Imagine being flung into an ecosystem not your own, where you not only survive but thrive—to the point where you begin to shake the very foundations of your new home.
Welcome to the world of invasive species—non-native life forms that can potentially wreak havoc on both the environment and the economy.
Take the Burmese python for example. Its introduction to the Florida Everglades displaced the area’s smaller local kin, leaving them scrambling for resources and shelter.
The concept of invasive species was first defined in President Clinton’s Executive Order 13112 – Invasive Species in February 1999. But let’s clear up a common misconception while we’re at it: invasive species aren’t always non-native. Sure, many are, but don’t be fooled into thinking the two terms are synonyms.
Many non-native species have proven to be economically beneficial, posing no significant danger to their new environments. However, invasive species frequently have disastrous effects on native species, ecosystems, and the economy itself.
Still need convincing? How about this staggering number: the global economic cost of invasive species over the past half-century is a whopping $1.288 trillion, according to the US Department of Agriculture’s National Invasive Species Information Center.
These colossal costs stem from efforts made to prevent, detect, control, and manage these unwelcome guests. With that said, are you aware of what’s invading your home? Let’s find out!
Top 10 US States With the Most Invasive Species
The United States is home to over a thousand confirmed instances of invasive species, with a few states having an especially high number.
To monitor and record the distribution of invasive species and pests across the country, the Early Detection and Distribution Mapping System (EDDMapS) is employed. This mapping system offers a thorough database of invasive species occurrences within the US, developed by the Center for Invasive Species and Ecosystem Health at the University of Georgia.
To ensure accuracy and reliability, information about invasive species and newly reported entries is updated and checked on a regular basis in the EDDMapS database. The following list presents the top 10 US states with the highest number of documented invasive species.
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Florida is home to 2,032 invasive species, holding the record for the most invasive species compared to all other states.
The Florida Fish and Wildlife Conservation Commission has a Nonnative Fish and Wildlife Program in place to help prevent and minimize the impact of invasive species in the state.
Some notable Florida invasive species causing negative economic and environmental impacts include the Burmese python and the European starling.
The Burmese python is native to Southeast Asia. It was introduced to the state as an escaped or released pet and has since threatened native Florida wildlife and ecosystems.
Burmese pythons are heavy-bodied and much larger than native Florida snakes. They pose a threat due to their opportunistic feeding habits and ability to outcompete native species. The Florida Everglades are home to a sizable population of Burmese pythons.
The European starling is a widely distributed invasive species native to Europe and northwestern Asia. European starlings were first introduced to the US in 1890.
About 100 birds were intentionally released in New York City’s Central Park by amateur ornithologist and Shakespeare-enthusiast Eugene Schieffelin. He was inspired to release the birds because they were referenced in a play by Shakespeare.
European starlings are capable of thriving in a wide variety of habitats, including urban areas. The first report of a European starling in Florida was in 1918, near Jacksonville.
European starlings have the ability to wreak havoc on buildings, automobiles, food availability, and agriculture. It is common for large flocks to cause damage to crops and drive native birds from their nesting areas.
California takes second place on the list, with 1,722 invasive species in the state. Commercial shipping is one of the main sources of the unintentional introduction of invasive species in California.
During the 1700s, Russian and Spanish settlers brought domestic pigs (Sus scrofa) to California. Then, in the 1920s, a landowner in Monterey County introduced a subspecies of Sus scrofa, the European wild boar.
The wild boar, which was native to Eurasia and northern Africa, bred with domestic pigs and became feral. Because of this, feral pigs are now widespread throughout the state.
The wild pigs are now present in all but two counties in the state. They pose several threats to California’s economy and ecosystems, including:
- Spread of pathogens, such as E. coli and Salmonella
- Devastation of food sources of native wildlife
- Damage to gardens, farms, and other lands due to rooting behaviors
The New Zealand mud snail (NZMS) is another invasive species that poses a threat to California’s economy and environment. The snails are named for their shell color and pattern, which resemble zebra stripes.
The species is native to rivers and lakes in New Zealand but has found its way into many lakes and river systems throughout the American West. It was first documented in California along the Owens River in 2000.
