Invasive species are plants and animals that are not native to a particular location. These species can cause significant ecological and economic damage. The United States has long struggled with invasive species — more than a few of which were introduced, whether purposefully or accidentally, with disastrous results. Here are seven examples of invasive species wreaking havoc across the country.
1. Feral Swine
Feral swine ( Sus scrofa ), also known as wild boars, hogs, or pigs, are native to Europe, Asia, and North Africa. European settlers introduced them to the U.S. as a food source beginning in the 1500s. Some were later introduced for sport hunting in the 1900s. They are also incredibly destructive, devouring crops and native vegetation and severely damaging agricultural lands and natural ecosystems. The problem of feral swine became national news in 2019 when a Twitter user’s desperate plea to her followers about “30 to 50 feral hogs” went viral. Although the meme satirized the situation’s absurdity, it also drove home the real threat these animals pose. The U.S. Department of Agriculture estimates that at least 6 million feral swine are dispersed across about 35 states.
2. Burmese Pythons
Burmese pythons are native to Southeast Asia and came to the U.S. via the exotic pet trade. The first python was spotted in Florida’s Everglades National Park in 1979. By 2000 some populations had been established. They can grow to be over 20 feet in length, and a female can lay 50–100 eggs a year. Without natural predators in the Everglades, Burmese pythons have ravaged native mammal populations, consuming more than 90% of small and medium-sized mammals. They are also known to eat larger prey, including deer. Despite infrequent attacks on humans, there have been isolated incidents, including the tragic case in 2009 where a python strangled a toddler.
3. Domestic cats
Domestic cats originated from North Africa and Southwest Asia and were brought to the U.S. by European settlers as pets. Destructive but beloved, cats are classified as an invasive species that decimates native bird and mammal populations. A 2013 study estimated that free-ranging domestic cats kill 1.3–4.0 billion birds and 6.3-22.3 billion mammals annually. According to the American Bird Conservancy, cats are responsible for the extinction of more than 60 species of birds, mammals, and reptiles.
4. European Starlings
Eurasian starlings native to Europe, Asia, and Africa were brought to the United States by a Shakespeare-loving man named Eugene Schieffelin, who released approximately 100 starlings in New York City’s Central Park in the early 1890s. Within 50 years, the starlings had made their way across the continent. Today, there are more than 200 million European starlings in North America. They are also described as harmful since they compete with native species, destroy crops, and pollute food and water sources. In 1960, a flock of 10,000 starlings caused a plane crash in Boston that killed 62 people.
5. Nutria
Nutria — also known as coypu or swamp rats are native to South America. They were brought to the U.S. in the early 20th century for the fur trade. When the market declined, they were released into the wild. Nutria damage crops and property, and they can contribute to severe soil erosion by eating through wetland plants. Their burrow systems can destabilize roads, bridges, levees, and golf courses. Nutria were wiped out in California in the 1970s, only to reappear in 2017, and the state has since re-established efforts to eradicate them.
6. Asian Carp
Asian carp, including bighead carp, black carp, grass carp, and silver carp — were brought to the United States in the 1970s to help keep fish farms clean. The fish escaped into the Mississippi River basin and have been outcompeting native fish for food and habitat ever since. Silver carp are notorious for jumping out of the water, posing a hazard to boaters.
7. Gypsy Moths
Gypsy moths were introduced to the U.S. in the late 1860s by Étienne Léopold Trouvelot, who thought they could produce better textiles than the silkworm. They escaped and spread throughout the northeastern U.S., stripping trees bare and leaving them susceptible to disease. They destroyed more than 2 million acres in less than three years.
The High Cost of Invasive Species
The cumulative impact of these and other invasive species in the United States is staggering. In addition to the immediate ecological harm, the economic burden associated with control, eradication, and loss of agricultural productivity is estimated to run into billions of dollars per year. Over time, this disruption can lead to loss of biodiversity, altered ecosystem functions, and increased vulnerability to other environmental pressures.
Approaches for Management and Control
Fighting invasive species requires a multi-faceted approach. Many preventative measures can be implemented, such as stricter regulations on the import of potentially invasive organisms and public education campaigns aimed at preventing accidental introductions. However, new invasions threaten to become widespread if not detected early and responded to quickly. Control methods vary from physical removal and trapping to biological control by introducing natural predators or pathogens.
The Role of Public Awareness
The general public awareness is another important factor in preventing and managing invasive species. Simple actions, like not releasing pets back into the wild, cleaning hiking boots and equipment to prevent the spread of seeds, and using local firewood, can have a big impact. This can be useful for management efforts, and citizen science initiatives, which allow volunteers to monitor and report invasive species, can help provide these data.
The Importance of Biosecurity Measures
Given the significant risks posed by invasive species, it’s essential to strengthen biosecurity measures at both national and international levels. These include enhanced screening of goods entering the country, quarantine procedures, and rapid response plans to deal with new invasions as they arise. Collaborative efforts among government agencies, researchers, and the public will be key to managing and mitigating the damage invasive species have on the U.S. environment and economy.
A Continuing Challenge
The battle against invasive species is an ongoing challenge that requires commitment and cooperation. The danger of new invasions lingers as trade and travel continue to grow across the globe. By understanding the pathways of introduction, implementing effective prevention and control strategies and raising public awareness, significant progress can be made to control invasive species and reduce negative impacts on our ecosystems.
