Sea-level rise threatens East Coast marshes

Salt marsh on the Connecticut coast.

Via ecoRI News

As the rate of sea-level rise quickens, a study published in Biological Conservation last November examines the ability of tidal marshes to keep pace. Conducted by the National Estuarine Research Reserve System, this nationwide assessment reveals that marshes along the Pacific Coast appear more likely to survive than those along the Atlantic. Two marshes in southern New England, in Massachusetts and Rhode Island, were found to be the most vulnerable of those evaluated.

Waquoit Bay’s Sage Lot Pond and Narragansett Bay's Nag West are more vulnerable than most along the East Coast.

Research Reserves conducted this study at 16 sites in 13 coastal states. It was based on an approach that evaluated the ability of tidal marshes to thrive as sea levels rise according to five categories of resilience: marsh elevation; change in elevation; sediment supply; tidal range; and rate of sea-level rise.

“This study shows that not all tidal marshes are equally vulnerable to sea-level rise,” Rebecca Roth, executive director of the National Estuarine Research Reserve Association (NERRA), said. “It also gives coastal managers the capacity to understand and compare the ability of marshes to persist in the face of rising seas. This will inform decisions focused on protecting marshes for generations to come.”

Tidal marshes provide many benefits. They protect people and property against storm surges and flooding, improve water quality, and create habitat for fish and wildlife. For millennia, most marshes have kept pace with rising seas by increasing in elevation, according to the 2016 NERRA study.

With sea levels projected to increase much faster in the future, the fate of many marshes is now uncertain. The NERRA says the ability to understand and compare the likelihood of marshes to persist in the face of rising seas can inform strategies to protect them. For example:

Marshes found to be highly resilient are likely to thrive and provide value for a long time; ensuring that they are protected is a good investment for the future.

Moderately resilient marshes can survive if actions are taken to help them thrive, such as reconnecting them to the rivers that nourish them with sediment.

The least resilient may not survive in their current locations; they might be saved through intensive management strategies or by finding opportunities for them migrate to higher ground.