Observations of the Blue Ridge Naturalist

I’ve been a nature writer/photographer in Crozet, Virginia, for more than 25 years. My freelance articles have been published in numerous national and state magazines and newspapers, and I’ve written nature columns for many newspapers, as well as Virginia Wildlife, the magazine of our state wildlife department. My yard was featured on Virginia PBS stations in 1994 and again in 2005, and is the basis of my book, The Nature-friendly Garden: Creating a Backyard Haven for Plants, Wildlife, and People (Stackpole Books, 2006).  In all of these venues, I discussed nonnative plants, including some considered “invasive”, without suffering much, if indeed any, blowback.

Home of Marlene Condon in Crozet, Virginia. Photo credit Marlene Condon

However, over the past quarter century, there has been more-and-more of a push by native-plant societies to get government entities and environmental groups to rid the natural world of so-called invasive plants, including even native plants considered “thugs” because their growth is exuberant.  Because I was concerned about the destruction of habitat and the often-extensive use of pesticides to accomplish their mission, I started writing explicitly about this movement, as in the article below.

After the publication of this article last year, nativists mounted a smear campaign against me personally, a sure sign of how weak their invasive-plant arguments are.  The lead writer never even publicly disclosed her affiliation with the Blue Ridge PRISM, a group “targeting common invasive plants in the Blue Ridge”, which would have allowed readers to question whether her comments about me were suspect. My editor certainly was duped, placing a headline of “Blue Ridge Naturalist–NOT!” over their comments. And perhaps not coincidentally, shortly thereafter, he fired me, even though I’d written for–and received high praise from–him for 11 years.

Since then, I’ve found it virtually impossible to write openly about any nonnative plants.  Media and environmental groups are cowed by these people, thanks to their numbers and involvement with various organizations and governments (local, state, and federal). Sadly, this movement is highly detrimental to our natural world that is already in very bad shape and can hardly withstand yet more negative impacts upon it. Folks who understand the senselessness of destroying functioning habitat and poisoning the Earth with pesticides must speak out publicly for the benefit of nature.

Marlene Condon, Blue Ridge Naturalist

FEBRUARY 2019
The Blue Ridge Naturalist
© Marlene A. Condon

Bees and other kinds of insects obtain nourishment from the blooms of Weigela, a spring-blooming shrub native to Asia. Photo credit Marlene Condon

Ecologists Recognizing Value of Alien Plants

Scientists are either waking up to what I’ve been saying for years, or finally becoming brave enough to speak out against the wide-spread invasive-plant movement. In an opinion piece signed by 19 ecologists in the journal Nature, they argue that “policy and management decisions must take into account the positive effects of many invaders.”

Recognizing that “It is impractical to try to restore ecosystems to some ‘rightful’ historical state”, they go on to point out that eradicating or drastically reducing the abundance of invasive plants is “an impossible goal.”

Critical thinking is a must for deciding invasive-plant policy to avoid harming wildlife and wasting millions in tax dollars. A situation in California illustrates the foolishness of blindly pushing an agenda without giving any thought to the real-world consequences of doing so.

In the name of “saving” the environment from so-called invasive plants, a movement has sprung up to remove Eucalypt (Eucalyptus globulus) trees from California. These trees, brought in from Australia, now serve as the most frequented overwintering sites for the western Monarch butterfly population.

Monarchs originally roosted in native conifer stands of Monterey Pine (Pinus radiata), Monterey Cypress (Cupressus maculatum) and Coast Redwood (Sequoia sempervirens). Sadly, extensive development, logging, and poor land-management decisions have reduced the number of these native-tree stands, leaving the butterflies to rely upon non-native Eucalypts.

Ignoring the fact that overwintering Monarchs are very much dependent upon isolated stands of these trees, government plans are mandating removal of them. Does this make environmental sense? Absolutely not; eradication of the Eucalypts means no wintering habitat for Monarchs, which means they will die.

In other words, this deliberate destruction of habitat is taking place because of ideology, an illustration of the danger posed by people who have been led to believe they are part of an environmentally moral crusade. Native-plant folks out west have managed, as they have here in the East, to convince environmental organizations and government entities at every level that it is a moral imperative to remove plants deemed invasive.

But, the whole point of conservation of the environment is conservation of wildlife, without which the environment cannot function properly. Yet, absolutely no thought is given to how much so-called invasive plants support wildlife or serve important environmental functions in degraded areas.

Thus, for example, in the city of Waynesboro, Virginia, the Parks and Rec department decided it had to remove Japanese Knotweed (Fallopia japonica, formerly known as Polygonum cuspidatum) from growing along the South River greenway (Waynesboro News Virginian, March 9, 2018, “War on Weeds”). The main reason given for the removal of these plants was that they are preventing native plants from growing, but this statement is nothing more than invasive-plant folklore that gains credence by the act of repetition.

Read about virtually any “invasive” species and you will find that these plants are typically growing in disturbed areas where man or a weather event destroyed the original soil profile. As a result, the plants that had been growing there previously did not come back because they could not handle the altered physical conditions of the site. It’s why you see so-called invasive plants mainly along roadways, in parks, and along river trails—all areas easily seen by people who then mistakenly believe the exotic plants pushed out native species.

The newspaper stated that knotweed is a “formidable culprit to the river’s health”, but the true threat lies in its removal. This plant has superbly performed erosion control of soil in which native plants struggle to grow; feeds numerous kinds of pollinators when it blooms; and provides wonderful cover and nesting sites for numerous species of birds and the non-herbivorous insects that feed them. One need only to walk the trail with open eyes and an open mind to ascertain the truth of this statement.

Additionally, park employees would use herbicides to kill the knotweed. How can poisoning the Earth be less harmful than allowing alien plants to grow in areas where they are currently the most suited to thrive and thus provide badly needed habitat for wildlife?

You might wonder how the invasive-plant movement became so entrenched in environmental and governmental circles. The answer lies in the treatment of it as a moral cause in which those who agree with removing “bad” plants are virtuous; those who disagree must be bad like the plants themselves. Under these circumstances, it is difficult for folks to take a stand in opposition; no one wants to be considered immoral.

However, this undertaking is deeply flawed. Rather than critically analyzing each situation and dealing with it in the most appropriate manner, plant nativists (people who practice a policy of favoring native plants over nonnative) take the simplistic approach that demands removal of every plant designated as “invasive”, no matter what function it is fulfilling in the local environment or how well it fills what would be an otherwise empty ecological niche.

Earlier this year, for example, someone removed a Leatherleaf Mahonia (Mahonia bealei) that was growing in a swath of red dirt along the road where I exercise. It was one of the few plants that had survived the highway department’s installation of a new guardrail. No native plants had been able to grow in the poor, dry soil exposed a few years earlier by construction, leaving an area several feet wide and long mostly devoid of plants to assist wildlife.

