Invasive Species

From Encyclopedia of Wisconsin Environmental History
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Wisconsin Invasive species are defined in Wisconsin as "non-indigenous species whose introduction causes or is likely to cause economic or environmental harm or harm to human health". In other words, they are rarely seen as good. For example, look at humans. Human beings are one of the most invasive invasive species on this planet. Of our many impacts on the environment, the spread of invasive species is usually overlooked by the common person. Because we have touched every corner of the globe, we often spread invasive species, albeit usually by mistake. For this article however, we will just be focusing on Wisconsin and the invasive species within and surrounding the state in the waters. When learning about invasive species, it is important to remember that the ecosystem is one body, and even the slightest disturbance or change will effect everything.

Aquatic Invasive Species

Of the many invasive species in the state of Wisconsin, many think about fish. This is partly because people are more interested in fish than in plants, but it's also because of the ease of which fish can enter new waters. With human intervention however, that movement becomes even easier. They can cling to the bottom of boats or ships, or even trailers. They can be inside the boat or trailer, and then escape when put into another body or water. Sometimes they can be purchased as bait, and then "thrown away" into a body of water. The DNR has put laws in place to prevent the spread of aquatic life. These laws include the inspection of your boat/trailer before removing it from the water, draining all boats, motors, and equipment, and never move live fish away from a body of water. The penalty for not adhering to these laws is a hefty fine. An example of an aquatic invasive species is the Big Head Carp. Originating from Asia, they arrived in Wisconsin waters via the Mississippi River. It is believed that in some period during the 1970's, fish farms were releasing these fish into the river. It wasn't until the 1980's that they were spotted in the Mississippi, but it wasn't until relatively recently that they were spotted in Wisconsin waters. Their impacts include massive population increase because of intense spawning, injured boaters and fisherman because of the fish's high jumping ability (they jump when they become startled or frightened, and the sound of boat motors startles and frightens them), and consuming so much food that other species suffer. In fact, "it is believed that big head carp will compete for food with fish that are still in the larval stage, and fish populations decrease because the larval fish do not get enough food to survive."[1] Usually, one of the major threats imposed by invasive species is their consumption of food, but in this case it is especially damaging because it is specifically harming the young of other species.

Terrestrial Invasive Species

Terrestrial Invasive species is a broad term that can refer to animals, plants and insects. It can also encompass certain types of fungi and diseases. Non-native invasive species are classified as such because of their destructive and aggressive nature. Preventative measures are necessary if the world’s habitats and ecosystems are to remain sustainable and thrive. In fact, “the United States suffers from $1.1-120 billion per year in economic losses due to exotic, invasive species and approximately 42% of Threatened or Endangered species are at risk due to non-native, invasive species”. [2]

The Mute Swan

One poorly known invasive species is the Mute Swan, which many see as a beautiful native bird. However it is an invasive species that damages the environment via its food consumption. On a document regarding the species on the DNR website it states, "While feeding, mute swans will uproot plants instead of grazing on leaves, destroying the vegetation (7). Mute swans can eliminate certain plant species from the area (7). Mute swans can severely impact SAV beds (8)."[3] SAV stands for Submerged Aquatic Vegetation and is the common food for most water foul. However because of the swans larger size and non-native arrival, they are impeding on the natural consumption of SAV. This will not only impact other water foul in terms of amount of food, but SAV is also essential in oxygenating the water for fish.

The Emerald Ash Borer Beetle

An invasive species that is having a large impact in Wisconsin is the Emerald Ash Borer beetle. This insect is originally from Eastern Asia and most likely came over via cargo ships carrying ash wood. When the Emerald Ash Borers lay eggs, they lay them in the bark of an Ash tree. When the eggs hatch, they burrow into the bark and feed on the tree's tissues, specifically the tissue that transports nutrients, killing the tree. In the US, human intervention helps spread the Emerald Ash Borer by the moving of firewood or by the transportation of infant ash trees, that are already infected, into new forests.

The Japanese Beetle

The Japanese beetle is an invasive species that is devasting to native vegetation and expensive to control for Wisconsin gardeners and farmers if they need to eliminate this insect from destroying crops. Scientifically known as the Popillia japonica, and according to Chris Williamson of Wisconsin Horticulture, this invasive species “are a major pest of over 350 species of plants, including fruits, vegetables, ornamentals, field and forage crops, and weeds”.

