Happy New Year and Farewell

The Million Trees blog is folding its tent and moving on because most of the projects in the San Francisco Bay Area that I have followed for 20 years have been approved, funded, and are being implemented.  Every public land manager in the Bay Area has made a commitment to destroying most non-native trees and using pesticides for that purpose.

If you wish to continue following the development of these projects, I recommend these websites:  San Francisco Forest Alliance Defend East Bay Forests, Save the East Bay Hills, and Hills Conservation Network.

For the record, this is a brief summary of my beliefs about the environment:

If I return to the blogosphere in the future, the title and mission of a new blog would change.  The focus would be the science that informs my commitment to the cosmopolitan landscape that exists, rather than the fantasized landscape of the past.  I will also continue to inform readers of new studies that find evidence of the damage that pesticides do to the environment and its inhabitants.  If you are a subscriber to the Million Trees blog, you will be informed if I publish a new blog.

Thank you for your readership.

Million Trees

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 Amazon.com 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 Amazon.com 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 Amazon.com.  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

A defensive tirade from invasion biologists

Pesticide use by land managers in California.  Source California Invasive Plant Council
Pesticide use by land managers in California. Source California Invasive Plant Council

An international team of invasion biologists has just published a defense of their academic turf, invasion biology.  (1) Daniel Simberloff, an American member of the team, is the most relentless defender of the crusade to eradicate all non-native species, wherever they are found, all over the world.  Their publication acknowledges the mounting criticism of this crusade and attempts to respond to that criticism, but what is most notable is what is missing from their attempt to defend their opinions.  They make no mention of the harmful methods used to eradicate non-native species:

Keep these damaging methods in mind as we visit the hypocritical and contradictory arguments used to justify the projects for which these invasion biologists advocate.  They set up “novel ecosystems” as the straw man to which they compare the goals of invasion biology.  They define novel ecosystems as “a new species combination that arises spontaneously and irreversibly in response to anthropogenic land-use changes, species introductions, and climate change, without correspondence to any historical ecosystem.”

“Lack of rigorous scrutiny”

Their primary criticism of the concept of “novel ecosystems” is that it has not been “subjected to the scrutiny and empirical validation inherent in science” and its definition is “impaired by logical contradictions and ecological imprecisions.”   These criticisms apply equally to invasion biology.

Hypothesis n % of supporting studies % of decline in support
Invasional meltdown




Novel weapons




Enemy release




Biotic resistance




Tens rule




Island Susceptibility




Although support is strongest for the invasional meltdown hypothesis, recent studies are less supportive than early studies, indicating substantial decline in supporting evidence.  Declining evidence of invasional meltdown is consistent with the fact that exotic species are eventually integrated into the food web which reduces their populations, stabilizing their spread. There is apparently little evidence that islands are more susceptible to invasion than continents and few studies have been done to test the hypothesis.

If empirical validation and semantic precision are required to establish the credibility of scientific hypotheses, invasion biology has failed that test.

“Precautionary principle of conservation and restoration”

These invasion biologists define the precautionary principle of conservation and restoration as follows:  “we should seek to reestablish –or emulate, insofar as possible—the historical trajectory of ecosystems, before they were deflected by human activity.”  This is an unusual use of the precautionary principle, which is more typically defined as avoiding damage to the environment by not using potentially harmful methods, even in the absence of solid evidence of such harm.  The precautionary principle was not used when the following “restoration” projects were defined or implemented:

Ivy in the Conservatory in Central Park, New York City
Ivy in the Conservatory in Central Park, New York City

In 1996, Daniel Simberloff made this statement in his publication about the hazards of biological controls:  “…are there any protocols for biological-control introductions that would prevent all disasters?  Probably not…” (2) Yet, in 2013, he expressed his support for the introduction of non-native insects to control cape ivy at a conference at UC Davis sponsored by the California Department of Food and Agriculture.  Although cape ivy is despised by native plant advocates, it is not an agricultural pest and therefore causes no economic damage to ecosystems, unless money is wasted on attempts to eradicate it.

“All ecosystems should be considered candidates for restoration”

In response to those who find value in novel ecosystems, these invasion biologists find none.  They reject the possibility that there is ever a point at which it may not be possible to re-create a historical landscape.  They continue to believe that ANY and ALL radically altered landscapes CAN and SHOULD be considered candidates for restoration.  Their only caveat to this universal goal is that “damaged ecosystems…should be evaluated for feasibility, desirability, and cost-effectiveness, on a case-by-case basis, so that informed and science-based policy decisions can be made, in consultations with scientists, restoration practitioners, stakeholders, and advisors.”

