THIS time of year the expansive flats of marsh grass in Cedar Beach Creek on Long Island’s North Fork usually turn lime green as the summer sunshine pushes the vibrant salt marsh ecosystem into overdrive. But that seasonal shift has increasingly been streaked with shades of mud-brown and gray.
A phenomenon commonly called sudden wetland dieback has denuded hundreds of acres of salt marsh in more urban environs like Jamaica Bay in Queens over the past decade. But its recent and aggressive advance across the New York area — and especially into more pristine environs like the North Fork — has some scientists worrying about what might happen if it keeps spreading.
“We need to find out the cause sooner than later,” said Fred Mushacke, a marine biologist with the New York State Department of Environmental Conservation. “We’re losing wetlands at a rate of half an acre per year in Cedar Beach alone. In Jamaica Bay, it’s 44 acres per year.
“If those rates get worse, we’re going to reach a tipping point, and then there could be a mass die-off.”
The problem is not just on Long Island. Each year in New Jersey, Westchester and Connecticut, dozens of acres of tall marsh grass, Spartina alterniflora, are dying off. Scientists are not sure what is causing the phenomenon or what they can do to end it.
“This loss of this productive habitat would have widespread implications,” said Nicole P. Maher, a wetlands specialist at the Nature Conservancy’s Cold Spring Harbor office on Long Island. “The marsh provides food, it filters water and it buffers storm and wave energy. It’s very valuable to wildlife. We need to do more than just keep an eye on it.”
Salt marshes are also vital sources of food, Mr. Mushacke said. Each acre of spartina grass produces four tons of organic matter, which works its way into the food chain through algae until big fish are eating little fish and birds are eating the fish.
“The tidal wetlands are the most important and naturally occurring ecological unit in the world,” Mr. Mushacke said. “If you lose four tons of organic material per acre per year, that translates into tons of fish and shellfish you’re losing.”
At the 173-acre Marshlands Conservancy in Rye, Westchester’s popular birding destination, losses that started a decade ago have gradually consumed about a dozen acres. While some regrowth was reported last year, losses continue to outstrip gains.
Along New Jersey’s Delaware Bay, wetlands from Canton to Dennis Township have suffered damage in spots, and scientists are now inspecting other parts of the state for more.
Marshes along a roughly 50-mile stretch of the Connecticut coastline between the Housatonic and Connecticut Rivers have been similarly stricken, said Ronald Rozsa, a marshland biologist with the State Department of Environmental Protection. The die-off is just part of a number of changes in these wetlands that scientists are having a hard time fully explaining.
“And we haven’t really been able to look at marshes east of the Connecticut River,” Mr. Rozsa said. Marsh vegetation changes through time, he said, but “all of a sudden we’re seeing this rapid movement of grasses.”
But the extent of the dieback is so unclear that officials in Connecticut, New Jersey and New York are asking for residents’ help in tracking it. On Long Island, the Nature Conservancy is hoping to assist the state by monitoring East End marshes where hundreds of acres of wetlands could be affected.
Theories abound for the cause of sudden wetland dieback. A fungus that attacks spartina grass, called fusarium, could be the cause, as could a tiny worm called a root nematode, Mr. Rozsa said.
A more ominous theory is that global warming is having an effect. Mr. Rozsa and Mr. Mushacke agree that rising sea levels are suspected of causing sudden wetland dieback, but Mr. Rozsa said a 20-year lunar cycle called the tidal epoch, which produces long-term tidal fluctuations, complicates that theory.
“Is this an accelerated response to global warming?” Mr. Rozsa said. “We don’t know. We saw grass dieback in the 1980s, and it grew back. The question now is: are we going to see that same grow-back again?”
Mr. Mushacke said he thinks not. He also argues that there is nothing sudden about the dieback, but that it has been gradually accelerating over the past decade.
Since the late 1800s, Long Island marshes have experienced declines, but in many instances they have grown back. Since 1974, however, Long Island has lost 1,400 acres, or 8 percent, of an estimated 17,000 acres of marsh, with little growing back, Mr. Mushacke said.
Much of that has been lost in the Jamaica Bay estuary to what is believed to be more of a development-related problem called marsh subsidence. But the recent emergence of wetland dieback in places on Long Island — like Flax Pond in Old Field and Cedar Beach and Corey Creeks in Southold — has included two versions of dieback also appearing in Connecticut, Cape Cod and up to Maine.
One form occurs close to where the marsh bank meets the water. It kills the roots and the plant, leaving the peatlike soil underneath resembling Swiss cheese. In higher elevations of the marsh, called the high marsh, the dieback is also advancing, leaving a similar pockmarked landscape.
The range of locations and the variety of symptoms make studying marsh dieback vexing, scientists say.
“We don’t know the full depth of the problem yet,” Mr. Mushacke said. “There are marshes that haven’t changed at all, and that’s also perplexing.”
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