An urban marsh’s unfinished saga
New York’s Jamaica Bay serves as a microcosm for the world’s wetland woes.
(Page 2 of 3)
Scientists and residents alike would like to avoid total marsh loss for a slew of reasons. The spongy soil, topped by tall grasses, buffers against storm surges. Many think that hurricane Katrina would have been less devastating had the Gulf Coast’s wetlands been intact and able to slow and absorb the storm surge. (Wetlands lining the Mississippi River could once soak up 60 days’ worth of floodwater, says the Environmental Protection Agency; what now remains can only hold 12 days’ worth.) A glance at a New York City flood-preparedness map shows that large swaths of Brooklyn and Queens directly behind Jamaica Bay are vulnerable to storm surges of only a few feet.Skip to next paragraph
Subscribe Today to the Monitor
Hotbeds of biodiversity
Wetland ecosystems also host a biodiversity rivaling that of coral reefs. They serve as a nursery for fish that, as adults, move to the open sea.
And they sequester carbon as peat, keeping climate-warming greenhouse gases out of the atmosphere.
At a July conference on wetlands in Brazil, scientists stressed the “carbon sink” function of wetlands. Worldwide, they estimate that, although they account for just 6 percent of the earth’s surface, the world’s wetlands – bogs, tundras, mangroves, swamps, and marshes – store between 10 and 20 percent of its terrestrial carbon. That’s an amount nearly equal the 771 gigatons already in the atmosphere. And if rising temperatures or more direct human disturbance lead to more wetland drying, scientists worry that the carbon released will further warm the planet.
“It’s a feedback loop,” says Eugene Turner, a professor at Louisiana State University’s Coastal Ecology Institute in Baton Rouge, who attended the Brazil conference. Sixty percent of the world’s wetlands have already been lost during the past century, according to conference organizers.
Saltwater marshes require specific conditions to thrive: enough seawater to stay wet, but not so much as to drown. Sea levels have already risen nearly a foot along the Eastern Seaboard during the past 150 years, due partly to subsidence and partly to thawing polar regions. Locally, dredging has further altered tidal fluctuations by changing the “prism” of the bay, says Larry Swanson, director of Stony Brook University’s Waste Reduction and Management Institute on Long Island. The increased depth amplifies the tide, with highs and lows 8 to 10 inches above and below historical extremes, he says.
“We’ve totally altered the bay in a physical sense,” he says. “You can’t do that and not have some impact.” Add that to sea-level rise, and, at times, there’s 1.5 to 2 feet of extra water, compared with 100 years ago, he says.
Four wastewater-treatment plants empty into the bay. Although treated, the plants’ effluent is still high in plant nutrients like nitrogen, a byproduct of human waste. Between 1990 and 1995, nitrogen influx to Jamaica Bay doubled. (It has since decreased somewhat.) That’s when residents noted an acceleration of the marsh loss, an observation later corroborated by the DEC. Although scientists are quick to point out that correlation does not prove causation, many suspect that excess nitrogen – currently between 30,000 to 40,000 lbs. daily – is contributing to marsh degradation.