A provocative essay calling on conservation biologists to stop bad-mouthing nonnative species has sparked a testy showdown in the pages of the prestigious journal Nature.

“Over the past few decades, ‘nonnative’ species have been vilified for driving beloved ‘native’ species to extinction and generally polluting ‘natural’ environments,” a team of 19 researchers wrote in the opening salvo in the June 9 issue. “Intentionally or not, such characterizations have helped to create a pervasive bias against alien species that has been embraced by the public, conservationists, land managers, and policy makers, as well by as many scientists.”

The problem, they wrote, is that the “native-versus-alien” worldview is “increasingly meaningless.” Although some introduced species can have harmful impacts—especially in places such as islands—they can also bring benefits, they note. And numerous efforts to eradicate invasives have proved to be expensive failures that make “little ecological or economic sense.” It is “impractical,” they add, “to try to restore ecosystems to some ‘rightful’ historical state.” Instead, conservationists and land managers need to “organize priorities around whether species are producing benefits or harm to biodiversity, human health, ecological services, and economies.”

The volley prompted a strong counterattack. In a letter published July 7, 141 researchers argued that the essay assailed “two straw men” and downplayed the risks posed by alien invasions. “First, most conservation biologists and ecologists do not oppose nonnative species per se—only those targeted by the Convention on Biological Diversity as threatening ‘ecosystems, habitats, or species,’” they wrote. “There is no campaign against all introductions: scarcity of resources forces managers to prioritize according to the impact of troublesome species.” Second, “invasion biologists and managers do not ignore the benefits of introduced species . . . Nobody tries to eradicate wheat, for instance.” But eradication is “possible”—and proper—in some cases, they argued. Twenty-seven species, they noted, “have been eradicated from the Galapagos Islands.”

In another letter, Andrei Alyokhin of the University of Maine wrote that “bias against nonnative species is not xenophobic—it has a sound scientific foundation.” And in a third, Manuel Lerdau of the University of Virginia and colleagues warned against “setting an unrealistically high bar for those making management decisions about exotic species. Control is often easier, cheaper, and more effective soon after detection.” The debate over immigration, it seems, isn’t confined just to people.

– David Malakoff

Davis, M. et al. 2011. Don’t judge species on their origins. Nature doi:10.1038/474153a and Letters, doi:10.1038/475036a, b and c.



  • Matt Chew September 1, 2011 at 9:43 pm

    There’s a fine crop of metaphors here, but they don’t clarify the issues. Consider the last one first: alien species are not immigrants in any meaningful sense. If we take the anthropomorphic tack, they are more properly abductees, castaways, survivors of catastrophic events and their progeny. But that offers little more ecological or evolutionary insight than even more absurdly calling them immigrants or invaders. Perhaps it is closer to the mark to say they’ve been entrained in the currents of commerce; a recent but real and plainly effective suite of dispersal mechanisms that characterizes today’s real world.

    Was the counterattack strong? Whether it was a counterattack at all rather hinges on whether the original commentary was an attack. “Don’t Judge Species by their Origins” wasn’t conceived or deployed as an attack. Nineteen authors from a wide range of ecological subdisciplines and regional expertise (including the Galapagos) worked for many months to translate their independent but shared perceptions and conclusions. In that view neither scientific nor wider public interests were served by dividing species into belonging and unbelonging according to archaic, pre-Darwinian criteria. Much as a “biological invasion” exists only in the minds of discomfitted humans whose naive expectations have been belied, “Don’t Judge Species” could only be construed as an attack by interests anchored to the status quo. A lot of time, effort, resources and goodwill are being squandered with only the prospect of failure to keep separate with one hand that which we are combining with many others. Speaking as one of the nineteen (and entirely for myself) our essay was conceived as a rescue mission, not an attack.

    Still, was the response (let’s give the respondents some credit too) well founded? I wasn’t impressed. To my eye the correspondents reiterated a litany of familiar post-hoc rationalizations for anti-alien sentiment. But you don’t have to take my word for it. I suggest that you read our Nature essay and the correspondence side by side, and think for yourself.