The Mahonia (a native of China) would have provided a very early source of nectar desperately needed by the first pollinators to become active in spring at a time when native plants in bloom are very few. Its fruits would later feed birds, such as Cedar Waxwings and American Robins. Now, not much exists in this area to feed either insects or birds, making the land a wasted resource.

Native or not, plants provide habitat whereas bare ground does not. Nativists disregard the reality that native plants struggle to survive under the adverse conditions of road salt, mowing, drought, and disturbed, compacted, and depleted soil. They would do better by the environment if, instead of pulling and pesticiding, they focused on eliminating the actual causes of alien-plant spread.

Removing the Mahonia near the bridge resulted in no benefit to the environment, whereas it very much negatively impacted ease of survival for many insects and birds. And in California, removing Eucalypts may well doom the wintering Monarch butterfly population.

Contradictions of the native plant movement

In a recent article in Bay Nature, the author tells the story of two California native trees and proposes to answer the question, “Now the question is, where do [these trees] belong?”  It’s a thorny question and one that illustrates one of the contradictions of the native plant movement.

The definition of “native” in California is based on the arrival of Europeans near the end of the 18th century, specifically 1769 in the San Francisco Bay Area.  Wherever plants or animals lived in 1769, they are considered native in the Bay Area.  If they were introduced or arrived after 1769, they are considered non-native, and in many cases designated as “invasive.”  Status as “invasive” makes them targets for eradication.

Monterey pine is a case in point. It has a small native range around Monterey, California, just 115 miles south of the East Bay. It was widely planted in the Bay Area by early settlers because the climate is similar to Monterey and much of the Bay Area was treeless. It is well adapted to conditions and thrives here.  Yet, it is being eradicated by most public land managers in the Bay Area because it is, strictly speaking, non-native according to the official classification of non-natives.

Bird’s eye view of San Francisco in 1868. US Library of Congress.  About half of San Francisco was treeless sand dunes before early settlers planted the non-native trees that now live there.

There is fossil evidence that Monterey pine has lived along the coast of California many times in the past, far outside its small present “native” range.  The evidence of its prehistoric past in the Bay Area has not saved it.  It wasn’t here in 1769, so it’s gotta go to suit the purist agenda of our public land managers.

But, wait!  Maybe our public land managers don’t have such a purist agenda. The same public land managers who are eradicating Monterey pine in the Bay Area are also planting Torrey pines and Catalina ironwood, which are native to the Channel Islands, off the coast of Southern California. These tree species weren’t here in 1769, nor were they here in the distant past.  In Monterey, where Monterey pines are native, Torrey pines are considered “invasive,” according to the interview with a tree advocate in Monterey who is quoted by the Bay Nature article.

Torrey pine, San Diego. Wikimedia commons
Catalina ironwood – Catalina Island. Wikimedia Commons

Where I have observed Torrey pines and Catalina ironwood being planted by East Bay Regional Park District and other public land managers, they seem to be doing well. Therefore, I have no objection to their being planted here, although they are not “native” as defined by local native plant advocates. I have one straight-forward criterion for “where trees belong:” they belong where they will survive.

The author of the Bay Nature article demurs, “Should we view Monterey pine as unwanted and possibly damaging invaders or welcome them as neo-natives? I couldn’t decide.” That seems to me an easy question to answer:  It makes no sense to destroy healthy Monterey pines that have lived in the Bay Area many times in the past, while simultaneously planting trees that have never lived here. If trees are adapted to present environmental conditions, they should be welcome here.

Nativist Dilemmas

The native plant movement is fraught with conundrums such as the vexing question of where Monterey pine and its close relative, Torrey pine, belong.

  • There are many unresolved debates about exactly where native ranges are. The rusty crayfish is “probably the most reviled crayfish species in North America,” yet there are as many opinions about its native range as there are publications about the species.  Pike is eradicated in Ireland, yet a recent genetic study revealed that there are actually two pike species, one of which is likely native and unique to Ireland.  (1)
  • There is little agreement among invasion biologists about the difference between non-native and “invasive.” Some consider all non-native species potentially invasive, some do not. (1) The California Invasive Plant Council recently designated nearly 100 plant species as invasive (in addition to 200 plants already on the list), despite the admission that they are not invasive in California.  Given that the behavior of plants depends to a great extent on local climate conditions, we cannot assume they will be invasive in California. When a plant is designated as “invasive” it becomes a target for eradication.  It is therefore a designation that should be used sparingly.
  • Public land managers in the Bay Area kill as many native plants as non-native plants because of their goal of recreating the landscape that existed here prior to the arrival of Europeans. That goal requires that early-succession native shrubs be killed when they naturally encroach on grassland if it is not burned periodically or grazed by animals.  Native coyote brush is eradicated as often as non-native broom when it “invades” grassland.  Are we trying to preserve native species or historical landscapes?  Those are different goals and they are often contradictory.

Invasion biology is an ideology, not a science

These—and many other—contradictions are symptoms of a pseudoscience, struggling to make sense, but failing to do so.  Invasion biology made the initial mistake of picking a specific point in time to define the “ideal” landscape.  Because nature is dynamic, in response to a constantly changing environment, the arbitrary selection of a static landscape will always be a source of contradictions.  The environment has changed radically since 1769 and even more radically since the 400-year baseline used on the East Coast.  We cannot expect to recreate that historical landscape because we cannot recreate the environment in which it existed. 

  1. C. Guiasu, C.W. Tindale, “Logical fallacies and invasion biology,” Biological Philosophy, Sept 2018, 33(5)

 

 

Doug Tallamy speaks…Art Shapiro responds…Million Trees fills in the gaps

Smithsonian Magazine published an interview with Professor Doug Tallamy, the entomologist who is committed to the eradication of non-native plants and most influential with native plant advocates in the United States.  The Smithsonian article gives Professor Art Shapiro an inadequate opportunity to respond to Tallamy’s assertions about the superiority of native plants.  Million Trees steps up to fill in the gaps in response to Tallamy.

  • The Smithsonian article says, “As a scientist, Tallamy realized his initial obligation was to prove his insight empirically. He began with the essential first step of any scientific undertaking, by applying for research grants, the first of which took until 2005 to materialize. Then followed five years of work by relays of students.”

