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Flatwoods and the Atlantic Coastal Ridge |
A color image of a pine rockland ecosystem showing mostly short palmettos and the tall thin trunks of South Florida slash pines |
The pine rockland ecosystem is dominated by South Florida slash pines and shrubs like saw palmettos. |
The prairies and sloughs of the Everglades system are bordered by two areas of poorly drained sandy soil on both sides of Lake Okeechobee: the Eastern Flatwoods and the Western Flatwoods just north of Big Cypress Swamp. The predominant ecosystem in the Flatwoods is pine forest, but there are also cypress swamps and sloughs in the Eastern Flatwoods.[48] Along the eastern border of the Everglades is the Atlantic Coastal Ridge, rising 20 feet (6.1 m) in elevation, and curving to the southwest, gradually decreasing in elevation until it meets Taylor Slough. The Coastal Ridge prevents Everglades water from flowing into the Atlantic Ocean to the east, directing it southwesterly into Florida Bay. The South Florida metropolitan area is located on a portion of the Atlantic Coastal Ridge, and much of the landscape has changed drastically within the past 100 years as a result of urban growth. |
Pine rockland |
Pine rocklands (also called pinelands) are found on uneven limestone substrates that contain pinnacles and solution holes. There are three primary locations of pine rocklands: the Miami Ridge, which runs from Miami into Long Pine Key near the main entrance of Everglades National Park; the lower Florida Keys; and the Big Cypress Swamp.[49] The most significant feature of the pine rockland ecosystem is the South Florida slash pine (Pinus elliotti var densa; also called Dade County pine) that reaches a height of 22 feet (6.7 m). Pine rockland communities require fire for maintenance; they have adapted to promote and resist fire at the same time.[50] These communities are located in the highest part of the Everglades with little to no hydroperiod, although some floors may have flooded solution holes or puddles for a few months at a time. The sandy floor of the pine rocklands is covered with dry pine needles that are highly flammable. South Florida slash pines are insulated by their bark to protect them from heat. Fire eliminates competing vegetation on the forest floor, and opens pine cones to germinate seeds.[51] A period without significant fire can turn pineland into hardwood hammock as larger trees overtake the slash pines.[52] The understory shrubs in pine rocklands include fire-resistant species like saw palmetto (Serenoa repens), cabbage palm (Sabal palmetto), and West Indian lilac (Tetrazygia bicolor). The most diverse group of plants in the pine community are herbs, of which two dozen species exist. These plants contain tubers and other mechanisms allowing for quick sprouts after charring.[53] |
Wildlife in pine rockland communities is diverse. In some forests, 15 species of birds can be found. Common among them are the pine warbler (Dendroica pinus), the red-bellied woodpecker (Melanerpes carolinus), and the eastern meadowlark (Sturnella magna). More than 20 species of reptiles and amphibians have been noted, such as the green anole (Anolis carolinensis), southern leopard frog (Rana sphenocephala), and southern black racer (Coluber constrictor priapus). Mammals such as the critically endangered Florida panther (Puma concolor coryi), Florida black bear (Ursus americanus floridanus), and several types of bats also live in the pine rocklands.[50] |
Before urban development of the South Florida region, pine rocklands covered around 161,660 acres (654.2 km2) in Miami-Dade County. Pine forests were extensively cleared by urban developers and the lumber industry in the 1930s and 1940s.[50] Within Everglades National Park, 19,840 acres (80.3 km2) of pine rockland communities are protected, but outside the park, 1,780 acres (7.2 km2) of pine forests remain as of 1990, averaging 12.1 acres (0.049 km2) in size.[50] Dade County pine has a remarkable longevity and has proven to be termite-resistant, though dense enough to make driving nails difficult.[54] In 1984 they were protected by a county ordinance, after many pine areas had been depleted. A misunderstanding of fire's role also played a part in the disappearance of pine forests, as natural fires were put out and pine rocklands transitioned into hardwood hammocks.[50] Today prescribed fires occur in Everglades National Park in pine rocklands every three to seven years. |
The Big Cypress |
West of the sawgrass prairies and sloughs lies the Big Cypress Swamp, commonly called "The Big Cypress", referring to its size rather than the height or diameter of its trees. It takes up the majority of Collier County; at its most limited measurement, the swamp measures 1,200 square miles (3,100 km2), but its hydrological boundary is nearly twice as large.[55][56] The Big Cypress is slightly elevated at 22 feet (6.7 m) at its highest point and slopes gradually to the coastline for approximately 35 miles (56 km). Because the defining feature of The Big Cypress is the abundance of trees it is considered a swamp, rather than a marsh where grass is the main characteristic. |
