5 Times Scientists Fought Back Against Invasive Species And Actually Won

When you consider all the factors that go into identifying a species as "invasive," it's a wonder that any of them are ever dealt with effectively. The term invasive species, unlike exotic or non-native species, does not simply refer to plant or animal life that has been introduced from a different country or region. In order to be invasive, the species has to become (or have the potential to become) a pest, taking over natural environments and pushing native species out, causing environmental or economic damage in the process.

A non-native species will often become invasive because the environment into which it is introduced has not developed defenses against its presence. These invaders typically enjoy a lack of natural predators and may even become the most dominant predator in their new environment. What's more, in the case of feral hogs, the invasive species currently destroying Texas, these invaders can often reproduce faster than prevention efforts can account for, allowing the invasive species to spread rapidly even while attempts are made to limit their numbers. The same is true of Asian carp, an invasive species that has been working its way towards the Great Lakes for decades, with adult females capable of laying up to 1 million eggs per year, making the fish extremely difficult to contain.

Even with all this, however, there have been some success stories where scientists have managed to not only fight back against specific invasive species, but have actually eradicated them altogether.

The European grapevine moth is native to southern Italy and can be found throughout Europe and many other countries including Africa, the Middle East, Russia, Japan, and Chile. But in 2009, the insect was found in the United States for the first time. Discovered in Napa County, California, the moth posed a potentially disastrous threat to grape production in the state. Indeed, the same year the insect was discovered in Napa County, the area saw 10 acres of vineyard lose 100% of their crops.

European grapevine moth feed on grapes, causing fungal rot, while their larvae feed on grape flowers and fruits, making their removal from Napa Country of the utmost importance. In 2010, a quarantine was instituted in multiple California counties to help stop the moths' spread, but that was just the beginning of the eradication effort.

As detailed in Entomology Today, grape growers, the wine industry, University of California researchers, and local, state, and federal officials all came together to rid the state of the pest. Aside from quarantines, traps were set up throughout the state to aid in detection, while vineyards were regularly inspected. Along with mating-disruption and insecticide treatments, this multi-faceted approach proved successful, with the European grapevine moth being declared eradicated from the state in 2016.

Roughly 10 miles off the Northern coast of Scotland, Orkney is an archipelago made up of 70 different islands, 20 of which are inhabited by humans. Home to a wide variety of native species, the Orkney islands haven't been immune to the threat of invasive species, having endured a wave of non-native stoat invaders since 2010. Though there are major differences between ferrets, stoats, and weasels, these small fluffy creatures actually belong to the same family as weasels, ferrets, badgers, and otters, and while undeniably cute, are also a major threat to the native wildlife of Orkney.

The Orkney Native Wildlife Project was set up in response to the arrival of stoats in Orkney in an attempt to protect the islands' diverse array of native wildlife. But doing so was a considerable task. As the project's official website explains, stoats are not only fast and agile, they can take down prey much larger than themselves, often killing more than they need to in order to store food for a later date. What's more, these omnivorous predators don't discriminate when it comes to prey, eating everything from eggs and chicks to insects and even small animals such as mice, rabbits, hedgehogs, and fish. As with many invasive species, the stoats faced no natural predators on Orkney.

Thankfully, the Orkney Native Wildlife Project has had a huge impact on the numbers of stoats on the islands. Using a network of more than 8,000 "lethal humane trap boxes" and professional trappers, along with what the project claims are Europe's first stoat detection dogs, the project has removed more than 6,000 stoats from Orkney since 2019. This has resulted in a surge of nesting success for native species, including curlews, oystercatchers, and the hen harrier.

Though efforts are ongoing, the organizers are now gearing up for what they call "the final phase of the eradication," which will see them use targeted trappings based on sightings and dog detections. This requires another crucial part of the project to remain in place: volunteer work. Organizers have relied on members of the public reporting stoat sightings in order to make their impressive progress, and that aspect will be key to fully eradicating stoats from Orkney.

Northern giant hornets (Vespa mandarinia) are the largest species of hornet on Earth and gained the nickname "murder hornets" due to their penchant for absolutely decimating honey bees and their hives. These giant insects are native to Asia but in 2019 were detected in the Vancouver Island area of Canada and the northwest corner of Washington State for the first time. At the time, officials were unclear on how the creatures made it to North America, but the arrival of murder hornets in the U.S. was big news, coming as it did just before the global pandemic, which made it seem as if the hornets were some sort of dreadful harbinger of doom. Though the insects posed much more of a threat to native honey bees than humans, the fact that they came with 6-millimeter-long stingers and were capable of spitting painful venom didn't really help their public image all that much.

