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Stemming the Invasion
One key to restoring the Long Island Sound’s health is ridding its marshes of a phragmites. Biologists have hit upon one successful formula.

This salt marsh at Connecticut’s Stewart B. McKinney National Wildlife Refuge aptly illustrates a major problem faced by defenders of the sound: invasive species. Here a small channel separates native salt hay and saltmarsh cordgrass (left) and invasive phragmites (right), which refuge biologists have made great progress eradicating.
Diane Cook and Len Jenshel

Phragmites, a hollow-stemmed grass that can soar to heights of 15 feet, is among the most destructive invasive species to overrun the Long Island Sound shoreline. The plant usually moves into coastal marshes when dikes divert tidal flows or when development changes the composition of nutrients, and then forms a dense network of roots and rhizomes that crowds out native plants and destroys habitat for birds, fish, amphibians, and macroinvertebrates. “We end up losing the array of species that characterized brackish tidelands for millennia,” says Scott Warren, a professor of botany at Connecticut College.

Fortunately, biologists have known for a while that salt marshes revive when the barriers to tidal flow are removed. So the U.S. Fish and Wildlife Service (USFWS), the state of Connecticut, environmental groups, and private landowners have teamed up to dig tidal pans and creeks, remove fill, and breach dikes on nearly 2,000 acres of Connecticut coastline since the mid-1970s. “If you bring salt water back in, you absolutely can restore those systems,” Warren says. “It’s one of the prouder, happier examples of restoration ecology.”

On the Great Meadows Unit of Connecticut’s Stewart B. McKinney National Wildlife Refuge, for example, restoration work was completed 18 months ago on more than 40 acres of degraded habitat. Already, an area once overloaded with phragmites and mosquitoes—which bred in stagnant water—has been repopulated by shorebirds and wading birds, and biologists expect cordgrass, fairy shrimp, snails, and killifish to be among the next wave of species to move in.

Restoring freshwater and brackish marshes is a bit more complicated. In those areas, government officials have used herbicides and mowing to control the spread of phragmites, though this strategy generally has to be repeated every few years to be effective. “Long-term inundation with full-strength seawater is enough to do it in,” says Bernd Blossey, an associate professor at Cornell University. “But that’s the only method that controls phragmites in perpetuity.” Warren adds that phragmites can be managed, but not eradicated. “I think it’s possible to control phragmites over the long haul,” he says. “But you’re not going to get rid of it.”

Not all phragmites are invasive—although the ones found in the Long Island Sound come almost exclusively from a European genotype—and they do provide some unintended environmental benefits. Red-winged blackbirds and other generalists nest in the long stalks, and waterfowl use small patches of phragmites as windbreaks.

In places like the Chesapeake Bay, phragmites can also protect coastal marshes from rising seas. “Down here it’s probably a blessing because it’s the only species we can point to that can keep up with rapid sea-level rise,” says Court Stevenson, a professor at the University of Maryland Center for Environmental Science. Nonetheless, most biologists and environmentalists agree the restoration efforts are worthwhile. “The world would be a very poor place if everything was a phragmites marsh,” Blossey says.

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