Retreat from invasion biology becomes a stampede

The New Wild by Fred Pearce (1) is the third book to be published in three years which challenges the conventional wisdom that native species are inherently superior to non-native species and the closely related corollary assumption that all non-native species are competitors of native species.  These are the assumptions that underlie invasion biology.  Each book has been progressively more pointed in its criticism of this ideology, masquerading as a scientific discipline.

Rambunctious Garden

Rambunctious GardenThe first book to be published in 2011—Rambunctious Garden by Emma Marris (2)—was timid in its approach in comparison to The New Wild.  Ms. Marris visited “restoration” projects all over the world.  She described unsuccessful efforts to eradicate non-native plants and animals as well as extreme attempts to “rewild” that are often a mishmash of plant and animal species from different native ranges and time periods.  She implied that these projects were futile as well as artificial, but she was not explicitly critical.  Despite her cautious approach, she has been subjected to intense criticism from both academics and practitioners of invasion biology.   The following excerpt of a reader’s review of Marris’s book found on is typical of the criticism:

“Earth as cookie jar”

“Emma Marris, the author of Rambunctious Garden (RG), loves the nature hiding in back street alleys and along the highway median strip. Marris believes it’s time to abandon (or de-emphasize) what she sees as outdated and naïve conservation strategies such as creation of national parks and wilderness reserves. She feels the biggest obstacles to a bold new world of “designer” and “novel” ecosystems is the “wilderness cult” that naively wants to preserve “natural” landscapes–which she says do not exist anymore.

Marris espouses the anthropocentric perspective that the Earth is more or less a resource cookie jar for humans–to be used carefully to be sure–but she doesn’t really question whether ethically or ecologically this is ultimately a good idea…

However, by moving the goalposts to vacant city lots as an acceptable desired future condition of the landscape, she implicitly, if not explicitly, provides cover for all manner of environmental degradation.”

Most of the 35 readers’ reviews about Rambunctious Garden on are equally critical.  This particular review was rated as “helpful” by 141 other readers and 21 comments were also posted in support of the critical review.  Marris and her book have been thrashed in many other venues, including conferences where she is called out by name as an enemy of nature by invasion biologists.

Where do camels belong?

Where do camels belongThe second book, which challenges the assumptions of invasion biology, was published in September 2014.  Where do camels belong? by Ken Thompson, a British academic, (3) is much more explicit in its criticism of invasion biology.  One of its strong suits is the examples of the ambiguity and absurdity of the often muddy distinction between native and non-native.  As we might expect, this distinction is less clear in Britain because it has a much longer history of “invasion” than North America (only because invasion biologists have chosen to define “native” in North America as any species that precedes the arrival of Europeans).  Professor Thompson offers some comic examples of how status as a native has been conferred in Britain and the contortions that are required to provide preferential treatment to these “natives.”

Despite kicking up the level of criticism of invasion biology a notch, reviews of Professor Thompson’s book are far more positive than those of Ms. Marris’s book.

The New Wild

The New Wild was published in the US in April 2015.  Fred Pearce does not pull his punches in The New Wild.  He methodically lays out all the reasons why invasion biology no longer deserves the status of a scientific discipline.  The readers of Million Trees are familiar with all of these arguments, so we will summarize them here and provide links to articles on Million Trees that illustrate each issue:

Although The New Wild is a full frontal assault on invasion biology, it has been very favorably received by reviewers on  Here is a review by a reader for whom the book was an epiphany:

“An important—even essential—look at our global challenges”

“Let me cut to the chase: read this book. I want to follow that statement with several exclamation points, but I’m trying to control my enthusiasm. Perhaps the book seems so important to me because I was so ignorant when I first started reading it. Perhaps my level of ignorance is extraordinary, but I just checked the websites of several environmental organizations I respect and it looks to me like they too need to read the book. Certainly it is provocative, controversial, and challenging. It will anger some, but it is not an ad hominem attack against anyone. Whatever you think of Fred Pearce, Daniel Simberloff, and others on either side of this debate, it is clear that the debate is important, even urgent. It made clear to me that I have put too much faith in environmental organizations to ferret out the facts and explicate the issues for me. Clearly, I have allowed myself to be misled. Even more important, scientific standards are not being rigorously followed. Have you noticed the headlines about all the “invasive” species that “need” to be eradicated? About the billions of dollars that are required to do this purportedly important work? I have been asking why so much killing is necessary. Pearce states that it isn’t. In fact, he goes further and suggests that the species targeted for eradication may be our salvation precisely because they have the adaptability and resilience to survive in environments disturbed and dramatically changed by mankind. His arguments are articulate and persuasive.

