Sedimentary, My Dear Watson: Saving Salt Marsh after Hurricane Sandy
Ask longtime coastal ecologist Marci Cole Ekberg what the biggest challenge is for the future of coastal marshes in Rhode Island, and she’ll tell you it’s the lack of sediment, a condition that became considerably more pronounced after the impact of 2012’s Hurricane Sandy.
“The Maidford Marsh region is accreting between 1 and 1.7 millimeters per year,” says the coastal ecologist for long-time Newport area environmental group and FWS partner Save the Bay. “So… not enough to keep up with sea-level rise.”
A lack of sediment can be a huge problem for coastal marshes that are facing rising seas and increasingly frequent and intense tropical storms fueled by climate change. Maidford Marsh is a relatively small area that shares an isthmus with Sachuest Point National Wildlife Refuge, but the challenge is a state-wide and even a global one. Ocean-borne storm and wave erosion combined with the lack of replenishment from estuaries whose rivers have been dammed or choked off by centuries of industrial development has left once-hardy tidal marsh ecosystems at a precipitous juncture where elevations cannot keep up with predicted sea level rise.
“You’ve heard it said in the world of real estate that it’s all about ‘location, location, location,’” says Susan Adamowicz, Ph. D., Land Management Research & Demonstration Biologist at Maine’s Rachel Carson National Wildlife Refuge. “In these coastal ecosystems, it’s all about ‘elevation, elevation, elevation.’”
Adamowicz acknowledges that the pace at which a salt marsh system might be able to naturally adapt to changing conditions as been far outstripped by human development, increased storm activity and climate change-fueled sea-level rise. As someone who’s been witnessing the ongoing struggle for decades, she’s excited by the possibilities afforded by Hurricane Sandy resiliency funding to pursue solutions that can help return larger amounts of sediment to the coast and boost marsh elevation. Exactly what solutions?
“We can try to figure out what human alterations have been made to these sites, and undo them,” she suggests for starters. “Have we restricted tidal flows by a road crossing or railroad crossing so tidal waters don’t come in with the force that they used to, so they’re not able to bring in sediments from the coastal waters? Have we dammed up some of our rivers and not only prevented fish passage upstream for migratory fish, but also dammed off these sediments way up in the watershed and prevented them from coming down to the seashore?”
Many U.S. Fish and Wildlife Service projects currently funded with Sandy resilience dollars, including marsh restorations in Delaware, New Jersey and a stretch from Rhode Island to southern Maine, focus on restoring sediment transport to help bolster healthy coastal marshes and enhance natural defenses that protect coastal communities and sustain people and wildlife. Damaged and undersized culverts are being replaced where needed, and obsolete dams are likewise being evaluated for removal, including several in Maryland, Massachusetts, Rhode Island and Connecticut. Other, similar projects are being funded through the Hurricane Sandy Coastal Resiliency Grant program from the Department of the Interior and administered by the National Fish and Wildlife Foundation (NFWF).
At John H. Chafee National Wildlife Refuge, ten miles southwest of Sachuest Point on Pettaquamscutt Cove, the effects of lost marsh elevation are being felt by the salt marsh sparrow, a bird species of high conservation concern that builds nests down inside the deep swirls of grass that make up a healthy salt marsh. When marshes don’t accrete (build up their own sediment) enough to keep up with sea-level rise, the low nests are flooded and the sparrows’ eggs will wash away; already-hatched young will drown. Here, the U.S. Fish & Wildlife Service is in the early stages of perhaps the most drastic of remediation measures: dredging river-bottom sediment and depositing a skim of clean, tested dredge materials onto disappearing salt marsh (a technique known as thin-layer deposition).
“Depending on the sea-level rise, various models have the population going extinct in 50-60 years,” says wildlife biologist Nick Ernst, whose team at the Chafee refuge is using Hurricane Sandy resilience funding and years of accumulated research from the SHARP and I&M programs to try to improve conditions for the sparrows. “There’s not a lot of sediment to build up the salt marshes here; it’s a sediment-starved system. So we’re going to try to jump-start that process by putting thin-layer deposition—dredge material from the river—onto certain areas of the marsh to try to increase that elevation so the sparrows have a place to nest in the meantime, [while we] try to combat the sea-level rise we’re going to be witnessing over the next couple of decades.”
Test dredging and sediment deposit are scheduled to begin in late fall or early winter at the Chafee refuge, Ernst says, with full-scale implementation commencing in 2015-2016.
For more information on how federal resilience funding is being used to clean, restore and enhance natural areas that were affected by Hurricane Sandy, please visit our Hurricane Sandy Recovery page. To read more detailed stories about funded projects in action, browse our blog posts here.