I AM WRITING in a coffee shop. Ostensibly, there is only one species in this crowded room, a medium-sized primate with a penchant for disruption. But knowing a thing or two about species diversity — I am a zoologist by training — I realize there are more species in the room than meet the eye. For now, though, think of each human as an ecosystem of sorts, complete with its native cells, tissues, and organs, and think of the non-human organisms as non-native invasive species. 

Put to the back of your mind images of those pestiferous insects and microbes that inhabit the pantries of every coffee shop on Earth. Also ignore thoughts of the family of mice scrambling for crumbs under the counter. After all, the bewildering diversity of organisms invading the primate body is unsettling enough, so let’s stick to these “invasives.” Amoebae glide over cankerous gums, armies of micro-invertebrates storm the hairier and damper alcoves of the body, and the skin itself is as coated with bacteria as a commode in a gas station. Inside the body, the species count is impressively high. Up to 1000 bacterial species inhabit the gut. Many are not casual hitch-hikers but essential to health, metabolizing nutrients and synthesizing key vitamins. To be sure, among the invading hordes are a few bad eggs. Plague, for example, is ghastly. And smallpox is to be avoided. But most cause nothing more than the sniffles, a mild rash, or a headache. Nothing to be too alarmed about — and, after all, you deserve that day off work.  

Despite the outright helpfulness of some members of our bodily menagerie, and the fact that many of the others felicitously augment diversity, we have declared an all-out war against microbes. All because of a few bad eggs! Rather than vilifying these aliens as intruders, I argue that it is now time to embrace them as the key to our salvation. 

I call this emerging revolution in the medical sciences the “New Health.” It’s a viewpoint that is, of course, opposed to the old orthodoxy. 

If the paragraphs above constituted a book proposal, it would not attract a publisher. Indeed, it should not. After all, we tend to be reasonably sophisticated in our understanding of bodily mischief, and we can usually distinguish between helpful and injurious organisms. However, despite encouraging indications of a more nuanced understanding of how bodily aliens enable human health, squeamishness about dirt and germs persists. Many medical practitioners therefore worry about damages incurred from their too-zealous eradication. Among the obvious damages: a suite of autoimmune syndromes. So, while “New Health” advocates would encourage us to cultivate healthful aliens — for example, by way of receiving a fecal transplant to get that healing goodness right up in there, they also retain a firm resolve to eradicate harmful invasives. After all, there’s no good case to be made for the plague. 

New Health advocacy that champions a healthy bodily community, but cavalierly downplays the negative impacts of disease organisms, I call “New Health 1.” I think we might all agree that such a scheme would be a menace to the public. Advocacy that retains a sensible distinction between neutral or beneficent bodily organisms and those we should eradicate, I call “New Health 2.” I’d certainly lend the New Health 2 an ear! 

Now, if in the sentences above one replaces “invasive species in the environment” for variants of organisms in and on the body, and “ecological health” for variants of personal wellbeing, might we have a robust model for thinking about emerging quarrels in biodiversity conservation? In other words, are we waging an unnecessary and expensive war against invasive species? Invasive species are, generally speaking, those species that humans transport to a new region, where they reproduce, spread, and do ecological harm. That many species have become globetrotters is not in doubt. The issue is this: Could it be that, contrary to prevailing assumptions, invasive species are helping rather than hindering nature? Might it be the case that “invasive species will be nature’s salvation,” as Fred Pearce opines in The New Wild (2015)?  

The eradication of invasives is often preparatory to restoring ecological systems to “health,” defined in various ways. Ecological restoration typically involves the reintroduction of native species — you can’t have a tallgrass prairie, a geographically restricted habitat, without native prairie plants. But if, as Pearce claims, the notion of restoration is predicated on an outmoded model of how ecosystems work, then is restoration doomed to fail? Might the act of returning an ecological system to some former state be an assault rather than a boon? 

