Quick Key Facts

• An invasive species is a living thing that, typically because of human activity, has gained a foothold in a new part of the world and is causing negative ecological or economic impacts.
• The term “invasive species” has become contentious among some observers because of concerns with how the subject intersects with climate change, colonialism, nativist ideology and parsing out unharmful, non-native species with harmful ones.
• Non-native species can be harmful if they outcompete native species, consume excess numbers of prey species that haven’t adapted to ward them off, destroy ecosystems, introduce new diseases or cause economic harm.
• Burmese pythons and some carp species were intentionally introduced to the U.S. and have since wreaked havoc in their new ecosystems, in part because of their ability to outcompete existing predators and consume large numbers of prey species that don’t have defense mechanisms against them.
• Some invasive species, like spotted lanternflies, are considered to be more of a threat to agricultural and economic activities than ecological wellness.
• In the U.S., some communities and organizations eradicate invasive wildlife by hunting and eating them. Invasive plants are uprooted through targeted removal campaigns or events.

What Are Invasive Species?

Whether an animal, a plant or a microbe, an invasive species generally describes a living thing that has not historically lived in a given region. An invasive species by definition has a decidedly negative ecological or economic impact on the habitat it has entered, according to the U.S. Department of Agriculture. That could be because it lacks natural predators in the area, so it eats a lot of prey that other native predators in the ecosystem rely on. Or perhaps it crowds out other species for space or necessary resources, killing off a vital crop that regional farmers sell.

An invasive species, as described by the USDA, is one that was likely spread by human activity — not one that naturally migrated or adapted to a new area.

Why Is The Term ‘Invasive Species’ Controversial?

While some non-native species have a devastating effect once they are introduced to an ecosystem, and thus rise to the definition of invasive species, most do not. And not everyone agrees as to whether we should be classifying any species as “invasive” at all. 

That controversy lies in part with the definition of what is native or not. Centuries of European colonization and exploration brought new species, intentionally or otherwise, to new lands. Plants and animals that feel distinctly, inextricably American — like apple trees and house cats, for example — were brought to what is now the United States, but attempts to remove or eradicate those from the country would likely face backlash.

Plus, as the climate changes, the related environmental impacts will influence where species are able to survive. Temperature bands are already shifting, forcing creatures to migrate into new territory they otherwise may not have ventured into if conditions in their former habitat were still amenable to them. That makes it tricky to categorize what is or isn’t a native species, which could result in whether conservation measures are taken in that species’ favor as the climate crisis continues. Because of this and other forces pushing wildlife out of their current territory span

Another concern expressed by experts is that the focus on the purity of native species and ecosystems echoes nativist thinking and racial purity ideologies, according to Vox.

Meera Iona Inglis, a professor of animal and environmental ethics at Newcastle University, argued in a 2020 paper that “we should discard the term ‘invasive species’ and instead use the term ‘potential problem species’ to describe species which appear to be causing harm in a given time and place,” noting that part of her philosophy stems from the “parallels between the portrayal of animal and human immigrants as dangerous invaders.”

Why Are Some Invasive Species Harmful?

Non-native species have the potential to harm native wildlife and plant species by outcompeting them for critical resources like prey and habitat or by overly consuming them in the case of prey species without suitable defense mechanisms. Although natural selection means that species can’t just survive or thrive unless they have evolved to earn a niche in their ecosystem, invasive species may have traits that give them a major evolutionary advantage over species in the native ecosystem. That would put native species at a severe disadvantage, considering they likely couldn’t evolve or adapt quickly enough to ward off the threat. And if an invasive species is able to both outcompete native predators and eat more than their share of species that are lower on the food chain, they could reduce the biodiversity of an area with relative speed.

Other invasive species may end up destroying the ecosystem itself. The emerald ash borer, a type of beetle that likely came from Asia via wood packing material, has killed hundreds of millions of ash trees across North America as its larvae eat the trees’ inner bark, according to the Emerald Ash Borer Network, which is affiliated with Michigan State University.

The threat of invasive species also can look like the importation of diseases that native species aren’t equipped to fend off. According to the National Wildlife Federation, one type of introduced elm bark beetles is an efficient vector of Dutch elm disease, which since 1930 has spread through these beetles “from Ohio through most of the country, killing over half of the elm trees in the northern United States.”

Are Invasive Species Ever Beneficial?

By definition, invasive species aren’t beneficial to an introduced ecosystem. But again, non-native species aren’t necessarily harmful — meaning they have the potential to be beneficial within new ecosystems. Some non-native trees provide shelter for local pollinators or migrating birds, while some non-native wildlife can increase the amount of food available for native predators, according to The New York Times. And a 2022 study in the journal Science noted that when populations of native, seed-dispersing species are threatened, non-native species can help to disperse seeds instead.

How are Invasive Species Impacting American Ecosystems?

The United States Geological Survey, an agency of the U.S. Department of the Interior that conducts invasive species research, notes that “more than 6,500 nonindigenous species are now established in the United States,” although that number is not necessarily the number of invasive species, i.e., potentially harmful species. Here are five that are known to be causing harm in ecosystems in the U.S. to which they have been introduced.

