Spades of work to save our salt marshes
by Karlo Berger, Summer 2021 habitat restoration intern
It is a fair, early April day out on Winnapaug salt marsh in Westerly, R.I., across from Misquamicut Beach. Finishing up a pandemic year of environmental coursework via Zoom, I am glad to finally be away from my computer screen and out on the marsh with Save The Bay’s Director of Habitat Restoration, Wenley Ferguson, and CoastKeeper, David Prescott. In the cab of what resembles a tiny steam shovel is John Fox, who has been trained by Alan Gettman from the Rhode Island Department of Environmental Management’s (RIDEM) Mosquito Abatement Unit to operate this low-ground pressure excavator that is specially designed to avoid damaging the surface of the marsh. We have gathered here to dig runnels.
What is a runnel? A runnel is a shallow channel or creek. The runnels being dug today, using the excavator as well as hand shovels, are no more than 12 inches wide by 12 inches deep. In a collaboration between RIDEM and Save The Bay, our team is creating runnels to drain standing water off the surface of the marsh and out towards Winnapaug Pond. RIDEM’s Mosquito Abatement Unit is taking part because the runnels will help drain water that can create ideal mosquito breeding habitat. For Save The Bay, draining this standing water can allow waterlogged and decaying marsh grass to revive, and allow areas that have died off to revegetate. We are also creating new habitat by utilizing chunks of the shoveled marsh soil to make slightly higher areas, enabling high marsh grasses to recolonize the area.
Salt marshes, like Winnapaug, across Rhode Island, face multiple and complex challenges to their continued survival. Generations ago, coastal farmers dug drainage ditches and built embankments in salt marshes in order to grow and harvest more “salt hay” (Spartina patens, the high marsh grass also known as saltmeadow cordgrass). Later, in an effort to control mosquitos, local authorities dug large ditches to drain the marshes. Over time, these many changes caused the marsh to decompose and subside, creating shallow standing water that drowned marsh grasses and ironically created an ideal breeding ground for mosquitos.
To make matters worse, accelerated sea level rise due to climate change is now causing more of these pools to form. While marshes naturally build up more soil and vegetation over time, they cannot do so as quickly as seawater is rising. As more and more water saturates the marsh, it may eventually die off without our help.
Winnapaug marsh and other Rhode Island salt marshes provide natural filtration against stormwater pollution, a buffer against storms, and habitat for at-risk species such as the saltmarsh sparrow. For these and other reasons, a healthy and resilient Narragansett Bay requires healthy and resilient salt marshes. Through its runnel projects at Winnapaug and elsewhere, Save The Bay is buying time for marshes to migrate to higher elevations as climate change continues to push sea levels higher.
I am particularly grateful to be out on the marsh with Wenley, as she is considered an authority on runneling among salt marsh restoration practitioners. Having undertaken her first runneling project in 2010, her expertise is sought as far afield as Chesapeake Bay and Nova Scotia, where ecologists and restorationists have observed the same marsh “drowning” in their salt marshes.
Save The Bay staff and volunteers have already worked on a range of runneling projects in Rhode Island and Massachusetts. The runnels are dug in a gently winding fashion to mimic natural water flows, minimize erosion, and reduce conditions that allow invasive species such as Phragmites australis to overwhelm the marsh. Runneling is also implemented in marsh restoration projects where dredged sediment has been spread on the marsh to raise its elevation so it can keep up with sea level rise. Following any of these interventions, the marsh platform remains in a dynamic state and runnels need to be maintained annually due to ever-changing soil, vegetation, and tidal conditions.
As we walk Winnapaug marsh, Wenley points out the damage that has been done to the marsh in the past while also observing the benefits of runneling completed by Save The Bay and partner organizations at Winnapaug a year before.
Ecological monitoring has been underway at Winnapaug Pond, the Narrow River, and other sites to help assess the value of runneling in supporting the restoration of local salt marshes. Under the coordination of post-doctoral researcher Alice Besterman, a coalition including Save The Bay and the Buzzards Bay Coalition is studying the effectiveness of runneling in reducing salt marsh loss. Utilizing a range of monitoring methods, the group is comparing over time a salt marsh experiencing ponding which has been treated by runneling with a marsh that has not been treated. If their findings suggest that runneling builds up marsh soils, elevation, and vegetation, there may be many more of these projects in Save The Bay’s future.
For today, the marsh soil is soft, the company is cheerful, and runnels need to be dug.
Karlo Berger is a Summer 2021 habitat restoration intern for Save The Bay. He is pursuing a master’s degree in environmental science and management at URI, specializing in ecological restoration and policy.