A swampy region in southern Florida, the Everglades are described as a vast, shallow sawgrass (Cladium effusum ) marsh with tree islands, wet prairies, and aquatic sloughs, the Everglades historically covered most of southeastern Florida, prior to massive drainage and reclamation projects launched at the turn of the century. The glades constitute the southern end of the Kissimmee Lake Okeechobee Everglades system, which encompasses most of south and central Florida below Orlando. Originally, the Everglades covered an area approximately 40 mi (64 km) wide and 100 mi (161 km) long, or 2.5 million acres, but large segments have been isolated by canals and levees. Today, intensive agriculture in the north and rapid urban development in the east are among the Everglades' various land uses.
Two general habitat regions can be demarcated in the Everglades. The first includes three water conservation areas, basins created to preserve portions of the glades and provide multiple uses, such as water supply. This region is located in the northern Everglades and contains most of the intact natural marsh. The second is the southern habitat, which includes the Everglades National Park and the southern third of the three water conservation areas. The park has been designated a World Heritage Site of international ecological significance, and the Everglades as a whole are one of the outstanding freshwater ecosystems in the United States.
Topographically flat, elevations in the Everglades are generally less than 20 ft (6.1 m). The ground slopes north to south at an average gradient of 0.15 ft per mile, with the highest elevations in the north and the lowest in the south. The climate is generally subtropical, with long, hot, humid, and wet summers from May to October followed by mild, dry winters from November to April. During the wet season severe storms can result in lengthy periods of flooding , while during the dry season cool, sometimes freezing temperatures can be accompanied by thunderstorms, tornadoes, and heavy rainfall.
Before the Everglades were drained, large areas of the system were inundated each year as Lake Okeechobee overflowed its southern rim. The "River of Grass" flowed south and was in constant flux through evapotranspiration , rainfall, and water movement into and out of the Everglades' aquifer . The water discharged into the tidewaters of south Biscayne Bay, Florida Bay, and Ten Thousand Islands.
In the early 1880s, Philadelphia industrialist Hamilton Disston began draining the Everglades under a contract with Florida trustees. Disston, whose work ceased in 1889, built a substantial number of canals, mainly in the upper waters of the Kissimmee River, and constructed a canal between Lake Okeechobee and the Calooshatchee River to provide an outlet to the Gulf of Mexico. The Miami River was channelized beginning in 1903, and other canals—the Snapper Creek Canal, the Cutler Canal, and the Coral Gables Waterway—were opened to help drain the Everglades. Water tabless in south Florida fell 5–6 ft (1.5–1.8 m) below 1900 levels, causing stress to wetlands systems and losses of peat up to 6 ft (1.8 m) in depth.
Full-scale drainage and reclamation occurred under Governor W.S. Jennings (1901–1905) and Governor Napoleon Bonaparte Broward (1905–1909). In 1907, the Everglades Drainage District was created and built six major canals over 400 miles long before it suffered financial collapse in 1928. These canals enabled agriculture to flourish within the region. In the late 1920s, when settlers realized better water control and flood protection were needed, low muck levees were built along Lake Okeechobee's southwest shore, eliminating the lake's overflow south to the Everglades. But hurricanes in 1926 and 1928 breached the levees, destroying property and killing 2,100 people. As a result, the Lake Okeechobee Flood Control District was established in 1929, and over the following fifteen years the United States Army Corps of Engineers constructed and enlarged flood control canals.
It was only in the mid-1950s, with the development and implementation of the Central and Southern Florida Project for Flood Control & Other Purposes (C&SF Project), that water control took priority over uncontrolled drainage of the Everglades. The project, completed by 1962, was to provide flood protection, water supply, and environmental benefits over a 16,000 square-mile (41,440 sq-km) area. It consists of 1,500 miles (2,415 km) of canals and levees, 125 major water control structures, 18 major pumping stations, 13 boat locks, and several hundred smaller structures. Interspersed throughout the Everglades is a series of habitats, each dominated by a few or in some cases a single plant species . Seasonal wetlands and upland pine forests, which once dominated the historic border of the system, have come under the heaviest pressure from urban and agricultural development. In the system's southern part, freshwater wetlands are superseded by muhly grass (Muhlenbergia filipes ), prairies, upland pine and tropical hardwood forests, and mangrove forests that are influenced by the tides.