Environmental writers and organizations sometimes make conclusory and inflammatory claims about the damage done by those species they choose to characterize as invasive. And supporters such as myself accept those claims unquestioningly. As Pearce points out in his eye-opening treatment of the subject, too often one environmentalist repeats or even amplifies the unsubstantiated claims of another, and when this happens again and again with no one questioning the science along the way, dangerous, counterfactual conclusions are spread and soon become gospel. Pearce’s probing, incisive exploration into several of those claims in his seventh chapter, “Myths of the Aliens” is alone worth the price of the book.

Pearce woke me up. I respect the scientific method and believe it must be adhered to without fail in environmental writings. I have naively accepted that other environmentalists feel the same. We cannot make intelligent decisions if we are uninformed about true facts. False allegations have no value for any of us. “Invasive” species need new, clear-eyed, unbiased consideration by environmentalists. We need to look again at our underlying assumptions. What does “native” really mean? Which species are natural to an area? Which can survive in the “wild”? Pearce asserts that there is a “New Wild” and that we will do better to respect it sooner rather than later, to work with it rather than against it. I learned so much from Pearce not only about the facts of our situation, but also about new ways of looking at our extremely challenged world. I highly recommend this book and hope you get the opportunity to read Pearce’s insightful and creative ideas.”

This reader understands for the first time that the environmental organizations he/she had previously trusted had misled him/her into believing that non-native species are the cause of environmental damage rather than symptoms of that damage.  He/She was always uncomfortable about all the killing that was motivated by that viewpoint, which is perhaps what opened his/her mind to Pearce’s message.  This sequence of realizations describes my own journey to the other side of invasion biology.  I was initially appalled by the killing, but I did not realize that the justification for the killing was entirely bogus until I began to do my own research.  I initially assumed that they knew what they were doing.  After reading innumerable books and studies, I began to understand that there is little evidence supporting their claims that non-native species are damaging the environment.  Quite the opposite is true.  We hope that Pearce’s book will start many other readers on the same journey of discovery.

(To be fair, the first critique of invasion biology was Invasion Biology:  Critique of a Pseudoscience by David Theodoropoulos, published in 2003.  Although it was ahead of its time, virtually every criticism of invasion biology in that book remains true to this day.  However, at that point in time there were few empirical studies testing the hypotheses of invasion biology and few “restorations” based on those hypotheses.  It was therefore more difficult to make the case against invasion biology.  Theodoropoulos foretold the fate of invasion biology as a discredited ideology based primarily on his personal observations in nature.)


In just three years, three hard-hitting books have been published which confront the unfounded assumptions of invasion biology.  Although each book is progressively more aggressive and explicit in its criticism, the reaction of the public has been progressively more positive.

We admired all three of these books, so we are reluctant to conclude that the more favorable reaction to the more recent books is because of improved quality.  Perhaps the more explicit criticism of the more recent books makes it easier for readers to appreciate the strength of the argument.  Although we are deeply grateful to Emma Marris for leading the way, Rambunctious Garden requires the reader to reach the conclusion she only implies. The New Wild makes no such demands on the reader’s judgment.

However, we have our own optimistic theory about why readers are welcoming The New Wild.  The more experience the public has with the destructive projects which attempt to eradicate non-native species, the more likely they are to understand the futility and the damage being done to the environment.  We choose to interpret the positive reception for The New Wild as an indication that the public is ready to abandon the fantasy of returning our public lands to some mythical ideal landscape.

  1. Fred Pearce, The New Wild, Beacon Press, April 2015
  2. Emma Marris, Rambunctious Garden, Bloomsbury, 2011
  3. Ken Thompson, Where do camels belong?, Greystone Books, 2014

24 thoughts on “Retreat from invasion biology becomes a stampede”

  1. It will become a stampede as soon as people reject the idea that these population phenomena are ‘invasions’ in any sense.

    *Matthew K Chew Ph.D.* Arizona State University School of Life Sciences

    2014-15 Huntington Exchange Fellow Corpus Christi College, Oxford University

    *ASU Center for Biology & Society PO Box 873301Tempe, AZ 85287-3301 USA* Tel 480.965.8422 Fax 480.965.8330 or

    1. Thank you for your visit and for your comment. I admire your work and I have quoted it many times on Million Trees. We are making progress. Unfortunately, not quickly enough to save our urban forest in the the San Francisco Bay Area.

