Project Information

Project Timeline: September 2014. This project has been completed.
Implements Science Theme: 3: Impacts of climate change on water resources, 4: Ecological research and modeling, 5: Impacts of climate change on coastal and nearshore marine environments
Principal Investigator: Michael Osland, USGS Wetland and Aquatic Research Center
Partners: Gulf Coastal Plain & Ozarks, Gulf Coast Prairie, Peninsular Florida, South Atlantic

Key Points

• Studied mangrove forest expansion by understanding the impacts of both increased mangrove habitat and decreased salt marsh habitat
• Identified threshold temperatures for where mangrove expansion could occur
• Highlights how changes in ecosystem services will vary from site to site

Overview

Coastal wetlands provide many benefits. They protect coastal areas from storms, sequester carbon, and provide habitat for fish and wildlife. They are also vulnerable to climate change. Warmer temperatures and fewer freeze events in winter may transform coastal wetlands in the northern Gulf of Mexico. Mangrove forests and salt marshes are two types of coastal wetlands. Both are important, but they provide different benefits. As temperatures rise, we expect mangrove forests to expand their range and replace salt marshes. 

This project studied the ecological impacts of mangrove forest migration. We identified temperature thresholds for ecosystem changes. Using this, we found coastal areas in the Southeastern U.S. (e.g., Texas, Louisiana, and parts of Florida) that mangroves are likely to migrate to. These areas are where small changes in winter conditions could cause big changes in coastal wetlands. 

Results show that mangrove forest expansion will bring several types of ecosystem changes. The clearest changes will happen above-ground as forests develop and replace grasslands. This will increase carbon storage and affect some societal benefits of coastal wetlands. Below-ground changes due to mangrove expansion will be more subtle and will depend upon the marsh that is being replaced. They will be greatest along dry coasts (Texas). This is where mangrove expansion is expected to result in greater peat development and soil carbon storage. But, there is no “one-size-fits-all” model for what will happen. The type and extent of changes will mostly depend on the specific site. The data from this work can help us prepare for future changes to coastal wetlands and the services they provide.