Invasive species can cause significant ecological and economic damage when introduced to environments where they do not naturally occur. Across North America, several invasive species have established themselves, disrupting ecosystems and outcompeting native species. Here, we explore eight of the most destructive invasive species wreaking havoc across the continent.
Feral Swine (Sus scrofa)
Originating from parts of Europe, Asia, and North Africa, feral swine were introduced to the U.S. by European settlers in the 1500s for food and later for sport hunting. These destructive creatures, estimated to number at least 6 million in 35 states, cause extensive damage to crops, landscapes, and native wildlife. They root through fields, forests, and even suburban areas, causing erosion and spreading diseases to livestock and humans.
Burmese Pythons (Python bivittatus)
Imported for the exotic pet trade, Burmese pythons were released into Florida’s wilds and rapidly established populations, decimating native small mammal populations in the Everglades. These large constrictor snakes have few natural predators in North America, allowing them to thrive and expand their range. Their presence has severely disrupted the balance of the Everglades ecosystem, leading to declines in populations of raccoons, rabbits, and even deer.
Domestic Cats (Felis catus)
Introduced by European settlers as pets, domestic cats have become a destructive invasive species, killing billions of birds and mammals annually. Despite their popularity as pets, their impact on native wildlife has sparked controversy. Free-ranging domestic cats prey on small animals, leading to declines in native bird and small mammal populations. Their hunting instincts and ability to reproduce rapidly make them a significant threat to biodiversity.
European Starlings (Sturnus vulgaris)
Originally introduced to North America by Shakespeare enthusiast Eugene Schieffelin, European starlings have become a widespread nuisance, destroying crops and outcompeting native species. These aggressive birds form large flocks that can devastate agricultural fields and outcompete native birds for nesting sites. Their adaptability and high reproductive rate make them difficult to control, causing ongoing problems for farmers and conservationists.
Nutria (Myocastor coypus)
Brought to the U.S. for the fur trade, nutria have spread across the country, causing extensive damage to crops, natural resources, and infrastructure. Described as a cross between a beaver and a sewer rat, these rodents are prolific breeders. They burrow into riverbanks and wetlands, causing erosion and destroying aquatic vegetation. Their feeding habits degrade habitats for native wildlife and compromise flood control systems.
Asian Carp (multiple species)
Imported to the U.S. in the 1970s for various purposes, Asian carp have invaded waterways across the country, outcompeting native fish for food and habitat. With some species capable of eating up to 100% of their body weight daily, they pose a significant threat to the Great Lakes and other aquatic ecosystems. Their rapid reproduction and ability to thrive in diverse environments make them particularly challenging to manage.
Gypsy Moths (Lymantria dispar)
Accidentally introduced by French artist Étienne Léopold Trouvelot in the late 1860s, gypsy moths have spread throughout the northeastern U.S., defoliating millions of acres of trees and shrubs. These voracious pests pose a threat to forests, where they can strip trees of their leaves, weakening and eventually killing them. The economic and ecological impact of gypsy moth infestations is severe, affecting timber industries and forest health.
American Bullfrog (Lithobates catesbeianus)
While native to large parts of North America, the American bullfrog has been introduced to new areas for food purposes, leading to disruptions in local ecosystems. These large frogs prey on native amphibians, contributing to declines in amphibian populations. Their voracious appetite and competitive nature make them a formidable invasive species, impacting the biodiversity and balance of aquatic habitats.