The South Florida Water Management District is the largest single landowner in the region with nearly 1.5 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.
On average, the District spends around $20 million a year on the prevention, control and management of priority invasive plants. Escalating costs are part of the problem, but South Florida has roughly 200 introduced plant and animal species established in the region. This is more than any other U.S. area and ranks highly 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.
In STAs, primrose willow, water lettuce, water hyacinth and West Indian marsh grass are targeted in areas where they can interfere with water quality improvement.
Efforts to control invasive plants must continue to keep up with the plants' rapid growth rates. The District has the country's largest aquatic plant management program, managing floating and submerged aquatic vegetation regionwide. As recently as 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 successfully dealing with a weed species, particularly with coordinating agencies' funding and authorities. Melaleuca has been systematically and successfully cleared from Water Conservation Areas 2 and 3 and Lake Okeechobee and is now described as under "maintenance control" in these regions.
Biological control of several invasive plants is showing promising results. Two melaleuca-feeding insects have been introduced across Florida to limit seed production and spread of the tree. An Australian Lygodium-feeding moth has also become established within the state, exerting significant damage upon this invasive fern without harming native plants. Under strict quarantine, more insects are being studied in the laboratory for these and other invasive plants. Each insect must be carefully researched to understand how it may affect the targeted problem plant while ensuring that native plants will not suffer.
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 southern Everglades. Interagency research aims to find which animals are most threatening. Ranking animals for control is a serious challenge, and prioritizing animal-related threats is complicated by the overlapping of multiple regulatory agencies' purviews.
The Florida Fish and Wildlife Conservation Commission has an emerging exotic animal management program. The Commission coordinates with the District and other partners to manage non-native animal species in South Florida, such as the Nile monitor, Argentine tegu and purple swamphen, in the Greater Everglades and Lake Okeechobee.
Extensive periods of freezing temperatures in the winters of 2009 and 2010 may have killed some Burmese pythons living in the Everglades. However, large numbers of the snakes remain in the area, with estimates ranging from 5,000 to more than 100,000. Several hundred snakes are being removed from Everglades National Park and surrounding areas each year. In early 2013, the Florida Fish and Wildlife Conservation Commission mounted a "Python Challenge" to engage the public in Burmese python management. Nearly 1,600 people registered for the month-long event, and 68 pythons were captured.
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. In addition, the non-native island applesnail, green iguana, African Nile monitor lizard and the Mexican bromeliad weevil are other exotic animals of growing concern.