Climate Matters•June 8, 2022
Coastal Wetlands at Risk
Coastal wetlands provide immense value to humans and nature—from flood protection and erosion control, to critical habitat for wildlife, recreation, and carbon storage.
Sea level rise threatens to destroy coastal wetlands, which can survive either by migrating into undeveloped areas or by growing vertically due to sediment buildup.
A new peer-reviewed Climate Central study explores how the choices we make could define the future of coastal wetlands. If we reduce heat-trapping emissions and conserve land, coastal wetlands could expand by 25% this century. But if we don’t take these steps, coastal wetlands could decline by 97% by 2100.
Humans can help preserve coastal wetlands even in the face of sea level rise, by conserving land for wetlands to migrate into, converting developed areas for reclaimed wetlands, and supporting or enhancing sediment supply to existing wetlands.
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Coastal Wetlands Matter
June 8, World Oceans Day, is a time to celebrate the oceans that cover more than 70% of our blue planet.
Most of us experience the vast global oceans only along the coasts—on beaches or in coastal cities. About 30% of the U.S. population lives in coastal counties. And wetlands are vital to these coastal communities, economies, and ecosystems. Despite occupying a small land area, coastal wetlands provide an estimated $746 billion of ecosystem services in the U.S.
Coastal wetlands provide flood and storm surge protection and erosion control for inland communities, habitat for ecologically and commercially important species, as well as water filtration, and recreation areas. Wetlands also store lots of carbon in their waterlogged soils, keeping it out of the atmosphere and thereby mitigating the effects of climate change.
Coastal Wetlands at Risk
In our warming climate, sea level rise threatens to accelerate the loss of coastal wetlands and their associated benefits. Coastal wetlands have natural defenses against rising waters: they can either migrate inland into undeveloped areas or grow vertically through sediment buildup and organic matter accumulation.
A new peer-reviewed Climate Central study explores an array of possible futures for America’s coastal wetlands. The study demonstrates that the future of America’s coastal wetlands depends on the choices people make—especially regarding future land conservation and emissions of heat-trapping gases.
In the most optimistic scenario, coastal wetlands could increase in area by 25% by 2100 and provide an additional $222 billion in ecosystem services—if we conserve all land available for wetland migration and cut heat-trapping emissions rapidly, and if wetlands grow upwards quickly.
But in a contrasting scenario, 97% of coastal wetlands and $732 billion in ecosystem services could be lost by 2100—if heat-trapping emissions grow unchecked, seas rise faster than expected, wetlands grow at a moderate rate, and no land is conserved for wetlands migration.
Other scenarios chart a course between the best- and worst-case extremes. But even with moderate emissions cuts and moderate wetlands growth, we could still lose 17% to 63% of coastal wetland area by 2100, depending on whether land is either fully developed or fully conserved.
Mapping the Future of Coastal Wetlands
Climate Central has also developed new interactive online mappingtools to help coastal communities understand the factors that impact wetland preservation or loss at the local level.
The tools show where wetlands could survive, expand, or recede each decade—depending on coastal development, pollution/sea level rise scenarios, and wetland growth rate.
These maps reveal the uneven distribution of coastal wetlands and their vulnerability to sea level rise.
The southern Atlantic and Gulf coasts are particularly at risk of wetlands loss.
Louisiana, home to a third of America’s coastal wetlands, is the state most at risk of wetlands loss, followed by North Carolina and Texas.
California and Florida face the added challenge of having little undeveloped dryland to accommodate wetlands migration.
Climate Central’s new study and mappingtools highlight where and how we can ensure the future resilience of our valuable coastal wetlands. As we face a warming future and rising sea levels, the ability of wetlands to store carbon—not only along the coasts but also in freshwater inland wetlands across the country—will be an increasingly valuable function to preserve and expand.
POTENTIAL LOCAL STORY ANGLES
What are the primary coastal resources in your local area, and what future risks do they face?
The NOAA Office for Coastal Management maintains the Digital Coast hub for data and tools relevant to coastal communities. Digital Coast includes coastal flood exposure mapping tools, reports on coastal economies across the U.S., and county-level snapshots of sea level rise impacts and flood resilience. For long-term demographic context, NOAA’s National Coastal Population Report summarizes coastal population trends from 1970 to 2020.
What wetlands conservation measures are (or could be) in place locally?
The EPA’s Wetlands Protection and Restoration website includes helpful resources about wetlands science, conservation, and policy as well as contact information for regional wetlands program managers. The National Association of Wetland Managers monitors state and tribal wetland programs, publishes reports, and may be able to connect you with local wetland management officials. The National Environmental Education Foundation maintains a list of resources to learn more about wetlands in all 50 states.
The SciLine service, 500 Women Scientists or the press offices of local universities may be able to connect you with local scientists who have expertise on wetlands and climate change. The National Association of Wetland Managers may be able to connect you with local wetland managers.
Benjamin Strauss, PhD
CEO and Chief Scientist
Related expertise: sea level rise, coastal flood risk, climate change impacts
Siddharth Narayan, PhD
Assistant Professor, Integrated Coastal Programs
East Carolina University
Related expertise: nature-based coastal adaptation
Coastal Resilience Manager
Restore America’s Estuaries
Related expertise: coastal resilience and resource management
Related expertise: floodplain management, land use policy, land conservation
We define coastal wetlands as undeveloped areas with elevations between the average local sea level (Mean Tide Level) and the mean peak water height during spring tides (Mean High Water Springs; MHWS). Starting in 2000, we model the upper bound of the wetlands elevation band tracking the rate of sea level rise, allowing migration to adjacent undeveloped land that becomes lower than MHWS. We model the movement of the lower bound of the wetlands elevation band as a function of the rate of sea level rise minus the surface elevation change of the wetland, which is bounded by the lesser of the maximum surface elevation change rate and the sea level rise rate. We then calculate the extent of coastal wetlands from 2000 to 2100 under two bounding coastal development scenarios (all refugia are conserved or all are developed), three sea level rise scenarios (low emissions, high emissions, and high emissions with rapid ice sheet collapse), and eight maximum surface elevation change rates (-1, 0, 1, 3, 5, 8, 10, and 15 mm/yr).
Land elevation data comes from NOAA’s coastal topographic lidar and land cover data comes from NOAA's Coastal Change Analysis Program (C-CAP) Land Cover Atlas. The sea level rise models used are described in Kopp et al. 2014 and Kopp et al. 2017.
For more detail, see Climate Central’s peer-reviewed paper.