Pescadero Marsh and Beach, California. Photo source: ©© John Weiss
By NOAA;
A NOAA-sponsored study shows that Pacific coast tidal marshes are more resistant to rising sea levels from climate change than marshes in the Atlantic. Pacific marshes are generally at higher elevations than Atlantic marshes, and Pacific oceanographic circulation tends to push water away from the coast, reducing the effect of sea level rise.
The study, conducted by NOAA’s National Estuarine Research Reserve System (NERRS), established a national baseline for monitoring the effects of climate change on estuaries. NERRS conducted this study at 16 sites in 13 coastal states.
The technical report, Assessing tidal marsh resilience to sea-level rise at broad geographic scales with multi-metric indicesoffsite link, was published in the journal Biological Conservation.
Of the areas evaluated, one marsh in Narragansett Bay, Rhode Islandoffsite link and another in Massachusetts’s Waquoit Bayoffsite link were found to be the most vulnerable.
The assessment was based on an innovative approach that evaluates 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,” said Jeff Payne, Ph.D., director, NOAA’s Office for Coastal Management. “Even more importantly, it gives coastal managers a much needed new tool – the capacity to understand and compare the ability of marshes to persist in the face of rising seas. This will help us make decisions on protecting marshes in the years ahead.”
Tidal marshes protect people and property against storm surge and flooding, improve water quality, and create habitats for commercially important fish and wildlife. In the past, most marshes have adapted to changing sea levels. What is unknown at this time is how marsh lands will react as rates of sea level rise accelerate. Documenting current conditions and providing a baseline for detecting future change is important to future research.
Coastal communities can use this marsh resilience assessment, and future studies based on it, as a guide to help them and their leaders determine the appropriate steps needed to protect their marshes. Examples include:
- Acquire land near highly resilient marshes as buffer zones.
- Reconnect moderately resilient marshes to the rivers that nourish them with sediment.
- Move the least resilient marshes to higher ground.
“Long-term monitoring across a national system allows reserves to act as sentinels for coastal environments,” says Kenny Raposa, Ph.D., research coordinator at Rhode Island’s Narragansett National Estuarine Research Reserve. “By collecting data that shows how estuaries respond to change, we can provide early warning signals that will help communities adapt to the effects of a changing climate.”
From federal agencies managing national refuge networks to managers of individual marsh sites, anyone with the relevant data also can use this new approach to compare marsh resilience at the local, state, regional or national levels. For a marsh assessment calculation tool visit nerra.org/marshoffsite link.
The National Estuarine Research Reserve System is a network of 28 coastal sites designated to protect and study estuarine systems. Established through the Coastal Zone Management Act, the reserves represent a partnership program between NOAA and coastal states. NOAA provides funding and national guidance, and each site is managed on a daily basis by a lead state agency or university with input from local partners.
