Invasive species in the Everglades are exotic plants and animals that are not native to the area and have aggressively adapted to conditions in wilderness areas in southern Florida. The Everglades are a massive watershed in the southern portion of the U.S. state of Florida that drains overflow from the vast shallow Lake Okeechobee that is in turn fed by the Kissimmee River. The overflow forms a very shallow river about 60 miles (100 km) wide and 100 miles (160 km) long that travels about half a mile per day. The network of ecosystems created by the Everglades are surrounded by urban areas to the east in the South Florida metropolitan area, to the west by Naples and Fort Myers, and to the south by Florida Bay, a marine environment that receives fresh water from and is maintained by the Everglades. As it is surrounded on three sides and close to a major transportation and shipping center, it is particularly vulnerable to the importation of exotic species. In the 20th century, Florida experienced a population surge unparalleled in the U.S., accompanied by rapid urban expansion made possible by draining portions of the Everglades. Flood control became a priority and the Central & South Florida Flood Control Project, from 1947 to 1971, constructed over 1,400 miles (2,300 km) of canals and flood control structures in South Florida. The widespread building created new habitats and disturbed established plant and animal communities. Many of the new residents or tourists in Florida were responsible for introducing plant species to the area by accident, or deliberately to improve landscaping. Many animals have been introduced similarly, and have either escaped or been released to proliferate on their own. Several terms are used to identify non-native species: exotic, invader, immigrant, colonist, introduced, nonindigenous, and naturalized. "Naturalized" usually refers to species that have adapted to a region over a long period of time, while "invasive" refers to particularly destructive or aggressive species. Approximately 26 percent of all fish, reptiles, birds, and mammals in South Florida are exotic—more than in any other part of the United States—and the region hosts one of the highest numbers of exotic plant species in the world. Many of the biological controls like weather, disease, and consumers that naturally limit plants in their native environments do not exist in the Everglades, causing many to grow larger and multiply far beyond their average numbers in their native habitats. Similarly, animals often do not find the predators or natural barriers to reproduction in the Everglades as they do where they originated, thus they often reproduce more quickly and efficiently. Concerns over the quality of the Everglades were raised in the beginning of the 20th century, and by 2000 a federally funded initiative was enacted that gave Everglades restoration the distinction of being the largest planned environmental rehabilitation in history. Exotic species control falls under the management of the U.S. Fish and Wildlife Service, which has been compiling and disseminating information about invasive species since 1994. Control of invasive species costs $500 million a year, but 1,700,000 acres (6,900 km2) of land in South Florida remains infested.
Plant species As the fields of ecology and environmental studies develop, exotic species attract more attention and their effects become more apparent. Mid-20th century biology texts about invading species reflected more complacency than alarm, as contemporary wisdom about them assumed the host environment would be largely immune. Everglades biologist Thomas Lodge writes that in the 1960s, evidence of non-native plant and animal life in South Florida was present but not particularly "worthy of notice." Over the past decades, however, the number of exotic species and their spread has increased dramatically. The Everglades hosts 1,301 species of native flora that are tropical or subtropical in nature, which arrived on the Florida peninsula about 5,000 years ago. Winds, water, and birds carried most of the tropical flora. The subtropical species spread from more northern locations. As of 2010 1,392 additional non-native plant species have been identified and established themselves in South Florida. A variety of avenues are available for species to be brought by humans deliberately or by accident: agricultural experiments, in shipping containers, or attached to vehicles. South Florida is a transportation hub for shipping and traffic between the U.S. and the Caribbean and Central and South America. In 1990, 333 million plants were brought into Miami International Airport. Both the United States Department of Agriculture (USDA) and the University of Florida Institute of Food and Agriculture Sciences (IFAS) experiment with plants in laboratories throughout Florida. State, local, and federal government agencies spend millions of dollars to rid South Florida of invasive species and prevent more from entering the region. Plants that are imported to Florida are subject to classification as "Restricted" or "Prohibited", but a new designation is being considered "Not Authorized Pending Plant Risk Analysis", to allow scientists to assess what damage exotic plants may cause to the South Florida environment. A nonprofit organization named The Florida Exotic Pest Plant Council lists exotic species as belonging in Category I: "altering native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with natives"; and Category II: "increased in abundance or frequency but have not yet altered Florida plant communities to the extent shown by Category I". More than 100 species have been placed in Category I, but a few have been singled out for the potential to cause the most destruction based on how rapidly they reproduce, their displacement of native flora by crowding, shading, or fire, excellent adaptations to conditions in the Everglades, and the potential to spread (or evidence that they have spread) into remote areas of the Everglades.
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