Female NZMS have a fast reproduction process, which allows them to take over areas quickly. They harm ecosystems by displacing and outcompeting native invertebrates and reducing aquatic insect populations.
Illinois has 1,124 documented invasive species. The Illinois Wildlife Action Plan (IWAP) was established by the Illinois Department of Natural Resources (DNR). It includes an Invasive Species Campaign program that works to identify threats from invasive species.
The campaign establishes plans for prevention, control, and eradication of invasive species with the help of the Illinois DNR staff and other partners.
The common carp and Japanese beetle are two invasive species negatively impacting wildlife and ecosystems in the state.
The common carp is native to Asia and Europe. It was documented in Illinois in the late 1870s.
The rapid reproduction process of common carp has led to their widespread distribution across almost every state in the eastern half of the US.
Females are capable of laying more than 50,000 eggs per brood, which take only 12 days to hatch. Sporadic populations occur in the West.
The Japanese beetle is a common pest throughout Illinois, but larger populations occur in urban areas. These beetles are easily identifiable by their metallic green heads and copper-colored backs.
Japanese beetles can devastate a wide variety of plants that they feed on, such as raspberry, rose, crabapple, and willow plants. They emerge during the summer and overwinter in the ground.
Large infestations can result in damaged gardens, lawns, tree leaves, and other desirable vegetation.
Wisconsin is home to 1,047 invasive species. The state enforces the Invasive Species Identification, Classification, and Control Rule to regulate and prevent the introduction of invasive species.
The Chinese mystery snail is an eastern Asian freshwater snail species. The invasive snail was first documented in the Great Lakes region in the 1940s. It arrived in North America in San Francisco as a food item in Chinese markets in the late 1890s.
Although their ecological impact is largely unknown, Chinese mystery snails may pose a threat to native freshwater snail species, wildlife, and humans through the transmission of diseases and parasites.
The Great Lakes area is home to an invasive species called the zebra mussel. Zebra mussels originate from the Caspian Sea, Black Sea, and Sea of Azov. Their introduction to the US is believed to have come from commercial cargo ships carrying ballast water.
These hardy mollusks are capable of surviving out of water for several days, which aids their potential to be transported long distances.
Due to their negative impact on native aquatic species’ food sources, zebra mussels pose a threat to local ecosystems. They can kill off native mussels by latching onto other species’ shells and smothering them.
Additionally, they have a reputation for clogging water intake pipes and damaging boat equipment.
5. New York
New York houses 1,024 invasive species. New York’s Department of Environmental Conservation (DEC) established the Bureau of Invasive Species and Ecosystem Health (BISEH) to address invasive species threats.
The DEC is in charge of several wildlife and environmental protection initiatives that lay the groundwork for how to deal with invasive species.
The spruce budworm is one of the most important pests in New York and other eastern US states. Spruce budworms are moths found in northern spruce and fir forests in the eastern half of the US and Canada.
New York is one of the most affected states by the species. The spruce budworm feeds and bores into spruce and fir trees, causing significant damage.
Outbreaks occur every few decades. The first outbreak was documented in the early 1800s in Maine. Browning needles in late summer is one of the signs of spruce budworm damage.
Red-eared sliders are terrapins native to the south-central US but considered invasive in New York. A subspecies of the pond slider, it’s a widespread but often appreciated invasive species. They can be found in large numbers in New York City parks that have permanent water features.
Introduction outside of their native range is likely due to released or escaped pets. Red-eared sliders can outcompete native turtle species and transmit harmful diseases and parasites that native species aren’t immune to.
Minnesota has 1,010 invasive species documented. In response to Executive Order 13112, the Minnesota Invasive Species Advisory Council (MISAC) was established in 2001.
Several local, state, and federal agencies and other partners work together to meet the goals outlined in the Minnesota Management Plan for Invasive Species.
The rusty crayfish is defined as an established, high-threat invasive species in the Minnesota Management Plan for Invasive Species.
Rusty crayfish are crustaceans native to freshwater habitats in the southern US. However, these species are considered invasive in Minnesota and other states outside of their native range.
