Southeast Environmental Research Program, Florida International University
Center for Plant Conservation

An Action Plan to Conserve the Native Plants of Florida


PART II: THE FLORIDA NATIVE PLANT RESOURCE

B. Current condition of Florida ecosystems


The following discussion focuses on the current areal extent of Florida ecosystems in comparison to pre-settlement standards, with most data derived from Kautz et al. (1993). One should recognize that the areal reductions documented below express only one dimension of the problem; in many cases, ecosystem quality has also been reduced by the same factors that have affected the viability of Florida plants of conserva tion concern. These factors are discussed in the next section.

Overall the Florida land mass comprises some 14.1 million ha. Today 4.9 million ha (35%) of Florida are uplands, 3.3 million ha (24%) are wetlands, and 5.9 million ha (42%) represent urban, agricultural or disturbed lands. Thus, 58% of Florida, or 8.2 million ha, is still covered by some form of native vegetation (Kautz et al. 1993). About 30% of this natural area, or 2.5 million ha, is afforded some level of protection by government agencies or private organizations and constitutes Florida's Conservation Areas (CAB; see Cox et al. 1994). Table 1 provides a summary of the pre-settlement and current areal extent of the ecosystems for which information isavailable as well as the extent of existing CAs. Table 2 summarizes the number of imperiled plant taxa by ecosystem type.

Uplands

Prior to European settlement, pine flatwoods constituted the most extensive terrestrial ecosystem in Florida, accounting for over one-third of the land area. Today, about half of Florida's pine flatwoods are gone, and about half of what remains has been converted to commercial pine plantations. Seventeen percent of the original pine flatwoods, or about 463,000 ha, is in CAs. Thirty-one species of plants occurring in pine flatwoods, mostly fortes and graminoids, are considered by the Florida Natural Areas Inventory (FNAI) to be imperiled or critically imperiled globally (G2 and G1, respectively; see Appendix A). Of these 31 species, 17 have the wet prairie subtype as their preferred habitat.

With about 20% of the pre-settlement land cover in the state, sandhills constituted the second most extensive ecosystem. Sandhill pine forests have been reduced in area by 88 %, much more than the flatwoods communities. Thirty-eight percent of remaining sandhills, or about 142,000 ha, is in CAs. FNAI lists 15 imperiled sandhill plants.

Pine rocklands have always constituted one of the least extensive Florida ecosystems, occupying about one percent of the state's land mass. The prototypic and most extensive pre-settlement pine rocklands were found on the Miami Rock Ridge. The Rock Ridge forests, which once covered approximately 70,000 ha, are now reduced by about 90%. Approximately 4,650 ha are currently protected on Long Pine Key within Everglades National Park (ENP) (Snyder 1986). Of the approximately 65,000 ha of pre-settlement pine rocklands on the Rock Ridge outside ENP, small parcels totaling perhaps 1,100 ha remain. These are beset by many problems associated with urbanization. Four hundred hectares of pine rockland are owned and managed by the Metro-Dade Parks Department, and efforts are underway to acquire and/or establish more favorable management on tracts currently in private ownership. The situation is somewhat better in the Florida Keys. Pine rocklands on Big Pine Key and adjacent islands today cover 900 ha, and most of the major tracts are protected within the National Key Deer Refuge. Compared to those on the mainland, Florida Keys pine forests are in reasonably good condition. Nevertheless, they are threatened by exotic plants, fragmentation, and salt water intrusion. The relatively pristine pine forests in the southern half of Big Cypress National Preserve are extensive (about 20,000 ha), but are floristically, hydrologically, and edaphically transitional between pine rocklands and pine flatwoods. With 24 G1 or G2 plants and a greatly diminished areal extent, pine rocklands are among the most critically threatened ecosystems in Florida.

Like pine rocklands, scrub habitats harbor many endemic taxa, including 22plants considered to be imperiled by FNAI. Overall about 60% of Florida's scrub has been destroyed, and much of what remains is in isolated parcels. The largest remaining areas of inland scrub occur within the 84,000 ha habitat mosaic in Ocala National Forest's Big Scrub. Historically, sand pine and xeric oak scrub covered over 30,000 ha of the southernmost third of the Lake Wales Ridge. About 15% (4,500 ha) of these areas remain. With about 180 ha of true scrub (Abrahamson et al. 1984), Archbold Biological Station maintains the most extensive remaining tract of Lake Wales scrub currently under conservation management. The U.S. Fish and Wildlife Service (USFWS), The Nature Conservancy (TNC), and the State of Florida are currently attempting to procure about 8,000 ha -- with a significant proportion in scrub -- to become the Lake Wales Ridge National Wildlife Refuge. If these efforts are successful, additional in situ protection would be afforded to about two dozen federally listed plant species.

