Florida Everglades

James S. Aber
Emporia State University

The Florida Everglades is a vast expanse of wet sawgrass prairie that extends from Lake Okeechobee in south-central Florida to the mangroves along the coast of southern Florida. Lake Okeechobee is the upstream source of surface water, which migrates slowly as shallow sheet flow over a flat limestone plateau that slopes imperceptibly southward to the sea. Everglades National Park, established in 1947, occupies the downstream portion of the water flow system. In between, a series of surface-water storage conservation areas are established along the Shark River Slough to control and distribute water throughout southern Florida.

True-color MODIS image of southern Florida, acquired from the Terra satellite, Feb. 17, 2002. A - Lake Okeechobee, B - Shark River Slough, C - Everglades National Park. Image adapted from MODIS gallery.

Landsat 4 TM false-color image of Pompano Beach vicinity, Florida, showing surface-water conservation areas 1, 2 and 3. Note how vegetation patterns reflect the direction of surface-water flow in the conservation areas. Image date 3/83; compare with MODIS image above. Image acquired from NASA GSFC.
Landsat 4 TM false-color image of Miami vicinity, Florida, showing surface-water conservation areas 2 and 3. Note numerous canals across the Miami region. Image date 3/83; compare with MODIS image above. Image acquired from NASA GSFC.

The climate of the Everglades region is semitropical, as freezing conditions rarely occur--plant hardiness zone 10 (see map). Thus, palms and tropical plants co-exist along side warm-loving temperate vegetation. The region experiences two main seasons--wet (summer) and dry (winter). The hurricane season is mainly in summer and early autumn, and drought conditions may develop some years in spring. Periodic fires, ignited by lightning, help to maintain the grassland habitat by limiting invasion of woody brush and trees.

Views of the wet sawgrass prairie.
Photos courtesy of P. Johnston.

A water turkey (Anhinga anhinga) dries its wings at a residual pool of water during the winter dry season, Taylor Slough, Everglades. Photo date 12/75, © J.S. Aber.

The Everglades comprises several types of wetlands. These are arrranged in a general progression from north to south, including freshwater marsh, deepwater swamp, tidal salt marsh, and coastal mangrove. The freshwater marsh is dominated by sawgrass and underlain by peat up to 1 m thick (see above). Deepwater swamps contain cypress and other woody vegetation (below).

Cypress trees stand in deepwater swamp
and display typical buttress trunks.
Photos courtesy of P. Johnston.

Tidal salt marsh and mangrove occupy the coastal zones, in which water chemistry varies from slightly brackish to fully marine. Mangroves are halophylic, adpated to living in saline water. The Everglades supports one of the largest mangrove swamps in the world.

Black mangrove (Avicennia germinans) growing in wet saline soil on Big Pine Key, Florida Keys. The black mangrove sends up numerous pneumatophores (breather roots) from the ground around the tree. Photo date 12/75, © J.S. Aber.
Red mangrove (Rhizophora mangle) growing in shallow sea water on the fringe of Big Pine Key, Florida Keys. The red mangrove is supported on stilt roots and grows in brackish to marine waters. Photo date 12/75, © J.S. Aber.

Human impact on the Everglades is substantial. Rapid population growth in southern Florida requires massive supplies of fresh water, and agriculture consumes more water. Water for human uses is derived from pumping ground water and diversion of surface water via numerous canals. The net consequence is diminished flow of surface water through the Everglades drainage system. Surface water in the Everglades is naturally nutrient poor. However, upstream agricultural runoff delivers large quantities of fertilizer, namely nitrogen and phosphorus, to the Everglades. Sawgrass prairie has converted to cattail marsh, where this has occurred, with deleterious effects on organisms and water quality.

Cattail marsh in the Florida Everglades.
Photo courtesy of P. Johnston.

A comprehensive review of the Florida Everglades is presented as a case study by Florida International University, which operates a Long Term Ecological Research (LTER) site. For more information, see Guide to wetlands (Dugan 2005, p. 88-91).

Everglades LTER.

Related sites

Wetlands syllabus.

© Notice: Wetland Environments is presented for the use and benefit of students enrolled at Emporia State University. Any other use of text, imagery or curriculum materials is prohibited without permission of the instructor, J.S. Aber (2016).