The first study that Tallamy conducted is not mentioned in this article because it disproved his hypothesis:  “Erin [Reed] compared the amount of damage sucking and chewing insects made on the ornamental plants at six suburban properties landscaped primarily with species native to the area and six properties landscaped traditionally.  After two years of measurements Erin found that only a tiny percentage of leaves were damaged on either set of properties at the end of the season….Erin’s most important result, however, was that there was no statistical difference in the amount of damage on either landscape type.” (1)

  • The Smithsonian article says, “… insects tend to be specialists, feeding on and pollinating a narrow spectrum of plant life, sometimes just a single species. ‘Ninety percent of the insects that eat plants can develop and reproduce only on the plants with which they share an evolutionary history’…:”
Anise Swallowtail butterfly in non-native fennel. Courtesy urbanwildness.org

A “specialist” insect is rarely confined to using a single plant species.  Mutually exclusive relationships in nature are very rare because they are usually evolutionary dead-ends.  The study in which this claim about “specialization” originated, actually concluded:  “More than 90 percent of all insects sampled associate with just one or two plant families.”* There are over 600 plant families and thousands of plant species within those families.  Most plant families include both native and non-native plant species.  An insect that uses one or two plant families, is therefore capable of using both native and non-native plant species.  For example, there are 20,000 plant members of the Asteraceae family, including native sagebrush (Artemisia) and non-native African daisy.  In other words, the insect that confines its diet to one family of plants is not very specialized.

  • The Smithsonian article says, But he [Tallamy] thinks this [transition of insects to non-native plants] is likely to take thousands of generations to have an impact on the food web. Shapiro maintains he has seen it occur within his own lifetime.”

There are many empirical studies that document the transition that insects make from native to non-native plants within generations.  Professor Tallamy provides a few examples of such rapid transitions in his first book, Bringing Nature Home:  wooly adelgids from Asia have had a devastating effect on native hemlock forests in the eastern United States; Japanese beetles introduced to the United States are eating the foliage of over 400 plant species (according to Professor Tallamy), some of which are native (according to the USDA invasive species website).

Soapberry bug on balloon vine. Scott Carroll, UC Davis

The soapberry bug made a transition from a native plant in the soapberry family in less than 100 generations over a period of 20 to 50 years. The soapberry bug-balloon vine story is especially instructive because it entailed very rapid morphological as well as behavioral change; the beak length was quickly (a few years) selected for the dimensions of the fruit of the new host. (2)

  • Doug Tallamy claims that Art Shapiro’s findings are “anecdotal.” They are not.  Art Shapiro’s published study is based on nearly 40 years of data. (3)
Monachs in eucalyptus, Pacific Grove Museum

In a recent NY Times article about declining populations of monarch butterflies on the West Coast, an academic scientist explains how he used Professor Shapiro’s data set to study the decline:  “The monarch’s decline is part of a larger trend among dozens of butterfly species in the West, including creatures with names like field crescents, large marbles and Nevada skippers, said Matt Forister, an insect ecologist at the University of Nevada, Reno, whose conclusions are based on a nearly 50-year set of data compiled by Art Shapiro, a researcher at the University of California, Davis. “The monarch is very clearly part of a larger decline of butterflies in the West.”  Clearly, other academic entomologists do not consider Professor Shapiro’s data “anecdotal.”

The Burghardt/Tallamy study (4) does not contradict the findings of Professor Art Shapiro because Professor Shapiro is studying butterflies (not moths) in “natural areas” that have not been artificially created by choosing a limited number of plant species, as Tallamy’s study did.  In other words, the adult and larvae stages of butterflies that Professor Shapiro studies have more options, and when they do they are as likely to choose a non-native plant as a native plant for both host plant and food plant.  You might say, Professor Shapiro’s study occurs in the “real world” and the Burghardt/Tallamy study occurs in an artificially created world.

Dismissing observations as anecdotal is a well-worn rhetorical device.  Creationists often claim that evolution cannot be proven because the theory is based on millions of observations, rather than empirically tested by experiments. Yet, virtually all scientists are firm believers in the validity of evolutionary principles.

  • Tallamy dismisses climate change as a factor in plant and animal extinctions, preferring to place the blame solely on the mere existence of non-native plants.

This claim is contradicted by a multitude of studies, such as a collection of studies recently reported by Yale E360 that concludes:  “A growing number of studies show that warming temperatures are increasing mortality in creatures ranging from birds in the Mojave Desert, to mammals in Australia, to bumblebees in North America. Researchers warn that heat stress could become a major factor in future extinctions.”

Climate change is the environmental issue of our time.  When the climate changes, the vegetation changes.  When the vegetation changes, wildlife adapts or dies.  Non-native plants are one of the consequences, not the cause of climate change or plant and animal extinctions.

_______________________________________________

*Professor Shapiro has provided a caveat to this definition of specialization of insects in a private communication, published with his permission:  A couple of observations: Hardly any insects feed on entire plant families. Rather, they feed on specific lineages within those families, typically defined by secondary chemistry (which is the necessary releaser for oviposition and/or feeding behavior). The relationship was summed up symbolically by A.J.Thorsteinson half a century ago: feeding=presence of nutrients+presence of required secondary chemicals-deterrents-antifeedants-toxins. Thus the Anise Swallowtail species-group feeds on the carrot family, Apiaceae, but NOT on Apiaceae lacking the proper chemistry.But they DO feed on some Rutaceae (including Citrus) that, though unrelated, are chemically similar. That was worked out by Vincent Dethier in the 1940s and further developed by John Thompson at UC Santa Cruz. A whole slew of things require iridoid glycosides as oviposition and feeding stimulants. Most plants containing these were in the family Scrophulariaceae before DNA systematics led to its dismemberment, but one whole branch of Scrophs is chemically unsuitable. Milkweed bugs eat milkweed, but they also eat the Brassicaceous genera Erysimum and Cheiranthus, which are chemically similar to milkweeds but not to other Brassicaceae…and so on. Native vs. non-native has nothing to do with it.”  (emphasis added)

  1. Tallamy, Doug, “Flipping the Paradigm:  Landscapes that Welcome Wildlife,” chapter in Christopher, Thomas, The New American Landscape, Timber Press, 2011
  2. Carroll, Scott P., et. al., “Genetic architecture of adaptive differentiation in evolving host races of the soapberry bug, Jadera haematoloma,” Genetica, 112-113: 257-272, 2001
  3. SD Graves and AM Shapiro, “Exotics as host plants of the California butterfly fauna,” Biological Conservation, 110 (2003) 413-433
  4. Karin Burghardt, Doug Tallamy, et. al., “Non-native plants reduce abundance, richness, and host specialization in lepidopteran communities,” Ecosphere,November 2010

Eradicating non-native plants does NOT benefit insects

We briefly reactivate the Million Trees blog to publish an interesting and important debate between Jake Sigg and Professor Art Shapiro about the relationship between insects and native plants.  Their debate was initiated by this statement published in Jake Sigg’s Nature News on April 26, 2019:

“Did you know that 90 percent of insects can only eat the native plant species with which they’ve co-evolved?”

Jake Sigg has been the acknowledged leader of the native plant movement in the San Francisco Bay Area for 30 years.  He is a retired gardener for the Recreation and Parks Department in San Francisco. Art Shapiro is Distinguished Professor of Ecology and Evolution at UC Davis.  He has studied the butterflies of Central California for 50 years. 

