The Florida Everglades -- a Wetlands Ecosystem

The Florida Everglades -- A Wetlands Ecosystem

The Everglades, a vast wetlands ecosystem made up of marshes and swamps, begins at Lake Okeechobee, a large lake in the center of Florida, and ends in the Gulf of Mexico and Florida Bay. It is nearly 50 miles across and 110 miles long (Hinrichsen), and when viewed from the air, appears to be miles and miles of shallow water flowing through thick mats of grass. This perception has earned it the name "River of Grass". Although it does flow like a river, the flow is so incredibly slow that, from a distance, it doesn't seem to move at all.

All of the wildlife in the Everglades is totally dependent on the cycling of water. One example of this dependence is the feeding relationship between the snail kite (an endangered bird species), and the apple snail (a freshwater mollusk the size of a golf ball) (Talley). The apple snails reproduce during the rainy season. When water levels are at their highest, they lay thousands of tiny pink eggs on the stalks of marsh grasses. As the water recedes, the snail kites fly all over the Everglades looking for them. Once they find them, they swoop down and use their specialized beaks to pluck the tender 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 is, in turn, affected by the amount of rainfall. Only recently have scientists been able to observe how close this relationship is. When humans drained large areas of the Everglades and converted them to 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 (Smith). The relationship among humans, snail kites, and apple snails illustrates the delicate balance of nature in an ecosystem. When humans alter the water cycle, 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 (Alligator Holes). As winter approaches, water levels begin to drop. Alligators, which need an ample supply of water to survive, sense the changing of the season and begin to prepare for the dry months ahead. Using their powerful snouts, tails, and legs, they make comfortable dens for themselves by slashing small plants, and muck out of the marsh. As it 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 beautiful birds, such as ibises, egrets, and herons, visit these sanctuaries to feed on the small animals that can be found there. Because alligators and the watery hollows they make play such an important role in the Everglades ecosystem, they are considered to be a keystone species since many other species depend upon them for their survival. This has earned them the nickname "keepers of the glades."

Due to constantly changing water levels, ecosystems like the Everglades can be very unpredictable places. Since 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 was drained, most of its water came from Lake Okeechobee, which sometimes overflowed along its southern edge. With an annual rainfall of nearly 60 inches (Everglades) and the overflow from the lake, a large area of the Everglades used to be wet for most of the year.

But the lake was a source of major flooding to towns, especially during the rainy season. In the 1920s, 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. More projects followed in the 1940s and 1950s. Today, about half of the original Everglades has been drained to create dry land for towns and farms and much of the region is crisscrossed by an elaborate system of canals, dikes, and levees. (Blake)

Water control efforts have benefited the residents of south Florida, but now nature no longer controls the flow of water into the Everglades; as a result, the natural balance of the ecosystem has been damaged.

The draining of the Everglades has harmed many animals that depend on water for reproduction, such as snails, fish, and frogs. Because these creatures are at the bottom of many Everglades food chains, their diminishing numbers have had a rippling effect throughout the entire community. Like the snail kite, other bird species -- such as the ibis, heron, and the endangered wood stork -- have suffered. In fact, scientists have estimated that some bird populations have dropped about 90 percent (Birds) over the past fifty years because of the low water levels. Now scientists are encouraging us to realize that a great number of plants and animals must survive to help maintain this delicate environment.

Because the canals and dikes have helped to dry up the land, part of the original Everglades has become a rich agricultural area. Yet, productivity within this marsh has had a negative effect on its wildlife. In the 1950s and 1960s, bald eagles and pelicans in the Everglades were among the many birds threatened with extinction by the chemical DDT. (Scott) Farmers sprayed DDT on their crops to control insects. They didn't realize that from heavy rains was 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 disrupts the Everglades ecosystem in other ways too. Fertilizers, which contain plant nutrients, are washed from the sugarcane plantations a few miles north. These fertilizers cause an excessive growth of algae. The algae can form large

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