Japanese beetles thrive on flowering plants and the leaves and foliage of practically any healthy native form of vegetation. Grape vines, rose bushes, rhubarb plants, (which technically have poisonous petals), don’t stand a chance against an infestation of this insect. They are resilient, similar to certain breeds of dangerous hornets in that they burrow and breed underground, so the average human doesn’t see the problem or extent of their reproductive capabilities until it becomes visible when a crop or garden is destroyed, or a child/adult is hospitalized due to a sting and allergic reaction. Regardless, the expense of removal of any pertinent threat is costly to both the individual and the economy as a whole.

“Removing beetles by hand, or trapping, may provide adequate protection for small plantings when beetle numbers are low. However, Japanese beetle adults are capable of migrating from other areas, and the presence of beetles on or near a plant will attract more beetles. Consequently, use of Japanese beetle traps often attracts more beetles, and results in subsequent damage to plants”. [4]

Invasive Plants and Vegetation

If the invasive species is not an animal, it is a plant that takes nutrients and carbon dioxide from native aquatic plants. This may not seem as damaging as an invasive animal, but in fact it can be even more damaging. Not only can this kill native plants, but the results of those deaths will also cause the deaths of native animals. It will take the nutrients killing the plants, which feed and provide oxygen to fish, which feed terrestrial animals. One example of an invasive plant is starry stonewort. Originally from Europe and Asia, it has spread to the US via ballast tanks of ships that transfer cargo over oceans and other unregulated water sources. It now resides in most of the Great Lakes and was discovered in Wisconsin in 2014.[5]

Black Locusts

The species of the Black Locust tree is an interesting topic in that it is considered a destructive and invasive species in Wisconsin but holds historic precedence and value for both European settlers and North American Native Americans. In Wisconsin, this species has been classified as “restricted,” in that, it damages local ecosystems through root suckering, spread and domination of landscapes, has no boundaries and is extremely hard to contain or quarantine.[6]

This is ironic considering this breed of vegetation has been considered one of the “founding” trees of the Industrial Revolution and trade and dates back even centuries before. Both Native American Indians, as well as, European settlers utilized this natural resource for the construction of weapons and lumber for construction. While it is common knowledge that European settlers used brutal tactics to ravage and abuse the environment for territory control and profit, it is important to note that the creation and trade of what is now known as a sturdy but invasive species of wood was a fundamental means of survival from different cultures and motives. [7]

Porcelain Berry

Porcelain Berries are a relatively new invasive threat in Wisconsin because little public education has evolved to inform people of their potential harm. This species, along with others, can be harmful not only to the environment but especially to children as bright and attractive colors can resemble edible grape-like fruits and berries which the average child will consume out of pure curiosity and the same could be said for some adults. While little research has been accumulated, the know fact is that this type of vegetation is a prohibited plant in Brown County, Wisconsin and research in Delaware has proved this to be a destructive invasive species to the environment introduced from Asia. [8]

Additionally, this theoretically edible is known to taste awful with a woody and slimy texture, thus health risks are currently unknown because it is simply one of the countless wild berries that becomes common sense, in that, if it is destroying the environment and doesn’t taste good, why take the risk of consuming it. [9]

Impact on the Environment and History

Even with all their negative impacts on certain ecosystems, sometimes an invasive species can offer something positive. For example, in Wisconsin one of the best known invasive species is the Zebra Muscle. It resides in lakes and is notorious for inflicting deep and painful cuts with its sharp shell. However, they are very useful in filtering toxins in the lake water. That being said, usually the negative greatly outweigh the positive impacts. Invasive species upset the natural order of an ecosystem by eating too much of other species' food, hunting native animals (which is currently happening with the reintroduction with wolves in Wisconsin, although they're not technically an invasive species), or destroying native ecosystems with their homes or reproduction. Also, they can come in a variety of ways. It won't always be possible to prevent all invasive species from spreading or being spread, but we can certainly try. It is a modern form of environmentalism, and not much is being done in those terms these days. But the government and citizens are trying to prevent the continuation of damage by invasive species.