Pearce raises these difficult and timely questions. Invasion ecology is, relatively speaking, in its disciplinary infancy, although it has already provided scaffolding for conservation-oriented land management strategies. An ecological restorationist in your neighborhood is right now chopping down an invasive shrub, poisoning an invasive herb, or perhaps setting a trap for a non-native mammal. And by chop, poison, and trap, I mean kill; this endeavor is not for the faint of heart. Besides, it is an expensive business. The subsequent restoration of the ecological community is likewise costly and fraught with practical difficulties. Problematic invasives regenerate as often as not, or scurry back to a trapped-out system, especially those with underlying problems resulting from historically poor human management. 

These challenges might encourage scientists to be cautious in dispensing advice, and encourage practitioners to wait for more complete information. But the Holocene extinction, or Sixth Mass Extinction as some call it, creates a sense of urgency. Supposedly, the rate of species loss under the influence of human disruption rivals past cataclysmic extinction events, like the one that eliminated dinosaurs at the end of the Cretaceous. This time, we humans are the comet, we are the inundating sea. Many ecologists claim that losses due to ecological damage from invasive species are among the top five factors driving contemporary extinctions. Putting this all together: the emerging science of invasion ecology is being wed to an unperfected practice of ecological restoration under the blood-red sky of a global catastrophe.  

Pearce takes aim at the edifice that has coalesced around conservation efforts in the face of invasion. He does not simply remove the dodgy bricks, nor does he merely replace the edifice with a new edifice. Rather, he inverts the edifice, standing the whole darned thing on its head. Setting out to upend the conservation worldview, he writes that “when invaded by foreign species, ecosystems do not collapse. Often they prosper better than before. The success of aliens becomes a sign of nature’s dynamism, not its enfeeblement.” Elsewhere, using a medical metaphor of his own, he writes: “Alien species […] are often exactly the shot in the arm that real nature needs.” Thus, the burly nature of the New Wild — the worldview that embraces invasive species as our new saviors — is “usually richer than what went before.” This is bold and exciting. Is it correct? For the most part, I think not.  

Pearce’s New Wild fails in the manner that the fictional “New Health 1” paradigm, described above, fails. The book takes a few moderately compelling points — more on those in a moment — and extrapolates them beyond reasonable limits. He bolsters these meager points with pithy-sounding generalities, some so sweeping they will make you whistle in bemusement. For example, Pearce declares, “when ecosystems change dramatically or simply fail to deliver our needs, we look for scapegoats and usually blame our alien companions.” The statement is peculiarly emphatic when one considers that the environmental sciences provide plenty of other anthropogenic pressures to suspect: climate change, polluted soil and water, and so on. In The New Wild, Pearce in fact is so concerned about not losing “the baby” (the notion of harmless or useful non-native species) with the bathwater that he elects to keep the bathwater, however grimy and even toxic.

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In favor of the New Wild, Pearce marshals the following supporting perspectives. One, invasives add to, rather than suppress diversity, and thus invasion biology mischaracterizes the dangers; two, the demonization of alien species says more about those who decry invasives (they are xenophobic racists) than it does about those species; three, denouncing what he calls a “dangerous mythology” concerning ecology, he illustrates how nature works differently than we imagine; and four, he outlines how conservation practice builds upon a false understanding of how nature works. He then offers to reboot conservation practice with his notion of “the New Wild.” Charming indeed is his vision of a world “composed of novel mixtures of native and alien species, happily getting along together, enriching our lives, maintaining ecosystems and recharging nature’s batteries.” 

If only this vision were correct. Pearce is clearly correct in arguing that many non-native species are harmless or can provide some service to us or to other components of nature. Dandelions, for example, make a delicious salad. In some cases invasive species have been incorporated into traditional medicine. Indeed, this is a fundamental axiom of invasion biology: not all non-native species persist in the environment, and of those that do, not all become problematic invaders. For the most part, invasive species biologists are in fact indifferent to most non-native species. 