The basin for The Big Cypress receives on average 55 inches (140 cm) of water in the rainy season.[57] Most of The Big Cypress sits atop a bedrock covered by a thin layer of limestone that contains quartz, creating a sandy soil that hosts a variety of vegetation.[56] The majority of trees are bald cypress (Taxodium distichum) and pond cypresses (Taxodium ascendens). Cypresses are conifers that are uniquely adapted to thrive in flooded conditions, with buttressed trunks and root projections that protrude out of the water, called "knees".[58] |
Cypress trees in the area can live for hundreds of years; some giants grow to 130 feet (40 m) and are 500 years old. Still, they may be only seventh- or eighth-generation cypresses. Few massive trees survived the logging operations that took place in the 1930s and 1940s. As a result, much of The Big Cypress is protected by various federal or state agencies that include Big Cypress National Preserve, Corkscrew Swamp Sanctuary, Fakahatchee Strand State Preserve and two Indian reservations.[59] |
Cypress head |
A color photograph of a pond surrounded by cypress trees in standing water, featuring their flared trunks at the bottom and some water plants bordering the pond in the foreground |
A pond in The Big Cypress |
Although The Big Cypress is the largest growth of cypress swamps in South Florida, such swamps—as well as portions of sawgrass marshes—can be found near the Atlantic Coastal Ridge and between Lake Okeechobee and the Eastern flatwoods. Hardwood hammocks and pineland are often interspersed with the cypress ecosystem. Much like tree islands that are colloquially referred to as "heads", cypress trees grow in formations that resemble domes, with the tallest and thickest trunks in the center, rooted in the deepest peat. As the peat thins out, cypresses continue to grow, but are smaller and thinner, giving the small forest the appearance of a dome.[60] They also grow in strands, slightly elevated on a plateau of limestone and surrounded on two sides by sloughs.[61] Other hardwood trees can be found in cypress domes, such as red maple (Acer rubrum), swamp bay (Persea palustris), and pop ash (Fraxinus caroliniana). If cypresses are removed, hardwoods take over, and the ecosystem is recategorized as a mixed swamp forest. |
Because the cypress domes and strands retain moisture and block out much of the sunlight, plants such as orchids, bromeliads, and ferns thrive in cypress domes and strands. Orchids bloom throughout the year in cypress heads, and bromeliads appear in many varieties; on Fakahatchee Strand alone, thirteen species have been documented.[62] Bromeliads collect moisture from rain and humidity in the bases of their leaves, which also nurture frogs, lizards and various insects. Wood storks (Mycteria americana) nest almost exclusively in cypress forests and in the past 100 years have seen a dramatic decline, probably due to lack of reproduction tied to controlled water. Wood storks' reproductive cycles coincide with the dry season, when small fish and amphibians are trapped in shallow pools and puddles. When water from canals or locks is released too soon or not at all, storks are unable to find enough food for themselves and their offspring. An estimated 20,000 wood storks nested in The Big Cypress in the 1930s, but by the 1990s less than 2,000 were counted.[63] |
Mangroves and coastal prairie |
Red mangrove trees bordering a canal in the Everglades near Flamingo |
Water from Lake Okeechobee and The Big Cypress eventually flows to the ocean. At a transitional zone where fresh water meets salt water, mangrove trees thrive, adapted as they are to both kinds of water. This brackish mixture of water and mangrove systems, crisscrossed by hundreds of tidal creeks, harbors a very productive ecosystem. The depth of these zones is dependent on how much water flows from the Everglades. In the wet season, fresh water pours into Florida Bay and sawgrass appears near the coastline. In dryer years, salt water creeps inland to the coastal prairie, an ecosystem that buffers the freshwater marshes by absorbing sea water. Mangrove trees grow in fresh water ecosystems when the salt water flows far enough inland.[64] The Everglades have the most extensive contiguous system of mangroves in the world.[65] The mangrove forests of the Ten Thousand Islands cover almost 200,000 acres (810 km2).[66] |
Mangroves |
Three species of mangrove trees exist in the region: red (Rhizophora mangle), black (Avicennia germinans), and white (Laguncularia racemosa), although all are from different families.[67] All have the same characteristics: they are tolerant of salt, brackish, and fresh water; they grow in oxygen-poor soil; and they can survive drastic water-level changes.[68] Black and white mangroves excrete salt from under their leaves, and red mangroves filter the salinity of sea water. All species are integral to coastline protection during severe storms. Red mangroves, for example, have far-reaching roots that trap sediments. The trees not only stabilize coastlines, but add land as more sand and decaying vegetation is trapped in the root systems. All three mangroves also absorb the energy of waves and storm surges. |
