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Subtropical Florida

At the southern tip of the Florida peninsula, through the West Indies, lies a region of subtropical vegetation. This low-elevation land was once beneath the ocean. The soils are sandy and the topography is mostly flat. Many of our winter fruits and vegetables are grown on land drained for agriculture. As a result, the web of subtropical ecosystems is taxed, wildlife is threatened, and water is scarce. Exotic vegetation is overrunning what is left of the native vegetation (see Invasive Plants). The endangered Florida panther and the alligator are the symbols of this small but precious part of the continent. Huge populations of wading birds and shorebirds are present, and migrant birds pass through the region in staggering numbers.

Plant Invaders

Exotic plants are those that were introduced into a certain locality by humans. In other words, they are not native there. A small percentage of exotic species have proven invasive, meaning that they grow out of control in their new environments. Invasive species displace local native species, alter the structure of plant communities, change moisture regimes, and alter nutrient cycles (see Vanishing Plants). Scientists consider them one of the top three threats to the biodiversity of wildlands.

The plight of the Florida Everglades is a prime example. Paperbark tree (Melaleuca quinquenervia) has invaded open marshes, altered the hydrology, and converted them into dense, single-species forests. In forested hammocks it has shaded out and displaced native species. At least 450,000 acres of diverse marshland have been destroyed by this plant. Melaleuca is just one of the detrimental exotics that was brought to Florida at least partly for its ornamental appeal. Earleaf acacia (Acacia auriculiformis), fig trees (Ficus species), Brazilian pepper (Schinus terebinthifolius), Bishopwood (Bischofia javanica), Australian Pine (Casuarina equisetifolia), and water hyacinth (Eichhornia crassipes) are a few of the species that are destroying what is left of Florida's native ecosystems.

Florida, along with California and Hawaii, appears to be the hardest hit by invasive species, but few, if any, regions of the United States and Canada are without non-native pests. As many as half of the 300 recognized invasive exotic plants throughout the U.S. were deliberately introduced as ornamentals. Some of them are still sold in nurseries despite their known invasive tendencies. Before you buy any non-native plant for your garden, check with park and preserve managers or the local chapter of The Nature Conservancy to make sure that the species has not shown any signs of invasiveness in your area. While most exotic plants are innocuous denizens of their adopted shores, invasive species have collided head on with the local flora.

Savannah

In central Florida, the land slopes gradually from Lake Okeechobee down to the sea. The region is covered by a sea of sedge known as sawgrass.

Hardwood Hammock

In the Everglades of southern Florida, islands of hardwoods rise up above lower-lying plant communities dominated by sawgrass. On these lofty perches, only a foot or two above the water table, tree palmettos, gumbo-limbo, paradise tree, pigeon plum, and coontie thrive. The hammocks are often impenetrable, as the sunny edge promotes lush growth. The center of the hammock may be quite open and shaded by the taller canopy trees.

Pinelands

Pine savannahs and sandhills occur over most of Florida. The soil is sandy, and lies on a limestone bedrock formed at the bottom of an ancient ocean. As in areas of the Coastal Plain province, these open-canopied communities consist of scattered clumps of longleaf and slash pines with an understory of grasses or a dense tangle of shrubs and saw palmettos. As in other pine communities, fire is important to the ecology of this association.

Swamp Forests

Cypress swamps are the most common forested wetland in Florida. Most of the old-growth trees have been cut, but a few old stands survive. These trees are often festooned with Spanish moss, a wiry plant that is actually a bromeliad. Tupelo (Nyssa species) is a common companion of both bald cypress and pond cypress in these wetlands. Sweetbay magnolias, titi (Cyrilla racemiflora), fetterbush (Leucothoe species), and sweet pepperbush (Clethra alnifolia) are common shrubs. In areas subject to seasonal inundation, willow and water oaks (Quercus phellos and Quercus nigra) and tupelo form dense stands with shrubs and catbriars (Smilax species).

Mangrove Swamps

Where the land meets the sea, vast mangrove swamps help fend off the force of hurricanes. Three species are found here, depending on the depth of the water. Red mangrove occupies the outermost zone, spreading into the water to claim new ground; as sediment is deposited around its roots, the land slowly impinges on the sea. Behind the red mangrove grows the black mangrove, followed, in turn, by the salt-sensitive white mangrove, which occupies the most sheltered part of the mangrove swamps. As the swamps move out into the sea, the dry land vacated by the mangroves is colonized by hardwood trees.