Fishermen who used the crustaceans as live bait are most likely responsible for introducing them to Minnesota. Since then, Minnesota has had restrictions and regulations in place for the transport, sale, possession, and use of rusty crayfish.
The large aspen tortrix is another invasive species that negatively impacts aspen forests in Minnesota. This moth species is native to North America, but its damaging effects on aspen trees make it invasive.
Its ability to defoliate aspen trees causes severe outbreaks that occur every few years. If the same trees are repeatedly affected, it can cause branches to die off. Larvae feed on the leaves, completely stripping away the leaf tissue and only leaving the veins.
Large aspen tortrix populations are usually naturally controlled by insects and birds that eat them.
There are 1,001 invasive species documented in Michigan. The state is divided into more than 20 Cooperative Invasive Species Management Areas (CISMAs) that are monitored by various groups and individuals who work to oversee invasive species impacts.
Some groups involved in invasive species research and monitoring in Michigan include:
- Aquatic Nuisance Species (ANS) Task Force
- Michigan Invasive Species Coalition (MISC)
- National Association of Invasive Plant Councils (NAIPC)
- North American Invasive Species Network (NAISN)
To address the threats posed by aquatic and terrestrial invasive species, several state management plans have been put in place.
The round goby is an Eurasian fish species with an established population in the Great Lakes. This freshwater fish was likely introduced to the area through ballast water from commercial cargo ships.
In non-native habitats, round goby fish have the ability to outcompete native fish due to their voracious appetites. The native sculpin fish of the Great Lakes is frequently mistaken for a round goby.
The spongy moth, also called the gypsy moth, is an invasive species native to Europe and Asia. It’s found in much of the northeastern US and westward to Minnesota.
Spongy moths threaten the quality of oak and aspen trees. Their feeding habits can cause trees to die due to severe defoliation.
Spongy moths were introduced to North America by an artist named Étienne Léopold Trouvelot in 1869. Trouvelot attempted to breed the species, but some escaped, causing an outbreak in his neighborhood of Medford, Massachusetts.
Washington has 954 invasive species. Under the Washington State Recreation and Conservation Office, the Washington Invasive Species Council was established in 2006 to combat harmful invasive species.
To aid in the detection, prevention, and eradication of invasive species, the Council currently has a strategic plan in place for the years 2020–2025.
The nutria is an aquatic invasive species that lives around wetlands, lakes, and other bodies of water in the state of Washington. Nutria are large rodents native to South America. In the early 1900s, they were transported to the US for aquatic vegetation control and the fur trade.
The burrowing and feeding habits of nutria pose a major threat to wetlands and native species. Nutria will gnaw down vegetation and tear up roots that are essential to holding wetland soils intact.
The invasive Douglas-fir beetle is a threat to Douglas-fir trees in Washington. Although a native species to western North America, the Douglas-fir beetle is invasive because it negatively impacts the quality and life of its host trees.
Large infestations can cause tree mortality of 100 or more Douglas-fir trees in one area. These bark beetles have a one-year lifespan, with 2-3 generations occurring between mid-spring and late summer.
Pennsylvania is home to 899 documented invasive species. The Governor’s Invasive Species Council is responsible for identifying current and potential invasive species and implementing the state’s invasive species management plan.
Two notable and widespread invasive species in the state include the American bullfrog and the European corn borer.
The American bullfrog is native to the central and eastern portions of the US. However, it’s classified as an invasive species in Pennsylvania.
Due to their opportunistic feeding habits, American bullfrogs outcompete other frog species. Females can lay up to 20,000 eggs in one brood, whereas other native frogs usually only lay up to 5,000 eggs.
The European corn borer is another non-native and invasive moth species that threatens corn-growing regions across the US. The College of Agricultural Sciences at PennState Extension recognizes the species as “one of the five most important vegetable pests” in the state.
European corn borer larvae weaken the stalks of corn due to their boring and feeding habits. Large waves of the pest can cause extensive crop failure and loss.
European corn borers cause enough damage to corn production that it is factored into crop planning. They can cost farmers more than $1 billion each year due to crop damage.
