Salt Marsh SOS: From Maine to Mississippi, Tidal Wetlands Are Degrading
Hendrick, Dan, E Magazine
A picture may speak a thousand words, but time-lapse photographs of an imperiled tidal marsh in Darien, Connecticut are more likely to leave viewers speechless.
In a scientist's photomosaic taken in 1972, wetlands along the Five Mile River included a small island surrounded by thin ribbons of water and covered in grasses that typify a healthy New England salt marsh. In a contrasting set of photos from 2000, all that remains of the island is a puddle-pocked mudflat. The watercourses are wider, no longer so meandering, and the surrounding stands of Spartina patens and Spartina alterniflora are frayed.
"Some residents on the Five Mile River showed us photographs from the 1960s, and today, they [the marshes] are virtually all gone. They were very lush before" says Ron Rozsa, a coastal ecologist at the Connecticut Department of Environmental Protection.
The photographs depict a troubling phenomenon along the U.S. Atlantic and Gulf Coasts: Tidal wetlands that have been healthy for hundreds, if not thousands, of years are rapidly breaking up and converting to open water.
Some of the losses are well understood, like in Louisiana, where diversions and levees on the Mississippi River have stopped nourishing sediments from replenishing the delta. Twenty-four square miles of the state's wetlands sink into the Gulf of Mississippi each year--the equivalent of one football field every 38 minutes.
Among the other widely known problem spots is the Jamaica Bay National Wildlife Refuge in New York, where salt marshes suffer from a perfect storm of sediment starvation, dredging, wastewater effluent and even wave action from boats that threatens to drown them by 2020. Maryland's Blackwater National Wildlife Refuge faces similar peril, made worse by normative rodents that are eating away the bulrush marshes.
Research by a team of University of Maryland scientists suggests these notable losses may just be the beginning. By analyzing NASA satellite imagery of the East Coast, the team is categorizing the health of wetlands to detect areas that are at risk for rapid loss. Their technique is not without its pitfalls, since atmospheric conditions can cloud the images and the satellites don't capture every detail. Still, the team's data pinpoint dozens of locations from Massachusetts' North River Estuary to Hunting Island off the South Carolina coast where marshes are in trouble.
The team is paying particularly close attention to Chesapeake Bay, the nation's largest estuary system. They found that in 1993, 50 percent of the bay's marshes could be classified as degraded, with 20 percent seriously degraded. …