Everglades National Park is the Largest Subtropical Wilderness in the United States

Everglades National Park is a national park in the U.S. state of Florida that protects the southern 25 percent of the original Everglades. It is the largest subtropical wilderness in the United States, and is visited on average by one million people each year. It is the third-largest national park in the lower 48 states after Death Valley and Yellowstone. It has been declared an International Biosphere Reserve, a World Heritage Site, and a Wetland of International Importance, only one of three locations in the world to appear on all three lists.

Unlike most U.S. national parks, Everglades National Park was created to protect a fragile ecosystem instead of safeguarding a unique geographic feature. The Everglades are wetlands created by a slow-moving river originating in Lake Okeechobee, fed by the Kissimmee River, and flowing southwest at about .25 miles (0.40 km) per day into Florida Bay. The park protects an interconnected network of marshland and forest ecosystems that are maintained by natural forces. Thirty-six species designated as threatened or protected live in the park, including the Florida panther, the American crocodile, and the West Indian manatee. The park protects the largest U.S. wilderness area east of the Mississippi River, is the most significant breeding ground for tropical wading birds in North America, and contains the largest mangrove ecosystem in the western hemisphere. More than 350 species of birds, 300 species of fresh and saltwater fish, 40 species of mammals, and 50 species of reptiles live within Everglades National Park. All of South Florida's fresh water, which is stored in the Biscayne Aquifer, is recharged in the park.

Although humans have lived in the Everglades for thousands of years, not until 1882 did the region begin to be drained for agricultural or residential use. In the 20th century the natural water flow from Lake Okeechobee was controlled and diverted to the explosive growth of the South Florida metropolitan area. The park was established in 1934 to protect the quickly vanishing Everglades and dedicated in 1947, the same year massive canal-building projects across South Florida began to divert water away from the park. The ecosystems in Everglades National Park have suffered significantly from human activity, and the repair and restoration of the Everglades is a politically charged issue in South Florida.

Climate

Unlike in the northern portion of Florida, no underground springs feed water into the Everglades system. An underground reservoir called the Floridan Aquifer lies about 1,000 feet (300 m) below the surface of South Florida. However, the Everglades has an immense capacity for water storage, due to the sponge-like permeable limestone underneath the exposed land. Most of the water arrives in the form of rainfall, and a significant amount is stored in the limestone. Water evaporating from the Everglades becomes rain over metropolitan areas, providing the fresh water supply for the region. Water also flows into the park after falling as rain on Lake Okeechobee and the Kissimmee River, to appear in the Everglades days later. Water overflows Lake Okeechobee into a river 40 to 70 miles (110 km) wide, which moves almost imperceptibly.

Most of the Everglades see only two seasons: wet and dry. The park's dry season lasts from December to April, when temperatures vary from 53 °F (12 °C) to 77 °F (25 °C) and humidity is low. Since water levels are low at that time, animals congregate at central water locations, providing popular opportunities for viewing the wildlife. During the wet season, from May to November, temperatures are consistently above 90 °F (33 °C) and humidity over 90 percent. Storms can drop 10 to 12 inches (300 mm) of rain at a time, providing half the year's average of 60 inches (152 cm) of rainfall in just two months.

Ecosystems

At the turn of the 20th century common concepts of what should be protected in national parks invariably included formidable geologic features like mountains, geysers, or canyons. As Florida's population began to grow significantly and urban areas near the Everglades were developed, proponents of the park's establishment faced difficulty in persuading the federal government and the people of Florida that the subtle and constantly shifting ecosystems in the Everglades were just as worthy of protection. When the park was established in 1947, it became the first area within the U.S. to protect flora and fauna native to a region as opposed to geologic scenery. The National Park Service currently recognizes nine distinct interdependent ecosystems within the park that constantly shift in size due to the amount of water present and other environmental factors.

Freshwater sloughs and marl prairies

Freshwater sloughs are perhaps the most common ecosystem associated with Everglades National Park. These drainage channels are characterized by low-lying areas covered in fresh water, flowing at an almost imperceptible 100 feet (30 m) per day.Shark River Slough and Taylor Slough are significant features of the park. Sawgrass growing to a length of 6 feet (1.8 m) or more, and broad-leafed marsh plants, are so prominent in this region that they gave the Everglades its nickname "River of Grass". Excellent feeding locations for birds, sloughs in the Everglades attract a great variety of waders such as herons, egrets, roseate spoonbills (Platalea ajaja), ibises and brown pelicans (Pelecanus occidentalis), as well as limpkins (Aramus guarauna) and snail kites that eat apple snails, which in turn feed on the sawgrass. The sloughs' availability of fish, amphibians, and young birds attract a variety of freshwater turtles, alligators (Alligator mississippiensis), water moccasins (Agkistrodon piscivorus conanti), and eastern diamondback rattlesnakes (Crotalus adamanteus).

