By Christine Harris
In 1908 the Herring River Estuary in Wellfleet, Massachusetts, a system supporting 1100 acres of salt marsh, was diked off, restricting normal tidal flow and eliminating all but 10 acres of the marsh. The reasoning behind the construction of the dike seems ludicrous in light of modern ecological understanding. Today an effort is being made to restore salt marshes throughout the country, including those of the Herring River Estuary.
At the turn of the twentieth century the quaint coastal town of Wellfleet, Massachusetts was becoming a popular resort area to which many wealthy city-dwellers flocked. One popular hotel, the Chequesset Inn, located near the mouth of the Herring River, attracted an elite clientele. Guests at the Chequesset, and other area establishments, enjoyed spending time relaxing by Wellfleet Harbor, but complained about the mosquitoes. At the time it was believed that the source of the mosquitoes was the Herring River, and it was thought that if the salt marshes of the estuary were eliminated, the mosquito population in the area would decrease significantly. Thus the Chequesset Neck Dike was constructed by the state in 1908, reducing the mouth of the river from a width of several hundred feet to six feet, and effectively cutting off tidal flow beyond the dike.
Cutting off tidal flow to the Herring River significantly affected the health of the ecosystem it supported. In place of native salt marsh plants the Herring River now hosts a number of invasive plant species, including a large amount of the invasive reed phragmites. Furthermore, without the flushing of the tides and the presence of saltwater minnows such as the mummichog, a type of killifish that feed on mosquito larva, the Herring River likely provides breeding grounds for more mosquitoes now than it did before it was diked off.
Once considered to provide little more than foul smells and insects, salt marshes are now recognized as biologically significant ecosystems on which many species, including humans, depend. Peat, the spongy layer of decomposing plant material which is the base of a salt marsh, has been recognized to provide a buffer from storm damage. When storm surges threaten coastlines, peat absorbs flood waters and reduces the height of these surges, protecting coastal communities from the impacts of severe flooding.
Another beneficial feature of salt marshes is their role as the nurseries of the ocean. Over two thirds of all commercially harvested seafood species, including shellfish, finfish, crabs, and lobsters, depend on the salt marsh for part of their life cycles. Salt marshes provide cover and camouflage for many of these harvestable species when they are young and most susceptible to predation, and provide a safe place for breeding and foraging. Salt marshes also have recreational value as popular places to fish, kayak, and contemplate the natural world.
With knowledge of the benefits which marshes provide, local communities, the state, the county and the Cape Cod National Seashore have taken on the task of restoring several previously degraded salt marsh systems on Cape Cod, including that of the Herring River. Most of these restoration projects focus on the use of gradual tidal restoration to reintroduce saltwater, along with the species of plants and animals it supports, over the course of many years. The Herring River restoration project centers around the reconstruction of the Chequesset Neck Dike. The proposed structure would provide access to the public for fishing and boating and have a series of sluice gates that could allow for incremental tidal restoration across a width of 100 feet. Construction of the new dike is set to begin in 2016.