Attached algae, also known as periphyton, are an important component of the Everglades food web, providing both organic food matter and habitat for various grazing invertebrates and forage fish that are eaten by wading birds, reptiles, and sport fish. These algae include calcareous and filamentous algae (Scytonema hoffmani, Schizothrix calcicola ) and diatoms (Mastogloia smithii v. lacustris ).Sawgrass (Cladium jamaicense ) constitutes one of the main plants occurring throughout the Everglades, being found in 65–70% of the remaining freshwater marsh. In the north, the sawgrass grows in deep peat soils and is both dense and tall, reaching up to 10 ft (3 m) in height. In the south, it grows in low-nutrient marl soils and is less dense and shorter, averaging 2.5–5 ft (0.75–1.5 m). Sawgrass is adapted to survive both flooding and burning. Stands of pure sawgrass as well as mixed communities are found in the Everglades. The mixed communities can include maidencane (Panicum hemitomon ) arrowhead (Sagittaria lancifolia ), water hyssop (Bacopa caroliniana ), and spikerush (Eleocharis cellulosa ).
Wet prairies, which together with aquatic sloughs provide habitat during the rainy season for a wide variety of aquatic invertebrates and forage fish, are another important habitat of the Everglades system. They are seasonally inundated wetland communities that require certain standing water for six to ten months. Once common, today more than 1,500 square miles (3,885 sq km) of these prairies have been drained or destroyed. The lowest elevations of the Everglades are ponds and sloughs, which have deeper water and longer inundation periods. They occur throughout the system, and in some cases can be formed by alligators in peat soils. Among the types of emergent vegetation commonly found in these areas are white water lily (Nymphaea odorata ), floating heart (Nymphoides aquatica ), and spatterdock (Nuphar luteum ). Common submerged species include bladderwort (Utricularia ) and the periphyton mat community. Ponds and sloughs serve as important feeding areas and habitat for Everglades wildlife .
At the highest elevations are found communities of isolated trees surrounded by marsh called tree islands. These provide nesting and roosting sites for colonial birds and habitat for deer and other terrestrial animals during highwater periods. Typical dominant species constituting tree islands are red bay (Persa borbonia ), swamp bay (Magnolia virginiana ), dahoon holly (Ilex cassine ), pond apple (Annona glabra ), and wax myrtle (Myrica cerifera ). Beneath the canopy grows a dense shrub layer of cocoplum (Chrysobalanus icacao ), buttonbush (Cephalanthus accidentalis ), leather leaf fern (Acrostichum danaeifolium ), royal fern (Osmunda regalis ), cinnamon fern (O. cinnamonea ), chain fern (Anchistea virginica ), bracken fern (Pteridium aquilinium ), and lizards tail (Saururus cernuus ).
In addition to the indigenous plants of the Everglades, numerous exotic and nuisance species have been brought into Florida and have now spread in the wild. Some threaten to invade and displace indigenous species. Brazilian pepper (Schinus terebinthifolius ), Australian pine (Casuarina equisetifolia ), and melaleuca (Melaleuca quinquenervia ) are three of the most serious exotic species that have gained a foothold and are displacing native plants.
The Florida Game and Fresh Water Fish Commission has identified 25 threatened or endangered species with the Everglades. Mammals include the Florida panther (Felis concolor coryi ), mangrove fox squirrel (Sciurus niger avicennia ), and black bear (Ursus americanus floridanus ). Birds include the wood stork (Mycteria americana ), snail kite (Rostrhamus sociabilis ), and the red-cockaded (Picoides borealis ). Endangered or threatened reptiles and amphibians include the gopher tortoise (Gopherus polyphemus the eastern indigo snake (Drymarchon corais couperi ), and the loggerhead sea turtle (Caretta caretta ).
The alligator (Alligator mississippiensis ) was once endangered due to excessive alligator hide hunting . In 1972, the state made alligator product sales illegal. Protection allowed the species to recover, and it is now widely distributed in wetlands throughout the state. It is still listed as threatened by the federal government, but in 1988 Florida instituted an annual alligator harvest.
Faced with pressures on Everglades habitats and the species within them, as well as the need for water management within the rapidly developing state, in 1987 the Florida legislature passed the Surface Water Improvement and Management Act (1987). The law requires the state's five water management districts to identify areas needing preservation or restoration. The Everglades Protection Area was identified as a priority for preservation and improvement planning. Within the state's protection plan, excess nutrients, in large part from agriculture, have been targeted as a major problem that causes natural periphyton to be replaced by species more tolerant of pollution . In turn, sawgrass and wet prairie communities are overrun by other species, impairing the Everglades' ability to serve as habitat and forage for higher trophic level species.
