through one of the most populated areas of the U.S. As developers raced to find room for the exploding population –building homes, highways, airports, bridges and dams– the Meadowlands was considered a nuisance, a swamp to be filled, drained, and built over. The first real crisis these wetlands faced was just after the turn of the twentieth century with the construction of the Oradell Dam. The dam restricted freshwater flows from the Hackensack River, creating a saltwater wedge that moved in from the Hudson Bay, squeezing out native life, decimating Atlantic white cedar forests, destroying arrowhead marshes and killing off the freshwater fish that swam there. Meanwhile, in a misguided effort to control mosquitoes, the Bergen County Mosquito Commission ditched and drained portions of the Meadowlands. But instead of reducing the number of these bloodthirsty insects, the efforts created stagnant pools of water and, in turn, mosquito breeding grounds. Later, the New Jersey Turnpike dumped muck and rocks into the wetlands. It also excavated wetlands fill for highway construction, creating unnatural hills and valleys while disrupting the wetlands' ecosystem. During this period, an aggressive reed-like grass known as Phragmites made its way into the Meadowlands. Within a few years, the Phragmites, which flourishes in coastal areas, took over. Small mammals fled to more hospitable sites. Only seven bird species, including the redwing black bird, sparrow and hawk found the site worth a visit, according to a recent Rutgers University report.

How the Meadowlands Were Saved

Marking time at the Charleston International Airport in South Carolina after attending a Society of Wetlands Scientists forum in June, Richard Mogensen, a geologist and certified wetlands scientist, reminisces about technologies he used to restore the Meadowlands Mitigation Bank when he worked for the mitigation banking company Marsh Resources. The Society of Wetlands Scientists, a group of university-affiliated wetland scientists, representatives of government enforcement agencies and wetland mitigation bankers, last year endorsed wetland mitigation banking. Making it work, Mogensen says, requires pulling together discoveries in botany, chemistry, biology and mechanics. That's what they did at the Meadowlands site, he continues. The first challenge was how to keep muck and tide out of the site so they could work there. To do this, they laid six-foot aqua tubes — blue-plastic pipes filled with water — along the edge of the area to de-saturate one quarter of the site at a time. Then they brought in enormous pallets called timber mats that enable heavy equipment to ride over the muddy surface. From there they could focus on their primary goal — eradicating the invasive Phragmites. Men sporting backpacks loaded with herbicides and helicopters descended on the site, spraying the area. Then rollogons – tractors with huge tires – rolled through the marshland, crushing any Phragmites they found. Still, the tenacious Phragmites remained. Botanists pitched in, determining that Phragmites, unlike the more desirable marshland plants they wished to introduce to the area, could not tolerate long periods with its roots buried under water. If heavy tidal flows could be successfully reintroduced to the area, they hypothesized, natural marshland plants would be able to out-compete the Phragmites. So Marsh Resources hauled in long-reach excavators and dredges that broke berms built along the river's edge, cutting meandering channels throughout the 206-acre site. Finally, tidal inundation returned. And so did a healthy ecosystem. Today brown-tipped spike rush, saltmeadow and smooth cord grass flourish along the shoreline. Oak trees, elderberry shrubs and giant chord dominate the upland islands. The company introduced a minnow-like fish called fundulus or mummichog into the wetlands. When these small food-chain items appeared, bigger predators followed. More than 80 species of birds now inhabit the site, according to a recent Rutgers University report, ten times the number of bird species spotted on the adjacent non-restored acreage. But revitalization technologies must be site-specific, Mogensen cautions. For example, in other wetlands biological controls have been used to eradicate purple-Loose-strife, a magenta-flowered grass whose tenacious root system has overtaken numerous marshes throughout the Northeast, turning them into unproductive monocultures. When pulling the plants proved fruitless, wetland scientists introduced European beetles that feed exclusively on these plants-after first determining that the beetles could be controlled. "There are too many things that preclude us from getting the natural system back the way you want without help." says Tom Cannon, an aquatic biologist for Wildlands Inc. "Wetlands degraded will come back quickly but you have to have the technology,"

You Still Can't Top Mother Nature

Yet even a successfully restored wetland such as the one in the Meadowlands rarely duplicates Mother Nature, many environmentalists point out. For example, the Meadowlands marshes, once home to freshwater vegetation and fish, have been restored to house saltwater life. Further, mitigation sites, by virtue of being situated in different locations from the destroyed wetlands, rarely provide immediate neighbors who have lost their wetlands with identical flood and erosion protection. Indeed, Zedler's study found that only 21 percent of mitigation sites met various tests of ecological equivalency to functions lost at destroyed sites. And, finally, say some conservation groups, mitigation bankers are not interested in repairing severely damaged sites. They leave the cleanup of brownfields, strip mines and landscapes contaminated with heavy metals to the government or businesses responsible for damaging them.

Getting the Biggest Environmental Bang for the Bankers' Buck

Despite these limitations, mitigation has often proven a boon for the environment and the wallet. In the Meadowlands Mitigation Bank, for example, the cost to restore the swamp land came in at $65,000 per acre, recounts Mogensen. That meant that over $13 million was spent to repair the 206 acres of wetlands, a significant amount of cash that taxpayers might otherwise have been asked to pay. The mitigation bank subsequently sold credits for $150,000 per mitigated acre, nearly three times the cost of the work, netting them nearly $31 million. Meanwhile, Marsh Resources continues spending thousands of dollars every year to monitor the marsh and control the Phragmites. The payoff comes when a Meadowlands interagency mitigation advisory counsel accepts the company's reports, allowing them to sell more credits from the Meadowlands Mitigation Bank. Already the bank has received payment in compensation for wetlands impacted by expanded runways at Newark Airport, as well as for widening the New Jersey Turnpike, and to mitigate for the construction of homes near the marshland.

A Wetland Scientist's Quandary

Repairing one wetland to destroy another comes at an obvious cost. But projects such as the Meadowlands Mitigation Bank indicate that with the right site, technology, determination and follow-up, mitigation can prove successful. And, of course, it is much better than no mitigation at all. "I'm a wetlands scientist," says Mogensen. "I love wetlands and would spend all my days there if I could. But our population is going to grow. When you need to widen a highway, you can't just move it somewhere else." And, he adds, in the real world -a world where development will continue to grow to keep apace with populations, incomes, and people's desire for a better life-difficult decisions will need to be made: "Would you rather build on old-growth forest to stay out of a swamp? Alice Kenny is a prize-winning science writer and a regular contributor to the New York Times Westchester Section. She may be reached at LAST EDITED 6/27/05