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Invasive Species: Ecological Bullies or the Scapegoats of Nativists?

Japanese stiltgrass, Microstegium vimineum. (Photo by Liz Loucks, TNC)

by Jeremy Houser

An uproar that began in the scientific community has recently found its way to the popular press, and now poses a challenge for conservation groups and land managers everywhere: Should we really be trying so hard to fight invasive species? And can we even trust the motivation or judgment of those who do? This piece in the Boston Globe is recommended, as it presents a fairly even-handed account of the controversy (though the counter-argument is relegated to the end).

Without a doubt, our island is no stranger to problematic invaders. The usual suspects occupy the usual locations – Asiatic bittersweet and Multiflora rose dominate roadsides and fencerows – but invasives threaten ecologically sensitive and valuable habitats as well, including our ponds (the reed Phragmites) and the sandplain grasslands near the southern shore (several, including Spotted knapweed and Cypress spurge). Because of the importance of these habitats, a considerable amount of effort from local land managers is spent trying to control them. Consistent with this effort, there is a budding enterprise to spread native gardening and landscaping, an effort which helps strengthen native ecosystems and build resistance to the threat of present and future invasions. Recently, though, the whole idea of “going native” has come under attack. From the Globe article:

. . . underneath all these efforts is a potent and galvanizing idea: that if we work hard enough to keep foreign species from infiltrating habitats where they might do harm, we can help nature heal from the damage we humans have done to it as a civilization.”

But is this so? In the absence of a survey of the opinions of the “ecologists and conservationists” that are the subject of the claim, this appears to just be attempted mind-reading. Others take their telepathic insights to more antagonistic levels. Mark Davis, the lead author of the Nature article (subscription req.) that helped spark the conflagration, sees nostalgia driving the fight against invasive species: “Newcomers are viewed as a threat because the world that you remember is being displaced by this new world.” Finally, some criticisms, such as this Op-Ed in the N.Y. Times, see a connection between efforts to control invasive species and the recent rise in anti-immigrant sentiment in America. Comparing the native species movement with the Minutemen (the militia group that patrols the Southwestern border), the author concludes that “both are motivated — in Margaret Thatcher’s infamous phrase — by the fear of being swamped by aliens.”

It’s a provocative subject, and to the extent that the controversy helps educate the public about the concepts of native, non-native, and invasive species, it’s a useful discussion. And they raise some good points, some of which will be explored in the next edition of the Almanac. For example, maybe we should ask whether it’s fair to denigrate non-natives simply because they’re exotic, without first considering whether the species is helpful or harmful, controllable or not, etc. But first, I would like to offer a word in defense of those (now, oddly enough, the traditionalists) who favor keeping up the fight against invasive species.

Underlying the more reasonable criticisms is an assumption that scientists and land managers are having a difficult time distinguishing between the concepts of non-native and invasive species, which results in a great deal of useless, or even harmful, effort fighting benign non-natives. This would be a very large problem if it was true in any meaningful sense. First, regarding the academic ecologists: sure, like other scientists, they are always revising and refining definitions, but is it really likely that many of them are unaware of the current meaning of the basic terms that define their field? Second, land managers have limited resources, and of course they focus their time and money on the most harmful invasive species threatening their properties. Conservation groups take advantage of the tremendous amount of scientific information that exists to prioritize their invasive control work. And contrary to the implications of Davis and his co-authors, the science is supplemented by common sense. No one is trying to eradicate the Beach Rose (Rosa rugosa, introduced from Asia) from Martha’s Vineyard, or prevent farmers from raising chickens or growing exotic vegetables.

Finally, regarding those less reasonable arguments quoted above: On a practical level, does it really matter whether one’s motivation to garden with native plants comes from a xenophobic botanical grudge against all things exotic, or a well-reasoned desire to promote healthy ecosystems? There is little reason to believe, even if the former were true, that this would lead to serious environmental harm in the pursuit of pointless or dangerous action against benign non-natives. Further, as long as we're talking about plants, it's not obvious that there is even anything morally wrong with favoring natives to exotics based on pure nativism. The analogy to anti-immigrant sentiment is witty perhaps, but inaccurate as plants can't actually feel the sting of prejudice, and could be taken as insulting by those humans who have. The academic controversy is interesting, but the inflammatory language unfortunate, especially in a political and economic climate where ecologists and conservationists face real, and coordinated, adversaries.