The factors that have led to wildlife changes range from hunting and collecting (“plume” birds, alligator hunting/poaching, and specimen collection, as for tree snails and orchids) to automobile roadkills, to direct loss of habitat (land development, introduced species), to large changes in habitat character.

Alligators were once extremely abundant in parts of the Everglades where they are rare or absent today. Alligator hunting for their hides and habitat drainage reduced populations through the 1930s and 1940s, but they rebounded to local abundance in the 1950s with protection afforded by Everglade National Park following its creation in 1947.

Of the huge changes in South Florida, taking specimens from the wild might seem minor. Yet, collectors have taken a large toll on wildlife. Many of the more unusual orchids and ferns of the region are now all but extinct. The intricately colored tree snails, once found in a myriad of varieties throughout the tropical hardwood hammocks of the area, have been collected so copiously for their beautiful shells that numerous varieties no longer exist. In fact, tree snail collectors in the past were even known to burn hammocks in order to facilitate collecting the local variety of tree snail, damaging both the hammocks as well as the snail populations.

The rise in the number of naturalized nonindigenous species and the extent of the damage done has risen dramatically. The extreme behavior of an introduced species is called “invasive,” the condition where it moves into man-made and/or natural environments, causing economic hardship and/or displacing native species, often radically altering environments and their ecological functions.

Plants are the basis of ecosystem productivity and provide most of the non geological structure of an ecosystem. Thus, alterations in plant communities can cause extensive ecological changes. The largest threat of invasive plants in natural landscapes is damage to the functions of native plant communities. In total, 829 introduced plants are successfully established in South Florida. Of the introduced flora, 119 kinds (7% of the total flora) have been designated as invasive exotics. Most of these have escaped from ornamental horticulture.

The greatest invasive threat to short-hydroperiod marsh and swamp habitats of the Everglades and Big Cypress Swamp is a tree from Australia called “melaleuca.” Melaleuca forms dense forests that exclude native vegetation and obstruct habitat use by wading birds. It was promoted in horticulture and agriculture for wind breaks and honey production, and was intentionally seeded into the Everglades for the purpose of land development—trees transpire more water than marsh vegetation, so it was thought that it would dewater the Everglades marshes. The spread of melaleuca was enhanced by its extreme tolerance for fire.

More versatile than melaleuca, especially in its invasion of upland communities, Brazilian pepper was itially called “Florida holly” for marketing of this large shrub as an ornamental in South Florida. Its seeds, in small decorative red berry-like clusters, have been widely spread by birds and mammals after passing through their digestive tracts. It has widely invaded many plant communities in the Everglades region, especially pinelands and a variety of coastal lowland habitats including shallow mangrove swamps. Particularly troublesome is its ability to form closed forests in abandoned agricultural land and shallow coastal marsh habitats, and to prevent the recovery of pinelands after hurricane damage.

Relative to melaleuca and Brazilian pepper, the Old World climbing fern is a new invader in South Florida. It became established in the wild in 1965 in Martin County, where it soon became a problem in the headwater cypress wetlands of the Loxahatchee River system. By 1989, it had spread into Loxahatchee National Wildlife Refuge of the northern Everglades where is has completely covered tree islands in large areas of the refuge. It has also become established in the Big Cypress Swamp and western Everglades National Park.

Photo from the Southwest Florida Water Management District

In addition to introduced plants, South Florida also supports innumerable introduced animals.

Two prominent examples that may alter plant communities are the lobate lac scale insect and the bromeliad beetle. These two recent arrivals have the potential for enormous ecosystem changes. The scale insect has infested over 39 species of native shrubs and trees, and a larger number of ornamental plants. The bromeliad beetle potentially affects over 20 species of native air plants, killing many of them. Bromeliads are not only an asset to South Florida’s natural beauty, but provide important habitat for many small animals such as tree frogs

The warm temperatures of South Florida’s waters have fostered the successful escape of many tropical freshwater aquarium fishes and the intentional introduction of a few. The key role that fish play in Everglades food chains makes introduced species an important concern. Introduced fish include the pike killifish — a small, voracious predator adept at catching mosquitofish, the walking catfish, seventeen species of cichlid now permanently established in Florida – seven specifically in Everglades National Park, and Blue tilapia.

A pike killifish. Photo by Tom Lodge

There are relatively few introduced amphibians that have succeeded in the wild in South Florida. Reptiles are a different story. Introduced lizards have outnumbered native species in Florida for a few decades. Nearly all lizards now seen in South Florida areas are introduced species. Formerly, the largest of the introduced lizards is the great green iguana, a herbivorous lizard established from the pet trade. Much more ominous from the human viewpoint is the equally large Argentine tegu, a predatory lizard from South America with a rapidly expanding South Florida population, and the well-established population of the huge Burmese python. Python numbers as high as 100,000 in Everglades National Park are essentially guesses — no credible population estimates exist. The crash of numerous mammal populations, including the once common marsh rabbit, in the Everglades is almost certainly due to python predation

Few introduced birds have invaded Southern Florida’s wilderness. Residential areas, however, abound with them. The Miami/Ft. Lauderdale areas harbors at least 10 parrot species, established from escaped pets. A recent introduction that shows an inclination to invade the Everglades is the purple swamp hen from the Middle East. It looks like a gigantic purple gallinule, being similarly colored but is several times heavier.

Lodge, Thomas E.. The Everglades Handbook. CRC Press. Kindle Edition.