Freshwater marl prairies are similar to sloughs, but lack the slow movement of water; instead, water seeps through a calcitic mud called marl. Algae and other microscopic organisms form periphyton, which attaches to limestone. When it dries it turns into a gray mud. Sawgrass and other water plants grow shorter in freshwater marl than they do in peat, the other type of soil in the Everglades which is found where water remains present longer throughout the year. Marl prairies are usually under water from three to seven months of the year, whereas sloughs may remain submerged for longer than nine months and sometimes remain under water from one year to the next. Sawgrass may dominate sloughs, creating a monoculture. Other grasses, such as muhly grass (Muhlenbergia filipes) and broad-leafed water plants can be found in marl prairies. Animals living in the freshwater sloughs also inhabit in marl prairies. Marl prairies may go dry in some parts of the year; alligators play a vital role in maintaining life in remote parts of the Everglades by burrowing in the mud during the dry season, and creating pools of water where fish and amphibians survive from one year to the next. Alligator holes also attract other animals who congregate to feed on smaller prey. When the region floods again during the wet season, the fish and amphibians who were sustained in the alligator holes then repopulate freshwater marl prairies.

Tropical hardwood hammocks

Hammocks are often the only dry land within the park. They rise several inches above the grass-covered river, and are dominated by diverse plant life consisting of subtropical and tropical trees, such as large southern live oaks (Quercus virginiana). Trees often form canopies under which animals thrive amongst scrub bushes of wild coffee (Psychotria), white indigoberry (Randia aculeata), poisonwood (Metopium toxiferum) and saw palmetto (Serenoa repens). The park features thousands of these tree islands amid sloughs—which often form the shape of a teardrop when seen from above (see park map) because of the slowly moving water around them—but they can also be found in pineland and mangroves. Trees in the Everglades, including wild tamarind (Lysiloma latisiliquum) and gumbo-limbo (Bursera simaruba), rarely grow higher than 50 feet (15 m) due to wind, cold weather, and lightning strikes.

The plant growth around the hammock base is nearly impenetrable; however, beneath the canopy hammocks are an ideal habitat for animals. Reptiles (such as various species of snake and anole) and amphibians (such as the American green tree frog, Hyla cinerea), find their homes in the hardwood hammocks. Birds such as barred owls (Strix varia), woodpeckers, northern cardinals (Cardinalis cardinalis), and southern bald eagles (Haliaeetus leucocephalus) nest in hammock trees. Mammal species living in hardwood hammocks include opossums (Didelphis virginiana), raccoons (Procyon lotor), bobcats (Lynx rufus), Everglades mink (Neovison vison), marsh rabbits (Sylvilagus palustris), white-tailed deer (Odocoileus virginianus), and the rare, critically endangered Florida panther (Puma concolor coryi).

Pineland

Dade County was once covered in 186,000 acres (750 km2) of pine rockland forests, but most of it was harvested by the lumber industry. Pineland ecosystems (or pine rocklands) are characterized by shallow, dry sandy loam over a limestone substrate covered almost exclusively by slash pines (Pinus elliottii var. densa). Trees in this ecosystem grow in solution holes, where the soft limestone has worn away and filled with soil, allowing plants to take hold. Pinelands require regular maintenance by fire to ensure their existence. South Florida slash pines are uniquely adapted to promote fire by dropping a large amount of dried pine needles and shedding dry bark. Pine cones require heat from fires to open, allowing seeds to disperse and take hold. The trunks and roots of slash pines, however, are resistant to fire. Prescribed burns in these areas take place every three to seven years; without regular fires, hardwood trees begin to grow in this region and pinelands become recategorized as mixed swamp forests. Most plants in the area bloom about 16 weeks after a fire. Nearly all pinelands have an understory of palm shrubs, and a diverse ground covering of wild herbs.

Pine rocklands are considered one of the most threatened habitats in Florida; less than 4,000 acres (16 km2) of pineland exist outside the park. Within the park, 20,000 acres (81 km2) of pineland are protected. A variety of animal species meet their needs for food, shelter, nesting, and rooking in pine rocklands. Woodpeckers, eastern meadowlarks (Sturnella magna), loggerhead shrikes (Lanius ludovicianus), grackles, and northern mockingbirds (Mimus polyglottos) are commonly found in pinelands. Black bears and Florida panthers also live in this habitat.

Cypress and mangrove

Cypress trees are conifers that are adapted to live in standing fresh water. They grow in compact structures called cypress domes and in long strands over limestone. Water levels may fluctuate dramatically around cypress domes and strands, so cypresses develop "knees" that protrude from the water at high levels to provide oxygen for the root systems. Dwarf cypress trees grow in drier areas with poorer soil. Epiphytes, such as bromeliads, Spanish moss (Tillandsia usneoides), orchids and ferns grow on the branches and trunks of cypress trees. Everglades National Park features twenty-five species of orchids. Tall cypress trees provide excellent nesting areas for birds including wild turkeys (Meleagris gallopavo), ibis, herons, egrets, anhingas (Anhinga anhinga), and belted kingfishers (Megaceryle alcyon). Mammals in cypress regions include white-tailed deer, squirrels, raccoons, opossums, skunks, swamp rabbits, river otters (Lontra canadensis), and bobcats, as well as small rodents.

