"Tropical hammocks are unique areas of hardwood forest that are found only in South Florida and the Keys.  These unusual coastal forests were first exposed about 8,000 years ago as sea levels fell and coral reefs were exposed.  The beds of coral died and left behind shelves of limestone bedrock which eventually fostered vegetation.  Over many thousands of years plants established in these ecosystems as their seeds were carried by winds, tides, and migrating birds.  Characterized by a closed canopy of low-growing hardwoods and palms with a fairly open shrub layer and sparse herb layer, the plants growing in these hammocks are a mix between tropical and temperate species."