Jake and Art are both passionately committed to the preservation of nature, but their divergent viewpoints reflect their different experiences.  Jake’s viewpoint is based on his personal interpretation of his observations.  As a gardener, his top priority is the preservation of plants rather than the animals that need plants.  As a scientist, Art’s viewpoint is based on empirical data, in particular, his records of plant and butterfly interactions over a period of 47 years as he walked his research transects about 250 days per year. The survival of butterflies is Art’s top priority.

Although their discussion is informative, it does not resolve the questions it raises because Jake and Art “agree to disagree.”  Therefore, Million Trees will step into the vacuum their discussion creates to state definitively that it is patently false to say that “90% of insects can only eat native plants.” That statement grossly exaggerates the degree of specialization of insects and underestimates the speed of adaptation and evolution.

There are several reasons why insects do not benefit from the eradication of non-native plants:

  • Insects use both native and non-native plants.
  • Pesticides used to eradicate non-native plants are harmful to both plants and insects as well as the entire environment.
  • There is no evidence that insects are being harmed by the existence of non-native plants.

Insects use both native and non-native plants

This statement was recently made in an article published by Bay Nature magazine about Jake Sigg:  “More than 90 percent of all insects sampled associate with just one or two plant families.”  (7,500 insect species were sampled by the cited study.  There are millions of insect species and their food preferences are largely unknown.)  This exaggerated description of specialization of insects seems the likely origin of the subsequent, inappropriate extrapolation to the statement that specialized insects require native plants.

Anise Swallowtail butterfly in non-native fennel. Courtesy urbanwildness.org

There are over 600 plant families and thousands of plant species within those families.  Most plant families include both native and non-native plant species.  An insect that uses one or two plant families, is therefore capable of using both native and non-native plant species.

We will use the Oxalidaceae plant family to illustrate that insects can and do use both native and non-native plants.  Oxalidaceae is a small family of about 5 genera and 600 plant species.  We choose that family as an example because Jake Sigg’s highest priority for eradication is a member of that plant family, Oxalis pes-caprae (Bermuda buttercup is the usual common name)In a recent Nature News (April 9, 2019), Jake explained why:  Oxalis is not just another weed; this bugger has a great impact on the present and it will determine the future of the landscapes it invades.” 

Five members of the Oxalis genus in the Oxalidaceae family are California natives. An insect that uses native oxalis can probably also use the hated Bermuda buttercup oxalis because they are chemically similar. 

Honeybee on oxalis flower, another non-native plant being eradicated with herbicide.

The consequences of eradicating non-native plants

Partly because of Jake’s commitment to eradicating non-native oxalis, San Francisco’s Recreation and Parks Department has been spraying it with herbicide for 20 years Garlon (triclopyr) is the herbicide that is used for that purpose because it is a selective herbicide that does not kill grasses in which oxalis usually grows.  Garlon is one of the most toxic herbicides available on the market.  More is known about Round Up (glyphosate) because it is the most widely used of all herbicides.  However, according to a survey of land managers conducted by California Invasive Plant Council in 2014, Garlon is the second-most commonly used herbicide to eradicate non-native plants. 

Garlon is toxic to bees, birds, and fish.  It is an endocrine-disrupter that poses reproductive and developmental risks to female applicators.  It damages the soil by killing mycorrhizal fungi that are essential to plant health by facilitating the transfer of nutrients and moisture from the soil to plant roots. 

A recent article in the quarterly newsletter of Beyond Pesticides explains that insecticides are not the only killers of insects: “Insecticides kill insects, often indiscriminately and with devastating consequences for biodiversity, ecosystem stability, and critical ecosystem services. Herbicides and chemical fertilizers extinguish invaluable habitat and forage critical to insect survival. Taken together, insecticides, fungicides, herbicides and chemical fertilizers make large and growing swaths of land unlivable for vast numbers of insect species and the plants and animals they sustain.” The loss of insects where herbicides are used to kill non-native plants are undoubtedly contributing to the failure of attempts to “restore” native plants which require pollinators and insect predator control as much as non-native plants.

In other words, eradicating non-native oxalis is damaging the environment and the animals that live in the environment.  Furthermore, after twenty years of trying to eradicate it, Jake Sigg admits that there is more of it now than there was when this crusade began:  “Maybe you’ve noticed that there’s more and more of it every year, and fewer and fewer other plants.  That is unlikely to reverse.”  (Nature News, April 9, 2019).

coyote in oxalis field. Copyright Janet Kessler

In fact, local failure of eradication efforts mirrors global failures of similar attempts:  “…despite international policies aimed at mitigating biological invasions, the implementation of national- and regional-scale measures to prevent or control alien species has done little to slow the increase in extent of invasions and the magnitude of impacts.” (1)

Update:  The California Invasive Plant Council has published “Land Manager’s Guide to Developing an Invasive Plant Management Plan.”  It says very little about the disadvantages of using herbicides to eradicate plants they consider “invasive” other than a vague reference to “unintended consequences,” without discussion of what they are or how to avoid them. 

However, it does give us another clue about why eradication efforts are often unsuccessful. When herbicides are used repeatedly, as they have been in the past 20 years, weeds develop resistance to them:   “The International Survey of Herbicide Resistant Weeds (2018) reports there are currently 496 unique cases (species x site of action) of herbicide-resistant weeds globally, with 255 species…Further, weeds have evolved resistance to 23 of the 26 known herbicide sites of action and to 163 different herbicides.”  The Guide therefore recommends that land managers rotate herbicides so that the “invasive” plants do not develop resistance to any particular herbicide.  The Guide gives only generic advice to use “herbicide X” initially and “herbicide Y or Z” for subsequent applications.

In other words, the California Invasive Plant Council continues to promote the use of herbicides to kill plants they consider “invasive.”  They give advice about ensuring the effectiveness of herbicides, but they do not give advice about how to avoid damaging the soil, killing insects, and harming the health of the public and the workers who apply the herbicides. 

Do insects benefit from eradicating non-native plants?

There is no question that insects are essential members of every ecosystem.  They are the primary food of birds and other members of wildland communities.  They perform many vital functions in the environment, such as consuming much of our waste that would otherwise accumulate. 

The Economist magazine has reported the considerable evidence of declining populations of insects in many places all over the world.  (However, the Economist points out that the evidence does not include large regions where insect populations have not been studied. The Economist is therefore unwilling to conclude that the “insect apocalypse” is a global phenomenon.) The report includes the meta-analysis of 73 individual studies that describe declines of 50% and more over decades. The meta-analysis concluded that there are four primary reasons for those declines, in order of their importance:  habitat loss, intensive farming, pesticide use, and spread of diseases and parasites.  The existence of non-native plants is conspicuously absent from this list of threats to insect populations.