It’s also true that in some circumstances invasive species may be more conspicuous than harmful; we do not always have evidence of harm. Invasive species are legion, researchers are few, and time is finite. But sometimes there is ample evidence that the impact is immense. Begrudgingly, Pearce agrees, sagely conceding that “sometimes we need to defend ourselves against pests, diseases, inconvenient invaders of our spaces.” I challenge you, however, to find an example of an invader that Pearce can’t invest with some charm or other. Kudzu, for example, is widely regarded as one of the most problematic invasive species in the U.S. Southeast. It’s a nitrogen-fixing vine that can cover shrubs, trees, and human structures, and is widely known to shade out other vegetation. Pearce acknowledges that kudzu “extends its grip by 120,000 miles a year.” Its growth, he marvels, “seems to fit an American image of the Deep South as somehow depraved and unruly.” Perhaps, he suggests, it could be used to make jam — no doubt a deliciously depraved and unruly one. In the meantime, kudzu provides metaphors for American-style growth. He concludes his account of kudzu on this hopeful note: “if I can unravel [the metaphors] I may have reached the heart of the American psyche.” 

A strategy in the book — certainly a reasonable one given that the book’s author intends to challenge orthodoxy — is to quote academic mavericks at length. For example, quoting Jim Dixon, a Glasgow University botanist, Pearce writes: “No endemic [in England] is remotely threatened by any aliens.” This is a bold, though provocatively misleading statement, given that there are over 300 British plant species on Britain’s “Red List,” a compendium of imperiled plants in that region. 

For the most part, though, the dissidents whose statements Pearce deploys to undermine prevailing opinions about invasive species are ecologists themselves — indeed many would identify themselves as invasion ecologists. This is unsurprising, of course, since testiness, supported by fresh data, can be the essence of paradigm-altering science. Such skirmishes move a discipline along. To give just one important example, Dov Sax of Brown University, whose important work with Steve Gaines of University of California, Santa Barbara, on invasion and extinction on islands, is summarized approvingly by Pearce. Sax and Gaines found that the number of bird species can remain constant or may drop after non-natives establish self-sustaining populations on islands. Plant diversity, however, goes up more often than not. Pearce counts this as a win for his thesis. According to him, the study puts Sax at the heart of “a new generation of researchers questioning the demonizing of aliens.”  

It is inarguably the case that these findings provoked vigorous debate among invasion biologists. One crucial point worth noting here (though Pearce fails to note it) is that Sax and Gaines themselves expressed concern about the significance of the island invasion data. Of the bird data they wrote that it means “that many unique endemic species have been lost and replaced by more cosmopolitan species from mainlands.” Furthermore, to their credit, they have a nuanced view of the significance of the increase in plant numbers in invaded islands. They speculated that the species count may indeed continue to rise as non-native plants colonize islands, and this rise may have no consequences for other species. According to them, it’s equally plausible that newly introduced exotic plants will continue to colonize islands, which may put “many native species to be on a pathway to extinction.” In short, Sax and Gaines carefully equivocate. Weighing the alternatives, they frankly concede that they don’t know which alternative is more likely. 

Pearce’s strategy of crudely summarizing an argument, or of deploying idiosyncratic quotes without nuance or context, may very well create advocates for his cause. However, the strategy will trouble those who want nuance, and so a more accurate account of the state of the field.  

There are of course no index entries in The New Wild for “xenophobe,” “Nazi”, or “eugenics.” The troubling implication running throughout the book, however, is that concerns about non-native invaders are rooted in our hard-wired xenophobic instincts. Pearce starts out innocently enough: “To be clear, I am not accusing environmentalists of being closet xenophobes, or misanthropists, still less racist.” Elsewhere he writes: “While nobody would accuse today’s environmentalists of being secret fascists, this political legacy […] is disquieting.” Yet it’s rare that Pearce passes up the opportunity to imply exactly such motivation. Of the work of invasion biologists, for example, he writes: “excited language, replete with military and xenophobic metaphors, has continued to feature in the everyday discourse of scientists investigating alien species, and it even appears in their research papers.” When not accusing disciplinary leaders of flirting with eugenics, he labels them “gurus.” Daniel Simberloff, one of the most renowned contemporary ecologists, and an editor of the scientific journal Biological Invasions, is a “guru”; Stewart Brand, the editor of the Whole Earth Catalog, is a “guru”; and even Charles Elton, the English zoologist who laid the foundation of 20th-century ecology and wrote the first book of biological invasions in 1958, is a “guru.” In short, if Pearce is to be believed, the science of invasion biology is ideologically suspect, its disciplinary leaders are quasi-religious zealots, conservation practitioners are hysterical, and the public is being brainwashed.  

