As Sea Levels Rise, Wetlands Must Migrate to Survive

High water from a tidal flood event meets a homeowner’s doorstep, with wetland plants surrounding the property.

SNAPSHOT: Virginia’s wetlands will drown in place unless we implement local land use strategies that help shoreline ecosystems adapt to sea level rise. Historically, wetlands have been able to grow vertically, outpacing rising tides, however, updated rates of sea level rise reveal our tidal wetlands can no longer keep pace and risk drowning. Horizontal migration is our wetlands’ only chance of survival, but it will only work with the right shoreline management decisions that prioritize and promote ideal open space areas with needed soil and slope conditions.

BACKGROUND: Virginia is home to roughly 190,000 acres of tidal wetlands known for their ability to provide habitat, erosion control, water filtration, and carbon sequestration that keep both human and natural communities along Virginia’s tidal shoreline safe, healthy, and biodiverse. Sea level rise continues to be an unsettling and urgent threat to coastal Virginia and its buffering shoreline ecosystems, which are experiencing the highest rate of relative sea level rise on the U.S. east coast. Wetlands are now unable to outpace this rate of sea level rise and will drown in place, unless they can migrate horizontally into the landscape. 

Wetlands migration (Delaware Department of Natural Resources and Environmental Control)

THE IMPACTS: The Virginia Coastal Resilience Master Plan projects Virginia will lose 89% state’s tidal wetlands by 2080 without factoring wetlands migration. Other studies from VIMS and Climate Central, that do account for migration, predict a 39-40% loss in the same time frame. But there’s a catch: wetlands can only migrate where there are no barriers and with suitable slopes and soil on adjacent, undeveloped space. 

Over the last century, with lower rates of relative sea level rise, Virginia’s tidal wetlands managed to survive through vertical growth. Now, with dramatic increases in relative sea level rise rates, the wetlands can no longer keep pace and must grow horizontally into the landscape as waters rise. An example of this horizontal migration is pictured below, where tidal wetlands were able to ‘jump’ over a roadway and occupy open upland land, despite disruption from the built environment. 

The images above show evidence of wetlands migration on Llewellyn Avenue in Norfolk, Virginia. The tidal creek to the left inundates the street with saltwater so frequently, wetlands plants have “migrated” across the street. The photo on the left was taken on November 13, 2017 and the photo on the right was taken on May 1, 2023.

When shoreline barriers are too high, such as with a bulkhead, the wetlands cannot move landward and drown in place. The presence of these hardened barriers results in the higher rates of tidal wetlands losses. Nature-based shoreline protection methods, like living shorelines,  offer a better chance of migration, marking one of the reasons Virginia lawmakers made them the preferred method of shoreline erosion control.

To allow tidal wetlands to survive future conditions, we need land-use and regulatory decision tools to allow the survival of our natural infrastructure as it migrates into the built environment. 

POTENTIAL SOLUTIONS: Local policies and decisions will determine the extent of tidal wetlands loss in coastal Virginia due to sea level rise. Localities can restrict or prohibit shoreline development or consider buyouts to remove structures to make space for landward wetlands migration. 

• Using living shorelines for erosion control, now a statewide mandate, will help encourage migration. Alternatively, hardened erosion control strategies, such as bulkheads and rip-rap, can block the migration path of wetlands due to the height and slope of the structure. 

• Identifying where wetlands can and cannot easily migrate landward will reveal how we should prioritize planning and funding resources for restoration and/or buyouts.

  • Knowing where wetlands migration will not happen is as important as where it could happen. Wetlands migration should not be prioritized in areas of significant investment in hard armoring, such as a flood wall built around an urban community or a ship repair or transportation facility dependent upon access to functioning docks.

  • Planning for migration pathways is critical. The Maryland Green Print project is an excellent example that should be replicated elsewhere.

  • Adopting wetlands migration zones through state or local codes, where development is prohibited, can socialize the concept of moving shorelines and migrating buffers over time. 

• Developing financial incentives and programs, such as rolling easements that remove structures from the path of migrating wetlands, can protect natural infrastructure, while promoting public safety in the face of increased flood risk. 

• Adopting zoning practices that encourage development in low flood risk zones can help shift development away from our shoreline ecosystems.

These strategies complement Virginia localities’ enforcement of the Tidal Wetlands Act and the Chesapeake Bay Preservation Act, which prohibits development within a 100-foot vegetated buffer, or “resource protection area (RPA),” of streams, tributaries, tidal wetlands, and some non-tidal wetlands. In theory, the 100 foot buffer will move inland as sea levels rise, and this RPA buffer of today will become the tidal wetlands of the future. Keeping the RPA’s free of development is essential for successful wetlands migration and ultimately, wetlands survival.

WHAT WE’RE DOING: At Wetlands Watch, it is our mission to work where land, communities, and water meet to conserve nature in a changing climate. We are closely monitoring the ability of wetlands to migrate horizontally into the landscape and launched a wetlands migration program to investigate solutions to this multi-sectional issue. We are collaborating with local and national stakeholders in a community of practice to work through challenges and develop strategies to overcome challenges associated with wetlands migration focused retreat. Join our Coastal Retreat Network to learn more!