The Everglades is a subtropical wetland ecosystem, often called a “river of grass,” that once spanned roughly 11,000 square miles across southern Florida. What makes it unlike almost any other wetland on Earth is its hydrology: water flows in a slow, shallow sheet from Lake Okeechobee southward to Florida Bay, driven by an elevation drop of less than 4.5 centimeters per kilometer. That barely perceptible slope creates a marshy river roughly 48 kilometers wide, averaging just 15 centimeters to 1 meter deep and moving about 34 meters per day.
But calling it simply a “wetland” undersells what’s actually there. The Everglades contains nine distinct habitats, from freshwater marshes to mangrove forests to open marine waters. More than a third of the park is saltwater. It functions as a mosaic of interconnected ecosystems rather than a single uniform landscape.
Nine Habitats in One Landscape
The National Park Service identifies nine distinct habitats within the Everglades, each shaped by subtle differences in elevation, water depth, and soil type.
Freshwater sloughs are the deepest channels of the wetland and serve as the primary corridors for water flow. They stay flooded for most or all of the year. Freshwater marl prairies sit slightly higher and drier, with sparser vegetation. Together, these two habitats make up the classic “river of grass” image most people associate with the Everglades.
Hardwood hammocks are dense clusters of broad-leaf trees growing on the highest ground in the park, elevated just enough to stay dry in all but the wettest years. Pinelands, found on rocky limestone outcrops, are one of the most endangered plant communities in the world. They depend on fire to survive and exist in only a small number of places globally. Cypress communities anchor another freshwater habitat, with cypress trees forming the backbone of their own distinct plant communities in wetter soils.
Coastal lowlands mark the transition zone where freshwater meets salt, hosting tough plant species adapted to harsh, shifting conditions. Mangrove forests form the largest continuous mangrove ecosystem in the Western Hemisphere, lining the coast and buffering inland areas from storms. Finally, marine and estuarine environments make up more than one third of the park, encompassing Florida Bay and the shallow coastal waters where freshwater and saltwater mix.
How Water Drives Everything
The Everglades runs on two seasons, not four. The wet season stretches from mid-May through November, delivering roughly 60 inches of rainfall, about three quarters of the annual total. Temperatures climb into the low 90s°F, humidity soars, and the landscape floods. The dry season runs from December to mid-May, bringing cooler temperatures (50s to upper 70s°F), low humidity, and dramatically less water.
This seasonal pulse shapes every living thing in the system. During the wet season, sloughs fill and the food web kicks into high gear. Periphyton, a spongy mat of algae, bacteria, and microbes, rehydrates and begins producing the energy that feeds everything above it. Periphyton is responsible for over half of all primary production in the Everglades, making it the single most important food source for small fish, crayfish, grass shrimp, and other animals at the base of the food chain. During the dry season, the mats dry into a crust on exposed ground, waiting for the next rains.
The Alligator as Ecosystem Engineer
The American alligator is considered a keystone species in the Everglades, meaning the ecosystem would function fundamentally differently without it. Alligators dig and maintain depressions in the limestone bedrock called “gator holes.” These pools retain water year-round except during the most severe droughts, and as surrounding marshes dry out during the dry season, they become critical refuges for fish, turtles, snails, and wading birds. The animals that crowd into gator holes become easy prey, but the tradeoff of surviving the dry season outweighs the risk.
Female alligators also contribute to soil building. Their nesting activity helps create peat, the organic soil that underlies much of the Everglades. Other species depend directly on alligator nests as well: Florida red-bellied turtles incubate their own eggs inside both active and abandoned alligator nests.
Biodiversity and Threatened Species
The mix of tropical and temperate climates, freshwater and saltwater, and dry and flooded ground creates habitat for an unusually wide range of species. Thirty-six native Florida species that may occur in the park are federally listed as threatened or endangered: 10 birds, 8 reptiles, 8 plants, 7 invertebrates, 4 mammals, and 2 fish. Seven of those species are now considered extirpated, meaning they no longer live in the park at all.
Half the Size It Used to Be
The Everglades today is roughly half the size it was in 1900. Decades of drainage, canal building, and agricultural development diverted water away from the natural system. The Tamiami Trail highway, built in the 1920s, effectively acted as a dam blocking the southward flow of water, a consequence that engineers warned about at the time.
The Comprehensive Everglades Restoration Plan, authorized in 2000, is a federal-state partnership working to undo some of that damage. Its goal is restoring the quantity, quality, timing, and distribution of water flowing through the system. Projects span multiple generations of authorization and include building new reservoirs, removing invasive plants like melaleuca, restoring the Picayune Strand, and constructing the Everglades Agricultural Area Reservoir to store and clean water before sending it south. Several major projects remain in the planning phase, including restoration efforts for the western Everglades, Biscayne Bay, and the Lake Okeechobee watershed.
The challenge is enormous. Restoring natural sheet flow to a landscape that has been carved up by hundreds of miles of canals and levees requires rethinking the entire water management system of southern Florida, balancing ecosystem needs against flood control, drinking water supply, and agriculture.