These criteria for potential “restoration” have nothing to do with reality:

  • Most projects in the San Francisco Bay Area have not provided cost estimates when they were planned. The public demanded cost estimates for the projects of the Natural Areas Program in San Francisco, but these demands were ignored.  Therefore, “cost-effectiveness” is not usually considered when these projects have been shoved down the public’s throat.
  • We consider the public to be “stakeholders” in decisions to radically alter our public open spaces. We are the visitors to these areas and our tax dollars pay for their acquisition, maintenance, and “restoration.”  Yet, managers of public land are consistently making those decisions without taking the public’s opinion into consideration.  Most projects are planned and executed without any public participation.  In the few cases in which there are environmental impact reviews, the projects are implemented regardless of overwhelming opposition of the public.

 “Human-damaged ecosystems can be at least partially restored”

The demonstrated futility of “restoration” projects is one of many reasons why there is waning public support for attempting them.  Yet, invasion biologists who authored this diatribe claim that “restored sites recovered on average 80-86% of biodiversity and ecosystem services…and showed improvements of 125-144% over degraded ones.”  This claim is contradicted both by other scientific studies and by experience with local projects:

  • “…this paper analyses 249 plant species reintroductions worldwide by assessing the methods used and the results obtained from these reintroduction experiments…Results indicate that survival, flowering and fruiting rates of reintroduced plants are generally quite low (on average 52%, 19%, and 16% respectively). Furthermore, our results show a success rate decline in individual experiments with time.  Survival rates reported in the literature are also much higher (78% on average) than those mentioned by survey participants (33% on average).” (3)
  • Dunnigan Test Plot, Augusst 2011.  The result of an eight-year effort to restore native grassland.  Does it look "biodiverse?"  ecoseed.com.
    Dunnigan Test Plot, August 2011. The result of an eight-year effort to restore native grassland. Does it look “biodiverse?” ecoseed.com.

    There is frequently a discrepancy between the success rates claimed in papers and those actually observed. For example, Cal-Trans gave researchers at UC Davis $450,000 to restore 2 acres of non-native annual grassland to native grassland.  UC Davis researchers spent 8 years and used multiple methods to achieve this transition.  When they ran out of money, they declared success in their published report.  They defined success as 50% native plants which they expected to last 10 years before being entirely replaced by non-native annual grasses again.  Do you consider that a success?

  • On a more anecdotal level, we watch established landscapes that have required no maintenance in the past being transformed into weedy messes by failed “restoration” projects. Then, adding insult to injury, we hear those who are responsible for these failures tell us how successful they are.

“Inadequate political will”

The authors of this publication conclude:

“No proof of ecological thresholds that would prevent restoration has ever been demonstrated.  Often the threshold that obstructs a restoration project is not its ecological feasibility, but its cost, and the political will to commit to such cost.” (1)

We are reminded of an old football adage:  “The best defense is a good offense.”  In other words, invasion biology is under fire, but the reaction of invasion biologists is to demand more….more money, more effort, and the commitment of public land managers to “restore” all ecosystems, regardless of what the public wants.  And in support of that aggressive strategy, they refuse to acknowledge the damage that is being done to the environment and the animals that live in it, by the projects they demand.

The authors of this defensive tirade have hammered another nail in the coffin of invasion biology.

  1. Carolina Murcia, James Aronson, Gustavo Kattan, David Moreno-Mateos, Kingsley Dixon, Daniel Simberloff, “A critique of the ‘novel ecosystem’ concept,” Trends in Ecology and Evolution, October 2014, Vol. 29, No. 10
  2. Daniel Simberloff and Peter Stiling, “How Risky is Biological Control?” Ecology, 77(7), 1996, pp 1965-1974
  3. Sandrine Godefroid, et. al., “How successful are plant species reintroductions?” Biological Conservation,   144, Issue 2, February 2011

Are critics of invasion biology pessimists or realists?

The California Department of Food and Agriculture held a symposium about invasive pest management in the 21st Century on October 17, 2013, at UC Davis.  This second in a series was focused on insects and diseases.  The first symposium held in Oakland in June 2013, focused on “invasive” plants.