In other words, although the preservation of insects is extremely important, there is no evidence that the eradication of non-native plants would benefit insects.  In fact, eradication efforts are detrimental to insects because of the toxic chemicals that are used and the loss of the food the plants are providing to insects.

Jake Sigg and Art Shapiro discuss insects and native plants

The discussion begins on April 26, 2019, with this statement published in Jake’s Nature News:

“Did you know that 90 percent of insects can only eat the native plant species with which they’ve co-evolved?”

On April 26, 2019, Arthur Shapiro wrote:

“No, I didn’t know 90% of insects can only eat the native plants with which they’ve co-evolved. I’ve only been studying insect-plant relationships and teaching about them for 50 years and that’s news to me, especially since on a global basis we don’t know what the vast majority of insects species eat, period! That’s even true for butterflies and moths, which are probably the best-studied group. And it’s even true here in California, one of the best-studied places on the planet (though way behind the U.K. and Japan). Where on earth did that bit of non-information come from?”

Jake Sigg responds:

“Art, I did my best to run down source for that statement.  As I suspected, it may lack academic precision.  That kind of precision is hard come by, and what exists is not entirely relevant.  Most of the information comes from Doug Tallamy.  But the statement is not accurate; it should have read “…90 percent of plant-eating insects eat only the native plants they evolved with”.  Whether that is true or not I don’t know, but it accords with my understanding and I am willing to go along with it, even if proof is lacking.  If you wait for scientific proof on everything you may wait a long time and lose a lot of biodiversity.  I have had too much field experience to think that exotic plants can provide the sustenance that natives do.

I expect you will be unhappy with this response.”

On May 2, 2019, Art Shapiro replies:

“If Tallamy said “90% of the plant-eating insects that I have studied…”  or “90% of the plant-eating insects that have been studied in Delaware…” or some such formulation I might take him more seriously. The phenomenon of “ecological fitting,” as described by Dan Janzen, is widespread if not ubiquitous. “Ecological fitting” occurs when two species with no history of coevolution or even sympatry (co-occurrence) are thrown together and “click.”  A.J.Thorsteinson summed up some 60 years ago what is needed for an insect to switch onto a new host plant: the new plant must be nutritionally adequate, possess the requisite chemical signals to trigger egg-laying and feeding, not possess any repellents or antifeedants and not be toxic. That set of circumstances is met very frequently. To those of us who study it, it seems to happen every other Tuesday.  As we showed, the urban-suburban California butterfly fauna is now overwhelmingly dependent on non-native plants. The weedy mallows (Malva) and annual vetches (Vicia) are fed upon by multiple native butterfly species and are overall the most important butterfly hosts in urban lowland California. . Within the past decade, our Variable Checkerspot has begun breeding spontaneously and successfully on Butterfly Bush (Buddleia davidii). The chemical bridge allowing this is iridoid glycosides. When I was still back East I published that the Wild Indigo Dusky Wing skipper, Erynnis baptisiae, had switched onto the naturalized European crown vetch (Coronilla varia) which had converted it from a scarce and local pine-barrens endemic to a widespread and common species breeding on freeway embankments. And the hitherto obscure skipper Poanes viator, the Broad-Winged Skipper, went from being a rare and local wetland species best collected from a boat to becoming the most abundant early-summer butterfly in the New York metropolitan area by switching from emergent aquatic grasses and sedges to the naturalized Mesopotamian strain of Common Reed, Phragmites australis. I can go on, and on, and on. If you find a sponsor for me to give a lecture about this in the Bay Area, I’ll gladly do it. If you promise to come!

I won’t snow you under with pdfs. Here’s just one, a serendipitous one that resulted from my walking near Ohlone Park in Berkeley. And one from the high Andes in Argentina. That paper cites one of mine in Spanish demonstrating that the southernmost butterfly fauna in the world, in Tierra del Fuego and on the mainland shore of the Straits of Magellan, is breeding successfully on exotic weeds.-! Copy on request.”

On May 2, 2019, Jake Sigg published his last reply:

“I believe many of your statements, Art, and many of these cases I am familiar with.  A conspicuous local example is the native Anise Swallowtail butterfly that still lays eggs on native members of the Umbelliferae, the parsley family, but which also breeds on the exotic fennel, which is an extremely aggressive weed that in only a few years can transform a healthy and diverse grassland supporting much wildlife into a plant monoculture—that, btw, won’t even support the butterfly, which shuns laying eggs where its larval food plant is too numerous and easy target for a predator, like yellow jackets.

What puzzles me is why you can keep your equanimity at the prospect of losing acres of very diverse habitat to a monoculture of fennel.  You live in the heart of the world’s breadbasket where for hundreds of miles both north and south there are almost no native plants except those planted by humans.  That would tend to distort one’s view.  I don’t mean to be flip, but it is not normal for even an academic to be indifferent about a loss of this magnitude.  I have worked hands-on on the land (I was raised on a ranch) all my life and still work every Wednesday maintaining our natural habitat in San Francisco—a task that hundreds of citizens pitch in on because they value the quality and diversity of the areas.  And why do you remain indifferent, are you just a contrarian?  You cite examples to bolster your view, but the examples are too small a percentage to be meaningful and wouldn’t stand up against a representative presentation.

I got my view from life.  I type this in my second-floor sunroom, which looks into a coast live oak growing from an acorn I planted in the late 1960s, about 50 years ago and which is immediately on the other side of the window.  It is alive with birds of many different species—flocks of bushtits, chickadees, juncos every day (plus individuals of other species), which species-number balloons in the migratory season.  What I can’t figure out is how the tree can be so productive as to stand up to this constant raiding.  I will take instances of this sort as my guide rather than the product of academic lucubrations.  And I will throw in Doug Tallamy; the world he portrays is one I recognize and love.

I think our battle lines are drawn.  This discussion could go on, as we have not even scratched the surface of a deep and complex subject.  But will either of us change our minds?  No.”

“Jake Sigg:  N.B.  Art responded with another long epistle, not for posting.  It clarified some of the points that were contentious and seemed to divide us.  We differ, but not as much as would appear from the above discussion.”


(1) “A four-component classification of uncertainties in biological invasions: implications for management,” G. LATOMBE , S. CANAVAN, H. HIRSCH,1 C. HUI, S. KUMSCHICK,1,3 M. M. NSIKANI, L. J. POTGIETER, T. B. ROBINSON, W.-C. SAUL, S. C. TURNER, J. R. U. WILSON,  F. A. YANNELLI, AND D. M. RICHARDSON, Ecosphere, April 2019.

Conference of the California Invasive Plant Council: Fallacies and Failures

The California Invasive Plant Council held their 27th annual conference in Monterey in November.  It was their biggest conference, with about 400 attendees and more sponsors than ever before.  Clearly the industry that promotes the eradication of non-native plants is alive and well.  However, a closer look at the conference presentations suggests otherwise.  Eradication efforts are growing, but eradication success is not and establishing a native landscape after eradication is proving elusive.