The estuaries act as fisheries for fry and nurseries for crustaceans. Shrimp, oysters, crabs, whelks, cockles, and snails thrive in these waters, as do primordial horseshoe crabs (Limulus polyphemus). The region supports a $59 million-a-year Tortugas pink shrimp (Farfantepenaeus duorarum) industry, and a $22 million-a-year stone crab (Menippe mercenaria) industry.[69] Between 80 and 90 percent of species that are harvested commercially in Florida are born or spend time in the shallow waters near the Everglades.[66][70] Oysters and mangroves work in tandem to build up the coastline. The sand around the coastline has minute white particles of quartz and fine shells. When currents are right, oysters grow in colonies or beds, and deposit their shells, reinforcing the bed. Mangrove seeds, called propagules, are full embryos and float in water until they reach a favorable location and take root, often on oyster beds. They shed skin and litter, ensuring other trees will not compete for space and nutrients.[71] |
Mangroves also serve as excellent rookeries for birds. Wading birds, such as roseate spoonbills (Platalea ajaja), egrets, and tricolored herons (Egretta tricolor) use the mangroves as a nursery, due to the proximity of food sources and the protection offered from most prey. Thousands of birds can nest in the mangroves at once, making a noisy and messy colony, but their droppings fertilize the mangrove trees.[72] Shorebirds like rails, terns and gulls; diving birds such as pelicans and grebes; and birds of prey such as ospreys, hawks and vultures are among the more than 100 species of birds that use Everglades mangrove trees to raise their young. |
Florida Bay |
A color photograph of the greenish blue water of Florida Bay, featuring a large Sabal palm to the left and a mangrove island in the distance |
A clump of mangroves in the distance, Florida Bay at Flamingo |
Because much of the coast and inner estuaries are built by mangroves—and there is no border between the coastal marshes and the bay—the ecosystems in Florida Bay are considered part of the Everglades. More than 800 square miles (2,100 km2) of Florida Bay is protected by Everglades National Park, representing the largest body of water in the park boundaries.[73] There are approximately one hundred keys in Florida Bay, many of which are mangrove forests.[74] Larger islands may be taken over by hardwood hammocks. The outer rims of the Ten Thousand Islands and Cape Sable share characteristics of the intertwining saltwater bays and fresh water marshes. |
The fresh water entering Florida Bay from the Everglades creates ideal conditions for vast beds of turtle grass and algae formations that foster animal life in the bay. Sea turtles and manatees (Trichechus manatus latirostris) eat the grass, while invertebrates such as worms, clams, and other mollusks consume algae formations and microscopic plankton.[75] Female sea turtles return annually to nest on the shore, and manatees spend the winter months in the warmer water of the bay. The Calusa Indians had various uses for shells of marine invertebrates, due to the lack of dense rock with which to make tools. They used the horse conch (Triplofusus papillosus), left-handed whelk (Sinistrofulgur), and the Florida crown conch (Melongena corona) as drinking vessels, picks, hammers, knives and awls.[76] |
Sea grasses stabilize sea beds and protect shorelines from erosion by absorbing energy from waves. Shrimp, spiny lobsters, and sea urchins live in and among the grasses and feed on phytoplankton; they in turn feed larger predators such as sharks, rays, barracuda, and king mackerel (Scomberomorus cavalla).[77] Due to shallow water and abundant sunlight, Florida Bay hosts communities of coral reefs and sponges, although the majority of the state's reefs are closer to the Florida Keys.[78] Everglades keys that foster mangroves also support nurseries for wading birds such as the Great blue heron (Ardea herodias), which was almost wiped out in the Labor Day Hurricane of 1935 (only 146 were counted afterward).[79] After recovering to number more than 2,000, they were further endangered by Hurricane Donna in 1960, which decreased their numbers by 35 to 40 percent.[80] |
Sea floor patterns of Florida Bay are formed by currents and winds. However, since 1932, sea levels have been rising at a rate of 1 foot (0.30 m) per 100 years.[81] Though mangroves serve to build and stabilize the coastline, seas may be rising more rapidly than the trees are able to build.[82] |
Biodiversity |
