Invasive Species: 4 That Wreak Havoc in America
Here are 4 of the most frightening and infuriating invasive species making their relentless spread across the US and what is being done about them.
Quick Reference: Invasive Species in the US
- The four invaders: feral pig, nutria, European starling, and the Africanized “killer” bee.
- The cost: about $120 billion a year in US economic losses, per the Center for Invasive Species and Ecosystem Health.
- The stakes: the National Wildlife Federation reports 42 percent of threatened or endangered species are at risk because of invasives.
- How they arrived: almost always by people, through intentional release or accidental escape.
- What you can do: report sightings, protect native habitat, and keep your yard and garden from becoming a foothold.
As of 2026, invasive species are still spreading across North America faster than anyone can trap, shoot, or poison them out. When a plant or animal lands somewhere it did not evolve, it can drive out beneficial native species, reshape the landscape, and threaten both farms and people. In almost every case the story starts the same way, with a human hand, and once the newcomer takes hold there is often not a lot we can do to stop the problem from growing.
How Invasive Species Got a Foothold
Through either intentional or accidental release, people are to blame for the many invasives now causing environmental, health, and economic mayhem across the land. Sure, it may have seemed harmless to release a few exotic birds during a ceremony in a park. Nobody thought that crate of fur-bearing little animals would cause any trouble. But in a few short years the sky was blackened by swarms of obnoxious birds and the ground was crawling with giant scurrying rodents.
The numbers tell the rest. According to the Center for Invasive Species and Ecosystem Health, the US suffers about $120 billion in economic losses caused by these non-native invaders. And the National Wildlife Federation reports that 42 percent of threatened or endangered species are at risk because of invasive species. Here are four of the most frightening and infuriating invaders making their relentless spread across the US, and what, if anything, is being done about them.
1. Feral Pig
(Sus scrofa)
What they are: A cross between the Eurasian boar and the domestic swine. Adults typically weigh up to 300 pounds and carry bristly hair in many color combinations, along with a rubbery snout and menacing lower tusks used for fighting.
How they got here: The boars were brought from Europe to the US in small numbers starting about 300 years ago, but the population only began to explode when hunters brought the animals to Texas in the past century. Hunters sometimes trapped the animals to introduce them to new regions. It is estimated that they have now made it into 47 US states, and their population may exceed 6 million.
What’s the big deal: Feral pigs maraud across the countryside, leaving in their wake billions of dollars in property damage from rooting, wallowing, and feeding on farm crops. The nocturnal beasts eat everything from acorns to a wide variety of animals, wipe out native nesting birds’ eggs, spread disease to livestock, cause traffic crashes, and compete for habitat with native species of all kinds. With sharpened tusks, the aggressive swine are known to charge humans. They thrive in many climates, and sows typically produce up to 10 to 12 young per year. Where they are most common, the hogs are starting to encroach on residential areas.
How they’re being managed: They are hunted for pest control, sport, and food. Dozens can be corralled and killed in baited enclosures, and shooting them from helicopters is becoming a popular pastime. Hunters are encouraged to kill as many of the pigs as possible and are often paid by ranchers to clear areas of the pest. But that is not enough. Researchers are developing new poisons and swine contraception in an attempt to slow their spread.
2. Nutria
(Myocastor coypus)
What they are: Furry, dark-colored, semi-aquatic rodents with bright orange buckteeth used for foraging. They can weigh up to 20 pounds and stretch over 2 feet long.
How they got here: Beginning in the early 1900s, fur farmers imported the South American nutria. Later, as the fur farming industry declined, the animals were released into the wild or escaped captivity during floods in Louisiana. They are now found in abundance in 40 US states.
What’s the big deal: Bearing some resemblance to native muskrats and beavers, nutria thrive in the swampy areas where land meets water. Able to eat up to 20 percent of their body weight daily and using large, webbed claws to burrow into shoreline banks, they quickly mow down thousands of acres of vegetation, eliminating critical marshland wildlife habitat, particularly in places like Louisiana. They damage sugarcane, rice, corn, milo, and sugar beet crops, along with other vegetables and grains. They also carry pathogens and parasites that can pass to livestock through their feces by way of the drinking supply. Their effects on humans include “swimmer’s itch,” which comes from waterways contaminated with nutria feces.
How they’re being managed: The fur market has collapsed for the most part, but nutria still provide hunting sport and a food resource in some parts of Louisiana. Some states now pay trappers and hunters about $5 per nutria tail as part of an eradication initiative. But the roughly 350,000 tails collected in Louisiana in one year is just a drop in the bucket for an invasive species that keeps reproducing in huge numbers. A female can mate 3 to 4 times a year and produce up to 14 offspring each time.
3. European Starling
(Sternus vulgaris)
What they are: An aggressive, glossy black songbird that develops white spots in wintertime.
How they got here: In 1890, a group of literary enthusiasts imported and released 100 pairs of the birds in New York’s Central Park in an effort to bring every animal mentioned in Shakespeare’s plays to America. Over the next century their numbers exploded to more than a billion, according to estimates, and they now reside in great numbers in every corner of North America.
What’s the big deal: Starlings are the most prolific invasive bird species in the US, and they sure like to throw their weight around. They push native birds such as bluebirds, owls, and woodpeckers out of their favored nesting sites, they compete aggressively for food, and swarms of starlings cause all sorts of trouble. Starling swarms have caused thousands of airplane-bird collisions. In fact, in 1960, 62 people were killed over Boston when the plane they were in struck a flock of starlings and crashed.
They also cause millions of dollars in crop damage every year as they descend on grain, fruit, and berry crops. What’s more, the droppings from large roosts of starlings threaten the health of farm animals and humans alike. And backyard birders curse the starling as it takes over their feeders. If you would rather feed the songbirds you want, our guide to setting up a bird feeder for the birds you want can help you tilt the odds.