The issue of invasive species is handled by the Wisconsin Department of Natural Resources, or the DNR. The first Department of Natural Resources was founded in 1921 in Michigan. Back when it was created, it was called the Department of Conservation and was a reaction to the realization that we didn't have an endless supply of natural resources. In Wisconsin, the Department was founded in 1968. For a century prior to 1968, Wisconsin had been setting up laws and regulations mainly regarding hunting and fishing. They were creating restrictions and licenses to control hunting and fishing. They founded the Wisconsin DNR mainly because of the same realization that Michigan had. The earliest recorded invasive species were recorded by the Michigan DNR, and one of the earliest ones was actually a plant. The Chinese Yam was believed to have been here since the 1800's and was introduced as a food source for humans. One of the earliest known invasive species in Wisconsin is the Zebra Muscle. It was discovered in Lake Michigan in the late 1980's and has since spread to a majority of the waters in the state. An even earlier example is the Sea Lamprey, which was discovered in all the Great Lakes in 1938. When the Wisconsin DNR was founded, it was one of the first species it sought to control.[10]

Invasive Species Control Measures

Common knowledge of control measures generally relies on mechanical, chemical and physically preventative actions and procedures to change and/or maintain naturally occurring events. One must choose wisely and consider not only their own well-being and goals, but also their overall “footprint” on their own land, their local ecosystem and the global impact, as a whole.

Mechanical Factors

Much change can be developed by mechanical means. An individual can cut down an invasive tree and replant a native breed to help facilitate the balance that invasive species have caused. The same could be said for invasive berry vines. Additionally, wild and invasive grass can be cut and collected for proper disposal as opposed to pretending it doesn’t exist and allowing it to flourish.

Chemical Control

Chemical control could be considered just as invasive as an invasive species itself in modern times. With the ever-growing popularity of organic products in recent times, a lot of natural science debate is relevant considering the rising rates of health ailments is anything but secret. However, due to abuse, waste and greed, especially from unstoppable corporations, pesticides are necessary to maintain the speed of their agricultural needs and the sustenance of a malnourished world. In other words, the world has millions of people starving to death and certain pesticides are necessary to ensure that crops aren’t destroyed by invasive species such as locusts. Control from a home perspective is similar. One could annihilate an infested garden with weed killer in an attempt to start from scratch but would essentially poison their soil and by the time it heals, the problem will return with its fertility and in the meantime, children and pets can be harmed in the process. Thus, chemical solutions must be used in extreme moderation or alternate natural forms deserve research.

Preventative Action

While the extermination or elimination of invasive species is practically impossible, preventative action is possible in many ways to at least help reduce the spread and thriving of many unwanted creatures. The greatest way invasive species are transferred are from water enthusiasts who don’t clean their equipment when removing from one water source and then using a new source. Zebra mussels are often transferred in this manner, but many species of invasive plants are transferred in a similar fashion and also by illegal sales. The sale and transfer of firewood is also highly regulated as this transfer of vegetation can easily become a means of conveyance for invasive insects. Several great volunteer programs also exist to aid in prevention such as the Citizen Lake Monitoring Network.[11]


  1. Aaron Conklin, "Bighead Carp (Aristichthys nobilis)", University of Wisconsin Sea Grant Institute (2012): accessed December 3, 2015,
  2. Pimentel, Zuniga and Morrison, "Invasive Species 101", "Invasive.Org", (2005): Accessed December 20, 2018,
  3. Bill Frederickson, Department of Natural Resources Review of the Mute Swan (2007): accessed December 3, 2015,
  4. Chris Williamson, "Japanese Beetle", "University of Wisconsin-Extension", (2013): Accessed December 19, 2018,
  5. M. McCarthy and A. Fusaro, "Starry Stonewort", United States Geological Survey (2012): accessed December 3, 2015,
  6. Susan Wieseler, "Least Wanted: Black Locust", "Plant Conservation Alliance, Alien Plant Working Group", (2006): Accessed December 19, 2018,
  7. Wesley Greene, "Black Locust: The Tree on Which the US Was Built", "Colonial Williamsburg Foundation", (2015): Accessed December 19, 2018,
  8. John Harrod, "Controlling Backyard Invaders", "Delaware Nature Society", (undated): Accessed December 19, 2018,
  9. Rockland Forager, "Porcelain berries are too pretty too eat", "Hot Topix", (2012): Accessed December 19, 2018,
  10. Bill Frederickson, Department of Natural Resources Review of the Sea Lamprey: accessed December 8, 2015,
  11. Erin McFarlane, "Prevention", "Wisconsin DNR", (2016): Accessed December 20, 2018,

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