Mangrove trees cover the coastlines of South Florida, sometimes growing inland depending on the amount of salt water present within the Everglades ecosystems. During dryer years when less fresh water flows to the coast, mangroves will appear among fresh water plants. When rain is abundant, sawgrass and other fresh water plants may be found closer to the coast. Three species of mangrove trees—red (Rhizophora mangle), black (Avicennia germinans), and white (Laguncularia racemosa)—can be found in the Everglades. Due to their high tolerance of salt water, winds, extreme tides, high temperatures, and muddy soils, mangrove trees are uniquely adapted to extreme conditions. They act as nurseries for many marine and bird species. They are also Florida's first defense against the destructive forces of hurricanes, absorbing flood waters and preventing coastal erosion. The mangrove system in Everglades National Park is the largest continuous system of mangroves in the world.

Within the Florida mangrove systems live 220 species of fish, and a variety of crabs, crayfish, shrimp, mollusks, and other invertebrates, which serve as the main source of food for many birds. Dozens of bird species use mangroves as nurseries and food stores, including pelicans, grebes, tricolored herons (Egretta tricolor), gulls, terns, hawks and kites, and arboreal birds like mangrove cuckoos (Coccyzus minor), yellow warblers (Dendroica petechia), and white-crowned pigeons (Patagioenas leucocephala). The mangroves also support 24 species of amphibians and reptiles, and 18 species of mammals, including the endangered green turtle (Chelonia mydas), Hawksbill turtle (Eretmochelys imbricata), and West Indian manatee (Trichechus manatus).

Coastal lowlands

Coastal lowlands, or wet prairies, are salt water marshes that absorb marine water when it gets high or fresh water when rains are heavy. Floods occur during hurricane and tropical storm surges when ocean water can rise several feet over the land. Heavy wet seasons also cause floods when rain from the north flows into the Everglades. Few trees can survive in the conditions of this region, but plants—succulents like saltwort and glasswort—tolerate salt, brackish water, and desert conditions. Animal life in this zone is dependent upon the amount of water present, but commonly found animals include Cape Sable seaside sparrows (Ammodramus maritimus mirabilis), Everglades snail kites (Rostrhamus sociabilis), wood storks (Mycteria americana), eastern indigo snakes (Drymarchon corais couperi), and small mammals such as rats, mice, and rabbits.

Marine and estuarine

The largest body of water within the park is Florida Bay, which extends from the mangrove swamps of the mainland's southern tip to the Florida Keys. Over 800 square miles (2,100 km2) of marine ecosystem lies in this range. Coral, sponges, and seagrasses serve as shelter and food for crustaceans and mollusks, which in turn are the primary food source for larger marine animals. Sharks, stingrays, and barracudas also live in this ecosystem, as do larger species of fish that attract sport fishing. Pelicans, shorebirds, terns, and black skimmers (Rynchops niger) are among the birds frequenting park shorelines.

Activities

The busiest season for visitors is from December to March, when temperatures are lowest and mosquitoes are least active. The park features four visitor centers: on the Tamiami Trail (part of U.S. Route 41) directly west of Miami is the Shark Valley Visitor Center. A fifteen-mile (24 km) round trip path leads from this center to a two-story observation tower. Tram tours are available during the busy season. Closest to Homestead on State Road 9336 is the Ernest F. Coe Visitor Center, where a 38-mile (61 km) road begins, winding through pine rockland, cypress, freshwater marl prairie, coastal prairie, and mangrove ecosystems. Various hiking trails are accessible from the road, which runs to the Flamingo Visitor Center and marina, open and staffed during the busier time of the year. The Gulf Coast Visitor Center is closest to Everglades City on State Road 29 along the west coast. The Gulf Coast Visitor Center gives canoers access to the Wilderness Waterway, a 99-mile (160 km) canoe trail that extends to the Flamingo Visitor Center. The western coast of the park and the Ten Thousand Islands and the various key islands in Florida Bay are accessible only by boat.

Camping and recreation

Camping is available year-round in Everglades National Park. Frontcountry camping, with some services, is available at Long Pine Key, close to the Ernest F. Coe Visitor Center, where 108 sites are accessible by car. Near Flamingo, 234 campsites with some services are also available. Recreational vehicle camping is available at these sites, although not with all necessary services. Backcountry permits are required for campsites along the Wilderness Waterway, Gulf Coast sites, and sites in the various keys. Several backcountry sites are chickees; others are beach and ground sites.

Low-powered motorboats are allowed in the park, although the majority of salt water areas are no-wake zones to protect manatees and other marine animals from harm. Jet skis, airboats, and other motorized personal watercraft are prohibited. However, many trails allow kayaks and canoes. A state license is required for fishing, and although fresh water licenses are not sold in the park, a salt water license may be available. Swimming is not recommended within the park boundaries; water moccasins, snapping turtles (Chelydra serpentina), alligators and crocodiles thrive in fresh water. Sharks, barracuda, and sharp dangerous coral are plentiful in salt water. Visibility is low in both kinds.