A federal lawsuit was filed against the South Florida Management District in 1988 for phosphorus pollution, and in 1989, President George Bush authorized the addition of more than 100,000 acres to the Everglades National Park. The law that authorized this addition was Public Law 101-229 or the Everglades National Park Protection and Expansion Act of 1989. Included in this legislation was the stipulation that the Army Corps of Engineers improve water flow to the Park. In 1994, the Everglades Forever Act was passed by the Florida State Legislature. The Act called for construction of experimental marshes called Stormwater Treatment Areas that were designed to remove phosphorus from water entering the Everglades. In 1997, six more Stormwater Treatment Areas were constructed and phosphorus removal was estimated to be as much as 50%, due in part to better management practices that were mandated by the Everglades Forever Act. In 2000, President Clinton authorized the spending of billions of federal dollars to restore the Everglades, while Florida Governor Jeb Bush agreed to a state commitment of 50% of the cost, in a bill called the Florida Investment Act. In 2001 and 2002, the state of Florida, under Governor Jeb Bush, and the federal government, under President George W. Bush, committed $7.8 billion dollars to implement the Comprehensive Everglades Restoration Plan (CERP).
[David Clarke and Marie H. Bundy ]
Douglas, M. S. The Everglades: River of Grass. New York: H. Wolff, 1947.
Johnson, R. "New Life for the 'River of Grass.'" American Forests 98 (July-August 1992): 38–43.
Stover, D. "Engineering the Everglades." Popular Science 241 (July 1992): 46–51.
Sometimes called the "River of Grass," the Florida Everglades is one of the most extensive, complex, and renowned wetland ecosystems in the world. Located in South Florida, the Everglades is really a long, shallow river nearly 80.5 kilometers (50 miles) wide and more than 161 kilometers (100 miles) long. It is home to a multitude of plants, animals, and birds—both resident and migratory—that live in some habitats not found anywhere else on the North American continent. Plant and animal species from both the West Indies and North America are found in this subtropical region. Tropical plants and animals predominate in southern regions of the Everglades, whereas temperate species are common in the north.
Fresh and Salt Waters
Although the Everglades is primarily a fresh-water ecosystem , it also encompasses nearly 196,280 hectares (485,000 acres) of the salty Florida Bay and Gulf of Mexico. The Florida Bay is a shallow salt-water bay found at the southern tip of Florida's 768 kilometer (477 mile) long peninsula, which is bordered on the east coast by the Atlantic Ocean, and on the west coast by the Gulf of Mexico. Its average depth is only 1.2 to 1.5 meters (4 to 5 feet), and 2.7 meters (9 feet) at its deepest point. The bay is cut off from the ocean by sandbars, dense mangrove islands, and the Florida Keys, and therefore has limited water circulation.
Just north of the Everglades is Lake Okeechobee, the second largest body of fresh water in the United States. Waters from Okeechobee and many other interconnected rivers, lakes, streams, sloughs , wet prairies, and wetlands from Orlando and regions farther north, and extending to the south of Florida Bay, flow into the Everglades. This combination of freshwater and salt-water systems creates the unique environment that formed the Everglades.
The Florida Bay and Gulf of Mexico marine areas and estuarine areas, where salt water and fresh water meet and mix, serve as breeding and spawning grounds for crustaceans, fish, and other species that comprise the Everglades food chain . The fresh-water flow from the Everglades is a vital component to the health of these areas, and also to the islands of the Florida Keys and their world-renowned coral reefs.
Weather and Rainfall
Unlike most areas of the United States, the Everglades experiences only two seasons: dry and wet, corresponding to winter and summer. The Everglades is designed by nature to experience alternating seasons of drought and flood.
The dry winter season, which runs from November through April, brings cooler temperatures and scant rainfall. This dry season is important for many birds' and animals' reproduction.
The wet or summer season accounts for approximately 80 percent of the region's average annual rainfall of 137 centimeters (54 inches). Rainfall within the Everglades system can vary dramatically from year to year. Historically, some wet years peaked at over 254 centimeters (100 inches) of rainfall, whereas some dry years received less than 76 centimeters (30 inches).
The almost daily afternoon thundershowers and occasional hurricanes bring rains that renew the region's fresh-water supply. More hurricanes have ripped through Florida than any other area of the country. At first glance, hurricanes may appear to be catastrophic storms that only destroy ecosystems. In fact, hurricanes open new areas for plant growth, spread seeds, and thoroughly mix and flush the waters of this shallow region, thereby changing nutrient levels and placement. The Everglades has adapted to this harsh regime of droughts, floods, and powerful storms.
