Silent invaders are infiltrating America’s lands and waters, leaving a trail of ecological destruction in their wake. These non-native organisms cause harm to the environment, economy, or human health and are responsible for the decline of nearly 42% of threatened and endangered species in the United States.1
As human activities continue to facilitate their spread, the threat of invasive species looms larger than ever. Here are America’s 12 most destructive invasive species, exploring their impacts and our challenges in managing them.
1. Asian Carp
Swimming through America’s waterways with reckless abandon, Asian carp have become the scourge of the Mississippi River and its tributaries. (ref)
These fish, which include several species native to Eastern Russia and China, were originally introduced to control algae in fish ponds in the Southern U.S. Unfortunately, Asian carp escaped during flood events and have since spread rapidly.
When startled, their habit of jumping out of the water poses a serious hazard to boaters. More importantly, these prolific breeders outcompete native fish species for food and habitat, disrupting aquatic ecosystems.
2. Zebra Mussels
Tiny but terrible, zebra mussels have invaded waterways across the eastern United States since their accidental introduction in the 1980s. (ref)
These small mollusks, native to Eastern Europe, arrived in ships’ ballast water and quickly spread through interconnected waterways. Zebra mussels form dense colonies that clog water intake pipes, causing millions in damage to infrastructure.
They also filter vast amounts of plankton from the water, depriving native species of food and altering entire aquatic food webs. Their sharp shells litter beaches, posing an ongoing hazard to swimmers and beachgoers.
3. Emerald Ash Borer
This small, metallic-green beetle leaves a trail of dead ash trees in its wake across the eastern United States. Native to Asia, the emerald ash borer was first detected in Michigan in 2002 and has since spread to over 30 states. (ref)
The larvae of this insect feed on the inner bark of ash trees, disrupting the tree’s ability to transport water and nutrients. This eventually kills the tree, often within 3-5 years of infestation.
The emerald ash borer threatens to virtually eliminate ash trees from North American forests, with potentially devastating ecological and economic consequences.
4. Feral Hogs
Feral hogs are a growing problem in at least 35 states, rooting and wallowing their way across the country. These invasive swine are descendants of domestic pigs that escaped or were intentionally released, and Eurasian wild boars were introduced for sport hunting.
Feral hogs cause extensive damage to crops, property, and natural habitats through their feeding and rooting behaviors. (ref) They compete with native wildlife for food and can transmit diseases to wildlife and livestock.
The cost of managing feral hog populations and mitigating their damage is estimated at nearly $1.5 billion annually.
5. Kudzu
Often called “the vine that ate the South,” kudzu is a rapidly growing plant that has smothered vast areas of the southeastern United States. (ref) This aggressive climber, native to Asia, was introduced in the late 19th century for erosion control and as an ornamental plant.
Kudzu can grow up to a foot per day, quickly engulfing trees, buildings, and anything else. It outcompetes native plants for sunlight and nutrients, dramatically altering forest ecosystems.
Despite decades of control efforts, kudzu spreads, costing millions in damage and eradication attempts.
6. Burmese Python
Slithering through the Everglades, Burmese pythons have become one of Florida’s most notorious invasive species. (ref) These massive snakes, which can grow over 20 feet long, were introduced through the pet trade and have established a breeding population in South Florida.
Burmese pythons are voracious predators that feed on various native mammals and birds. Their presence has been linked to dramatic declines in small mammal populations in the Everglades.
Efforts to control their spread have proven challenging, as these snakes are excellent at hiding in the dense vegetation of the Everglades.
7. Lionfish
With their striking appearance and venomous spines, lionfish have become a beautiful menace in the waters of the southern United States. Native to the Indo-Pacific, these fish were likely introduced through the aquarium trade and have since spread throughout the Caribbean and along the Atlantic coast. (ref)
Lionfish are prolific breeders and have few natural predators in their introduced range. They feed voraciously on small fish and crustaceans, competing with native species and disrupting reef ecosystems.
Control efforts have included encouraging human consumption of lionfish and organizing “lionfish derbies” to remove as many as possible from affected areas.
8. Asian Long-Horned Beetle
The Asian long-horned beetle, a menacing insect that tunnels through trees’ heartwood, poses a grave danger to numerous species of hardwood trees across the United States. (ref) This large, distinctive beetle was accidentally introduced in Asia through wooden packaging.
The larvae of the Asian long-horned beetle tunnel through trees’ heartwood, weakening them structurally and disrupting their vascular systems.
This eventually leads to the tree’s death. If left unchecked, this beetle could destroy millions of acres of hardwood forests, causing enormous ecological and economic damage.
9. Cane Toad
The cane toad, which hops across Florida, is a toxic invader that causes problems for native wildlife. (ref) Originally introduced to control agricultural pests, these large toads have become pests.
Cane toads produce a potent toxin that can be fatal to native predators that attempt to eat them. They also compete with native amphibians for food and breeding sites.
Their rapid reproduction and lack of natural predators have allowed cane toad populations to explode in some areas, leading to ongoing control efforts.
10. European Starling
The European starling is one of North America’s most successful avian invaders, flocking in massive numbers across the continent. In the late 19th century, a group intentionally introduced these birds to America, aiming to bring all the birds mentioned in Shakespeare’s works to the continent. (ref)
European starlings compete aggressively with native birds for nesting sites and food. Their large flocks can cause significant damage to crops and create nuisance problems in urban areas.
Starlings have spread across the continent despite control efforts and are now one of North America’s most common bird species.
11. Nutria
Nutria, which swim and burrow through wetlands, are causing significant damage to coastal ecosystems. These large rodents, native to South America, were introduced for their fur but have since become a major problem in many states. (ref)
Nutria feeds voraciously on wetland vegetation, often consuming the roots and rhizomes of plants. This can lead to the collapse of marsh ecosystems, exacerbating coastal erosion and land loss.
Their burrowing habits can also damage levees and other water control structures. Despite ongoing eradication efforts, nutria continues to spread and cause damage in many areas.
12. Spotted Lanternfly
Last but certainly not least, the spotted lanternfly is a recent invader causing growing concern in the northeastern United States. First detected in Pennsylvania in 2014, this colorful insect has since spread to several neighboring states. (ref)
The spotted lanternfly feeds on the sap of various trees and plants, potentially causing significant damage to orchards, vineyards, and forests. It also produces large amounts of honeydew, which can lead to the growth of sooty mold on plants.
With its potential to spread nationwide, the spotted lanternfly quickly becomes a top priority for invasive species management.
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Davin is a jack-of-all-trades but has professional training and experience in various home and garden subjects. He leans on other experts when needed and edits and fact-checks all articles.