Last on our list is Indiana, which has 885 invasive species documented. Several groups and government agencies are involved in identifying and managing invasive species in the state, including the:
- Indiana Invasive Species Council
- Indiana DNR
- Indiana’s Division of Fish & Wildlife
- Indiana’s Division of Entomology & Plant Pathology
The European pine shoot moth and its larvae are responsible for attacking pine trees in the northern and central regions of Indiana.
Unlike the moths previously discussed, these invasive moths usually don’t cause tree mortality. However, they affect the commercial pine industry, in which the quality and appearance of trees are important.
Infestations of European pine shoot moths can lead to stunted tree growth and deformation.
The Japanese honeysuckle is a fairly common vine found throughout the eastern half of the US. Although its sweet fragrance may be enticing, it’s an invasive species native to eastern Asia.
It was first brought to the US in 1806 as an ornamental plant. However, its spread has led to the smothering and mortality of native vegetation.
Small infestations may be removed by hand. On the other hand, larger infestations may need to be mowed and followed up by treatment to be completely eradicated.
Top 5 US States With the Least Number of Invasive Species
While invasive species pose significant challenges in many parts of the United States, certain states have managed to maintain lower levels of invasion.
The susceptibility of a state to invasive species can be influenced by various factors, including its history of invasion, environmental conditions, and the effectiveness of management strategies.
Here are the top 5 US states that boast the fewest recorded invasive species:
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Alaska has the least number of invasive species, with 339 documented.
Alaska has a short growing season and harsh conditions that many plant and animal species can’t survive. However, climate change and increased human activity have made the Arctic region more vulnerable.
Some invasive plants and animals that manage to conquer the wild lands of Alaska include:
- Common dandelion
- Reed canary grass
- American bullfrog
- European green crab
- Asian carp
- New Zealand mud snail
There are several groups and management plans responsible for combating invasive species in the state. The Alaska Invasive Plant Management Team (IPMT) and the ANS Task Force are two examples of groups that work to prevent, control, and eradicate invasive species.
In 2021, the Alaska Department of Fish and Game established a number of regulations that prohibit the sale, importation, transportation, and release of banned invasive species. Permits may be attainable for certain species.
2. North Dakota
North Dakota has 379 invasive species. One of the most abundant invasive species in North Dakota is the leafy spurge plant.
Leafy spurge has impacted over 1 million acres of land in the state. It also impacts livestock, as cattle tend not to feed in areas overwhelmed by leafy spurge.
According to the Defenders of Wildlife conservation organization, infestations of leafy spurge have cost the states of North Dakota, South Dakota, Montana, and Wyoming about $129 million.
Other invasive species found in North Dakota include:
- Emerald ash borer
- Gypsy moth
- Asian long-horned beetle
The North Dakota ANS Management Plan was established in 2005 to address potential invasive species impacts. It also lays out plans to lessen the blow of established aquatic invasive species.
The Aquatic Invasive Species Committee is responsible for implementing the guidelines set forth in the ANS Management Plan.
Emergency regulations were established in 2015 to address the discovery of zebra mussels in the state. Thanks to the management plan, no new zebra mussel infestations were detected in 2016.
There are 476 invasive species in Wyoming. The dalmatian toadflax is the most abundant invasive species in the state, with 59,190 records.
Dalmatian toadflax can be found in a variety of open habitats, such as fields and pastures. It was introduced to North America around the late 1800s and early 1900s as an ornamental plant.
Despite its decorative appearance, dalmatian toadflax is considered a noxious weed. This means it’s harmful to agriculture, ecosystems, or livestock.
Some of the top aquatic invasive species in Wyoming include:
- Zebra mussel
- Rusty crayfish
- New Zealand mud snail
- Asian carp
According to the Wyoming State Forestry Division, the mountain pine beetle and spruce beetle are major insect pests in the state’s forests. Over the past few decades, these pests have caused tree mortality across millions of acres of land throughout the state.
Invasive plants are managed by the Bureau of Land Management (BLM) Wyoming Weeds and Invasives Program. The BLM is working in partnership with several local and state agencies and private landowners to implement the program.
The Teton Conservation District encourages individuals who want to volunteer to help control invasive species in the Teton Valley to join their Weed Warriors program.
