Tidal Wetland Restoration
in Connecticut (Part 1)
(Part 2)
(Part 3)
Tidal Wetland Restoration
in Connecticut (Part 1)
| |
 |
Ron Rozsa, Ecologist,
Office of Long Island Sound Programs
Connecticut Department of Environmental Protection
Ecological Restoration is defined as the intentional alteration of a site to establish the approximate biological, geological and physical conditions that existed in the predisturbance indigenous ecosystem or habitat. Restoration projects attempt the re-establishment of all the predisturbance characteristics of a site, including plant and animal species and a variety of community attributes such as structure, function, and habitat values. This should not be confused with wetland creation in which a habitat that did not previously exist, at a particular site, is brought into existence.
As previously explained, tides are the primary abiotic factor organizing these complex wetland ecosystems. Most restoration projects in Long Island Sound have targeted salt marshes that were degraded as a result of activities which reduced or eliminated tidal flooding. In such marshes, the tidal marsh plant communities are usually replaced by a monoculture of Phragmites (also called Common Reed, Phragmites australis), a characteristic which makes identification of degraded sites quite easy. In some systems Narrow-leaved Cattail (Typha angustifolia) may replace the salt marsh species (see Barn Island example below). One of the problems resulting from this vegetation change is a drastic decrease in plant species diversity and reduced access to the marsh by the larger species of waterfowl, shorebirds and wading birds. Restoration of tidal flow is a highly successful method for the removal or suppression of Phragmites, because it is intolerant of salinity levels above 18 parts per thousand (ppt).
The following restoration case studies illustrate various bio-physical changes that result from human activities. Each is also an example of how habitat restoration can proceed. Since the 1970s Connecticut has restored over 600 hectares (1500 acres) of salt marsh, with most of the work supervised by the Department of Environmental Protection (DEP). In New York, restoration efforts have been directed largely towards the south shore of Long Island, where there are many more salt marshes than along the northern, Long Island Sound shore. As a policy, restoration projects are only implemented once it has been shown that the benefits of restoration outweigh the alternative of taking no action at all.
BARN ISLAND WILDLIFE MANAGEMENT AREA, STONINGTON IMPOUNDED MARSHES
The Barn Island Marshes are a series of flooded valley tidal wetlands near the Rhode Island border in Stonington, Connecticut, which have been managed by the State as a hunting and fishing area (Fig. 1). In the late 1940s, the Connecticut Board of Fisheries and Game began constructing a series of impoundments across the valley marshes at Barn Island to offset the loss of waterfowl habitat caused by mosquito ditching. Low earthen dikes were built across several marshes, converting upstream, interior portions to non-tidal, shallow water habitat through the ponding of upland stream flows.
Fig. 1 Click on figure to see map of Barn Island marshes. (153K)
Waterfowl use initially increased, but declined over the long term as the new open water habitat was encroached upon by a new set of plants. By the 1970s, the impoundments were dominated by Narrow-leaved Cattail and expanding colonies of Phragmites. The muskrat population also increased dramatically. To reduce the amount of Cattail and Phragmites, which cannot tolerate salt water, in 1978 the DEP installed a four foot wide culvert on the westernmost impoundment (called No. 1). Restoration of tidal flushing resulted in the demise of the cattail and the re-establishment of salt marsh vegetation (Fig. 2). However, this only occurred in the southern part of the marsh, suggesting that the culvert was too small to pass sufficient volumes of saltwater to regularly flood the middle and upper marsh areas. The culvert was also found to restrict drainage of water off the impounded marsh back into the Sound, so a higher than average low tide elevation was maintained behind the dike.
In 1982, a seven foot diameter culvert was added to the same impoundment, and today nearly all of the Cattail and much of the Phragmites has been replaced by salt marsh vegetation. Two former large open water pannes now support Smooth Cord-grass (Spartina alterniflora), and numerous shallow pools attract large numbers of shorebirds and wading birds. Re-establishment of the salt marsh vegetation occurred through spontaneous means and without planting, demonstrating that plant species restoration occurs naturally without the need for implementing expensive and often ineffective planting programs. With the re-establishment of salt marsh vegetation, typical marsh invertebrates and fish recolonized the area. Studies by students and staff at Connecticut College have documented this process of restoration (see Suggested Readings). Using similar methods three other impounded wetlands have been restored at Barn Island.
SUGGESTED READING
Barrett, N.E. and W.A. Niering. 1993. Tidal Marsh Restoration: Trends in Vegetation Change Using a Geographical Information System (GIS). Restoration Ecology 1(1): 18-28.
Dent, D. 1986. Acid Sulphate Soils: A Baseline for Research and Development. International Institute for Land Reclamation and Improvement, Publication No. 39. The Netherlands.
Peck, M.A., P.E. Fell, E.A. Allen, J.A. Gieg, C.R. Guthke, M.D. Newkirk. 1994. Evaluation of Tidal Marsh Restoration: Comparisons Of Selected Macroinvertebrate Populations On A Restored Impounded Valley Marsh And An Unimpounded Valley Marsh Within The Same Salt Marsh System In Connecticut, USA. Environmental Management 18:283-293.
Portnoy, J.W, 1991. Summer Oxygen Depletion in a Diked New England Estuary. Estuaries 14: 122-129.
Roman, C.T., W.A. Niering and R.S. Warren. 1984. Salt Marsh Vegetation Change in Response to Tidal Restriction. Environmental Management. 8:141-150.
Sinicrope, T.L., P.G. Hine, R.S. Warren, and W.A. Niering, 1990. Restoration of an Impounded Salt Marsh in New England. Estuaries 13:25-30.
 Home | Previous Chapter: Human Impacts on Tidal Wetlands  |
Next Chapter: Tidal Wetland Restoration in Connecticut (Part2)  |
June 21, 1997 / DEP's Tidal Wetland Restoration Program / webmaster@po.state.ct.us