A few common themes emerged from the presentations:

  • Eradication cannot be accomplished without using pesticides.
  • When eradication is achieved with pesticides, non-natives are rarely replaced by native plants.
  • Planting natives after non-natives are eradicated reduces re-invasion, but secondary invasions of different non-native plants are common.
  • “Managing” forests with prescribed burns did not result in more biodiversity than leaving the forest alone.

Goals of these eradication projects have shifted in response to these failures to achieve original goals:

  • Replacement plantings after eradication are sometimes a mix of natives and non-natives.
  • Inability to establish native grassland has given way to different goals.
  • Language used to describe the projects are evolving to be more appealing to potential volunteers.

Here are a few examples of presentations that illustrate these themes:

Eradicating beach grass in Point Reyes National Seashore

About 60% of sand dunes in the Point Reyes National Seashore were covered in European beach grass when the eradication effort began in 2000.  The goal of the project was to restore native dune plants and increase the population of endangered snowy plovers that nest on bare sand.

The project began by manually pulling beach grass from 30 acres of dunes at Abbott’s Lagoon.  The grass grew back within one year, presumably because the roots of the beach grass are about 10 feet long.  Manually pulling the grass from the surface does not destroy the roots.

A new method was devised that was more successful with respect to eradicating the beach grass.  The grass and its roots were plowed up by bulldozers and buried deep in the sand.  The cost of that method was prohibitively expensive at $25,000 to $30,000 per acre and the barren sand caused other problems.

The barren dunes were mobile in the wind.  Sand blew into adjacent ranches and residential areas, causing neighbors of the park to object to the project.  The sand also encroached into areas where there were native plants, burying them.  The bare sand was eventually colonized by “secondary invaders.”  Different non-native plants replaced the beach grass because they were more competitive than the desired native plants.

In 2011, the National Park Services adopted a third strategy for converting beach grass to native dune plants.  They sprayed the beach grass with a mixture of glyphosate and imazapyr.  At $2,500 to $3,000 per acre, this eradication method was significantly cheaper than the mechanical method.

However, it resulted in different problems that prevented the establishment of native dune plants.  The poisoned thatch of dead beach grass was a physical barrier to successful seed germination and establishment of a new landscape.  Where secondary invaders were capable of penetrating the dead thatch, the resulting vegetation does not resemble native dunes.

Presentation at California Invasive Plant Council conference regarding attempt to eradicate European beach grass at Point Reyes National Seashore

The concluding slides of this presentation were stunning.  They said it is a “Restoration fallacy that killing an invader will result in native vegetation.”  My 20 years of watching these futile efforts confirm this reality.  However, I never expected to hear that said by someone actually engaged in this effort.  The presenter mused that such projects are like Sisyphus trying to roll a boulder up hill. 

Presentation at California Invasive Plant Council conference regarding attempt to eradicate European beach grass at Point Reyes National Seashore

Attempting to plant Douglas fir after eradication of broom

Over a period of 5.5 years, broom was eradicated in plots in Oregon by spraying glyphosate.  The plots were then planted with Douglas fir seedlings that soon died.  They were replanted the following year and died in the second year.

There were two theories about why the plantings failed, both broadly described as “legacy” effects in the soil left by the broom.  One theory is that nitrogen levels were too high for successful growth of Douglas fir.  That theory is consistent with the fact that broom is a nitrogen fixer.  That is, broom—like all legumes—have the ability to transfer nitrogen in the atmosphere to nitrogen in the soil with the help of bacteria that facilitate that transfer.  Nitrogen generally benefits plant growth, but there can also be too much nitrogen.

The second theory is that Douglas fir requires a specific suite of mycorrhizal fungi for successful growth.  Mycorrhizal fungi live in roots of plants and trees.  They transfer moisture and nutrients from the soil to the plants.  Plants with a healthy suite of mycorrhizal fungi are more drought tolerant because they extract more moisture from the soil.

Neither of these theories has been successfully proven by this project.  They remain unanswered questions.  We were struck that the researchers had not considered the possibility that the repeated use of glyphosate could have been a factor in the failure of the Douglas fir.  Glyphosate is known to kill bacteria in the soil.  Could it also kill mycorrhizal fungi?  (We know that triclopyr kills mycorrhizal fungi.) That possibility was not considered by this project. Did the project consider that glyphosate also changes the consistency of the soil by binding certain minerals together?  It is more difficult for roots and water to penetrate the hard soil.  Were soil samples taken before and after repeated applications of glyphosate to determine how the soil had been changed by pesticide applications?

The published abstract for this project made this observation:  “It is typically assumed that once an invasive species is successfully removed, the impact of that species on the community is also eliminated.  However, invasive species may change the environment in ways that persist, as legacy effects, long after the species itself is gone.”  In fact, it seems likely that the pesticides used to eradicate the “invasive” species could also be the source of the “legacy effects.”

Does “managing” a forest result in greater biodiversity in the understory?

California State Parks tested that hypothesis by conducting prescribed burns in some of their forests in the Sierra Nevada 20 years ago, while leaving other portions of the forest “unmanaged.”

The abstract for this presentation describes the goals and expectations for the prescribed burns:  “Prescribed fire is a tool used to reduce fuels in the forests in the Sierra Nevada and mimic the low and moderate severity wildfires that burned before the onset of fire suppression.  A manager’s hope is that prescribed fire will create the disturbance necessary to stimulate the development of species rich understory communities and increase species richness, compared to unburned forests, which are often viewed as species depauperate.”

Twenty years after the burns, abundance and species composition of the understory in the burned areas were compared to the unburned areas.  They found little difference in the biodiversity of the understory of burned areas compared to unmanaged forests:

  • “Species richness was highly variable within burned and passively managed areas but was not statistically different.”
  • “Passively managed areas did not appear to be depauperate in understory species diversity compared to areas managed with prescribed fire.”
  • “Fire did not appear to reduce or enhance species richness numbers in burned areas, as compared to passively managed areas.”

No fires occurred in either the burned areas or the unmanaged areas during the 20-year period.  Therefore, this study did not test the theory that prescribed burning reduces fire hazards in forests.  This study found no significant differences in diversity of forest understory resulting from prescribed burns.

There are significant risks associated with prescribed burns.  They cause air pollution and they frequently escape the controlled perimeter of the fire, becoming wildfires that destroy far more than intended.  This study does not provide evidence that would justify taking those risks.  In fact, available evidence supports the “leave-it-alone” approach to land management.

Moving the goal posts

If at first you don’t succeed, you have the option of redefining success.  Here are a few of the projects presented at the conference that seemed to take that approach.