Arkansas has 592 invasive species documented.
The tropical soda apple shrub is one of Arkansas’ top 10 invasive species. The shrub is native to South America and was first identified in Florida in the late 1980s.
Tropical soda apple shrubs invade open habitats, such as pastures, fields, and parks. It impacts agriculture, livestock, and native mammals due to its dense growth.
The Support Committee of the Arkansas Landscape Management Plan is made up of representatives from state and federal agencies.
The plan is designed to educate landowners about the control of invasive species and other best management practices to support the overall landscape and its wildlife.
Lastly, Delaware has recorded 501 invasive species.
Various government and nonprofit organizations and teams of scientists, botanists, and ecologists make up the Delaware Invasive Species Council (DISC).
The Council is responsible for implementing strategies that minimize the impact of invasive species and prevent the introduction of new invasive species.
Some invasive species monitored and managed in Delaware include:
- European corn borer
- Japanese beetle
- Multicolored Asian lady beetle
Several invasive species laws are enforced by the state’s Department of Agriculture (DDA) and Department of Natures Resources and Environmental Control (DNREC).
For example, beekeepers in Delaware need to register with the state, seek a permit for importing bees and used equipment, and are subject to an annual examination of their apiaries.
Invasive Species Prevention, Control, and Eradication Success Stories
Many invasive species have been eradicated thanks to the combined efforts of local, state, and federal agencies, as well as other groups, academic institutions, and private citizens.
Partnerships are a vital component in invasive species management plans because it takes the collaboration of several teams and individuals to accomplish management goals.
Native plant and animal species, as well as their ecosystems, benefit from the successful prevention and eradication of invasive species.
Without the implementation and enforcement of various wildlife and land management plans and programs, it would be difficult to control and eradicate invasive species.
Eradication of the European Grapevine Moth in California
The European grapevine moth is an invasive species native to Europe. It’s also considered an invasive species in Africa, South America, and the Middle East.
The invasive moth was first found in California at a Napa County vineyard in 2009.
State and federal agencies, researchers, vineyard owners, and California residents banded together to help with the control and eradication of the species.
Some of the rapid response efforts to eradicate the species included:
- Inspections of vineyards
- Outreach and education programs
- Insecticide treatments
- Traps placed across the state for detection
The European grapevine moth poses a major risk to all grape varieties found in vineyards. An Early Detection and Rapid Response approach was taken, which led to the eradication of the species by 2016.
If the European grapevine moth population got out of control, it could’ve had a devastating impact on vineyards, wine, and grape production in the famous Napa Valley wine region.
A follow-up plan for post-eradication was created in 2016 to continue monitoring procedures to prevent reintroduction.
Eradication of Nutria in the Blackwater National Wildlife Refuge, Maryland
Nutria are major pests that can destroy wetlands, which are highly productive ecosystems that provide breeding and feeding grounds for many native species.
Since its introduction to the Delmarva Peninsula of Maryland in the 1940s, nutrias have destroyed thousands of acres of marshlands.
Several state and federal agencies, including the Maryland DNR and US Fish and Wildlife Service, spent decades working to eradicate the species in the Blackwater National Wildlife Refuge.
Sea-level rise and land subsidence, combined with the nutria’s harmful feeding and burrowing habits, devastated over 5,000 acres of the refuge.
In 2004, it was estimated that nutria damage caused an annual loss of about $5.8 million. The last known nutria was removed from Maryland in 2015 with the help of dogs trained to detect nutria scat, trapping, and data gathering.
In September 2022, the Chesapeake Bay Nutria Eradication Project (CBNEP) formally announced that the Blackwater National Wildlife Refuge was free of nutria.
Prevention of Invasive Mussels in the Blue Mesa Reservoir, Colorado
Prevention and early detection of invasive species are the most effective methods to prevent invasive species from causing harm to native wildlife and ecosystems.
Colorado’s largest reservoir, the Blue Mesa, has continuously been monitored and protected from a zebra mussel and quagga mussel invasion.
In 2008, the Curecanti National Recreation Area implemented a prevention program that involves zebra and quagga mussel inspections on watercraft before entering the Blue Mesa Reservoir.
