Buying Time with Runnels: NE CASC Fellow Helps Advance Salt Marsh Restoration

Spanning nearly 4 million acres of coastal land in the United States, salt marshes provide immense benefits for wildlife, fish, and people. In addition to serving as essential habitat for many finfish, shellfish, and migratory bird species, these wetlands also play a crucial role in maintaining ocean water quality by filtering harmful runoff. Equally important, salt marshes combat climate change through natural mechanisms. Capturing wave energy that leads to coastal erosion, salt marshes act as natural flood barriers and counteract the effects of storm surges amplified by climate change-induced sea level rise. Because they are densely vegetated, marshes also fulfill an important role in removing carbon from the atmosphere and minimizing global warming. Without salt marshes, which are sometimes described as “ecological guardians of the coast” by conservation groups, much of our nation’s coastline would be less desirable for human occupation and incapable of sustaining fish and wildlife species.

Despite the security they afford to humans and animals, however, salt marshes across the Northeast are imperiled. “A combination of rising sea level and a long legacy of destructive human development threatens to drown marshes from the inside out,” says Alice Besterman, a coastal ecologist and NE CASC postdoctoral fellow working at the Buzzards Bay Coalition and Woodwell Climate Research Center. “As a result, many marshes in our region have entered a state of significant decline. Vegetation is being killed off and habitats are being destroyed as marshes convert to open water.” 

Advancing strategies to improve marsh health has become a focal point for Besterman, who has been working with NE CASC principal investigator Linda Deegan and Rachel Jakuba of Buzzards Bay Coalition for the past two years to assess the efficacy of a climate adaptation technique known as runneling. As Besterman explains, runneling involves digging shallow channels to drain areas of impounded water within marshes, promote revegetation, and restore tidal hydrology.  “Runneling offers a short-term solution to interior marsh loss,” says Besterman. “It effectively extends the life of marshes in the face of sea level rise, buying additional time either for the implementation of new management strategies to protect them or for adaptation by marshes themselves through accretion or upland migration.” 

Although runneling has become an increasingly popular management strategy for marsh restoration and mosquito control, data from controlled scientific studies testing the effectiveness of this technique are limited.  “The goal of our work”, says Besterman, “is to take the informal knowledge about how runnels can be used–the more anecdotal, case-specific adaptive knowledge of the technique acquired in various individual projects–and turn it into something more generalizable for managers and the scientific community to use across a broad range of marshes. Our research will help both regulators and the scientific community understand how runneling works mechanistically.” 

To accomplish this task, Deegan, Jakuba and Besterman are conducting analyses at two salt marshes in Buzzards Bay, Massachusetts. There they have subdivided each of the marshes into five control and five experimental sites to collect data that reveals how runneling impacts marsh vegetation density and variety, physical and chemical soil characteristics, water level and quality, and sediment dynamics. “The work that Alice is doing here is invaluable,” says Wenley Ferguson, director of habitat restoration for Save the Bay and a project collaborator who has used runnels to remediate marsh degradation since 2010. “She is looking at a variety of factors that practitioners like me may not have the time or training to assess, particularly in the area of quantitative monitoring. Her research is playing a key role both in establishing a comprehensive understanding of how runneling works and in increasing the applicability and acceptance of runneling as a management technique.” 

Developing broad acceptance for runneling is crucial to the future health of salt marshes because their vulnerability is amplified by the complex regulatory context in which they are embedded. Across the Northeast, marshes are regulated by both state and federal agencies who have long discouraged management interventions on these wetlands due to a pattern of unintentionally destructive human behavior on them. In the 1930s, for instance, the Civilian Conservation Corps created a gridded ditch system across New England salt marshes to control mosquitos. These ditches radically altered marsh hydrology, at first over-draining and drying marshes out. Later, the over-drainage of marshes resulted in subsidence. In interaction with sea level rise, gridded-ditches have indirectly resulted in massive quantities of impounded water that significantly contribute to salt marsh degradation.  Prior to that, coastal farmers created ditches and embankments on salt marshes to encourage the growth of salt hay (Spartina patens), a type of marsh grass, but the vestiges of this agricultural method left on marshes today have yielded large pools of water that undermine salt marsh health. As a result, skeptical regulatory bodies require managers to complete a multi-tiered permitting process that involves review by the Army Corps of Engineers and state departments of environmental protection, a public comment period, response to public comments and other steps. 

“While my office has been granted access to a streamlined permitting process due to our focus on mosquito control, our runneling projects still require six to nine months of review before they are approved,” says Diana Brennan, wetlands coordinator for the Bristol County Mosquito Control Project and one of Besterman’s collaborators. “This means that we can initiate only one runneling project per year at a time when many more are needed due to the increasingly rapid pace at which salt marshes are dying off.”

By providing the data and analysis needed to persuade regulators and the broader scientific community that runneling benefits rather than harm marshes, Deegan and Besternman’s research may provide a rare opportunity to break the current cycle of salt marsh decline in the Northeast. “The permitting process poses an immense roadblock to restoring marsh health,” Brennan says. “But the work Alice is doing should remove that obstacle. By systematically collecting data and subjecting it to peer review, Alice will help make regulators more comfortable with simplifying the permitting process and clearing the way for the initiation of new runneling projects on a much larger scale. Our work already illustrates the positive impact runneling has on salt marshes. But now this point needs to be proven to the relevant regulatory agencies. Our research partners are crucial in making this happen.” 

While Deegan and other team members will continue monitoring their experimental runneling sites throughout the next year and beyond, Besterman’s role in the project has nearly concluded. She recently accepted a faculty position in the Biology Department at Towson University, where she is teaching and continuing her coastal research program. As she prepares for a new stage of her career, she observes that her work on the NE CASC runnels project has played a major role in preparing her for this challenge.  “Universities are increasingly seeking environmental researchers whose work benefits management, or policymakers, or is applied in some way,” she says. “NE CASC fellows like me are in a good position to make the transition from researcher to faculty because we can highlight the positive impact we have had on society while developing skills that allow us to successfully engage with diverse sets of stakeholders. My work with Linda on this project has helped me acquire and refine the skills necessary to make such an impact, and I look forward to expanding my work as an action-oriented scientist in my new position.”