Make projects so small that success can be achieved

Eric Wrubel introduced himself as the National Park Service staff who is responsible for prioritizing invasive plants for removal in the National Parks in the Bay Area (GGNRA, PRNS, Muir Woods, and Pinnacles).  His work is based on the premise that the most successful eradications are those that are small.  The bigger the infestation, the greater the investment of time and resources it takes to eradicate it and the smaller the likelihood of success.  This is illustrated by a graph showing this inverse relationship between the size of the invasive population and the success of eradication.

Source: Rejmanek and Pitcairn, “When is eradication of an exotic pest plant a realistic goal?,” 2002

The process of prioritizing eradication projects began over 10 years ago with a survey of over 100 species of plants considered invasive.  Cal-IPC’s “watch list” was used to identify the plants that are not yet widely spread in California, but considered a potential problem in the future.  Cal-IPC’s risk assessment was the third element in the analysis.  Plants with “High” risk ratings by Cal-IPC were put higher on the priority list than those with “Moderate” or “Limited” ratings.  Plants that did not exist elsewhere in the region or watershed were also given higher priority, based on the assumption that re-invasion was less likely.

This is the list of eradication projects in the National Parks in the Bay Area that was presented at the conference of the California Invasive Plant Council. The projects marked with the red symbol for crossing out are completed projects. Nearly half of the plants on this hit list are not considered invasive in California.

The priority list showed that the highest priority eradication projects were quite small.  Some were just a few acres.  Buddleia jumped out as the 7th highest priority on only 13 acres.  Buddleia was recently added to a new category of plants on Cal-IPC’s “invasive” inventory.  It is not considered invasive in California, although it is considered invasive elsewhere.

In placing buddleia on its “hit list,” Cal-IPC illustrates one of the fundamental weaknesses of its evaluation method.  Cal-IPC does not evaluate pros and cons of non-native plants.  Only traits considered negative are taken into consideration.

Monarch sanctuary in Monterey, California. November 2018

Buddleia is one of the most useful nectar plants for pollinators in California.  We took the time to visit the monarch butterfly sanctuary in Monterey while attending the conference.  The monarchs are arriving now to begin their winter roost in the eucalyptus, Monterey pine and cypress in this small grove.  At the entrance to the sanctuary a sign instructs visitors to plant only native milkweed as the monarch’s host plant and only native flowers for nectar.  Fortunately whoever planted the flowering shrubs in the sanctuary didn’t follow the advice of the sign-makers.  They planted buddleia and other flowering non-natives such as bottle-brush.  Several species of butterflies and hummingbirds were enjoying those plants in the Sanctuary. Strict adherence to the native plant agenda is not beneficial to wildlife because animals do not share our prejudices.

Monarch nectaring on butterfly bush. butterflybush.com

Acknowledging the difficulties of converting non-native annual grass to native perennial grass

Pinnacles National Park acquired 2000 acres of former ranchland in 2006.  The park wanted to convert the non-native annual grasses and yellow-star thistle on the former ranch to perennial bunch grasses and oak woodland.  They were able to reduce the amount of yellow-star thistle by burning and spraying with herbicide, but cover of native species remained low.  Conversion of grasses from non-native annuals to native perennial grass has been tried many times, in many places, and for long periods of time.  These projects were notoriously unsuccessful.

The project at Pinnacles has changed its goal to plant forbs (herbaceous flower plants) instead of grasses and they report that they are having some success.   They justify that shift in goal on soil analysis that suggests forbs were more prevalent than perennial grasses in inland valleys in California than previously thought.

This change in goal could be described as “adaptive management,” which adjusts methods and goals in response to observable outcomes of existing methods.  You could also call it “trial and error.”  We would like to see more land managers make such adjustments to their strategies, rather than doing the same thing over and over again and expecting a different outcome.

Recruiting volunteers with appealing messages

There were several presentations about effective methods of recruiting volunteers to participate in restoration projects.  Some of their messages seem to acknowledge that the language used in the past may have alienated some potential volunteers.  Speaking from personal experience, I can confirm that observation.  Here are just a few of the cringe-worthy native plant mottos that I hope have been abandoned in favor of a more positive message:

  • “That plant doesn’t belong here.”
  • “That is a good plant and the other is a bad plant.”
  • “The invasive landscape is sick and requires chemotherapy.” (to justify the use of pesticides)
  • “That’s a trash bird.” (said of common, introduced birds, such as starlings and house sparrows)

The speaker advised those who work with volunteers to focus on why an unwanted plant is a problem rather than where it comes from.  Unfortunately, the list of problems is heavily influenced by the preferences of native plant advocates.  If their criticisms are not accurate, or they don’t acknowledge the advantages of the plant, little has been achieved by using euphemisms.  Here are a few of the inaccurate criticisms made of eucalyptus:

What was missing?

Ecological restoration is a major industry. Thousands of people are employed by the industry, which is funded by many different sources of public money.  Whether individual projects are successful or not, the industry will survive and thrive as long as it is funded.  Greater care should be taken to design and implement projects that will be successful.

Stepping back from the conference presentations of specific restoration projects, here are a few issues that were conspicuously absent from the conference. 

  • Pesticides are being widely used by the restoration industry. When projects don’t achieve desired outcomes, pesticides should be considered as a factor.  Did pesticides alter the soil?  Were beneficial microbes and fungi killed? How persistent was the pesticide in the soil?  How mobile was the pesticide in the soil?  Was pesticide applied in the right manner?  Could aerial drift account for death of non-target plants?  There are many other useful questions that could be asked.

Update:  The California Invasive Plant Council has published “Land Manager’s Guide to Developing an Invasive Plant Management Plan.”  It says very little about the disadvantages of using herbicides to eradicate plants they consider “invasive” other than a vague reference to “unintended consequences,” without discussion of what they are or how to avoid them. 

However, it does give us another clue about why eradication efforts are often unsuccessful. When herbicides are used repeatedly, as they have been in the past 20 years, weeds develop resistance to them:   “The International Survey of Herbicide Resistant Weeds (2018) reports there are currently 496 unique cases (species x site of action) of herbicide-resistant weeds globally, with 255 species…Further, weeds have evolved resistance to 23 of the 26 known herbicide sites of action and to 163 different herbicides.”  The Guide therefore recommends that land managers rotate herbicides so that the “invasive” plants do not develop resistance to any particular herbicide.  The Guide gives only generic advice to use “herbicide X” initially and “herbicide Y or Z” for subsequent applications.

