Measuring the Rate of Mangrove Encroachment into Tampa Bay

by Ryan Moyer

The FWRI Coastal Wetlands team is also evaluating the rate of mangrove encroachment into salt marsh habitats in Tampa Bay. As the atmosphere warms and sea level continues to rise, researchers have noticed an expansion of mangrove habitat into wetland areas formerly occupied by marsh habitats.

In Tampa Bay, mangroves have replaced salt marshes as the dominant coastal habitat type along most natural shorelines. However, habitat restoration efforts with the Bay focus on planting salt marsh grasses due to the low cost and high survivability of marsh plants vs. mangrove seedlings. However, many restoration sites that were planted as salt marsh have naturally converted to mangrove systems in the years following restoration. Although coastal resource managers have grown to expect this so-called habitat switching, a major gap in understanding is the rate of change in these ecosystems and how long it will take for a newly restored salt marsh to completely switch to a mangrove-dominated habitat.

To assess this, the Coastal Wetlands group has been measuring mangrove density in restored salt marshes of various ages across Tampa Bay at sites ranging from restored within the past 18 months to sites where restoration was completed over 20 years ago. The information gained from this study will help coastal resource managers better plan for future habitat switching and prioritize conservation in resilient systems vs. those that are expected to experience marsh-to-mangrove habitat switching over fairly short time spans (<5 years). Data from this study will also be used to support FWRI Fish and Wildlife Technician Emma Dontis’ graduate studies, where she is pursuing an M.S. in Environmental Science at the University of South Florida Saint Petersburg. FWRI Associate Research Scientist Ryan Moyer, Ph.D. and Biological Scientist III Kara Radabaugh, Ph.D. are co-managing the research project and co-advising Emma’s graduate research related to the project.