Perhaps you've since wondered what happened to those murder hornets in Washington state? Well, they've gone. All of them. That is to say they've been eradicated by the Washington and U.S. Departments of Agriculture, which announced the news in December 2024. In fact, the agency confirmed that there had been no murder hornets detected in the state since 2021.

Suitably for a group of insects dubbed murder hornets, the story of how the pests were wiped out includes some strikingly unorthodox methods, including strapping tiny tracking devices to the backs of three of the pests with dental floss and following one back to its nest. A much less exciting method used to eradicate the pests involved Washington state residents reporting sightings and placing traps on their properties. Meanwhile, British Columbia has also reported the eradication of murder hornets, making this one of the most impressively comprehensive wins against an invasive species in North America to date.

Indiana Dunes National Park, on the shore of Lake Michigan, is one of the most biologically diverse parks in the country, featuring an ecosystem made up of sand dunes, wetlands, prairies, and forest. But at one time, this diverse environment was struggling with a serious invasive plant problem. Specifically, the wetlands that lay between the individual dunes had been overrun by invasives, which was a real tragedy because these areas don't only host multiple plants and wildlife but help to improve water quality and aiding in flood and erosion control.

By 2005, in an area of the park known as West Beach, one of these intradunal wetlands, or pannes, had been completely taken over by invasive plants, which had all but eliminated the native plantlife of the wetland, with only a small portion of the original plants remaining. These invasives included common reed (Phragmites australis), hybrid cattails (Typha X glauca), purple loosestrife (Lythrum salicaria), and non-native thistles (Cirsium sp.) — all of which not only displaced native plants and wildlife, but served as a source of seeds which could potentially spread to other areas of the park.

So, in 2005, Indiana Dunes National Park began monitoring the situation, then they partnered with the Great Lakes Invasive Plant Management Team (IPMT) in 2009 to take control of the situation. Herbicide was applied annually, targeting specific invasive species year after year to ensure new plant growth was eliminated. The process was long and arduous, but almost 20 years of consistency resulted in what the National Park Service termed "restoration and revegetation," with the formerly overrun wetland now a "healthy panne" full of biodiversity. The wildflowers that now grow in the panne are a symbol of an entire ecosystem reborn.

In 2023, an unprecedented outbreak of invasive fruit flies occurred in California that saw multiple quarantines imposed across the state. In fact, this was the largest outbreak of the pests the Golden State had ever seen, and included the Tau and Queensland fruit flies which had previously never been seen in the United States. Invasive fruit flies, which USDA Under Secretary for Marketing and Regulatory Programs Jenny L. Moffitt called "among the most destructive and costly pests globally" (via the USDA's Animal and Plant Health Inspection Service), have been an issue in California before, but this was a particularly major outbreak that saw state residents prohibited from sharing produce. Thankfully, after a year of fighting back against these invaders, California came out on top.

The U.S. Department of Agriculture's (USDA) Animal and Plant Health Inspection Service (APHIS) teamed up with the California Department of Food and Agriculture (CDFA) and agricultural commissioners to combat the invasive fruit flies. This massive effort to eradicate the pests focused on five species: Oriental (Bactrocera dorsalis), Tau (Zeugodacus tau), Queensland (Bactrocera tryoni), Mexican (Anastrepha ludens) and Mediterranean (Ceratitis capitata) fruit flies.

The considerable project involved setting up a large-scale trapping apparatus, alongside fruit removal, and surveys to keep tabs on the fruit fly numbers. One of the more ingenious methods used to whittle down the numbers of fruit flies involved releasing sterile Mediterranean and Mexican fruit flies, which interrupted the ability of the pests to reproduce. Elsewhere, an organic treatment called Spinosad was used alongside a host of new regulatory treatments which allowed for citrus fruits to be shipped from quarantined areas.

All of which paid off. In August 2024, The U.S. Department of Agriculture's Animal and Plant Health Inspection Service, and the California Department of Food and Agriculture announced that California was fruit fly free.