The United States has since the 1960s worked hard and made significant progress in environmental protection. Before the 1990s, the state and the federal government have concentrated in weed control through the creation of pesticides, and more importantly, better management methods after chemical methods were found to endanger human health and the environment . However, after the 1990s emerged invasive plants which have presented a new and even more severe environmental problem.
Invasive plants are among nonnative species that have high potential to harm to the economy, human health, and the environment . Notably, these invasive plants have “been introduced into an environment in which they did not evolve and thus usually have no natural enemies to limit their reproduction and spread” .
Just like weeds, invasive plants have a peculiar ability to spread fast and thrive in places other plants can barely survive [3-4], a biological wildfire that starts when invasive nonnative plants encroach wetlands, croplands, waterways, pastures, parks, and forests is threatening. This is the current situation in America as these invasive plants sweep across the nation
The invasion is damaging worth millions of dollars as natural, managed, and agricultural ecosystems get engulfed. When nonnative invasive plants get to these ecosystems, they damage plant and animal communities, increase soil erosion and sedimentation, and interfere with outdoor recreation, all of which are long-lasting effects [1-2]. What worsens the effects of invasive plants is the rapid growth, adaptation, multiplication, and spread of their populations to extensive levels with time.
Invasive plants are a serious environmental threat, particularly to the eastern US, putting the survival of woodland plants in this region under threat. While not all nonnative invasive plants are harmful, the small percentage that counts as harmful can lead to extensive damage unless they are controlled. These plants cost a great deal, about $120 billion per year in terms of losses arising from loss of crop and indirect costs concerning management and infestation when preventing the spread of the plants [1-2].
Another severe threat associated with invasive plants is replacement of native species, which in turn, leads to decreased biodiversity of native species, and in more severe cases, extinction of endangered indigenous plant species . According to research, the United States alone has “nearly 1000 plant species listed as either threatened or endangered and of these, roughly 40% are considered at risk from invasive species due to direct contact, such as predation or indirect influences like competition” .
In the Woodlands of Eastern America, some of the impacts that invasive plants have had include increased predation of other species. Invasive species such as Lonicera maackii are believed to be the cause of increased seed predation by small mammals which obtain additional cover from the plants, and this is believed to be the reason behind declining native tree seedlings as Stephanie et al. report.
The presence of Lonicera maackii is also associated with increased mortality rates of songbirds; the reasons put forward to explain this trend include that invasive shrubs commonly thrive in forest edges, hence exposing songbird nests within them to a more significant risk of predation . Stephanie et al. further note that the height of invasive shrubs is small, thereby placing the songbird nests close to the ground and thus vulnerable to predation. Most of these shrubs also lack defensive features of indigenous species, among them thorns, which makes the bird nests easily accessible.
The presence of Lonicera maackii is also known to increase ticks and tick-borne diseases, which leads to not only increased exposure of humans to tick-borne diseases but also spread of infected tick population, according to Stephanie et al. The second common invasive shrub in the eastern United States Woodlands is Elaeagnus umbellate, which, as Stephanie et al. reports, has been associated with reduced native plant species, diversity, and productivity.
Another form of invasive plants described as herbaceous species also invade forests, which, with their ability to out-compete native species, are a problem that has been observed in eastern hardwood forests. A type of herbaceous species known as Alliara petiolate, as Stephanie et al. report, has been found to pose a threat to the extinction of native species such as native butterfly known as mustard white butterfly, a rare species that exist in the northeastern United States. Another type of herbaceous species known as Phalaris arundinacea, despite a number of benefits, is also noted to be problematic to young forest stands, and the ability of the species to form dense monotypic stands threatens the diversity and productivity of native plant species, as Stephanie et al. report.
The preceding section introduces just a few of the negative impacts of invasive plants. As can be seen, invasive plants are a serious threat to fauna by disrupting the natural balance of ecosystems. While invasive plants are not entirely problematic as their presence provides various benefits, especially bearing in mind that the introduction of invasive nonnative species was motivated by a desire to provide an additional food source and cover for wildlife , the debate concerning the control of invasive plants is still undecided in the ecological community.
As Stephanie et al. note, controlling invasive plants may need resources so high that the benefits thereof cannot outweigh. This means more research is necessary for a conclusive understanding of the course to pursue concerning the future of invasive.
- Westbrooks, R. 1998. Invasive plants, changing the landscape of America: Factbook. Federal Interagency Committee for the Management of Noxious and Exotic Weeds (FICMNEW), Washington, D.C. 109 pp. Retrieved from https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1489&context=govdocs
- United States Department of Agriculture, National Institute of Food and Agriculture. What Are Invasive Species, and Why Should We Be Concerned About Them? 2019. Retrieved from https://climate-woodlands.extension.org/what-are-invasive-species-and-why-should-we-be-concerned-about-them/
- Hayes, Stephanie J., and Eric J. Holzmueller. “Relationship between invasive plant species and forest fauna in eastern North America.” Forests 3, no. 3 (2012): 840-852. Retrieved from https://www.mdpi.com/1999-4907/3/3/840/pdf
- Robert J Warren, Matt Candeias, Adam Labatore, Michael Olejniczak, Lin Yang, Multiple mechanisms in woodland plant species invasion, Journal of Plant Ecology, Volume 12, Issue 2, April 2019, Pages 201–209, https://doi.org/10.1093/jpe/rty010