  2. I am shocked and saddened that Milliontrees persists in promoting her opinion that invasive non-native vegetation causes no harm. I’ve brought up kudzu as a well-enough known example……Milliontrees refuses to comment. I’ve sent photos and links to reports and studies about the worst invasive in my midwest region, Asian (Amur) Honeysuckle (Lonicera maackii) that chokes out new generations of trees and causes other havoc to ecosystems. With no evidence to the contrary, Milliontrees nevertheless refuses to acknowledge these facts, moreover, she refuses to include my posts in the comment section. This willful disregard for examples of destructiveness to the environment (no less than E. O. Wilson cites “invasive non-native species” as one of 4 top reasons for habitat loss) goes beyond irresponsibility to downright intentional repression of information as it serves her purposes. Shame!!!

    1. The readers of Million Trees have seen many comments from gw. I have posted most of her comments. When she says the same thing several times on each post, it is pointless to post them again. We have nothing to hide here. GW never offers anything other than her personal opinions, yet we post them for all to see. Our opinions are based on hundreds of empirical studies which support our opinions.

  3. wow, thanks for the intro to this book! and thanks for being such a staunch advocate of real science over the nonsense promoted by nativists.
    we NEED trees and any plants that can adapt to our new climate. all this killing and poisoning of trees is beyond upsetting…it’s just insane.

    1. Who is “we”? Certainly the native species don’t “need” eucalyptus! “We” need to stop thinking that we own the Earth, and can do to it what we wish, with impunity. The idea that humans own the Earth is the most destructive idea ever invented.

  4. Hello Millie.

    Here’s another book you might like to catch up with.

    Best wishes.

    Bill Benfield.

  5. There is another recent book with similar view in part of it: a chapter in the new Jepson manual speaks beautifully of reality.

    The Jepson Manual, 2nd edition: has a section called: GEOLOGIC, CLIMATIC, AND VEGETATION HISTORY OF CALIFORNIA by Constance I. Millar. Starts on page 49. Here are the highlights:

    “Earth’s environment– land, sea, air, and the organisms that inhabit these– is in a state of continual flux… As the earth below and the atmosphere above changes, plants migrate, expand and contract in range, and die out locally and recolonize. Vegetation composition is scrambled as new patterns emerge …Subspecies evolve, hybridization and gene flow dissolve taxonomic boundaries, and species go extinct as new biodiversity flourishes…… plant species have been subject to continuous change over time…The present condition of California’s environment and the future that is unfolding are complex expressions of natural forces intertwined with increasing anthropogenic influences. A key lesson from history is to work with change and harness inherent capacities for adaptation..” Isn’t that beautiful ! I admire her.

    1. It’s dishonest of her not to warn people not to introduce exotics (or did you omit that part?). Not only do they often cause disaster, but humans don’t own the Earth, though they think they do.

  6. I am thrilled for this new book. I can’t wait to read it. Another nail in the coffin for Invasion biology. By the way honeysuckle is one the most beneficial species ever to ‘invade’ with fruit equivalent to corn in nutrition and highly beneficial to those ‘native’ pollinators. Maybe the nativists with their continued blindness to the benefits of these species is really the undoing of this whole philosophy. Thank you milliontrees.

  7. I spent two days at Lake Tahoe reading The New Wild amidst beautiful old pine trees. However, I’ve learned that what we think of as “primeval” forests are, for the most part, recent growth of the last few thousand years. They are re-growth forests after ancient cultures farmed (or, in the case of Native Americans, burned) the vegetation for agricultural benefits. There is no going back to some pristine age because most forests are the result of human disturbances. We seem to need to romanticize our landscapes in order to enjoy them. Pearce’s book helped me understand these ideas.

    1. Poppycock. This philosophy is being used to justify whatever the speaker wants to do. The reasoning is “It’s already messed up, so that makes it okay to mess it up some more.”. That is specious reasoning. For example, just because native Americans used fire, that doesn’t make it okay to continue doing the same. Humans have only been in North America maybe 20,000 years – insignificant on an evolutionary scale. We still don’t tell the trees how to grow. Eucalyptus will NEVER be an integral part of our ecosystem in any amount of time relevant to humans. Living things (except for bacteria and viruses, of course) just don’t evolve that fast!

      I’d like to know what the author’s recommendations are, and whether they further a human-preferred agenda..

      1. If Mr. Vandeman had read Mr. Pearce’s book, he would know that his description of Pearce’s philosophy isn’t accurate and he would also know what Pearce’s recommendations are for successful conservation strategies. Mr. Pearce tells us about the many specific cases in which non-native species are performing valuable ecological functions as well as many specific cases in which futile attempts to eradicate them have done more harm than good.