Zebra mussels are native to the seas of eastern Europe. Quaggas are native to the Dnieper River in Ukraine. Both species are non-native and invasive in North America.
Another initiative to prevent invasive mussels from entering the waterways of the American West was implemented in 2017. State wildlife agencies and national parks have worked together on the Safeguarding the West from Invasive Mussels initiative.
If an infestation of invasive mussels occurred in the Blue Mesa Reservoir, it could cost the state millions of dollars to control and remove the species.
Thanks to those involved in the prevention programs and campaigns, Colorado is free of quagga mussels. According to Colorado Parks and Wildlife, the only known infestation of zebra mussels in the state occurs in Highline Lake.
What Does the Government Do to Stop Invasive Species
In order to deal with potential and existing invasive species issues, it is crucial that local, state, and federal agencies coordinate prevention and management plans.
The most effective method to manage invasive species is through an Early Detection and Rapid Response strategy. Not only is it more cost-effective, but it’s also easier to identify threats from invasive species and tackle them before populations get out of hand.
If invasive species are already established, several control and management strategies are used, such as:
- Biological control: Use of natural enemies to control and remove pests, such as releasing native insects and other organisms that feed on the invasive species.
- Chemical control: This method can be expensive and have negative impacts on the environment. It involves the use of various chemicals, such as insecticides and pesticides, to control and manage invasive species.
- Mechanical and physical control: These methods include manual removal techniques that act as a temporary solution to get rid of invasive species. Some techniques include mowing, tilling, hand-pulling, digging, and removal of invasive species by hand.
The creation of the National Invasive Species Council under Executive Order 13112 helps coordinate federal invasive species activities. Representatives on the Council include members of the US Department of Agriculture (USDA) and the US Department of the Interior (DOI).
Several intergovernmental agencies and committees are involved in helping the Council address invasive species issues, including the ANS Task Force and the Invasive Species Advisory Committee (ISAC).
Together, these agencies coordinate with conservation organizations, industry groups, academia, and private landowners to prevent, detect, and control invasive species through a series of programs and campaigns launched at the local, state, and federal levels.
How You Can Help
One of the most crucial aspects of management plans is informing the public about the difficulties associated with invasive species.
There are several opportunities available for you to get involved in helping with invasive species prevention and management.
Local and state volunteer programs may be offered in your area to go out into the field and help remove invasive species.
Other ways you can help prevent, control, and eradicate invasive species include:
- Use the Wild Spotter app on your mobile device to learn how to identify and help map the spread of invasive species.
- Clean off your clothes and equipment after exploring the great outdoors to ensure you’re not carrying any hitchhiking invasive species or their eggs.
- Do not remove or transport any plants, seeds, or other things from their habitat. If you believe you’ve found an invasive species, contact your local or state wildlife agency to report it.
- Properly dispose of live bait.
- Do not import invasive animals or plant seeds that aren’t native to your area.
- Research how to identify invasive species and use tools recommended by government agencies to report findings.
The USDA Animal and Plant Health Inspection Service offers a guide specific to certain outdoor activities that you can follow to help prevent the spread of invasive species.
Knowing the difference between native and invasive species in your area is an important first step. Preventing and controlling invasive species is a collective effort. It takes large teams and the help of the general public to accomplish invasive species management goals.
To maintain a healthy environment for native wildlife, it is crucial to stop and slow the spread of invasive species. Many invasive species threaten native animal populations because they are able to reproduce more quickly and find more food and habitat than the native species.
Invasive species have the ability to spread diseases and parasites to native plants and animals that aren’t immune to them. Some invasive species can also transmit pathogens to humans, such as E. coli and Salmonella.
Threatened and endangered native species are especially vulnerable to invasive species. Most invasive species are introduced through human activities, whether intentional or accidental.
A little bit of caution and awareness can go a long way toward preventing the accidental spread of invasive species.
- We wanted to find out which US states have the most invasive species. To do this, we used data from the Early Detection and Distribution Mapping System (EDDMapS) of the Center for Invasive Species and Ecosystem Health at the University of Georgia, which revealed the number of invasive species for every US state, as well as the name of the species.
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