Around 1980 is when it’s believed some aquarium fish, including lionfish, were released in the wild. Since then, they’ve become the most destructive exotic species in the waters off Florida and the Caribbean. Lionfish have a seemingly insatiable appetite; they are known to eat more than 70 marine fish and invertebrate species and drastically reduce other fish populations. A recent find in Florida suggest that lionfish have resorted to cannibalism, possibly because they’ve depleted their own food source. The 18 fan blades on their backs are venomous, which greatly reduces their list of predators. Florida is trying to fight back with Lionfish Removal and Awareness Day as well as the Reef Rangers program, but it seems to be a hopeless battle.
Image of zebra mussels courtesy of U.S. Fish and Wildlife Service.
Although small in size, zebra and quagga mussels are causing major issues for lakes, rivers and other waterways in the U.S. These mussels, originally from Eastern Europe and Western Russia, were brought over to the Great Lakes in the ballast water of ships. They were first discovered in the Duluth/Superior Harbor in 1989. Environmentally, zebra and quagga mussels strip the water of plankton, an essential member of the ecosystem, which leads to a lack of food causing populations of salmon, whitefish and native mussels to plummet. Through intensive filter feeding, zebra and quagga mussels promote water clarity. This allows sunlight to warm the bottom of lakes, creating ideal conditions for the growth and spread of deadly algae. That deadly algae has caused botulism outbreaks that have killed countless fish and over 70,000 aquatic birds in the last 10 years. Economically, the exotic mussels can clog pipes, drains and filters which leads to a hefty bill for the affected communities.
In 1889, nutria, native to South America, were brought to the U.S. for their fur. Yet in the Forties, the nutria market collapsed and thousands were released into the wild. Today, this large, semi-aquatic rodent can be found in 22 states. Their impact is strongly felt in the Gulf Coast states and in marshes and wetlands across the U.S., where they feed on native plants that hold wetland soil together. The weakened density of the soil and rising sea levels means major destruction for coastal marshes and wetlands. These rodents are often confused with beavers, but their yellow to orange teeth, bright white whiskers and rat-like tail are identifying characteristics. They can be hunted and trapped legally in most places where they occur (always check your local laws, of course), and it’s said that their meat tastes very similar to pork.
Giant hogweed was introduced to the United States in 1917 for ornamental purposes. Today, due to its prolific seed production and rapid growth rate, hogweed can be found in 11 states. The plant outgrows others, overtaking the area they previously grew. It’s also a thick plant, creating a canopy which can block out necessary sunlight for native plant growth. Hogweed can reduce the utility of the area for wildlife, and can displace riparian plants which leads to stream bank erosion. The most horrific aspect of this invasive species is what it can do to humans. If the sap of giant hogweed touches sweaty or moist skin it can cause severe skin irritation—and never, never, get it in your eyes. The sap contains psoralens, which in even minute amounts can lead to temporary or permanent blindness.
Known as “the vine that ate the South”, kudzu is a fast-growing invasive plant species that’s ruining entire forested areas. Just like hogweed, kudzu was originally brought over for ornamental purposes, and for obvious reasons. It’s a sweet-smelling plant, with large leaves and sturdy vines that engulf average terrain turning it into a work of art. Yet like many works of art, kudzu has a dark side. A single root crown can contain up to 30 vines that grow an average of 1 foot per day. The vines, loaded with leaves, blanket other plants, blocking their access to sun and crushing them under their weight.
Image courtesy of Wisconsin Department of Natural Resources.
The Asian carp is a silver, hard-headed storm heading towards the Great Lakes. These fish (silver, with hard heads) are fast-growing, aggressive and voracious eaters. They’re outcompeting native fish for food and now call much of the mid-section of the U.S. home. Asian carp are originally from Southeast Asia and were brought over in the 1970s to filter pond water in fish farms in Arkansas. Through floods and daring escapes, they can now be found in 23 states and represent over 97 percent of the biomass in portions of the Illinois and Mississippi Rivers.
No matter water, land or sky, invasive species are impacting the U.S ecosystem in negative ways. The fight seems too far gone against some of these culprits, but hopefully we can learn and stop the spread of another invasive species.