What comes to mind when you hear the phrase “invasive species”? Perhaps native trees cloaked in a cape of English ivy, which runs rampant all throughout Virginia, including on UVA’s campus [1]. Maybe mussels clinging in a sheet to the bottom of a boat, as they are transplanted from one body of water to another. The phrase “invasive species,” rarely elicits pleasant feelings; rather, it is often coupled with warnings of environmental mayhem — and for good reason. Since invasive species have few to no predators in non-native environments, they often explode in population, outcompete local species, send the ecosystem out-of-balance, and require costly plans to counteract. However, the ethics of the usual response to invasive species - purposeful extermination of all invasive organisms - may not be as simple as often thought [2].
Firstly, removing a non-native species from an environment it is established itself into is exceedingly difficult [2, 3], financially costly (proportionally so with the geographical area being treated) [2, 4], and risks further damaging the ecosystem in unexpected ways, such as cytotoxic agents meant for the invasive species also exterminating a native ones [2]. The actual treatment plan, therefore, requires a cost-benefit analysis between human interests and the desire to restore an environment’s ecosystem balance (an ‘ethical’ balance that promotes a mix of both human and ecological interests most efficiently).
A recent case involving invasive species control highlights the tension between effective treatment and additional damage to the ecosystem. Imagine an eel. Now, mentally remove the fins, replace its bones with cartilage, and substitute a circular plate of chainsaw-like teeth for a jaw. A bit disturbing, right? Well, what you’re now imagining is a lamprey – a primitive fish species that evolved more than 360 million years ago (humans evolved five to seven million years ago, for comparison)[5, 6]. Although they may be ancient, these finless fishes have an important modern presence – as an incredibly invasive, parasitic species. In fact, lampreys single-handedly devastated the ecosystem of every single Great Lake in the US in the mid 1900s [7], destroying the traditionally seven-billion-dollar fishing industry while contributing zero economic value themselves. This dynamic between the lampreys and human utilitarian interests, which favors the maximum benefit an ecosystem can provide to human interests, highlights the ethics of invasive species control from a human-benefit perspective. Since a single lamprey can destroy 40 lbs of fish in its lifetime, the exponentially exploding population decimated human food production in the area and posed an immediate threat to human interests. Thus, it was ethically favorable, from a utilitarian perspective, to eliminate lampreys despite the anticipated financial cost. However, it is not always ethical from the same utilitarian perspective to eliminate spreading species. A case where invasive species control may be unethical would be one where the exploding species does not impede human interests - or even enhance them - such as a food-quality fish spreading and contributing financially to the fishing industry.
However, the lamprey population explosion also highlights how the ethics of utilitarianism must be balanced against the ethics of biophilia when considering action regarding invasive species. Biophilia ethics, different from utilitarianism ethics, prioritize the restoration of the ecosystem to a pre-human-involvement-state – or at least as close as possible in today’s age – while granting little thought to human interests. Given the parasitic nature of lampreys [7], as well as the human responsibility for their introduction, it's no surprise that lamprey removal was deemed ethical through this lens as well. However, an example where invasive species control through the biophilia perspective would regard additional invasive species control as unethical would be, for instance, if one invasive species is released to control another.
Take, for example, spotted knapweed, a highly invasive plant species that spreads wildly in the western United States [8]. Recognizing that removal of the weed by herbicide or hand would be incredibly expensive and time consuming, a natural predator of spotted knapweed - the gall fly - was released into the territory of the knapweed within the US [9]. The gall fly is a ‘biological control’ - a non-native species transplanted to control another invasive one. Despite being a ‘biological control,’ the gall fly itself is also technically considered invasive, as it is thriving in a non-native habitat. By introducing a natural predator to the damaging knapweed, knapweed can be controlled ecologically without the presence of humans, leading to a partial restoration of the environment by mitigating the effects of knapweed. Through this perspective, removing the now-invasive gall fly would be unethical from a biophila viewpoint. (It should be noted that any introduction of a new species is bound to be ecologically complicated. The introduction of gall flies indirectly led to a boom in the deer mice population, which may, in turn, lead to more herbivory on the native plants [9].) Although both knapweed and gall flies corrupt the natural ecosystem by being non-native, gall flies indirectly promote a healthier ecosystem by controlling the knapweed. Therefore, because the flies are serving to maintain environmental health, their removal is considered unethical from a biophilia viewpoint.
As seen through these examples, the independently considered ethics of utilitarianism and biophilia may contradict each other in regard to invasive species control and greatly complicate the matter beyond simply asserting that extermination is the best answer. A balanced response is required to weigh all interests to reach an ethical plan of action. This compromise between humans and ecological interests highlights that both factors must be understood and weighed for each situation.
References:
“English Ivy.” Loudoun County Master Gardeners, https://loudouncountymastergardeners.org/programs/tree-stewards/english-ivy/.
https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1150&context=envstudtheses
“Combatting Invasive Species.” National Wildlife Federation, https://www.nwf.org/Our-Work/Environmental-Threats/Invasive-Species.
U.S. Fish & Wildlife Service the Cost of Invasive ... - FWS. https://www.fws.gov/verobeach/PythonPDF/CostofInvasivesFactSheet.pdf.
Xu, Yang, et al. “Lamprey: A Model for Vertebrate Evolutionary Research.” Zoological Research, Science Press, 18 Sept. 2016, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5071338/.
Wilford, John Noble. “When Humans Became Human.” The New York Times, The New York Times, 26 Feb. 2002, https://www.nytimes.com/2002/02/26/science/when-humans-became-human.html.
Sea Lamprey - A Great Lakes Invader. Glfc, http://www.glfc.int/pubs/annualreports/1957.pdf.
“Spotted Knapweed.” Minnesota Department of Agriculture, https://www.mda.state.mn.us/plants/pestmanagement/weedcontrol/noxiouslist/spottedknapweed.
“Efficacy of Biological Control for Weed Management.” Efficacy of Biological Control for Weed Management - Wildlife and Terrestrial Ecosystems - RMRS - US Forest Service, https://www.fs.fed.us/rm/wildlife-terrestrial/invasive-species/projects/biological-control.php.