The Problem

Wisconsin Landscapes are in Jeopardy due to Invasive Plants!

An invasion is under way that is endangering our health, undermining our economy and destroying our most precious natural treasures. The incursion comes not from foreign armies, political terrorists, or extraterrestrials. Instead, the stealthy aliens are invasive species. These plants and animals have been introduced – either intentionally or by accident – into areas outside their natural ranges. Unchecked by natural controls, invasive species are spreading across our lands and through our waterways, and wreaking havoc with already fragile native species and ecosystems. Invasive species are now regarded as the second-leading threat to imperiled species, behind only to habitat destruction.

Invasive plants can change the food web in an ecosystem by destroying or replacing native food sources. Invasive plants may provide little or no food to value for wildlife. Some invasive plants are capable of changing the conditions in an ecosystem, such as changing the soil chemistry. Not only do invasive plant species pose a direct threat to native species by out-competing them for space or nutrients, but they also pose indirect threats.

The following are only a small example of how invasive plants can pose a threat to:

Your Health

Wildfire Risks

Your Hunting

Tree Regeneration

Native Birds

Detrimental to Your Health

Wild parsnip (Pastinaca sativa) grows along roadsides, in pastures, edges of fields and in prairies. Although it is an invasive plant, wild parsnip is growing in all of Wisconsin’s 72 counties. Wild parsnip is one invasive plant that causes intense, localized burns from the chemicals in its sap. Burns from wild parsnip can be so severe that they require medical attention, possible hospitalization. Unsuspecting children are especially at risk to this harmful invasive.

Japanese barberry (Berberis thunbergii), creates an environment where ticks and white-footed mice thrive and reproduce, increasing the risk of the transmission of Lyme and other potentially dangerous infectious diseases. Studies have shown that an acre of forest containing Japanese barberry has over 10 times the number of Lyme disease-carrying ticks, then an acre of forest without barberry.

Increases Wildfire Risks

Do you know, one reason that Western wildfires are becoming more and more dangerous is because of an invasive plant? Cheatgrass (Bromus tectorum) is spreading across the country. It outcompetes native plants and dries out early in the growning season, making it combustible and is twice as likely to burn as native plants.

Thankfully, cheatgrass is not a huge threat for Wisconsin yet, but the invasive phragmites (Phragmites australis) is becoming one. Phragmites has been linked to increased fire risk. It can burn at a rate of one to three football fields a minute. On the East Coast, government officials have issued a fire protection plan that requires residents of high-risk areas near the shore to use flame-resistant materials for new roofs, decks and fences and to mow around houses and buildings.

Negatively Impacts Your Hunting Success

Studies have shown that most of the impacts on wild turkeys are indirect because of long-term habitat changes. Buckthorn (Rhamnus spp.), garlic mustard (Alliaria petiolata) and other invasive species make it difficult for forests to regenerate resulting in fewer acorns and roost trees. Fewer acorn-producing trees mean lower food availability and reduced habitat quality for wildlife such as white-tailed deer, squirrel, grouse, and turkey.

The fact that these species tend to establish and grow quickly means that they take up usable space and resources that could be utilized by native species. Many times, it is these native species that provide critical habitat and forage that many different species like whitetail deer require throughout the year. If left unchecked, these are some of the invasive species that can ruin your deer hunting and have a detrimental impact to the overall quality of the habitat on your property. And in cases where invasive species are too established, wildlife such as whitetail deer can begin to seek out other areas where the forage and habitat are of higher quality.

Reduces Tree Regeneration

Japanese barberry (Berberis thunbergii), was introduced to the United States in the late 1800s as an ornamental plant. It is used widely as landscape material, due in part to its resistance to deer browsing. Where deer numbers are high, palatable native species are replaced by barberry. It thrives both in full sun and deep shade. Like many invasive shrubs, it leafs out early, retains its leaves late into fall and forms dense thickets, shading out native tree seedlings. Barberry also alters soil conditions to its benefit. Deer avoid eating this spiny shrub, which means they browse more on native trees, slowing the growth of seedlings or even killing them.

Invasive plant species will increasingly spread and respond positively to changing climatic conditions. Invasive plants outcompete native vegetation, reduce plant diversity, and inhibit forest regeneration. Some species, such as Oriental bittersweet (Celastrus orbiculatus), can take over a tree crown and weaken or even kill a tree while spreading seeds, forming dense thickets and suppresses native plant growth.

Decreases the Number of Native Birds

Invasive plants affect birds in several ways. They replace native vegetation needed for food, shelter and nesting. Invasive plants, such as multiflora rose (Rosa multiflora), produce fruit that is of lower nutritional value to our native birds than the fruit from our native shrubs, like blackberry, blueberry and dogwood species. Invasive plants are also unpalatable or even toxic to our native insects. What negatively affects insects, will negatively affect birds. Many native song birds feed their young on insects, so fewer insects means that free young birds reach maturity.

Other studies have shown that certain species of birds, such as the northern robin and wood thrush, are lost to predation when they nest in invasive, exotic shrubs, such as amur honeysuckle (Lonicera maackii) or buckthorn (Rhamnus spp.), as opposed to nesting in native shrubs with which they have co-evolved.

Native vegetation supports a much greater variety of birds than areas infested with the invasive plants.

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