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Starting this winter, crews could begin a multiple-year process to try to reverse harmful effects of agriculture on Long Marsh. If the Harpswell Heritage Land Trust and its partners are successful, the salt marsh will provide more habitat for animals and be more resilient to rising sea levels.
Salt marshes are tidal wetlands where salt-tolerant grasses, shrubs and other plants grow. They can serve as nurseries for young fish and as habitat for birds and animals. Long Marsh, which parallels Route 24 from the Gurnet area south almost to the Trufant-Summerton Athletic Field, is the largest salt marsh in Harpswell.
Beginning as far back as the 1600s, Colonial settlers and their descendants farmed hay and other crops on the tidal salt marshes that dot the Maine coast. Farmers built embankments and dug trenches to improve productivity.
With industrialization, agriculture moved inland. But those structures remained, and experts on marsh restoration say they are degrading the marshes.
Large pools of standing water are a common sight in salt marshes today, but they are not a natural feature, said Tatia Bauer, marsh restoration program manager at the Maine Coast Heritage Trust. The organization is one of the Harpswell Heritage Land Trust’s partners in the Long Marsh restoration.
In addition to providing habitat for different animals, salt marshes deposit and store carbon, and they can blunt the effects of flooding from storm surges.
A healthy salt marsh slowly grows taller year by year as plants die, decompose and turn into soil. Bauer said stagnant pools create dead areas where native vegetation can’t grow, and the weight of the water compacts the soil. Human-made drainage ditches increase erosion. Together, these remnants of salt marsh agriculture can cause the marsh to stop building height and even sink, according to restoration experts.
While salt marshes may be able to overcome these impacts on their own, sea level is rising at about two-tenths of an inch per year and accelerating, according to the National Oceanic and Atmospheric Administration.
“Without sea-level rise, maybe the marsh could restore itself. But we don’t have time for that,” said Emma Balazs, lands and stewardship director at the Harpswell Heritage Land Trust. If the restoration work can give Long Marsh a head start, she hopes it will be able to keep up with rising seas on its own.
To start to reverse the effects of historical agriculture, crews will begin by digging trenches to drain the large pools of standing water, and filling in some of the ditches with grass cut from the marsh. Initial work will be done by hand, but bigger trenches will be dug using a small excavator.
The hand work could start as early as the end of the winter of 2026-27, according to Bauer, but the project is awaiting permits from the U.S. Army Corps of Engineers and the Maine Department of Environmental Protection. Work will continue each year for three to five years, and could be revisited after that.
A ford or bridge was built by placing large rocks across the marsh at one point. The Harpswell Heritage Land Trust hopes to remove that obstacle to restore natural flow to the southern part of the marsh.
The goal, the partners said, is to create what marsh restoration experts call single-channel hydrology, where water flows unimpeded in and out of the marsh with the tides through a main channel.
One of the partners, the Casco Bay Estuary Partnership, already had been monitoring Long Marsh for more than a decade through a contract with the Maine Department of Transportation. The contract came about because the department was rebuilding the Long Reach Lane causeway to improve water flow to the marsh.
The Casco Bay Estuary Partnership’s habitat manager, Matt Craig, said he started conversations with the Harpswell Heritage Land Trust after “we saw the marsh wasn’t recovering the way we would want.”
The Maine Coast Heritage Trust will handle much of the project planning and management with a $584,000 grant from the U.S. Environmental Protection Agency, of which $252,000 will go to Long Marsh. Geoff Wilson, of Northeast Wetland Restoration, will create the plan and carry out the work, along with volunteers and others.
The Casco Bay Estuary Partnership will provide technical assistance, including monitoring of the marsh. The Harpswell Heritage Land Trust is helping with access to the marsh and coordination with local landowners. Much of the land surrounding Long Marsh is preserved or in a conservation easement, and the Land Trust will be the long-term steward of the marsh.
Craig acknowledged that the work that will happen at Long Marsh and other salt marshes is somewhat experimental.
“We actually don’t know what it was like before Colonial settlers came in,” he said. And experts also don’t know how sea-level rise will proceed, or what marshes will look like at the end of this century. Nor do Craig and his colleagues know exactly what impact their interventions will have over the span of decades.
They do feel confident that they can start to undo some of the effects of agriculture in the short term, and they agree that they need to act now.
“These restorations are designed to extend the lifespan,” Craig said. Beyond that, only time (and tide) will tell.
