June 2015 – Conservation Sense and Nonsense

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

The 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 Marris believes it’s time to abandon (or de-emphasize) what she sees as outdated and naïve conservation strategies such as creation of national parks and wilderness reserves.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?

The 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:

There is very little empirical evidence that supports the assumptions of invasion biology:
- Native animals quickly adapt and/or evolve to use new introduced plants.
- There is no measurable loss of biodiversity resulting from the newly introduced plants. In fact, biodiversity has consistently increased all over the globe as a result of introduced species.
- No extinction of a native plant has occurred in the continental US as a result of an introduced plant.
There is usually some underlying reason why an introduced plant has become invasive, such as pollution, changed climate, etc. Eradicating plants does not reverse underlying conditions and therefore does not result in the return of native plants that are no longer adapted to changed conditions.
Non-native plant species are often performing valuable ecological functions, such as improving the soil or feeding and sheltering other plants and animals.
There are often negative unintended consequences when attempts are made to eradicate non-native species, such as damage or deaths caused by pesticides and trophic cascades resulting from eradicating one species that has been performing a role in the ecosystem, which was not known or understood.
The “new wild,” the unmanaged novel ecosystems with a rich and diverse mix of native and non-native species working out their own arrangements, is nature at work. In novel ecosystems, vigorous evolution and adaptation to new circumstances produce self-sustaining ecosystems that are truly wild. The carefully tended restoration and re-wilding projects of “invasion biologists” will be theme parks, gardened forever; there is nothing wild about them.

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.)

Progress!!

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.

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

“Drought-Adapted Eucalyptus NOT Dying by the Thousand”

Native plant advocates in the Bay Area have always had trouble convincing the public and their elected representatives that it is necessary to destroy every non-native tree in our urban forest. They have therefore resorted to fear-mongering to convince the public that it is necessary to eradicate all non-native trees for public safety.

Fear of fire has been effective in the East Bay where there have been fires, although claims they were caused by non-native trees are a distortion of the facts. For the past year, native plant advocates in San Francisco have been using a variation on that theme to support their demands to destroy all non-native trees. They now claim our eucalyptus forest is dying of drought and must be destroyed before it causes a disastrous fire. You can read that story line in Jake Sigg’s Nature News (here) or in his recent public comments to San Francisco’s Urban Forestry Council (here), which is in the process of developing Best Management Practices for San Francisco’s urban forest.

It is our pleasure to republish this post from Save Mount Sutro Forest, responding to those claims. As usual, it is meticulously researched and documented. We only wish to add this small bit of common sense: The drought is hard on all plants. If the drought were capable of singling out one species of tree to kill, it would not be the drought-tolerant eucalyptus.

Jake Sigg, retired San Francisco Recreation and Parks Department (SFRPD) gardener who is considered the doyen of the Native Plant movement in San Francisco, has a widely circulated email newsletter. In it, he has been pushing the argument that thousands of eucalyptus trees in San Francisco are dying of drought, as evidenced by epicormic growth on these trees: “2015 is the year of decision, forced upon us by 20,000 to 30,000 dead trees.” He is suggesting they will be a fire hazard and that SFRPD must act, presumably by cutting down the trees. In a recent post, he published a picture of a tree covered in young blue-green leaves, and predicted it would be dead within a year.

But he’s mistaken.

Eucalyptus trees are drought-adapted, and the shedding of mature leaves followed by sprouting of juvenile leaves (epicormic sprouting) is one of their defense mechanisms. These trees survive in areas far drier than San Francisco, where fog-drip provides an important source of summer moisture.

EUCALYPTUS RESPONSE TO DROUGHT

Eucalyptus trees are adapted to drought. They shed mature leaves and twigs so they don’t lose water through transpiration (the tree version of breathing, which takes place mainly in the leaves.) Later, they can replace the lost branches and leaves through “epicormic sprouting.”

Blue gum eucalyptus trees have buds buried deep under their bark. When the tree is stressed, they may shed adult leaves and later sprout new leaves along their branches. When you see a eucalyptus tree that seems to have shaggy light bluish-green new leaves along its branches or trunk – that’s epicormic sprouting.

Here’s what Jake Sigg said in a recent newsletter: “According to arborists, the trees produce these abnormal shoots from epicormic buds when their lives are seriously threatened. In this case, the tree is expected to be dead by the end of 2015. On Bayview Hill, barring heavy unseasonal rain, hundreds of the trees will be dead this year. Yet the City continues to not see a problem.”

We asked UC Berkeley Professor Emeritus Joe McBride and California’s leading expert on eucalyptus for his opinion. He’s observed this condition in trees along the edge of the Presidio forest and explains, “This response is common in blue gum as a mechanism to reduce transpiration rates in order to survive drought years.”

He continues: “I am not convinced that the trees will die in large numbers.”

THE GIRDLED TREES OF BAYVIEW HILL

As an aside, we find it ironic that Mr Sigg should be so concerned with dead trees on Bayview Hill, given that’s where nativists girdled hundreds of healthy eucalyptus trees to kill them.

(This is done by cutting around the tree, thus starving it of nutrients that are carried only in the outer layers of the tree-trunk.) It’s clearly visible in the two photographs here, both taken on Bayview Hill.

EUCALYPTUS ADAPTS

In fact, one of the reasons eucalyptus is so widely planted – including in climates both hotter and drier than in San Francisco – is that it adapts to a wide range of conditions.

