Southwest Florida Assesses Salt Marsh Vulnerability to Sea Level Rise

Southwest Florida Assesses Salt Marsh Vulnerability to Sea Level Rise

Project Summary

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Salt marshes are vitally important to Southwest Florida. They serve as storm surge buffers, shoreline stabilizers and breeding grounds for wildlife. The 2014 National Climate Assessment projects that salt marshes are at risk both in Florida and around the country from anticipated climate impacts including relative sea level rise, coastal erosion and more intense storms. The Charlotte Harbor National Estuary Program and Southwest Florida Regional Planning Commission, supported by an assistance grant from the U.S. Environmental Protection Agency, collaborated to assess the historic and current range of salt marshes in this region and identify their vulnerability to changing climate conditions.

The Climate Change Vulnerability Assessment and Adaptation Opportunities for Salt Marsh Types in Southwest Florida study determined that the current pace of sea level rise appears to allow some locations for marsh migration on mainland shores. However, “in other locations salt marshes are drowning where there is no location to move to.” The study further mapped these areas to better determine the barriers to movement and understand where salt marshes are able to, and in the future expected to, move as they adapt to higher sea levels. By providing information on expected migration and isolation areas, the report helps local governments identify priority conservation areas to preserve salt marshes and their associated benefits under current and future conditions. The study included recommendations that governments, stakeholder groups or the public should take as part of their adaptation strategies (e.g., protecting or armoring of shorelines).

Implementation

Southwest Florida identified key climate risks to marshes including sea level rise, more intense hurricane and storm surges, saltwater intrusion and greater levels of sedimentation or erosion. The Charlotte Harbor National Estuary Program and Southwest Florida Regional Planning Commission, supported by the U.S. Environmental Protection Agency, identified the most at-risk marsh land using a sea level response map scenario that considered the likelihood of land use protections (e.g. conservation designation) and residential adaptation responses (e.g., protecting or armoring shorelines).

Next, the three partners developed actionable adaptation recommendations. The specific recommended actions for municipalities were to:

  • Identify existing marsh migration corridors for maintenance and conduct further research to identify the highest priority corridors to protect from future development.
  • Support restoration of existing salt marshes by removal of exotic vegetation, removal of barriers to tidal connection and degradation of exotic dominated adjacent uplands.
  • Discourage or stop shoreline hardening including seawalls, bulkheads, rip-rap and "living shorelines" backed by rip-rap.
  • Restore impaired water flows to enhance sediment supply for marsh deposition.
  • Back-fill mosquito control ditches, borrow pits and agricultural pits to reduce depth and sediment loss and facilitate salt marsh establishment and migration.

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