Tropical Florida Ecoregion
Description/Physiography
Surrounded by the Gulf of Mexico to its west, the Atlantic Ocean to its east and the Florida Straits to its south, Tropical Florida is a landscape under siege. It is also a landscape of great contrasts between highly fragmented upland terrestrial ecological communities/systems and vast expanses of herbaceous wetlands.
The Everglades basin is partially formed by lands of slightly higher elevation along both coasts. Perhaps the most significant, from an ecological and conservation perspective, is the Atlantic Coastal Ridge, a Pleistocene-aged geologic formation. Consisting of thin, sandy soils overlying a limestone bedrock along the northeastern coast of the ecoregion, the Atlantic Ridge was once vegetated by a Florida Scrub system dominated by sand pine (Pinus clausa) and various species of scrub oaks. Along the southeastern coast of the ecoregion, however, the sandy Scrubs and pinelands give way to the Miami Rock Ridge composed of a soft, mostly exposed, oolitic limestone precipitated from marine systems during Pleistocene interglacial periods when the tip of the Florida peninsula was completely, and very recently, submerged
The Miami Rock Ridge was once vegetated by a unique and endemic ecological system, the Pine Rockland (although similar to some communities in the Bahamas), that covered roughly 100,000 acres in the Miami area. Driven by the appetite of the American public for winter vegetables, much of this area was converted – by rock-plowing – to virtually hydroponic farmland in the 1950’s and early 1960’s. As Miami continued to grow southward, these agricultural areas were converted to housing and commercial developments. It is estimated that greater than 98% of the Pine Rockland community, including (sub)populations of its highly endemic flora, have been destroyed. Today, the Pine Rocklands exist as fragments of 10- to 40-acre parcels, but still support what many think are viable populations of their endemic flora.
Also occurring as small patches on the Miami Rock Ridge, and extending throughout the Everglades and into the Florida Keys, are a series of tropical hardwood-dominated forests referred to locally as “hammocks”. This Tropical Hardwood Hammock system, supporting a mixed canopy of up to 65 Caribbean-derived hardwood trees, once covered thousands of acres along the southeastern coast of the ecoregion in what is now Miami and Ft. Lauderdale. Although no precise estimates are available because so much of the hammocks were converted before anyone took much notice, it is thought that greater than 99% of this community type has been lost on the mainland.
Climate
The Tropical Florida Ecoregion has a mild climate with temperatures typically ranging between 47 degrees Fahrenheit and 90 degrees Fahrenheit during an “average” year. The entire ecoregion is characterized by relatively high rainfall averaging 60 inches per year (although it is somewhat less in the Florida Keys).
Plants/Animals
The species and communities are shaped by several dominant forces: pronounced wet and dry seasons, once frequent fires that swept unimpeded for miles across the landscape, a high water table, mucky or peaty soils that have developed in numerous depressional features in a limestone-based substrate, a relatively flat terrain where even slight changes in topography can dramatically influence the kind of community that develops, the recent geology of the region, the proximity to the tropics and Gulf Stream, and catastrophic large-scale disturbance events in the form of hurricanes.
Humans/History
Unfortunately much of the Everglades system has been ditched, diked, and drained. Its waters now flow mostly through canals, and levels and flows are highly engineered by control structures that artificially regulate the timing and quantity of waters reaching the southern extent of the Everglades – including Everglades National Park and the productive estuary of Florida Bay.
A 600 square-mile area along the southern shore of Lake Okeechobee – the so-called Everglades Agricultural Area (EAA) – has been completely cleared and converted to agricultural land, particularly sugarcane, that grows well in the mucky and peaty soils of this area. As if the highly engineered “plumbing” system controlling flows through the Everglades were not injurious enough to this fragile ecological system, high levels of nutrients, particularly phosphorous, have greatly impacted the quality of the waters that move southward from the EAA through the Everglades. For years the waters have also been diverted from the Everglades through the elaborate canal system and dumped into Biscayne Bay, the Atlantic Ocean, and the southern extent of the Indian River Lagoon estuarine system. A multi-billion dollar federal and state effort to restore the Everglades through a plan devised by the Army Corps of Engineers is now being implemented.
Today
The northwestern portion of the ecoregion includes the Big Cypress swamp ecosystem, much of which is now protected as a National Preserve. The deep, bald cypress (Taxodium distichum)-dominated Tropical Strand Swamp system (a large patch community) also includes scattered pinelands on higher ground and pond apple/pop ash swamps embedded in deeper water depressions within the bald cypress strands. These latter areas within the Tropical Strand Swamp mosaic support particularly diverse assemblages of epiphytes, including numerous species of orchids, bromeliads and ferns. This portion of the ecoregion is the last stronghold for the Florida panther, an endemic subspecies that is listed as federally endangered. It is estimated that only 9 panthers remain in the wild in southern Florida; a population of at least 70 is required to sustain them over the next 200 years.
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