The temperate-to-subtropical climate transition invites a wide variety of species to settle down. The lagoon also has many points of entry from both land and sea, with canals that drain upland portions of the watershed as well as open inlets to the Atlantic Ocean where the Gulf Stream passes relatively close to the coastline.
Hundreds of non-indigenous plants and animals have been introduced in the five centuries since the arrival of the first Europeans in Florida. Many have greatly benefited humans. For example, cultivated plants of the genus Citrus, which originated in southeast Asia, India and West Asia, are now a billion-dollar industry in the state.
However, along with intentional and beneficial introductions have come plenty of accidental and harmful new arrivals. Released from predators, competitors, parasites and disease that keep them in check in their native ranges, some introduced species may proliferate to the point where they become invasive. Their presence in the ecosystems they have invaded has resulted in significant economic or environmental harm.
Estuaries and shallow-water muddy sediments have proportionately more invasive species than rocky shores and open coast sandy shores. This difference probably results from the fact that most introductions, intentional or not, take place within estuaries like the Indian River Lagoon.
Invasive non-natives can cause ecological damage by competing with, displacing or otherwise negatively impacting native populations. These species can also cause economic harm by damaging valuable agricultural products as well as human-built infrastructure.
The impacts can be substantial, but it is difficult to predict which species will be harmful. Very often, the invaders go largely unnoticed until populations have grown and spread to a point where eradication is difficult and costly, or even impossible.
In Florida, the introduced nutria, Myocastor coypus, contributes to the loss of marsh acreage by foraging on vegetation. Changes in water flow around salt marshes and mangroves have allowed for expansion of the invading Brazilian pepper, Schinus terebinthifolius, and the Australian pine, Casuarina equistifolia. Closing portions of these habitats for mosquito impoundments has reduced the salinity, allowing the invasion of more oligohaline vegetation and animals such as the blackchin tilapia, Sarotherodon melanotheron.
Disturbed or barren areas will often be colonized by invasives before native plants can become established. Efforts are ongoing to remove invasive plants from terrestrial areas, but aquatic invasions of fishes and invertebrates are often difficult or impossible to reverse, and can only be managed to prevent further range expansion.
In the Indian River Lagoon region, notably harmful species include:
Other factors contribute to the spread of harmful invasive species in Florida and the Indian River Lagoon:
Storms. Seasonal tropical storms and hurricanes can also facilitate the spread of exotics throughout the lagoon watershed and Florida broadly, by physically dispersing individuals, seeds and propagules.
Development. The third most populous state in the nation, Florida’s resident population numbers nearly 22 million people (as of 2020); and several times that number visiting each year. Much of Florida is dominated by habitats created or extensively modified by humans. In the IRL, as in many other parts of Florida, human disturbance exposes local ecosystems to invasion by harmful newcomers.
Trade and shipping. Florida’s status as an international transportation and shipping hub also contributes to the exotic invasive crisis. Hundreds of millions of imported live plants pass through the Port of Miami each year, and many species of animals shipped to the U.S. for the exotic pet trade also pass through Florida.
