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The Dangers of Invasive Species across the United States
Alien plant species are threatening the natural ecosystems of America, their widespread
invasion patterns and dominance over native species makes them a pressing national
environmental issue. More dangerous than the invasive plants is the lack of public knowledge
about the effects invasives have on our nation’s wealth: economically and biologically
(“Education and Public Awareness”). While the economic costs are important, the biological
impacts are devastating: these alien plant species are dominating ecosystems across the country,
resulting in a lack of biodiversity (Eberhardt 21).
Invasive species can be introduced via agriculture and home gardens, but the alien plants
migrate into other ecosystems. While there is initial benefit for farmers to plant these invasives,
as the plants have high yields and tend to thrive because of a lack of predation pressure, the
eventual cost is hundreds of millions of dollars in agricultural loss (Pimentel et. Al 273-288) .
Meanwhile, not only have crops been affected, but the invasives have spread into neighboring
forest environments. The very things that make the invasives good crop candidates make them
dangerous: the ability for rapid growth in a habitat with no natural predators means that the
invasives take over an ecosystem. They outcompete, out-shade, and outlive the native plant
species that are originally present. Some alien plants even alter soil conditions that kill off
existing natives, while simultaneously creating a more beneficial environment for themselves
(“Invasive Plants in the Mid-Atlantic”). The danger of these invasive species being so dominant
is the lack of biodiversity that results, an issue that has led invasive species to be cited as “‘[O]ne
of the most serious environmental threats of the 21st century’” (Eberhardt 22).
Lacking biodiversity is dangerous for several reasons: not only does the extermination of
native species alter an environment and therefore affect the ecosystem’s food web, but it also
results in a lack of genetic diversity (Pimentel et. Al 273-288). Genetic diversity is necessary for
an ecosystem to thrive, otherwise a single pathogen or environmental disaster could lead to the
death of an ecosystem. Invasives like European cheat grass and yellow star dramatically alter the
vegetation and fauna natural ecosystems, in California where there was once productive
grassland, yellow star thistle now dominates up to 8 million ha, resulting in the total
extermination of the once productive grassland (Pimentel et. Al 273-288) . Invasive species are
destructive to the point that they have become a “leading cause of threatened and endangered
species in the United States” (Eberhardt 21).
There is a general consensus in the scientific community that invasive species are
detrimental to species diversity (Pimentel et. Al 273-288) . Not only is there mature science to
support this, but that opinion is further supported by the Environmental Protection Agency, the
USDA, and the National Invasive Species Council. Where the science is less conclusive is in
regards to how these invasive species are managing to be so dominant. Scientists worldwide are
attempting to answer this question and multiple studies have been conducted for this very
purpose. There was an Australian study that concluded “[s]eed production was greater for
invasive species overall” in an individual year (Mason et. Al 633-640), meanwhile a study of
Pines in California concluded “ Invasive species outperformed non-invasive congeners by
growing 28% faster, on average”, while also having a higher phytosynthetic nitrogen-use
efficiency (Matzek and Virginia 3005-3014). Essentially, the mechanism by which the invasives
dominate is still under investigation, and the answer could vary according to species or
environment.
While the EPA warns against the dangers of invasive species, farmers and home owners
continue to cultivate and spread these alien plants. The initial economic benefit farmers can reap
from efficient alien biofuel crops has a greater collective mental presence than the realization
that growing these crops could mean “unleashing the next big invasive species catastrophe”
(Mikell 2). Homeowners could potentially play the same role, as many alien plant species are
utilized in home gardens for their ornamental and deer resistant qualities (Knight et. Al 110-116).
Deer tend not to graze on invasives, because they prefer the native plant species. This is human
intervention that directly undermines native species in favor of invasives, but the homeowners
are not solely to blame as it is home gardening centers who sell these plants and legislators who
allow these plants to go to market.
Currently the issue of invasive species is a national issue that needs to be addressed.
Some states do have regulations and policies that limit the sale of certain plants, but many do
not. The disagreements that are currently being had between scientists about the mechanism of
dominance by invasives are one reason policy makers are able to side step the issue. However,
there is enough conclusive scientific evidence about invasives causing a lack of biodiversity
across our nation’s ecosystems that the scientific community and American public can get
behind to demand legislation.
The matter of invasive species has ties to many aspects of American culture. Not only
does it affect our economy, but it also affects our biological wealth. Declining biodiversity across
our nation’s ecosystems, and even within our agricultural business, is a biological issue which
requires immediate action. Funding should be allocated to continue the study of these alien
plants and their mechanisms, but effective legislation should also be introduced to rectify this
scientific issue.
Works Cited
David Pimentel, Rodolfo Zuniga, Doug Morrison, Update on the environmental and economic
costs associated with alien-invasive species in the United States, Ecological Economics,
Volume 52, Issue 3, 15 February 2005, Pages 273-288, ISSN 0921-8009, Web. 07 Sept.
2013. http://dx.doi.org/10.1016/j.ecolecon.2004.10.002.
(http://www.sciencedirect.com/science/article/pii/S0921800904003027)
Eberhardt, Roger.”Lake Superior.” EPA.gov. 2008. Web. 6 Oct. 2013.
http://www.epa.gov/solec/solec_2008/2/1_Superiornotes.pdf
Environmental Protection Agency. “Invasive Plants in the Mid-Atlantic.” Epa.gov. Web. 01 Oct.
2013 http://www.epa.gov/reg3esd1/garden/invasives.htm
Knight, T. M., et al. "Deer Facilitate Invasive Plant Success in a Pennsylvania Forest
Understory." Natural Areas Journal 29.2 (2009): 110-6. ProQuest. Web. 01 Oct. 2013.
Mason, Robert A. B., et al. "Reproductive Output of Invasive Versus Native Plants." Global
Ecology and Biogeography Letters17.5 (2008): 633-40. ProQuest. Web. 01 Oct. 2013.
Matzek, Virginia. "Superior Performance and Nutrient-use Efficiency of Invasive Plants Over
Non-Invasive Congeners in a Resource-Limited Environment." Biological
Invasions 13.12 (2011): 3005-14. ProQuest. Web. 01 Oct. 2013.
Mikell, Mekell Ph.D. “Growing Risk for Taxpayers and Wildlife National conservation group
urges precaution on cultivating invasive plants for bioenergy.” Invasivespecies.gov. Web.
01 Oct. 2013
The National Invasive Species Council. “Education and Public Awareness.” Invasivespecies.gov.
Web. 01 Oct. 2013.
http://www.invasivespecies.gov/global/education_public_awareness/public_awareness_in
dex.html