Ecosystems in the Everglades have been described as both fragile and resilient.[83] Author Michael Grunwald wrote about the observations of the Everglades' first American visitors: "If the Grand Canyon was a breathtaking painting, the Everglades was a complex drama, and everything in it had a role."[84] An estimated 11,000 species of seed-bearing plants and 400 species of land or water vertebrates live in the Everglades, but slight variations in water levels affect many organisms and reshape land formations. The health and productivity of any ecosystem relies on the number of species present: the loss of one species weakens the entire ecosystem.[85] |
For example, Florida apple snails (Pomacea paludosa) are an amphibious fresh water mollusk.[86] They have a single gill and lung, and live on stalks of sawgrass in water depths no more than 20 inches (51 cm). They are the primary food of the endangered snail kite (Rostrhamus sociabilis) and limpkin (Aramus guarauna) as well as the raccoon, otter, and young alligator. Apple snails lay their eggs on sawgrass stalks about 6 inches (15 cm) above the water line, and they are intolerant of being submerged for long periods of time. When the eggs hatch, young snails must enter the water quickly or face death. When water levels are too low or rise too quickly while snail eggs are developing, apple snails do not flourish, affecting the many reptiles, mammals, and birds that feed on them.[87] With regard to the ecology of trophic dynamics, or food chains, the 174 species of invertebrates play a vital role in the Everglades.[88] Crayfish, insects, scorpions, and other invertebrates also support a web of animals. |
The group of animals most integral to the overall success of Everglades wildlife is freshwater fish. Few places in the Everglades stay submerged from one year to the next, so alligator holes and deep clefts in the limestone are vital to the survival of fish, and the animal community as a whole. Freshwater fish are the main diet of most wading birds, alligators, and otters, and require large areas of open water in order to repopulate. Young amphibians also play an important role in the food chain. Tadpoles spread quickly in isolated areas where fish do not have the time or access to reproduce in numbers necessary to support larger animals. Hundreds of species of amphibians are found in the Everglades, and their availability helps support wildlife during short hydroperiods or in remote locations.[89] |
These smaller animals support communities of larger animals, including 70 species of land birds that breed within the Everglades, and 120 water birds, of which 43 breed in the area. Many of these birds go on to migrate through the West Indies and North America.[90] Several dozen species of mammals also thrive in the region, from tiny bats and shrews to midsize raccoons (Procyon lotor), otters (Lontra canadensis), opossums (Didelphis virginiana), and foxes. The largest include white tailed deer (Odocoileus virginianus), the Florida black bear, and the Florida panther.[91] |
Although slight changes in water level affect many species, the system as a whole also cycles and pulses with each change. Some transformations to the diversity of plant and animal life are natural, caused by fire or storms, and some are induced by humans, such as urban encroachment, the introduction of exotic species, and rapid global warming. Environmental conditions in the Everglades favor no particular species. Some species, such as snail kites and apple snails, do well in wet conditions, but wood storks and Cape Sable seaside sparrows (Ammodramus maritimus mirabilis) do well in dryer circumstances.[83] |
Human impact |
Development |
Main articles: Draining and development of the Everglades and Restoration of the Everglades |
People have lived in the Everglades region for thousands of years. Within the past 100 years however, they have changed the natural landscape dramatically. Settlement of urban areas in South Florida was facilitated by large drainage projects intended to create more land. The drainage was often implemented without a full understanding of the intricacies of ecosystems and shaping processes of the Everglades.[92] The South Florida metropolitan area grew exponentially, causing problems in ecosystems throughout the Everglades. By the 1990s, the diminishing quality of life in many of these urban areas was linked to the degraded local environment.[93] The State of Florida and the U.S. government devised and passed a plan in 2000 to restore as much of the Everglades to pre-drainage conditions as possible. It is the costliest and most comprehensive environmental restoration project in history.[94] |
Invasive species |
Main articles: List of invasive species in the Everglades and Burmese pythons in Florida |
Humans have also adversely impacted the ecology of the Everglades by introducing numerous invasive species, which may prey on or compete with native species. A spectacular and particularly damaging example of this phenomenon is the recent proliferation of the Burmese python in the Everglades, as well as elsewhere in Florida. First observed in the wild in 1979 and not again until 1995,[95] they have increased alarmingly since 2000.[96] By 2011, decreases of 87.5%, 94.1%, 98.9% and 99.3% in sightings of bobcats, white-tailed deer, opossums and raccoons, respectively, were reported in park road surveys, while rabbits were no longer being seen at all.[96] |