The keynote speaker at the second symposium was Professor Daniel Simberloff of University of Tennessee.  He is a prominent invasion biologist and a self-appointed defender of that scientific discipline.  When the assumptions of invasion biology are questioned by other scientists, Professor Simberloff often publishes a heated response and recruits others to join him.  (For an example, see our recent post about Ascension Island and visit his “Counterpoint” to the article on which our post was based.)

Given the many recent defections of scientists from the central assumptions of invasion biology, we anticipated that Professor Simberloff would acknowledge that invasion biology is under siege.  We were not disappointed.  He started his talk by showing a quote from a scientist on the Galapagos Islands who, after decades of trying to eradicate non-native blackberry, was admitting defeat.  To paraphrase the scientist, he no longer believes that eradication is possible.  Therefore, he is now willing to call it a native plant.

These blackberries were mowed to the ground sometime in the past year.  Herbicides haven't been used in the Sutro forest for several years, but UCSF plans to use them in the future.  Courtesy Save Sutro
These blackberries in the Sutro forest were mowed to the ground sometime in the past year. Herbicides haven’t been used in the Sutro forest for several years, but UCSF plans to use them in the future. Courtesy Save Sutro

We were reminded of Professor Matt Chew’s criterion for what species “belong” in any particular location.  If the species persists unassisted in that location, Professor Chew believes it belongs there.  Surely a corollary to that criterion should be, “if you can’t eradicate it, it belongs there.”

Professor Simberloff diagnoses this acceptance of non-native species as pessimism.  He is not alone in this characterization of people who are no longer willing to spend unlimited amounts of time and money trying to kill non-native species.  This is the standard criticism of that viewpoint.  We are called defeatists who have “given up” in the internet debates we read.

Why are we critics of invasion biology?

Although we agree that it is usually futile to try to eradicate non-native plants with large, well-established populations that have long ago naturalized in our environment, this is not the primary reason why we reject the notion that there is some benefit to trying anyway.  The main reason why we reject the fruitless crusade against non-native plants is because of the damage it does:  the herbicides that are sprayed on our public lands; the release of tons of carbon dioxide into the atmosphere when trees are destroyed; the loss of habitat for wildlife, etc.

At the same time, we acknowledge that some invasions of insects and diseases have posed such serious economic and health threats that we have no choice but to make every effort to eradicate them.  The species of mosquitoes that carry yellow fever and malaria are examples of justified eradication efforts.  We hope that those who are engaged in that effort are also mindful that the methods used are not more harmful than the targets.

Scientists defend “novel” ecosystems

We harp on these issues because they are not discussed by the scientists who either defend or critique invasion biology.  Their concerns are, so to speak, academic.

Sutro Forest is a novel ecosystem. Courtesy Save Sutro

There is an excellent description of the scientific debate about “invasive species” in the on-line newsletter of the American Society of Landscape Architecture (ASLA).  They report that novel ecosystems were featured at the recent conference of the Society for Ecological Restoration (SER) held in Madison, Wisconsin.  Novel ecosystems were defined by one of the speakers (Eric Higgs, University of Victoria) as ecosystems in which changes from historical conditions are considered irreversible: “Even if plants are removed, ‘the system will revert back immediately’ to a state of invasion.”  This is an accurate description of 15 years of effort by San Francisco’s so-called Natural Areas Program.  Non-native plants are repeatedly yanked out and/or poisoned, native plants are planted, native plants die, non-native plants return.  That cycle is repeated annually in some high-priority locations.

Apparently, we are not alone in observing this futile cycle.  The ASLA description of the conference of the Society of Ecological Restoration summarizes current thinking of practitioners of that profession:

“In the face of this overwhelming struggle against novelty, there has been a shift in values among society. Years ago, restoration ecologists wanted to restore ecosystems to their “historic fidelity” as much as possible. Now, ecologists, scientists, and landscape architects discuss the value of novel ecosystems’ services, which to some extent are plant-agnostic.”

While this viewpoint is a welcome improvement over the previous fantasies of restorationists, this information has not yet reached managers of public lands in the San Francisco Bay Area.  Nor does it acknowledge the very real damage that is being done by those who cling to the fantasy that non-native plants can be eradicated and replaced with native species, particularly in an urban setting such as the Bay Area.

The mission of Million Trees is not an academic exercise.  Our objective is to stop the damage being inflicted on our environment and the animals that live in it.  And we don’t intend to shut up until the damage has stopped.  We hope to be put out of business within our lifetime.