Plant Community: Dune

All You Need to Know About the Dune Communities

By Ethan Freid, PhD
Botanist, Leon Levy Native Plant Preserve

Herb/vine dominated

Shrub dominated

Invasive dominated

Dune systems occur along shorelines primarily on Atlantic-facing shores. The system as a limestone sand substrate is produced inorganically (oolites) and organically from coralline algae, broken shells, and corals.  The sand is deposited on the shore and is moved inland from wave action and wind.

The dune consists of a foredune, a top dune, and a back dune.  The foredune is typically steep, with the leading edge having species that can withstand consistent wave action at high tide and often have stolons or rhizomes that spread out across the open sand.  The top and back dune is usually a gradual slope away from the shoreline and dominated by herbs and shrubs, often with Uniola paniculata (Sea Oats) dominating.  In many areas of the central and southern Bahamas, different endemic species of Agave may be common in top and back dunes.

Over time the plants in the fore and top dune will trap sand and build the dune higher and further outward. In many areas of the central Bahamas, as dunes accrete sand, a series of ridges and valleys form depending on the rate of sand production over time.  In other areas of The Bahamas, as the dune builds outward, the back edge of the dune changes to a shrubland.  These areas can be dominated by species such as Chrysobalanus icaco (Cocoplum), Coccoloba uvifera (Sea Grape), Coccothrinax argentata (Silver Top), Genipa clusiifolia (Seven Year Apple), and/or Croton linearis (Granny Bush).  These areas have ceased being dunes and are classified here under DBEF-Shrublands.

Wetlands may form in low-lying areas behind the back dune when the water level is low enough to intersect the lens. These are usually slightly saline to brackish and can change in size and salinity depending on rainfall.

Dune systems in the northern and central Bahamas have been heavily invaded by Casuarina equisetifolia (Australian Pine) and Scaevola taccada (Sea Lettuce).  Both species have devastated dunes, reducing their biodiversity (including birds and insects) and causing erosion. The level of invasion can vary, and dunes may still be partially physically functional, even if not biologically so, even after heavy invasion.  Over a relatively long time, dunes with invasive species, in particular Casuarina (Australian Pine), lose their sand and height and will eventually have little to no sand.

Additionally, in many areas inhabited by humans, the dunes have been razed and built upon, and non-native species have been introduced.

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