Everglades

Everglades National Park safeguards the southernmost fifth of Florida’s original Everglades. It’s the biggest tropical wilderness in the U.S., and the largest wilderness of any type east of the Mississippi River. Around one million people visit annually. Among national parks in the contiguous U.S., only Death Valley and Yellowstone are larger. It became a national park in 1947. UNESCO named the Everglades and Dry Tortugas a Biosphere Reserve in 1976, listed the park as a World Heritage Site in 1979, and the Ramsar Convention added it to its Wetlands of International Importance in 1987. The Everglades is one of just three places worldwide to appear on all three lists.

Most national parks protect distinctive landforms; Everglades was the first created to shield a fragile ecosystem. The Everglades are a web of wetlands and forests fed by a river that creeps about a quarter-mile per day out of Lake Okeechobee, flowing southwest into Florida Bay. The park is the most important breeding ground for tropical wading birds in North America and holds the largest mangrove ecosystem in the Western Hemisphere. Thirty-six threatened or protected species live here, including the Florida panther, American crocodile, and West Indian manatee, plus 350 bird species, 300 fresh and saltwater fish species, 40 mammal species, and 50 reptile species. Most of South Florida’s fresh water, stored in the Biscayne Aquifer, gets recharged within the park.

People have lived in or near the Everglades for thousands of years. Plans to drain the wetlands for farming and development appeared in 1882. As the 20th century went on, water flow from Lake Okeechobee was increasingly controlled and diverted to fuel the rapid growth of the Miami area. The park was authorized in 1934 to protect the fast-disappearing Everglades and dedicated in 1947, just as major canal projects began across South Florida. Human activity has heavily damaged the park’s ecosystems, and restoring the Everglades remains a politically charged issue in South Florida.

**Geography**

Everglades National Park covers 1,508,976 acres (2,357.8 square miles; 6,106.6 square kilometers) across Dade, Monroe, and Collier counties at the southern tip of the Atlantic coastal plain. Elevation usually ranges from 0 to 8 feet (2.4 meters) above sea level, though a Calusa-built shell mound on the Gulf Coast rises 20 feet (6.1 meters).

**Geology**

South Florida’s terrain is consistently flat. The limestone beneath the Everglades is key to its diverse ecosystems. Florida was once part of the African section of the supercontinent Gondwana. After it broke away, shallow marine conditions deposited calcium carbonate from sand, shells, and coral, which turned into limestone. Tiny bits of shell, sand, and bryozoans compressed into structures called ooids, creating permeable rock that holds water. The Florida peninsula emerged above sea level between 100,000 and 150,000 years ago. As sea levels rose at the end of the Wisconsin ice age, the water table came closer to the surface. Lake Okeechobee began to flood, and convection thunderstorms formed. Thick peat deposits south of the lake show that regular flooding started about 5,000 years ago. Plants migrated—subtropical ones from northern Florida, tropical ones carried as seeds by birds from Caribbean islands. The limestone shelf looks flat but has slight rises (pinnacles) and depressions from erosion by acidic water. How long water sits in a spot determines the soil type. There are only two soils in the Everglades: peat, from years of decomposing plant matter, and marl, from dried periphyton (algae and microorganisms that form grayish mud). Areas flooded more than nine months a year are usually covered in peat; areas flooded six months or less have marl. Plant communities depend on soil type and water amount.

**Climate**

Under the Köppen climate system, Royal Palm at Everglades National Park has a tropical monsoon climate (Am). Summers are long, hot, and very wet; winters are warm and dry. Recently, scientists have found that inland freshwater sites in the park are seeing water-level increases that match regional sea-level rise, showing how vulnerable the park’s low-elevation freshwater habitats are to climate change and saltwater intrusion.

**Hydrography**

Unlike northern Florida, no underground springs feed the Everglades system. An underground reservoir called the Floridan aquifer lies about 1,000 feet (300 meters) below South Florida’s surface. The Everglades can store huge amounts of water because of the permeable limestone beneath the land. Most water comes as rainfall, and a lot is stored in the limestone. Water evaporating from the Everglades becomes rain over metropolitan areas, supplying the region’s fresh water. Water also flows into the park after falling as rain to the north on the watersheds of the Kissimmee River and other sources of Lake Okeechobee, appearing in the Everglades days later. Water overflows Lake Okeechobee into a river 40 to 70 miles (64 to 113 kilometers) wide that moves almost imperceptibly.