Geography and Ecology of The Everglades - Biodiversity

Biodiversity

Ecosystems in the Everglades have been described as both fragile and resilient. 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." 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.

For example, Florida apple snails (Pomacea paludosa) are an amphibious fresh water mollusk. 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 Everglades 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. With regard to the ecology of trophic dynamics, or food chains, the 174 species of invertebrates play a vital role in the Everglades. 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.

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. 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.

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.