Southwest Florida Coastal Dune Grassland

This system occurs along the southwest coast of Florida, one of the four distinctive coastal regions of Florida. It includes herbaceous vegetation on dunes and just inland of the dunes, often on recently deposited sands. These are generally upland plant communities and less commonly non-flooded dune swale wetlands. Although the vegetation is mostly herbaceous, there are typically scattered shrubs of various heights present. The dune vegetation includes Uniola paniculata, Panicum amarum var. amarulum, and Iva imbricata. Scaevola plumieri, Chamaesyce mesembrianthemifolia, and Coccoloba uvifera help distinguish this system from similar dune and coastal grasslands found farther north.

Although the vegetation is mostly herbaceous, there are typically scattered shrubs of various heights present. Although the vegetation may overlap in species composition with other Florida coastal regions, there are important differences based on plant species composition, vegetation structure, and physical site characteristics (Johnson and Muller 1993a). The dune vegetation, like that of other Florida regions, includes Uniola paniculata, Panicum amarum var. amarulum, and Iva imbricata. Scaevola plumieri, Chamaesyce mesembrianthemifolia, and Coccoloba uvifera help distinguish this system from those to the north. However, while all other dune communities in Florida have frequently occurring distinctive species which help distinguish them, such species are lacking in this system. However, more inland coastal grassland components of this system sometimes include Schizachyrium sanguineum (= Schizachyrium semiberbe) and Bouteloua hirsuta, among other species not found in coastal grasslands elsewhere in Florida (Johnson and Muller 1993a).

The vegetation consists largely of herbaceous vegetation and patches of shrublands on barrier islands and other coastal areas where salt spray, saltwater overwash, and sand movement are important ecological forces. Soils are sandy, with little organic matter and little or no horizon development. Soils may be excessively drained on the higher dunes. Soils are low in nutrient-holding capacity, but aerosol input of sea salt provides a continuous source of nutrients. Winter low temperatures are warmer along the southwest coast of Florida, than along the coast further north. Killing frosts are more unusual further south along the coast of the Florida Peninsula.

The natural coastal dynamics include the movement of sand from wind, tides, and storm surge along this low-energy coastline. This includes transport of sand along the coast, and movement of sand by wind or water between the dunes, beach and subtidal areas, and the movement of sand from the foredunes to the interior. If not restricted by infrastructure or engineered hard structures, beaches and dunes can migrate as coastlines change over time in response to the action of wind and water. The Gulf of Mexico coast is affected by one tide per day. Coastal grassland develops as a barrier island builds seaward, developing new dune ridges along the shore which protect the inland ridges from sand burial and salt spray, or as a beach recovers after storm overwash and a new foredune ridge builds up along the shore, protecting the overwashed area behind it from sand burial and salt spray (FNAI 2010a). Wrack and seaweed deposited along the shore is an important source of nutrients for the coastal ecosystem, and helps promote revegetation in newly disturbed areas. Fire is rare and local to small areas.

Threats include recreation, beach cleaning (removal of wrack), beach renourishment (if not planned and carried in a way compatible with the beach ecosystem), sea-level rise, coastal development, and coastal engineering such as beach armoring, seawalls, jetties and other structures which interfere with sand movement and shoreline migration (Defeo et al. 2009). Coastal engineering hard structures reflect wave energy, constrain coastal sand migration and often lead to greater loss of beach and dune sand (Defeo et al. 2009). Structures such as jetties around inlets restrict the natural movement of sand, starving coastal ecosystems of sand. The developed residential and tourism infrastructure of coastal areas has restricted natural dune and beach migration. Increasing sea-level rise associated with global climate change will lead to more loss of beach, especially in developed areas where infrastructure such as seawalls, buildings and coastal roads restrict the potential for inland migration of the beach and dunes. Beach renourishment has been carried out on many beaches along the Florida coast. The use of sand for renourishment which does not match the grain size and composition of the beach to be restored can be a threat, especially where sand is applied deeply. This can be disruptive to the beach and dune ecosystem. Invasive exotic plants which are threats include Casuarina equisetifolia and Scaevola sericea var. taccada (= Scaevola taccada) which can alter beach and dune sand vegetation dynamics (FNAI 2010a). Invasive animals include imported red fire ants (Solenopsis invicta) and feral hogs (Sus scrofa) which prey on the eggs of various animals (Defeo et al. 2009). Feral house cats, dogs, and coyotes are a threat to nesting birds and other small animals which occur in coastal habitats.

Found along the western coast of Florida south of the Big Bend region to the Florida Keys, one of the four distinctive coastal regions of Florida.