East Aiken continued their hike south from Lake Okeechobee, and arrived near Biscayne Bay on December 6, 1999. The trek from the south shores of Lake Okeechobee afforded glimpses of the Everglades, old and new.
Much of what was once Everglades is now agricultural land. The things that have brought wealth and prosperity to some South Floridians—conversion of land to agriculture, construction of levees and diversion of water, phenomenal population growth—have taken a toll on the ecosystem. A basic principle of ecology is that all organisms require certain resources such as food, water, and habitat in order to survive. In today’s Everglades one resource, unpolluted water, has become a scarcity.
The diagram illustrates the basic water flow (hydrology) patterns that once occurred in South Florida. Today, much of the landscape consists of urban areas and vast agricultural fields. One consequence of this conversion of the land to more "people friendly" habitat is that canals now crisscross the state—these canals are used for flood control and irrigation, and are part of the Central and South Florida Flood Control Project. The project is a complex water management system that covers 16,000 square miles starting just south of Orlando and extending southward through the Kissimmee River Basin to the Everglades National Park and Florida Bay.
The water management program may have achieved its intended purpose of facilitating increased development of South Florida. In the process, however, the Everglades environment has suffered. The quantity, quality, timing, and distribution of water throughout the natural ecosystem have been altered. One suspected consequence of the reduced volume and unnatural timing of the water flow is the severe decline in wading bird numbers in the southern Everglades, down over 90% from the 1930s.
Historically the flow of water southward from Lake Okeechobee created the River of Grass through which water flowed at a rate of about 100 feet (30 meters) per day. As more area was flooded during the wet season, fish and other animals dispersed to newly flooded, nutrient rich parts of the glades. Occasionally lightning would start fires that would burn until stopped by rainfall or a water body. With the onset of the winter dry season, shallow areas dried and only the deeper pools retained water. Plant and animal species were well adapted to these predictable seasonal changes.
Mangroves are a common sight in Biscayne NP
The population growth of South Florida, with its accompanying construction of canals and conversion to agriculture, has profoundly influenced the quantity, quality, and seasonal availability of water in the Everglades. The changes, in human terms, may have been somewhat gradual, but in evolutionary terms the changes are abrupt. Species with reproductive seasons adapted to the ‘old’ seasonal patterns of hydrology have not adjusted to the ‘new,’ which entail lesser amounts of more polluted water at unpredictable times. Most species will not be able to cope with these rapid changes. Unless old flow patterns can be restored (see current issues, Everglades National Park), the Everglades and its vast array of species will be lost.
One of the protected areas in South Florida where wildlife is abundant is Biscayne National Park. Be prepared to swim, since 95% of the Park is underwater!
(Visit the Biscayne National Park website).
The Green Iguana (Iguana iguana) and Invasive Exotic Species
The green iguana is a lizard species native to the tropical forests of parts of Mexico, Central America, and South America. But when the East Aiken kids pay a visit to Crandon Park on the outskirts of Biscayne Bay, iguanas are certain to be seen. Iguanas are but one of many non-native, tropical reptile and amphibian species that have been introduced into South Florida as a result of escaped or released pets, accidents of the commercial pet trade, or some other means of invasion. More non-native herp species (approximately 30) have been introduced into Florida than into any other state. Because the results of such introductions are often harmful to native species, PARC has identified invasive species as one of the six major threats to native herpetofauna. (To find out more about effects of invasive species, see the invasive species fact sheet by the Ecological Society of America; for specifics on reptiles and amphibians, check out the US Geological Survey web site; for info specific to Florida, browse the University of Florida’s web book on invasives).
It isn’t just invasive animal species that cause problems for native organisms and ecosystems. Exotic plants are causing problems just about everywhere, and Florida is certainly no exception. For detailed info on invasive plants in Florida, look at information from the Florida Exotic Pest Plant Council.