Marshes and Mangroves on the Move
A marsh in Florida’s Guana Tolomato Matanzas Reserve. The white cubes are warming chambers, which simulate future conditions where mangrove trees may overtake the marsh. Photos courtesy of the WETFEET Project.
The Guana Tolomato Matanzas (GTM) Reserve protects more than 76,000 acres of vital habitat, 42 miles of Northeast Florida’s coast, and one important border—the line between the mangroves to the south and the salt marshes to the north. As the climate warms and sea levels rise, that line is shifting, and mangroves are expanding northward into regions that had previously been too cold for them to survive.
In response, the Reserve is spanning another important boundary: the one between researchers working to understand how climate change will impact these important habitats and the communities who depend on them for quality of life.
“Our city has extensive square mileage that interfaces with our coastal environment,” says Jessica Beach, Chief Resilience Officer for the City of St. Augustine. “The threat that changes in coastal environmental conditions presents to the longevity and resilience of our community is of concern.”
Both mangroves and marshes provide important benefits to St. Augustine and other local communities. They nurture commercial and recreational fisheries, store carbon, and protect people and infrastructure from waves and storms. Understanding how the transition from one habitat to another affects these benefits is key to making decisions to manage these resources in the future.
Led by scientists from Villanova University and aiming to support local decision makers, the Reserve collaborated to launch the Wetland Ecosystem Temperatures in a Florida Ecotone Experiencing Transition Project (WETFEET) in 2017, with funding from the National Science Foundation. The team has placed “warming chambers” that simulate predicted future temperatures and sea levels in the field to determine how mangrove and marsh habitats will fare in the future.
“Our initial findings suggest that mangroves may keep up with sea level rise more successfully than marshes, while continuing to provide storm surge protection and carbon storage,” observes Lia Sansom, Manager of the GTM Reserve. “The transition to mangroves could prove to be an advantage for Northeast Florida’s communities.”
A mangrove grows inside a warming chamber.
Knowing for sure relies on the kind of long-term collaborative research and monitoring Reserves were designed to provide. WETFEET, along with the Reserve’s marsh elevation monitoring data, has catalyzed two other projects. The first, Experimenting with Elevation, funded by the NERRS Science Collaborative, is helping land managers understand their options for maintaining or increasing wetland surface elevation in the most vulnerable habitats. The second, Preparing for Thin Layer Placement, funded by the US Fish & Wildlife Service, is exploring the viability of different management strategies for vulnerable habitats. The Reserve’s Coastal Training Program works to ensure that local decision makers have ample opportunities to learn about this research and how to apply the results.
“The Thin Layer Placement project and the Reserve’s Coastal Training Program opened up the opportunity for our community to participate in this issue,” says Beach. “At our most recent workshop and site visit, local stakeholders provided input as we explore possible applications for the reuse of dredged sediment strategically placed to combat the changes in our coastal systems that we are already seeing.”
When the study is complete, Beach says, St. Augustine may apply the results to other areas and/or projects.
“The work that our staff does to engage the community brings awareness to the importance of healthy coastal wetlands in mitigating the effects of sea level rise. Together we can protect these habitats by understanding how they adapt to change and supporting their resilience,” says Sansom.