Time to Invest in Marshes Is Now

Apr 15, 2024

Salt marsh along Great Bay, New Hampshire.

A National Estuarine Research Reserve System (NERRS) led study has found that 22 percent of tidal marshes in the continental United States should be high priorities for conservation, while 17.5 percent are not likely to survive as sea levels rise. Of the 22.5 million acres of marsh in the lower 48 states that are in good condition and able to migrate landward, less than 5 million have been protected.

“This study helps communities prioritize project investments, including those made through the federal Bipartisan Infrastructure Law, to ensure all efforts are strategic and provide the greatest impact,” says Dr. Jeffery Payne, director of NOAA’s Office for Coastal Management. “As a nation, we have a narrowing window of opportunity to protect these areas. The time to invest in marsh resources is now.”

The partnership with NOAA’s Office for Coastal Management ranks marsh resilience—the ability to persist in place or migrate to another location as sea levels rise. Communities can use this information to help them be more strategic in regards to marsh conservation and restoration projects. 

The study rated marsh resilience on a scale of one to ten, using thirteen GIS-based metrics that include current marsh conditions, vulnerability to sea level rise, and adaptive capacity. Southeastern marshlands, and those along the Gulf of Mexico, were found to be the most resilient. Marsh in the Northeast was found to be the least resilient. The study also identified undeveloped land in each region that has the capacity to support healthy tidal marshes as they migrate landward. 

The study also makes recommendations for management options. For example, a marsh area ranked as highly resilient is a strong candidate for protection. Marshes vulnerable to sea level rise but in good condition and with a high adaptation potential are likely candidates for restoration efforts. Those in poor condition with nowhere to migrate as sea levels rise may be too expensive to save. 

“Different factors contribute to the resilience of each region’s marshes,” says Rachel Stevens, lead author of the study and stewardship coordinator at New Hampshire’s Great Bay Reserve. “The presence of large, unfragmented stretches of marsh contributes to their general resilience in the Gulf of Mexico, while in the Southeast, resilience is supported by the connectivity of the region’s large marshes. This, along with the lower development density and flat topography, can facilitate future migration of the marsh landward.”

The study provides a strong foundation for states and coastal communities to access the information needed to meet local priorities. To make this study more actionable for New Hampshire, for example, the local team used NOAA’s high-resolution land cover data and locally relevant metrics, such as the presence of invasive species, to make parcel-level decisions. 

“This information helped us work with communities to compare the feasibility and likely success of different marsh restoration and conservation projects,” says Cory Riley, manager of the Great Bay Reserve. “Now we have a more comprehensive marsh management plan for Great Bay that is guiding plans for specific restoration projects and proposals for land protection grants to help marshes thrive.”

“Because New Hampshire’s coastal zone management program has been an integral part of this work, we have a new reporting process for tidal wetland projects that complements the Bay’s marsh management plan,” says Riley. “We all understand where the opportunities are and what it will take to leverage them.”

Want more Reserve stories delivered to your inbox? Subscribe to our newsletter.

ReservesGreat Bay, New HampshireTime to Invest in Marshes Is Now