Vol. 1, No. 3
Headline Back Issues
|
NH seacoast-area partners pool efforts to restore strangled salt marshes Durham, New Hampshire - Groups in the state's seacoast area are collaborating to restore tidal flow to salt marshes strangled by years of road-building and other land uses. Thanks to this restoration work, some salt marshes are already beginning to recover, according to biologist Alan Ammann of the Durham office of the Natural Resources Conservation Service (NRCS), a branch of the US Department of Agriculture. New Hampshire's 18-mile (29-kilometer) coastline includes at least 6,200 acres (2,509 hectares) of salt marsh, formed over the last 4,000 years or so on sediment deposits behind sand bars, barrier beaches, and rocky spits. Describing salt marshes as an important component of the New Hampshire seacoast's natural heritage and picturesque coastal landscape, Ammann explained that they also serve important functions in the coastal ecosystem, preventing shoreline erosion; improving water quality by filtering pollutants; and serving as habitat or foraging grounds for wildlife. Also, he said, "It's believed that marshes process and export nutrients important for coastal fisheries but that's not that well-documented in New Hampshire." Generations of people hunted, fished, and foraged in the marshes. More recently, farmers harvested hay from this rich resource. But seacoast residents have also damaged salt marshes by building roads and railroads, under which were installed narrow culverts designed for upland drainage rather than tidal flow of saltwater. Many of these old metal culverts are now corroding and collapsing, further blocking the passageways. In some cases, people installed tidal gates, blocking passage for mummichogs - mosquito eating fish that had kept mosquito populations under control. Although federal legislation has protected US salt marshes from filling and other damaging activities since 1972, many sites continue to suffer the ongoing effects of past activities. According to Ammann, 20 percent of the state's salt marsh acreage has undergone at least some deterioration as a result of human-caused restrictions to the tidal flow. Freshwater systems not as productive for wildlife Without sea water, salt marshes gradually convert to freshwater marshes and even wooded swamps. Saltwater vegetation can grow in freshwater, but is crowded out by freshwater plants such as cattails, purple loostrife, and the tall grass phragmites, which grows too densely to serve as wildlife habitat, poses a fire hazard, and doesn't necessarily contribute the nutrients that saltwater plants provide, Ammann said. But now, seacoast-area agencies, organizations, and municipalities are trying to reverse the results of past actions undertaken due to lack of understanding of the value and ecology of salt marshes. So far, partners in efforts to reverse salt marsh deterioration have restored tidal flow to 179 acres (about 72 hectares). While the economic benefits of salt marsh restoration haven't been quantified, Ammann noted that seacoast towns spend more than $100,000 annually on insect control - an investment that bears little fruit in salt marshes where restrictions in tidal flow have kept mosquito-eating fish out of the marsh while creating stagnant pools where insects breed. Restoration work coordinated by Ammann's office has included replacing old metal pipe culverts - some only two feet wide - with concrete ones as large as 12 feet (3.7 meters) across; reopening farm ditches; and digging new tidal ditches. Peat and soil dug from the marshes are used as landfill cover, composted, or in some cases, are used for eel grass restoration, Ammann said. Joint efforts paying off "Other agencies have been involved long before we were," Ammann emphasized, but while restoration efforts were under way when NRCS joined in, lack of funds or organization stalled some projects. NRCS helped coalesce these efforts by developing - with help from numerous federal, state, and local organizations - a 1994 report, Evaluation of Restorable Salt Marshes in New Hampshire. The document, which identified more than 80 restorable salt marsh areas, and provided engineering cost estimates on a per-acre basis, was distributed to seacoast town officials. Ammann credits the document with helping the towns develop successful grant proposals for salt marsh projects. Local residents support the restoration efforts, and some of the work is done by volunteers, but most of the labor requires the heavy equipment and expertise of contractors or town road crews, Ammann said. Collaborators in efforts to restore tidal flow to several marshes have provided or secured financial support, land access, or in-kind donations, and have included private landowners, the New Hampshire Coastal Program, the New Hampshire Department of Transportation, the University of New Hampshire Jackson Estuarine Laboratory, the New Hampshire Wetlands Bureau, The Wells (Maine) Estuarine Research Reserve, the Great Bay Estuarine Research Reserve, the National Oceanic and Atmospheric Administration, US Fish and Wildlife Service, US Environmental Protection Agency, the Natural Resources Conservation Service, and other entities. The partnership has worked to restore tidal flow to several salt marsh sites, including Awcomin Marsh in Rye Harbor, where crews had to remove dredge spoils dumped on the marsh in the 1940s and 1960s, and in the Locke Road marsh, where 20 different property owners cooperated to move the project forward. These collaborative restoration efforts are still relatively informal, simplifying the process, somewhat, said Ammann. But complications do arise, he said, noting that completion of the Little River marsh restoration in North Hampton has been delayed by the project's complexity and expense. Ammann said he expects that work to cost more than $1 million and doesn't anticipate its completion for several years. Recovery time varies with site In a typical New Hampshire salt marsh, marsh grasses grow to form a dense turf, building a layer of peat that keeps pace with the ongoing rise in sea level. In highly degraded marshes, this turf is replaced by the less cohesive root systems of freshwater plants. It becomes soft and spongy and may not support new growth of saltwater vegetation, even once tidal flow is restored. At one site, Ammann said studies show anadromous fish that swim from the sea inland to spawn) "were present only a year or so after the marsh was opened up." But in some cases, a marsh can require years - even decades - to recover. The amount of time, money, and effort being invested in salt marsh restoration is significant, but, according to Ammann, keeping them healthy could help prevent unforeseeable problems. "Before people settled this area, all of these diverse ecosystems were functional. Now they're not as much, and we don't know the bottom line. At one time people didn't know what your liver did, but they sort of knew that you don't just yank it out of there." |
||||||||||
Gulf of Maine Council on the Marine