Burmese Pythons

Burmese pythons are native to several Asian countries, including India, China and Malaysia. But during an explosion of the U.S. exotic pet trade in the 1980s, according to the History Channel, Burmese pythons were imported for pets, often destined for South Florida homes —  but the 20-foot-long snakes don’t make good pets and were often dumped by their owners once they became difficult to keep.

Those snakes soon reproduced in the swamps across the region. Without native predators, the Burmese python has been tied to the decimation of many native species of mammals, birds and reptiles. Attributing the decline to the growth of the Burmese python, the U.S. Geological Survey notes that “raccoons [have] dropped 99.3%, opossums 98.9%, and bobcats 87.5% since 1997” in the southern portions of the Everglades National Park.

“While pythons will eat common native species and nonnative species such as Norway rats, they can also consume threatened or endangered native species,” including endangered Key Largo wood rats, explains the Florida Fish and Wildlife Conservation Commission.

Certain Carp Species

Several species of carp are considered invasive, including bighead, black, grass and silver carps, according to the U.S. Geological Survey. The fish were intentionally introduced in the 1970s to the U.S. to help control algae blooms and for human consumption, but the agency explains that the fish “escaped confinement and spread to the waters of the Mississippi River basin and other large rivers like the Missouri and Illinois.

Now, the invasive carp populations have exploded, reducing the amount of food and habitat available for aquatic species native to the area — which in turn makes it harder for commercial and recreational fishers to catch what they want. 

“As filter feeders, [different invasive carp species] consume the base of the aquatic food chain, starving out and outcompeting native fish species,” explains the National Wildlife Federation on their website. “Additionally, silver carp become a safety hazard to boaters and anglers on waters they inhabit, leaping feet out of the air and weighing up to 40 pounds.”

Spotted Lanternflies

Originally from China, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service says that the spotted lanternfly was first found in the U.S. in 2014 and has since spread to 14 states. Currently considered to be more of an agricultural threat than an ecological one, spotted lanternflies are known to feed on fruiting trees, including apples, cherries, peaches, plums and walnut trees, as well as other crops like grapes and hops.

Water Hyacinths

Water hyacinths — a leafy, aquatic plant with light purple flowers — were introduced for ornamental purposes in the U.S. in the late 1880s from South America’s Amazon Basin. But according to the National Invasive Species Information Center, the freshwater plant also “forms dense colonies that block sunlight and crowd out native species.” The University of Florida’s Center for Aquatic and Invasive Plants finds that this blanketing effect makes human water activities “impossible” once they move into an area. The water hyacinth has made its way across two-thirds of the U.S., but Florida has been able to keep the plant’s abundance under control.

How Do Invasive Species Hurt Economic Activities?

Invasive species aren’t just an ecological concern; they can also cause strong economic problems. Spotted lanternflies, for example, threaten Pennsylvania’s grape, apple and stone fruit industries, as well as its pine and hardwood logging sector. Those industries account for billions of dollars of sales and economic activities in the state, according to the Invasive Species Centre, based in Canada.

Another example can be found in the case of the zebra mussel. Originally from the Black and Caspian seas, the zebra mussel has proliferated across the Great Lakes region, according to the Cary Institute of Ecosystem Studies. In addition to its voracious appetite for critical prey species — namely, plankton and microzooplankton — that threatens or endangers native mussel and other aquatic species, the zebra mussel attaches en masse to water intake pipes and industrial equipment, causing damage.

How Can I Reduce The Impact of Invasive Species?

Preventing species that are known to harm local ecosystems from entering the region is key to reducing their harm. The U.S. Department of Agriculture notes that invasive species can hitch a ride to new destinations on imported cargo and commercial shipments, in addition to passenger vehicles, in addition to ocean containers, aircraft, rail cars and commercial trucks. Checking personal vehicles and clothing for plants, seeds or wildlife before traveling between regions can help reduce invasive species contamination. 

Once a harmful non-native species appears in a new area, there are different ways that nonprofits, governmental agencies, communities and even commercial entities opt to eradicate before the creature can cause problems or further existing concerns. In areas where lionfish have become invasive, for example, hunting competitions are held to catch and kill them for both sport and for consumption. Whole Foods even sells lionfish in some of its stores, noting on its website that the Monterey Bay Aquarium’s Seafood Watch considers the fish to be a “best choice” for consumption because of their invasive species status. And spotted lanternflies have been the subject of informational campaigns encouraging people to squish them on sight.

Some observers of the invasive species conundrum debate the ethics of culling creatures because of their potential for injurious behavior in their introduced habitat. People for the Ethical Treatment of Animals, or PETA, has condemned decapitation that is allowed during contests to kill an invasive python species. However, the organization doesn’t necessarily believe that all invasive species should be allowed to remain in the introduced environment, proclaiming that house cats should never be allowed outside because of their outsized impact on native wildlife.

In places where invasive plant species have begun to take root, volunteer events are sometimes held to teach community members which species are harmful and should be removed, as well as how to safely dispose of them. To find such events in your community, reach out to local extension schools, nature clubs or environmental agencies to understand what the options are — or use an internet search engine to seek out “invasive species removal projects in” your area.

The post Invasive Species 101: Everything You Need to Know appeared first on EcoWatch.