How they’re being managed: There are no restrictions on killing starlings, and target shooters and farmers do their best to reduce the population. Some attempts have been made to scare the birds away with sound and trapping programs, but it is a losing battle, as females continue to reliably produce hardy offspring every year.
4. Africanized “Killer” Bee
(Apis mellifera scutellata)
What they are: An aggressive bee, a hybrid of an African bee and the docile European honeybee. It is slightly smaller than the European bee but similar in appearance. Unlike the European honeybee, though, the Africanized bee does not produce a lot of honey.
How they got here: Entomologists in 1950s Brazil, looking to build the honey industry, imported the African bees because of a poor long-term survival rate among European honeybees. In 1957, a few dozen African queen bees were accidentally released, and they quickly produced hybrids after mating with honeybees. They spread north to Central America, then Mexico, and finally to the US in 1985, arriving first in California. They are now flourishing throughout the southern United States.
What’s the big deal: The sting of the Africanized bee is no worse than that of other bees, but they swarm aggressively and are quick to attack when they feel threatened. Queens can mate with several male drones at a time and store the sperm for a lifetime to keep producing new generations. They can take over honeybee hives, but often take up residence in man-made crevices like cracks in houses, old tires, and abandoned cars. Easily provoked, the so-called “killer bees” will swarm at a moment’s notice, chase targets for a quarter mile or more, and sting relentlessly. Mass stings can result in serious illness or death. It is estimated that 1,000 people have been killed by Africanized bees.
How they’re being managed: Bees in general are beneficial insects that pollinate plants and crops, and the European variety makes delicious honey, so it is tough to selectively eradicate the Africanized bees. Instead, experts recommend tidying areas to eliminate favored habitat and calling a pest management professional. Our roundup of natural ways to handle wasps and other stingers covers the same tidy-up-the-yard approach. If a swarm of bees pursues you, run away in a zigzag pattern and seek shelter indoors. Do not jump into a body of water, as the bees will wait for their target to surface and attack.
Where These Invaders Hit Hardest
Invasive species do not spread evenly. Each of these four has a stronghold, usually the region that best matches its native climate or the place it first escaped. Here is where each one does the most damage today.
Warmer-than-usual winters tend to help all four hold ground and push into new territory, since fewer hard freezes mean fewer losses over the cold months. If you are curious how much winter cold really knocks back a pest population, our look at whether cold winters kill bugs lays out what survives and what does not.
What You Can Do About Invasive Species
No single homeowner is going to stop a 6-million-strong wave of feral hogs. But small, steady choices across many yards and farms add up, and a few of them are worth making this season.
- Report what you see. The Center for Invasive Species and Ecosystem Health runs public reporting tools that help researchers track where invaders are moving. A single report can flag a new front.
- Do not move firewood, fill dirt, or plants far from home. Hitchhiking eggs, larvae, and seeds ride along, and a long car trip can plant a new problem hundreds of miles away.
- Protect the natives you have. Support the bluebirds, owls, woodpeckers, and native bees that invaders push out. Our guide on how to help honey bees and native pollinators is a good place to start.
- Keep your yard from becoming a foothold. Clear the cracks, old tires, and clutter that bees and other pests move into, and clean up feed and fallen fruit that draw hogs and birds.
None of this is a cure. Invasive species are here to stay, and honest management is about slowing the spread and protecting what is native, not winning outright. Do what makes sense for your land and your family, and leave the rest to the trappers, researchers, and pest professionals working the bigger fight.
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We’d love to hear your thoughts. Have you run into any of these invaders on your own place? Share your story in the comments section below.
Invasive Species: Frequently Asked Questions
What are the worst invasive species in the US?
Four of the most destructive are the feral pig, the nutria, the European starling, and the Africanized “killer” bee. Together they damage crops, wetlands, and native wildlife, and the Center for Invasive Species and Ecosystem Health estimates invasive species cost the US about $120 billion a year.
How did invasive species get to North America?
Almost always through people. Feral pigs were brought by hunters, nutria escaped fur farms, starlings were released in Central Park in 1890, and Africanized bees escaped a Brazilian lab in 1957 before reaching the US in 1985. Some releases were intentional and some accidental, but the human hand is the common thread.
Why are invasive species such a big problem?
They out-compete or prey on native plants and animals, wreck habitat, and spread disease. The National Wildlife Federation reports that 42 percent of threatened or endangered species are at risk because of invasives, and the economic toll runs to about $120 billion a year in the US alone.
Can invasive species actually be eradicated?
Rarely, once they are widely established. Hunters, trappers, and researchers work hard to slow the spread, with bounties like $5 per nutria tail and new tools like swine contraception. But with feral pigs topping 6 million and starlings over a billion, the honest goal is management, not total removal.
What should I do if I see an invasive species?
Report it. The Center for Invasive Species and Ecosystem Health runs public tracking tools that help researchers spot new fronts. Beyond that, avoid moving firewood, soil, or plants long distances, protect the native wildlife on your property, and clean up the clutter and feed that give pests a foothold.
What should I do if killer bees start swarming me?
Run away in a zigzag pattern and get indoors as fast as you can. Do not jump into water, because the bees will wait for you to surface. Africanized bees can chase a target for a quarter mile or more, so keep moving toward shelter and call a pest management professional to deal with the hive.
Jim Kneiszel
Jim Kneiszel is a freelance writer based in De Pere, Wisconsin. He edits a number of trade publications and runs The Word House with his wife, Judy. His article, Infuriating and Frightening Invasive Species appears in the 2021 Farmers' Almanac.
- Jim Kneiszel
- Jim Kneiszel
- Jim Kneiszel
- Jim Kneiszel