Rainfall is the primary method by which water enters the Everglades ecosystem; evapotranspiration is the main mechanism by which water leaves the ecosystem. It is estimated that approximately 70 to 90 percent of the rainfall entering the system is lost due to evapotranspiration. The rates of evapotranspiration vary greatly with the seasons, with higher rates occurring during the hot, sunny summers and fueling the frequent thunderstorms.
In the last few million years, the Everglades was repeatedly inundated or covered by shallow ocean waters. This inundation process was repeated five times during the glaciation periods of the Pleistocene epoch, approximately 1.8 million to 11,000 years ago. During these periods of sea-level rise, deposits of sediments settled onto Florida's bedrock base. When sea levels fell, these deposits experienced erosion. Much of the current geography of Florida and the Everglades resulted from these changes.
Today the Everglades resembles a flat but gently tilted limestone plate covered with peat and marl . It is upturned on the Atlantic coast by the rocky Atlantic Ridge and at its western Gulf coast by a mangrove and marl dam.
Early Florida settlers believed if sufficient breaks could be created in the walls of the natural geologic basin, the center part of Florida would drain and become useful for human enterprises. Originally, the Everglades flowed unobstructed from Lake Okeechobee to the Florida Bay. But during the development of Florida, the Everglades and surrounding areas were ditched and diked , altering the flow of water and its seasonal fluctuations.
Much of Florida's early development was based upon draining and removing excess water from wetlands as quickly as possible. Wetlands, specifically the Everglades, were seen as worthless, and it was thought if drained, the land could be put to better use.
Initially, agriculture was the main human endeavor conducted in what is known as the Everglades Agricultural Area (EAA). The EAA is one of the major producers of vegetables, sugar cane, sod, and rice. It is responsible for contributing over $800 million to the state's economy. Yet it also is blamed for contributing massive amounts of nutrients and other pollutants into the Everglades system. However, the EAA is not entirely to blame for contamination of the Everglades: bordering urban areas also contribute significant amounts of pollution.
As a result of massive drainage projects, mild weather, and beautiful beaches, South Florida is the most densely populated region of the state, surrounding the Everglades with large urban areas. And still, development continues.
Comprehensive Everglades Restoration Plan
Governor Napoleon Bonaparte Broward was elected in 1905 based on a platform to drain the Everglades; subsequently, development of one of the world's most extensive "plumbing" systems began. This system includes more than 2,000 kilometers of levees and canals, 150 gates and other water-control structures, and 16 major pump stations. This engineering success altered the quantity, distribution, and timing of fresh water entering the Everglades.
Beginning in the 1960s and continuing through the 1990s, an increased awareness of the importance of wetlands fostered a movement to protect and preserve this unique ecosystem. In 1994, Florida Governor Layton Chiles signed the Everglades Forever Act, which ended a 6-year lawsuit brought by the federal government against the State of Florida for failing to protect the Everglades. This act addressed the issue of fertilizer runoff from sugar and vegetable farms by creating filter marshes to absorb fertilizers, particularly phosphorous. In July 1999, the U.S. Army Corps of Engineers submitted a Comprehensive Everglades Restoration Plan (CERP) expected to cost at least $8 billion and take 20 to 30 years to complete. If implemented, CERP will rework the massive Everglades drainage system to mimic natural functions of the system.
Only time will tell whether these efforts will be successful in rescuing the Everglades, one of the most threatened ecosystems in the United States.
see also Douglas, Marjory Stoneman; Florida, Water Management in.
and Cindy Johnson
Lodge, Thomas E. The Everglades Handbook, Understanding the Ecosystem. DelrayBeach, FL: St. Lucie Press, 1994.
Davis, Steven M., and John C. Ogden, eds. Everglades: The Ecosystem and Its Restoration. Delray Beach, FL: St. Lucie Press, 1994.
Fernald, Edward A., and Elizabeth Purdum, eds. Water Atlas of Florida. Institute ofScience and Public Affairs, Florida State University. Tallahassee, FL: University Press, 1998.
Milon, J. Walter et al. "Public Preferences and Economic Values for Restoration of the Everglades/South Florida Ecosystem." In Economic Report 99-1. University of Florida, Food and Resources Economics Department.
Caulfield, Patricia. 1997 Everglades Annual Report. South Florida Water ManagementDistrict. <http://www.dep.state.fl.us/water/everglades/docs/97report.pdf>.