        Mr. Vandeman is mistaken that evolution is too slow to accommodate the arrival of introduced plants and animals. For example, there are hundreds of weed species that are now immune to the herbicides that have been used on them because they have evolved defenses against the herbicides. There are also many examples of insects that have evolved adaptations to changes in the ecosystem. The fact is, evolution occurs rapidly, especially in a rapidly changing climate. Here is a report from an academic scientist who studies rapid evolution:

        1. I don’t think that you know what evolution is, so let me elaborate. By “evolution”, I mean the development of successful new alleles, by means of genetic mutation. That is an extremely slow process, because (1) mutations are already rare, (2) most mutations are harmful, and don’t survive. What you are calling “rapid evolution” is, therefore, most likely simply the result of the success of an existing allele. For example, if having blue eyes were to suddenly gain survival value (e.g. if they became socially important), the incidence of blue eyes could increase. That would not be “evolution”. On the other hand, if a mutation created people with bright orange eyes (due to a mutation creating a brand new allele), THAT would be evolution. What you are citing as “rapid evolution” is most likely NOT evolution, but just normal genetics.

          1. Let’s start with a standard definition, from UCB’s Museum of Paleontology: “Biological evolution, simply put, is descent with modification. This definition encompasses small-scale evolution (changes in gene frequency in a population from one generation to the next) and large-scale evolution (the descent of different species from a common ancestor over many generations).” UCB Museum of Paleontology, Evolution 101

            Notice this definition does not require the introduction of new alleles. It clearly includes changes involving existing alleles. Darwin’s classical theory of “evolution by natural selection” requires two ingredients: 1) genetic variation within the population, and 2) selection pressure. So any population with individual genetic variation (virtually any natural population) experiences evolution when selection pressures change. Some already existing alleles confer survival and reproductive advantages over other already existing alleles in the new environment. The population then changes in gene frequency, morphology, physiology, etc. That’s evolution.

            Your definition of evolution that requires new alleles before “real” evolution can occur is simply not shared by the scientific world. Your blue eyes example is an (hypothetical) example of real evolution, just as much as your orange eyes example. Both involve selection pressures operating on variation in the population, i.e. evolution. Medical scientists routinely speak of the evolution of antibiotic-resistant bacteria, genetic frequencies changing in response to selection pressure. Agricultural scientists speak of the evolution of pesticide resistant weeds. They are using the word “evolution” correctly. When Dr. Scott Carroll, Institute for Contemporary Evolution at UC Davis, talks about the evolution of the Soapberry Bug, he is entitled to use the word because he is an expert, unlike you and me. Sorry, but you can’t just change the language to suit your fancy. Of course, ultimately genetic variation has come, and will continue to come, from mutations (“new alleles”), but evolution by natural selection is working away every day on currently existing genetic diversity.

  8. My problem with invasion biology is that it isn’t neutral enough. There’s certain ideologies – subjective views – of how nature should be, such as the pristine and untouched nature idea. In my native country in Europe, there was a longer history of intensive land use, and as such there’s more focus on preserving cultural landscape and the species that lived in them. What both of these ideologies, if I may call it that, have in common is that they rely on a past status of an ecosystem. As such they are usually hostile towards any changes in them, and specifically if these changes are anthropogenic. Which is interesting, because most non-native branded invasive – sometimes without evidence of a negative effect – are anthropogenic. Species that expand naturally are not that often considered to be invasive, but those that are introduced are. There’s a specific dislike of those species that were introduced, and thus anthropogenic. Those species that benefited from anthropogenic changes in the environment (turtle doves and recently jackals in Europe, coyotes expanding into South America) are not victim. There is however some basis for introduced species to be a kind of bad thing, but this doesn’t apply to all environments. What invasion biology does, or those who support it, is applying the negative to all non-native species. Even if invasion biology does acknowledge that not all species become invasive, many do not.

    What I find important, is that not every environment is the same. Islands are the hardest hit when it comes to introduced species. This is because islands have a long isolated evolutionary history, and as such there are co-evolutionary elements missing. Take a lot of flightless birds, they did not evolve alongside certain predators and so when those are introduced they often go extinct. I consider Australia also such a island, since it has a long isolated evolutionary history, and so just a large one. On the mainland, species have evolved that are more adaptable than those on islands since they are more competitive. The mainlands, those other continents, also have a history of interaction and invasion. To refer to Australia and islands, such as New Zealand, Hawaiian islands and so on and so on, when talking of non-native species in Europe, North or South America, Asia and Africa is nonsense. It is possible that co-evolution is missing and thus the same situation happens, but to say that the island invasions are as bad as the mainland invasion is, again, nonsense. Example; the mainland complex (Eurasia, Africa and the Americas) have foxes, while Australia did not, this means a fox to Australia is different as a fox to the mainland complex. It remains in the possibility that a specific fox species is more adaptable, and would outcompete a species in another range if introduced, but it seems unlikely that prey species are impacted by its presence. In a range with no ecological equivalent of a species, yes, you could expect some impact by its presence. If a prey species is impacted by other environmental changes, it is also more vulnerable.

