The Ecosystem Of The Florida Everglades

The Ecosystem of the Florida Everglades

The Florida Everglades is a vast wetland ecosystem made up of marshes and swamps. This ecosystem begins at Lake Okeechobee, a large lake in central Florida, and ends in the Gulf of Mexico and Florida Bay. It is nearly 50 miles across and 110 miles long and contains mile after mile of shallow water flowing through thick mats of grass (Hinrichsen, 1995). Although it does flow like a river, the flow of water is so slow that from a distance it doesn't seem to move at all.

The wildlife contained within the Everglades is very dependent on the cycling of this slow moving water. One example of this dependence is the feeding relationship between the snail kite and the apple snail. The snail kite is an endangered bird and the apple snail is a freshwater mollusk the size of a golf ball (Talley, 2003). The apple snails reproduce during the rainy season. The snails will lay thousands of tiny eggs on the stalks of marsh grasses when the water levels are at their highest. As the water recedes, the snail kites fly over the Everglades looking for them. Once the snail kite finds them, they swoop down and use their specialized beaks to extract the snails from their shells. The water cycle and the lives of apple snails and snail kites are intertwined. Snail kites depend on the successful reproduction of apple snails, which in turn is affected by the amount of rainfall. Recently scientists have been able to closely observe this relationship. When humans drained large areas of the Everglades and converted them into agricultural lands, the population of apple snails decreased sharply. This had a dramatic effect on the snail kite population. In 2003, only 1600 snail kites remained in Florida, the bird's only U.S. habitat (Talley, 2003). The relationship among humans, snail kites, and apple snails illustrates the delicate balance of nature in an ecosystem. When humans alter the terrain

they directly affect the food chain.

Alligators are animals that often come to mind when people think of the Everglades. The American alligator, once a highly endangered reptile, plays a critical role in the Everglades ecosystem, especially during the dry season. As winter approaches the water level of the Everglades begins to drop. Alligators, which need an ample supply of water to survive, sense the change of seasons and begin to prepare for the dry months ahead. By using their snouts, tails, and legs, they make comfortable dens for themselves by slashing small plants, and muck out of the marsh. As the alligator thrashes its body from side to side, it creates a small hole filled with water. Plant matter and mud piled up around the edges of the hole create dry ground on which other plants eventually grow. After many years, grass, trees, and other plants surround these "gator holes" like fences. Gator holes are important to other species as well, as the water becomes scarce during the dry season many animals search for food and remaining pockets of water. The gator holes attract crayfish, frogs, turtles, fish, and other aquatic species, all seeking refuge in the deeper waters of the gator holes. Muskrats, otters, deer, and raccoons, as well as a wide variety of birds, such as ibises, egrets, and herons, visit these areas to feed on the small animals that can be found there. Alligators are considered a keystone species in the Everglades ecosystem due to the fact that many other species depend upon them for their survival.

Due to constantly changing water levels, ecosystems like the Everglades can be very unpredictable places. As early as the 1800s, people have tried to control the Everglades to prevent flooding (Blake). Large canals were built to send the water into the

ocean and away from the Everglades. The land along the canals dried up and became more useful to people. Before so much of the Everglades were drained, most of its water came from Lake Okeechobee which sometimes overflowed along its southern edge. With an annual rainfall of about 60 inches and the overflow from the lake, a large area of the Everglades used to be wet for most of the year (Scott, 2004). Unfortunately, the lake was a source of major flooding to towns, especially during the rainy season. In the 1920's, other flood control projects were started, including the construction of a dike along Lake Okeechobee's southern rim. Because the water no longer overflowed from the lake, farmers and ranchers now had more dry land on which to live and work. Similar projects followed in the 1940's and 1950's. Currently about half of the original Everglades have been drained to create dry land for towns and farms and much of the region is now an elaborate system of canals, dikes, and levees (Blake,1980). Water control efforts may have benefited the residents of southern Florida, but now nature no longer controls the flow of water into the Everglades, and as a result the natural balance of the ecosystem has been compromised.

The draining of the Everglades has harmed many animals that depend on water for reproduction, such as snails, fish, and frogs. These creatures are at the bottom of many of the Everglades' food chains and their diminishing numbers have had a rippling effect throughout the entire ecosystem. Like the snail kite, other bird species such as the ibis, heron, and the endangered wood stork, have all suffered. In fact, scientists have estimated that some bird populations have dropped about 90 percent over the past fifty years because of the low water levels (Scott, 2004). Now scientists are encouraging the

public to realize that a greater number of plants and animals must survive to help maintain the ecosystem. Because the canals and dikes have helped to dry up the land, part of the original Everglades has become a rich agricultural area. Unfortunately, productivity within this marsh has had a negative effect on the wildlife. In the 1950's and 1960's bald eagles and pelicans in the Everglades were among the many birds threatened with extinction by the chemical DDT (Scott, 2004). Farmers sprayed DDT on their crops to control insects without realizing that heavy rains were washing the poisonous chemical into the Everglades. Scientists discovered that DDT caused the shells of birds' eggs to thin, resulting in the death of many young birds before hatching. The U.S. government finally banned the use of DDT in 1972.

Agricultural runoff affects the Everglades ecosystem in other ways as well. Fertilizers are washed from the sugarcane plantations