    • Kieran Suckling February 16, 2015 at 10:28 am

      Here, and in an odd postscript to one of his published articles, Matt attempts to erect a wall between cultural colonization and extinction, and the anthropogenically caused colonization and extinction plants and other animals.The reason for this is clear: having framed the latter as essentially free of ethical considerations, he must firewall it from the former lest one notice that his exact arguments were commonly used to justify the colonization, displacement, subjection and even extinction of non-white cultures around the world.

      But what foundation could such a wall be built on other that anthropocentrism, exceptionalism, and ultimately, religion?

      Above he tells us that alien species are not immigrants in any meaningful sense, preferring to say they have “been entrained in the currents of commerce; a recent but real and plainly effective suite of dispersal mechanisms that characterizes today’s real world.” But human migration, as any sociologist would agree, is radically “entrained in the currents of commerce.” And movement of plants, humans and other animals is deeply influenced by the historically “recent” growth of global capitalism.

      One can logically adopt an extra-moral position in which since everything is natural,” everything is acceptable. In such a world, there is no ethical dimension to invasive species. But what one can’t do, is adopt this position and exclude humanity from it. It must accept that murder, rape, war and colonization, being “natural” are equally outside the ream of ethics. The untenableness of this position shows the vacuousness and unavoidable contradictions in using “natural” in this manner.

      Extinction is an ethical issue. The human impact on the planet is an ethical issue. Anthropogenic species movement is an ethical issue. Invoking “naturalness” to dismiss the ethical dimension can never work, because it requires proclaiming that when humans harm non-humans it is “natural” but contradictorilly claiming that when humans harm humans it is “ethical”. You can’t have it both ways.


  • Ajay Desai September 25, 2011 at 4:37 am

    Humans are a natural part of this planet and as such all their activities are a natural part of this planet. That as a species we have become super successful and pose danger to the survival of other species (and possibly to ourselves through overuse of resources)is also acceptable to nature. Natural selection will decide where we and all life on this planet will end up. Technically (or biologically speaking) there is nothing wrong with us causing mass extinctions or in self-destructing; life itself will carry on with or without us. So there is no biological basis for us taking any action to stop any of the harm we are committing or to even bother about stopping things like wars or crime. It is only when we take responsibility for our actions, when we look at the moral or ethical issues involved, that we need to think of altering our behavior to reduce our adverse impact on our planet.

    Conservation is about recognizing that we have altered our natural world in a way that is detrimental to many species (and even to large ecosystems and their contained biodiversity). Conservation is also about recognizing that we are present in a particular window of time. And where we have some knowledge of how things have reached their current status through the process of natural selection and evolution. But we are unsure how the numerous changes we have made will eventually play out although we know that many things are detrimental and not in tune with the natural process of natural selection and evolution. So as scientists or conservationists the most logical approach would be to adopt a ‘holding strategy’ i.e. maintain status quo (to the extent possible) in those areas that we have defined or consider as conservation areas (protected areas or otherwise). We need to maintain status quo in situations where we lack the knowledge needed to accurately assess impacts or trends originating from our action or where we do not know what inputs are needed to halt or reverse our adverse impacts. In areas where we know what inputs are needed we need to act. But in many cases we lack the resources needed to bring about such action. Maintaining status quo will help (hopefully) more knowledgeable future generations with better resources to stop and restore natural processes (hard to believe!) and minimize our impacts on nature. It (knowledge) will also allow them to decide meaningfully on more complex issues like how best to deal with non-native species as a whole.

    It is in this context that we need to look at how we deal with non-native species in the current scenario. Again we need not talk of non-native species in a general context but of very specific species that are having observable adverse impact on native species or even ecosystems. Here a part of the management action needed is to maintain status quo of the affected speices or ecosystem (without the harmful non-native species). So management would be faced with the task of containing or eradicating the non-native species. Just as hunting for meat becomes poaching when a species being hunted is endangered and needs to be stopped, dealing with clearly harmful non-native species becomes equally important. Also despite the huge spend on poaching, it has not actually stopped… we need to recognize that most human actions to do good, fall short or far short of universal success. So priority, logical approach, feasibility and necessity all would need to be taken into account when addressing non-native species. Failure to do so, whatever the reason, is failure for conservation based on a thinking approach.


    • Portia Brown November 9, 2011 at 9:48 am

      This is the most well reasoned approach I have seen in the literature and the media to date– this gets at the heart of our dilemma and asks us to take a realistic stance.



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