Eucalyptus globulus thrives in Southern California, Spain, Portugal, India – all places hotter and drier than San Francisco.

Here’s a quote from R.G. Florence’s textbook, Ecology and Silviculture of Eucalyptus Forests:

From p.121 of the same book: “… they regulate their water usage in hot dry summers by closing their stomata [breathing pores in the leaves] during the day and lowering their rates of gaseous exchange. They adapt by their elastic cell structure to water stress.”

EPICORMIC SPROUTING IS IMPORTANT IN EUCALYPTUS

Mr Sigg describes “how to identify a dying blue gum” as follows: “Look for trees with thinning foliage and copious juvenile leaves (called coppice shoots) hugging the main stems. These coppice shoots are easy to see because of their blue color and tight clustering, as opposed to the adult leaves, which are 6-8 inches-long, dull-olive-colored and sickle-shaped and which hang from the ends of long branches. These coppice shoots are the give-away that the tree is in trouble and is destined to die soon…” (He later corrected “coppice shoots” to epicormic growth.)

But again, this is not actually true.

In fact, epicormic sprouting allows eucalyptus to survive not only drought, as described above, but even fire. The epicormic sprouting grows into new branches to replace the ones that have been damaged in the fire. This is from Wikipedia: “As one of their responses to frequent bushfires which would destroy most other plants, many Eucalypt trees found widely throughout Australia have extensive epicormic buds which sprout following a fire, allowing the vegetative regeneration of branches from their trunks.[4][5] These epicormic buds are highly protected, set deeper beneath the thick bark than in other tree species, allowing both the buds and vascular cambium to be insulated from the intense heat.[4]”

(The references are: [4] “Effects of fire on plants and animals: individual level”. Fire ecology and management in northern Australia. Tropical Savannas CRC & Bushfire CRC. 2010. Retrieved 27 December 2010. [5] “Learn about eucalypts”. EUCLID – Eucalypts of Australia. Centre for Plant Biodiversity Research. Retrieved 27 December 2010.)

And sometimes, dead branches and leaves and epicormic growth don’t even indicate stress – it’s part of the normal growth cycle. R.G. Florence’s book on eucalyptus says: the “mature crown of a eucalypt maintains itself by the continual production of new crown units, which die in turn. There will always be some dead branches in a healthy mature crown.” He goes on to say an “undue proportion of dead branches is an unhealthy sign” but a “reasonable proportion of death of crown units should be accepted as normal.” He also discusses the “epicormic shoots from dormant buds on the top and sides of the branch develop into leaf-bearing units of the mature crown.” (p.13) Eucalypts go through stages of development that include extensive self-thinning, particularly in younger trees. (p. 194)

Another reason for epicormic sprouts on eucalyptus is increased light. From Wikipedia, with references: “Epicormic buds lie beneath the bark, their growth suppressed by hormones from active shoots higher up the plant. Under certain conditions, they develop into active shoots, such as when damage occurs to higher parts of the plant or light levels are increased following removal of nearby plant. Epicormic buds and shoots occur in many woody species, but are absent from many others, such as most conifers.” [The Wikipedia article references the Encyclopedia Britannica.]

We have seen these epicormic sprouts in eucalyptus trees around the clubhouse in Glen Canyon after many trees were removed.

We also saw them on Mount Sutro near where 1,200 trees were removed for “fire safety.”

MISTAKING DEFENSES FOR DEATH THROES

In summary, then, epicormic sprouting does not indicate that the tree is near death. It may indicate that the tree is responding to drought (or even to other stresses like pesticide use or damage to its root systems) with defensive measures. It’s like declaring that everyone who has a fever is bound to die of it. The trees below are the same ones featured in the picture at the start of this article – one year later, they’re surviving, not dying.

In some cases, epicormic sprouting may indicate nothing at all, except that the tree is going through a normal growth phase, or changed light conditions following removal of nearby trees.

LIVING WITH A FEW DEAD TREES

We asked Dr McBride if it made sense to cut down these trees. “I do not think the city would be justified in cutting trees down as a fire prevention action,” he says. “Cutting down drought-stressed trees at this point would be much more costly, sprouting would be difficult to control without herbicides, and the litter on the ground would have to be removed to decrease the fire hazard.”

“The problem as I see it is the accumulation of leaves, bark, and small branches on the ground. This material presents a serious fuel problem when it dries out sufficiently.” However, he points out that “In many eucalyptus stands in San Francisco the eucalyptus ground fuel (leaves, bark, and small branches) seldom dries to a point that it can be ignited because of summer fog and fog drip.” In dry areas, the best course is to “launch a program of ground fuel reduction by removing the litter from beneath eucalyptus stands.”

The eucalyptus-tree nest hole of the red-shafted flicker - San Francisco. Janet Kessler — Eucalyptus-tree nest hole of red-shafted flicker – San Francisco. Copyright Janet Kessler

A few trees may indeed die, with the drought or without it. If you think of a forest as a normal population, you expect to find some trees that are thriving and some that are hanging on, and some that are dying – just like in any population. And dead and dying trees are very valuable to wildlife: They’re more likely to have cavities that are suitable for nesting (and are easier to excavate for woodpeckers and other cavity-building species). They also have bugs that come to feast on the decaying wood, and that’s bird-food.