The South Florida Water Management District is the largest single landowner in the region with more than 1 million acres of public land within our boundaries. Our continued ability to successfully restore and manage these important natural resources is hampered by the growing presence of non-native invasive plants and animals. Non-native plants and animals often aggressively invade natural habitats and drastically alter the ecology of natural systems.
The District is responsible for managing nuisance and invasive exotic vegetation throughout the agency's 16-county region. The District manages invasive exotic plants in canals and on levees of the primary water control system (Central and Southern Florida Project). This system includes public lakes and rivers, water conservation areas, stormwater treatment areas (STAs), interim lands (lands slated for either STAs, Everglades restoration projects or water preserve areas) and on public conservation lands.
Control efforts include prescribed burns, mechanical removal, herbicide application and use of biological controls such as insects and herbivorous fish.
In 2009, the South Florida Water Management District spent roughly $25 million on the prevention, control and management of priority invasive plants. Escalating costs are only part of the problem, as South Florida has roughly 200 introduced plant and animal species – more than any other U.S. region – and ranks high in this regard globally. This presents a huge challenge for the District and other governmental agencies tasked with managing and restoring South Florida's ecosystems.
A total of 66 species of non-native plants are District priorities for control. Old World climbing fern (Lygodium), melaleuca and Brazilian pepper are generally a priority in the entire region, while aquatic plants such as hydrilla and water hyacinth are high priorities in the Kissimmee Basin and Lake Okeechobee. Downy rose myrtle, shoebutton ardisia, cogongrass, torpedograss and tropical watergrass are other invasive plants among the high priority plants requiring control.
Widespread efforts to control invasive plants are ongoing. The District has the country's largest aquatic plant management program, managing floating and submerged aquatic vegetation regionwide. In 2009, the District treated nearly 65,000 acres of priority exotic plants across South Florida ecosystems. As part of these efforts, the agency's melaleuca management program has become a national model for successful interagency coordination in dealing with a weed species. Melaleuca has been systematically and successfully cleared from Water Conservation Areas 2 and 3 and Lake Okeechobee, and it is now under maintenance control in these regions.
Biological control of several invasive plants is showing promising results, including two types of melaleuca-feeding insects released in 2009. Such insects have been introduced across Florida to limit seed production and spread, including a Lygodium-feeding moth that has shown the ability to establish itself and significantly damage the invasive fern without harming native plants. More insects are also being studied in the laboratory and field to better understand how their biology and host-specificity may be useful for local applications.
Considerable numbers of non-native animals are known to occur throughout South Florida, ranging from approximately 55 species in the Kissimmee Basin to more than 150 species in the Greater Everglades. Ranking animals for control is a serious challenge, and prioritizing animal-related threats across regulatory agencies is needed.
The Florida Fish and Wildlife Conservation Commission has an emerging exotic animal management program. The Commission coordinates with the South Florida Water Management District and other partners to manage non-native animal species in South Florida, such as the purple swamphen in the Greater Everglades and Lake Okeechobee.
Burmese python populations continue to expand at an alarming rate in South Florida, with estimates ranging from 5,000 to more than 100,000 in the Everglades. As of October 2009, the total number of snakes removed from Everglades National Park and surrounding areas that year was nearly 300, continuing the rising trend seen in recent years. The District continues to cooperate with federal and state agencies to halt the unprecedented spread of this species identified as a "Reptile of Concern," in the Everglades and throughout Florida. The applesnail, green iguana, African Nile monitor lizard and the Mexican bromeliad weevil are other exotic animals of growing concern.