Climate change and sea level rise |
Main article: Climate change in Florida |
Mangroves are threatened in the Everglades, due to climate change resulting in sea level rise.[97] |
The Comprehensive Everglades Restoration Plan (CERP) is the plan enacted by the U.S. Congress for the restoration of the Everglades ecosystem in southern Florida. |
When originally authorized by the U.S. Congress in 2000, it was estimated that CERP would cost a total of $8.2 billion and take approximately 30 years to complete. More recent estimates (2014) indicate that the plan would take approximately 50 years to implement, and would cost approximately $1.63 billion more than originally thought, plus additional adjustments for inflation.[1] |
Overview |
The Comprehensive Everglades Restoration Plan (CERP)[2] provides a framework and guide to restore, protect and preserve the water resources of central and southern Florida, including the Everglades. It covers 16 counties over an 18,000-square-mile (47,000 km2) area and centers on an update of the Central & Southern Florida (C&SF) Project also known as the Restudy. The State of Florida (via the South Florida Water Management District) and the U.S. Army Corps of Engineers are undertaking various projects under CERP to help ensure the proper quantity, quality, timing, and distribution of waters to the Everglades and all of South Florida. |
The goal of CERP is to recapture the fresh water that is currently pumped out to the Atlantic Ocean and the Gulf of Mexico in order to reduce water levels in Lake Okeechobee and redirect it south to the Everglades National Park that has been receiving greatly reduced inflows since the 20th century drainage of the landscape. |
The majority of the water will be devoted to environmental restoration, reviving the degrading Everglades terrestrial, wetland and marine ecosystems[citation needed]. The remaining water will benefit cities and farmers by enhancing water supplies for the South Florida economy[citation needed]. |
Historical |
The Central and Southern Florida (C&SF) Project,[3] which was first authorized by the U.S. Congress in 1948, is a multi-purpose project that provides flood control, water supply for municipal, industrial, and agricultural uses, prevention of saltwater intrusion, water supply for Everglades National Park, and protection of fish and wildlife resources. The primary system includes about 1,000 miles (1,600 km) of levees, 720 miles (1,160 km) of canals, and almost 200 water control structures. The C&SF Project has performed its authorized functions well, however, the project has had unintended adverse effects on the unique and diverse environment that constitutes south Florida ecosystems, including the Everglades and Florida Bay. |
Legal |
The Plan was enacted into law by the U.S. Congress in the Water Resources Development Act (WRDA) of 2000. It includes more than 60 elements, will take more than 30 years to construct, and was originally estimated to cost $7.8 billion. |
Numerous lawsuits affecting Everglades restoration are pending before the courts.[citation needed] |
Water Storage |
CERP called for eighteen above ground reservoirs for water storage, totaling 180,000 acres. Of these, 60,000 acres of water storage was called for in the Everglades Agricultural Area.[4] |
U.S. National Research Council reviews |
A series of biennial reports from the U.S. National Research Council have reviewed the progress of CERP. The fourth report in the series, released in 2012, found that little progress has been made in restoring the core of the remaining Everglades ecosystem; instead, most project construction so far has occurred along its periphery.[5] The report noted that to reverse ongoing ecosystem declines, it will be necessary to expedite restoration projects that target the central Everglades and to improve both the quality and quantity of the water in the ecosystem.[6] |
To better understand the potential implications of the current slow pace of progress, the report assessed the current status of ten Everglades ecosystem attributes, including phosphorus loads, peat depth, and populations of snail kites, birds of prey that are endangered in South Florida. Most attributes received grades ranging from C (degraded) to D (significantly degraded), but the snail kite received a grade of F (near irreversible damage). The report also assessed the future trajectory of each ecosystem attribute under three restoration scenarios: improved water quality, improved hydrology, and improvements to both water quality and hydrology, which helped highlight the urgency of restoration actions to benefit a wide range of ecosystem attributes and demonstrate the cost of inaction.[7] |
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