Invasive plants threaten the integrity of ecosystems and natural processes by displacing native plants and damaging wildlife habitat and food sources.
It’s difficult to imagine what America may have looked like before European settlers arrived. America’s flora and fauna were once abundant and biodiverse. But with colonization came deforestation and extirpation of many of our large predators. And deforestation is just part of the story. Invasive plants share a burden of blame for habitat loss and biodiversity plummets.
Whether by land or by sea, people have been moving goods for centuries. As transportation methods evolved, moving goods from one area of the country (or continent or globe) became easier. But while the transport of raw materials and products lead to economic development, it also brought some negative unintended consequences. Plants and animals native to one area of the world often ended up across the globe, and while some species had difficulty adapting to their new environment, others thrived. Those species that thrived sometimes became invasive, causing great economic and environmental damage.
What are Invasive Plants?
We use many words to describe invasive species, but several standard definitions prevail. The following definitions come directly from President Bill Clinton’s 1999 Executive Order about invasive species:
Invasive Plant: A plant that is both non-native and able to establish on many sites, grow quickly, and spread to the point of disrupting plant communities or ecosystems.
Native Plant: A plant that is a part of the balance of nature that has developed over hundreds or thousands of years in a particular region or ecosystem. Only plants found in the United States before European settlement are considered to be native to this country.
Introduced Plant – with respect to a particular ecosystem, any plant, including its seeds or other biological material capable of propagating that plant, that is not native to that ecosystem.
For more plant definitions, visit our article on native plants.
Why are invasive plants a problem?
Invasive plants can dominate an entire ecosystem within just a few short years after establishment. Established invasive plant communities decrease biodiversity and result enormous control costs for landowners and landscape managers. In fact, resource managers estimate the control of invasive species costs Americans $138 billion each year in economic damages. This cost includes damage from both invasive plant and animal species. In a 2001 study, scientists estimated that invasive plants cause $1.4 trillion in damage worldwide. Given the rate at which invasive plants reproduce and spread, the cost of invasive plants today is likely to be much higher.
The negative impact of invasive plants is apparent in both public and private sectors. Loss of crops, impediment of recreational activities, and reduction of aesthetic value are only a few of many examples of how invasive plants impact the economy. The agricultural industry incurs an estimated $27.9 billion in crop loss occurs each year due to non-indigenous plants.
The shift from exotic to invasive
Although the negative impacts of invasive plants are well known today, the benefits of these plants are what encouraged their introduction into the American landscape many years ago. Early colonists began introducing plants to the U.S. for use as food, medicine, and for ornamental purposes. Some plants, however, were introduced accidentally in ballast water from ships, in animal feed, or in grain. In their book, Invasive Plants: Guide to Identification and the Impacts and Control of Common North American Species, Kaufman and Kaufman (2007) describe how plant introduction was once a popular activity saying, “Introducing new plants to America was once so popular that the activity was encouraged by the United States Office of Plant Introduction whose officials once boasted of introducing 200,000 species and varieties of non-native plants (p. 13).” (Even more surprising, perhaps, is the notion that the United States once had an Office of Plant Introduction.)
From Pretty to Problematic
Some of the many plants considered invasive in the U.S. share an ironic history. The U.S. Soil Conservation Service, for example, promoted the use of multiflora rose for erosion control, wildlife habitat and food, and as a soft crash barrier in highway medians. Years later, we realized that the attractive plant is highly invasive and can cause detrimental damage to ecosystems. Landscape managers and homeowners have spent countless hours removing the prickly plant from sensitive areas ever since. Privet and barberry share similar histories. Barberry and privet share similar histories. Once promoted in agriculture as living fences and touted as quick-growing and attractive ornamentals, barberry and privet are now considered highly invasive in some areas. Despite their invasive label, varieties can still be found for sale in many nurseries today.
Lend a Helping Hand
While the war against invasive plants is perhaps most apparent in agriculture and natural resource industries, gardeners and landscapers also share a portion of the damage, and the blame. Many nurseries continue to sell varieties of invasive plants, contributing to their spread. But you can help in the effort to eradicate and prevent invasive plant invasions.
Always research plants before you purchase or plant. Check with your state’s Department of Natural Resources or Department of Agriculture for up-to-date lists of invasive plants in your region. If you notice problematic plant, take action! Remove and replace invasive plants with something that will play nicely with other plants while supporting wildlife (think native!).
Can a native plant be invasive?
By definition, a native species cannot be invasive. However, there are some native species that are aggressive. We call these plants opportunistic native plants. An opportunistic native plant is a native plant that is able to take advantage of disturbance to the soil or existing vegetation to spread quickly and out-compete the other plants on the disturbed site. The common factor with native plants considered to be opportunistic is the ability to outcompete other flora despite disturbance. The disturbance is usually what causes the right conditions for these plants to thrive.
What You Can Do
- Learn which plants are invasive in your area
- Identify and remove the invasive plants you have growing in your landscape. Some invasive plant seeds can persist in the soil for years, so routine maintenance and removal may be necessary.
- Replace invasive plants with native alternatives to avoid reintroduction. If not replaced, invasive plants will often return.
- Participate in invasive plant removal volunteer initiatives in your community
Additional Reading and Resources
Invasive Plants (U.S. Forest Service website)