Estimates for the historic extent of temperate hardwood or mixed hardwood-pineforests in Florida are not available. Together, a little over 1 million ha remain, with about 190,000 ha in Conservation Areas. FNAI lists 17 species of G1 or G2 plants native to these ecosystems.

While never more than a few thousand ha, tropical hardwood hammocks were the predominant upland plant community in the Keys. They also occurred along the Miami Rock Ridge and on slightly elevated locations in the Everglades, the Ten Thousand Islands, and on Sanibel and Captiva Islands. Today about 6,000 ha of tropical hammock remain, of which 3,500 ha are in CAs. Fourteen imperiled species are listed by FNAI from this vegetation type, including four orchids and four ferns.

In pre-settlement days, more than 80,000 ha of upland habitat (both forested and non-forested) occurred on Florida's barrier islands; today, 36,000 ha remain. Mainland coastal upland habitat has also been reduced, leaving only 5,260 ha (Johnson and Muller 1993). FNAI lists 16 imperiled coastal upland species.

Figures for the pre-settlement extent of dry prairies and scrubby flatwoods are not available. These habitats are relatively extensive today and harbor only one and two imperiled species respectively. Dry prairies are important habitat for several wildlife species, including Crested caracara (Polyborus plancus), Sandhill crane (Grus canadensis), and Burrowing owl (Athene cunicularia).

Freshwater wetlands

Florida's freshwater wetlands are no less reduced in area than the upland ecosystems. Prior to European settlement, most of the southern third of the state -- from Lake Okeechobee to Florida Bay -- was dominated by freshwater forested or herbaceous wetlands. Together, freshwater swamps and marshes are found today on about 20% of Florida's land mass, or 3 million ha. According to Kautz (1993), more marsh has been destroyed since 1936 (1.6 million ha) than remains today (1.1 million ha). Much of this loss has occurred in the Everglades-Kissimmee marsh system, which once formed a wide, continuous flowway down the center of the peninsula. Loss of swamp habitat is more difficult to quantify because of the patchy nature of swamp distribution, but destruction has been substantial.

As a result of widespread concern expressed over the precipitous loss of wetland acreage in the state, more than 1 million ha of Florida wetland receive some level of protection today. However, it has proven to be tremendously difficult to reestablish natural hydrologic regimes on the reduced remains of this formerly continuous wetland system. Florida's freshwater wetlands are not especially species-rich communities, but they do constitute significant habitat for rare plants. FNAI considers five marsh and 20 swamp plants to be at a G2 level of endangerment or higher.

Salt water wetlands

Florida's saltwater wetlands -- tidal marshes and mangrove swamps -- have also declined in area, though not to the degree of freshwater wetlands. Reliable pre-settlement figures for the areal extent of these ecosystems are unavailable. Substantial acreage in both types has been destroyed to accommodate coastal development. Recent estimates of the extent of tidal marsh range from a low of 155,000 ha to a high of 196,500 ha (Kautz et al. 1993; Montague and Wiegert 1990). Estimates for mangrove swamp range from 200,000 to 272,000 ha. A significant part of these remaining wetlands is protected (60% for salt marsh; 81 % for mangrove forest). FNAI lists no imperiled species for either habitat.

Overall, FNAI considers 167 Florida terrestrial vascular plant species to be globally imperiled; these are listed by preferred habitat in Appendix A. Forty-three of these taxa are listed as "Endangered" and 11 as "Threatened" by USFWS. According to Cox et al. (1994), more than 100 of these globally rare taxa are found in fewer than 10 Conservation Areas. Fifty-two -- nearly one-third of the total -- are not known to occur in any Conservation Area; 11 of these are federally listed as "Endangered" or "Threatened. "


[NEXT] [PREVIOUS] ['ACTION PLAN' TOC]


This document is designed and maintained for the >Everglades Digital Library by:
Project Director
Everglades Information Network & Digital Library
Florida International University Libraries
Copyright © 1997. All rights reserved.