    Another problem I have, is the “there’s no natural predators” argument. Usually research shows that there are in fact some predators. Cane toads were predated by several species; it just didn’t help stop their expansion. It is a fallacy to think that all species are “controlled” by predation. It is possible. But in some species food limitation, favorable environment or disease is the factor that limits a population. So when it comes to predators, there are usually some, and it also isn’t always needed.

    There’s also still this idea of ecosystems in balance because of years of co-evolution. Most ecologist today would prefer to refer to the flux of nature, instead of the balance of nature. We also see that evolution is much more faster as believed, and so we see some species adapting to non-native species. In my region, native animals impacted other species in the same way that non-natives do it. Foxes forced ground-nesting birds out of dune areas into the city, and the same kind of phenomenon was happening as goshawks forced birds from nesting in forests to the city. I suspect that there’s more to it, since agricultural changes made the wood pigeon population decline and this forced goshawks to prey on crows and sparrowhawks which are the ones that moved to the city to breed.

    I want to sketch some more examples from my region. In prehistoric times, at least two species that are introduced, the raccoon and raccoon dog, had once lived in Europe. True, it were different species, but more or less the same. Luckily, in my region some ecologists take a more neutral approach; raccoons and raccoon dogs are not considered to be much of a threat, only locally, but that applies to native foxes too. American oaks tend to crowd out other trees, so it is claimed, but ecologists point out that American oaks are the favored tree of bats and pine martens. I want to point out that beech trees and oak trees tend to do a similar thing, beech forests usually only consist of beech trees. It is because their leaves are acid. Even beech trees and oaks aren’t that native, my region used to have birch, pinus and linden trees instead. The linden trees were disfavored, since oaks and beech provide food for pigs – if I remember it correctly, I could be wrong. The linden trees are better for the soil. Having said that, beech and oak trees are the trees with the highest insect diversity. The introduced trees are usually less diverse, but wait! The European yew is amongst the trees together with a few introduced trees with the lowest diversity. The American oak scores okay, and we might expect some native oak insects to discover and even evolve to the American oak. This is the reason the European yew isn’t that diverse; it doesn’t have much if any related family members in Europe, and so no insects can make the jump from one tree to another.

    I do think, that introducing species isn’t always a good thing. But if I focus on my region, and mainland areas in general, those are few in number. As so, I want to describe a few that are generally bad. Non-native squirrel species, with a few exceptions, would replace the native squirrel. You lose a species to gain a species. I must say however, our native species seems poorly adopted to the environment and seems to be related to the ice age; it is much better adopted to boreal forests. Another, the European mink and the American mink. Again, you lose a species to gain a species. However, to blame the American mink for the European mink is nonsense. The European mink had already declined because of other reasons, and it seems that the American mink is less picky as the European so it does better. For my region I can hardly think of anything that causes a few species loss, one species gain, as happens with islands (feral cat in, several flightless birds out). With crayfish, we lose the noble crayfish, but gain several crayfish species in return.

    Not to say that non-native species in Europe (or other mainlands) cannot be more severe, just that I think it is unlikely. It is possible that the environment is changed, that favors some species but others not. Some plants make places drier, or turn environments from one to another. This happens with natives too in my region. Those cultural landscapes that conservationists want to protect, would be forests if left alone, which would be most of the original landscape anyway. But forests do not allow certain species that conservationists have picked they want to protect. And so they battle the changes, instead of letting develop on its own.

    I can talk much longer about this subject, but leave it for what it is with this. I will contribute another time again.

    1. I forgot, I want to add that I think it is better to prevent species from establishing. By forbidding it to be kept in captivity or by trade regulations. But those that have established, please leave those alone.

      1. We agree. It is the futile attempts to eradicate firmly entrenched species that have been with us for generations that is causing the most damage to the environment. The “million trees mantra” is “PLANT WHATEVER YOU WANT, JUST QUIT DESTROYING EVERYTHING ELSE!”

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