On a brighter note, Pearce does a serviceable job in reporting how ecologists’ understanding of nature’s dynamics has evolved. Gone from the discipline is the notion of a “balance of nature.” Gone, too, is the idea that, in the absence of human disruption, ecological communities remain static. Disturbance in the “new ecology” is not external to an ecological system but essential to it. This all seems quite reasonable. If all of nature is in flux, and if systems coalesce, break up, and re-form, then surely the distinction between a human disruption and a natural one is debatable. The transportation of species around the globe is arguably an extension of the natural traipsing of organisms around the globe. This dynamic view of nature plays a key role in Pearce’s argument. And such perspectives do indeed support a new view of invasive species. He writes, “if ecosystems are open and dynamic, then aliens have as much a right as natives to join in —  and can be just as useful.”  

But none of this is completely new. Views on the balance of nature have, after all, long been “attacked by dissident scientists, who see it as romantic or even religious flummery with no scientific basis.” In fact, one of the first dissident ecologists to express doubts about the existence of a balance of nature was Charles Elton. You will recall that Elton founded the discipline of invasion biology and was one of the “gurus” castigated above. Elton had this to say in 1930: “‘The balance of nature’ does not exist, and perhaps never has existed. The numbers of wild animals are constantly varying to a greater or lesser extent, and the variations are usually irregular in period and always irregular in amplitude.” Daniel Simberloff (also listed as a “guru” above) has written more recently on this topic, and concluded that, for academic ecologists, “the notion of a balance of nature has become passé.” The concept, Simberloff concluded, “is useless as a theoretical framework or explanatory device.”  

I quote Elton and Simberloff because I’d like it to be clear that, contra Pearce, one can simultaneously embrace a contemporary perspective about the fluxes of nature and yet still hold the view that many invasive species are problematic, and that their removal is a prerequisite to conservation efforts. Thus, restoration efforts, the form of conservation that often advocates the removal of invasives as a first step in repairing damaged ecosystems, does not, in fact, attempt to return nature to a former balance. Rather, it tries to reestablish the historical trajectory of ecological systems. Think of it this way: the restoration of degraded ecosystems is like the restoration of personal health. In restoring the health of a loved one, no one, I presume, expects that the sick person returns permanently to their youthful selves. Rather, that person is, at best, returned to the path they were on before they fell ill.

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In all likelihood, we are going to get the New Wild whether we like it or not. In some cases, the New Wild will contain novel ecosystems without historical analogue. This will certainly be the case in urban environments, where conservation is not always feasible or desirable. The problem is that we may also get the New Wild in places where conservation has been established as a priority, and where we wish, for some combination of scientific and ethical reasons, to protect rare creatures. I fear we may get the New Wild on the strength of a flimsy and beguiling argument.  

Pearce has given us New Wild 1, when New Wild 2 is what’s needed. The book is under-researched and one-sided, perhaps recklessly so. Part of its danger lies in the fact that it provides false comfort and may thus encourage complacency. It is a lullaby, when what is needed is a surer guide to conservation action. If, as the book suggests, we need not be concerned about invasive species, and if our ambitious plans — to protect small conservation-significant areas from being overrun by invasives — are all ill-conceived, then what action does Fred Pearce’s New Wild call for? None at all. We need never leave the soft comforts of our armchairs.

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Liam Heneghan is a professor and the department chair of Environmental Science and Studies at DePaul University.