In other words, the California Invasive Plant Council continues to promote the use of herbicides to kill plants they consider “invasive.”  They give advice about ensuring the effectiveness of herbicides, but they do not give advice about how to avoid damaging the soil, killing insects, and harming the health of the public and the workers who apply the herbicides.  May 20, 2019

  • Are workers who apply pesticides being adequately trained and supervised by certified applicators? The safety of workers should be one of many goals of restoration projects.
  • When non-native plants are eradicated, serious thought should be given in advance to the probable outcome. Will native plants return?  Will wildlife be harmed?  Will the risks of failure outweigh the potential benefits of success?
  • Is climate change taken into consideration when planning the replacement landscape? Are the plants that grew in the project location 200 years ago still adapted to that location?  Is there enough available water?
  • If new plantings require irrigation to be established, what is the water source? Is it recycled water with high salt content that will kill many plants, including redwoods?
  • Are the new plantings vulnerable to new infectious diseases, such as phytopthera or infestations of new insects such as shot-hole borer?
  • Does the project team have sufficient horticultural knowledge to choose plants that can survive in current conditions? Does the project team know the horticultural needs of the plants they are planting?  Is there enough sunlight, water and wind protection for the trees they are planting?

The public is investing heavily in the “restoration” of ecosystems.  We can only hope that our investment is being used wisely and that projects will not do more harm than good.  Cal-IPC can play a role in raising the questions that have the potential to improve projects and enable them to succeed.  The long-term survival of the “restoration” industry depends on it.


Most quotes are from abstracts of presentations published in the conference program.

Action Opportunity: Speak up about Oakland’s Vegetation Management Plan

The stated purpose of Oakland’s Vegetation Management is to reduce fire hazards in Oakland.  Oakland’s Vegetation Management Plan will determine the fate of 2,000 acres of public parks and open spaces and 300 miles of roadside in Oakland.  It will also substantially increase the use of pesticides if approved in its present form.  Two public meetings will take place in November to discuss revisions of the draft plan:

Date: Thursday, November 15, 2018
Time: 5:30-7:30 PM
Location: Richard C. Trudeau Training Center, 11500 Skyline Blvd, Oakland, CA 94619

Date: Tuesday, November 20, 2018
Time: 5:30-7:30 PM
Location: Oakland City Hall, 1 Frank Ogawa Plaza, Hearing Room 2, Oakland, CA 94612

The agenda for these meetings has been carefully crafted to accommodate the wishes of native plant advocates, as expressed in their public comments on the draft plan.  This is the agenda for these public meetings:

  1. “The Plan should better incorporate the role of volunteers and stewardship groups that actively maintain vegetation at various City-managed parks/open space areas. The City should conduct additional outreach to such groups to continue to receive their input and feedback.”
  2. “The Plan should include more specificity regarding vegetation management recommendations at each City-managed parcel.”
  3. “The Plan should include cost estimates, or a range of potential costs, for the recommended treatments to assist the City for longer-term work budgeting and planning. The cost estimates and site-specific plans for City-managed parks would also help identify activities that volunteers can conduct.”

The first meeting on November 15th is “targeted towards the park steward/volunteer groups working on City-owned parcels.”  The second meeting on November 20th “will focus on the issue of plan specificity.  It is requested that participants come prepared to discuss their recommended edits/comments.  At each meeting we will briefly discuss each project site/area, and your feedback will be collected and considered for the revised draft Plan to be released in 2019.”

In other words, the public process that will result in a Vegetation Management Plan for Oakland is now entirely in the hands of native plant advocates (“park stewards/volunteer groups”), despite the fact that there were other important issues raised in the public comments.  Only the public comments of native plant advocates are being considered in the revision of the draft.  None of their requested revisions have anything to do with reducing fire hazards.  Their revisions are intended to greatly increase Oakland’s commitment to native plant “restorations.”

These are the issues being ignored

If you are an Oakland resident with a sincere interest in fire hazard mitigation, who does not believe the draft plan will reduce fire hazards, please attend one of these meetings.  These are the issues we believe are being ignored and must be addressed by the City of Oakland.

  • Pesticides are being used in the parks of the East Bay Regional Park District after completion of an Environmental Impact Report in 2009. The pesticide applications of the Park District are a preview of what will happen in Oakland city parks if the Vegetation Management Plan is approved as presently drafted.

    Pesticide use in Oakland city parks and open spaces is presently prohibited by Oakland’s city ordinance because no Environmental Impact Report has been completed for a revision of the ordinance that was proposed by the City Council in 2005. If the draft Vegetation Management Plan is approved and an Environmental Impact Report is completed as planned, pesticides will be permitted in Oakland’s parks, open spaces, and roadsides. 

  • Pesticide use will increase greatly because pesticides are required to prevent the tens of thousands of trees that the draft plan proposes to destroy from resprouting. Pesticides will also be needed to eradicate the flammable weeds that will colonize the unshaded ground.
  • Native plant advocates are opposed to goat grazing because goats eat both native and non-native plants. Goat grazing is a non-toxic alternative to pesticides.  Shade is the most benign method of weed control.
  • Native plant “restorations” do not mitigate fire hazards because native vegetation is as flammable as non-native vegetation. When non-native trees are destroyed, as proposed by the plan, no native trees will be planted to replace them.  Therefore, the moist forest will be replaced by grassland that ignites more easily than forests.
  • Every wildfire we have witnessed in California in the past 20 years has occurred exclusively in native vegetation. Wildfires in California have become more frequent and more intense because of climate change.  Deforestation is the second greatest cause of climate change because trees release the carbon they have stored throughout their lives, and in their absence carbon storage is reduced in the future.

The native plant movement has a death grip on our public lands in the San Francisco Bay Area.  Few would object to their advocacy if their projects were as constructive as they are destructive.  They are welcome to plant whatever they want, but they should not have the right to destroy everything that is non-native, particularly using pesticides, which is their preferred method.

I would like to believe that public policy is in our hands if we will participate in the political process.  It is becoming more difficult to believe in that ideal.  Please attend one of these meetings, if only to keep our democracy alive and well.

Wildfire cover story is the lie that binds

Native plant advocates originally thought they would be able to destroy all non-native trees in California based entirely on their preference for native plants.  People who value our urban forest quickly challenged that assumption.  Native plant advocates devised a new strategy based on fear.  Fear is the most powerful justification for many public policies that deliver a wide range of agendas, including the current prejudices against immigrants that is shared by many native plant advocates.  After the destructive wildfire in Oakland in 1991, native plant advocates seized on fear of fire to convince the public that all non-native trees must be destroyed.  They made the ridiculous claim that native plants and trees are less flammable than non-native plants and trees.

Scripps Ranch fire, San Diego, 2003. All the homes burned, but the eucalypts that surrounded them did not catch fire. New York Times

Like most lies, the wildfire cover story has come back to bite the nativists.  As wildfires rage all over the west, becoming more frequent and more intense, the public can see with their own eyes that every fire occurs in native vegetation, predominantly in grass and brush and sometimes spreading to native forests of conifers and oak woodlands.  It has become difficult for nativists to convince the public that native vegetation isn’t flammable because the reality of wildfires clearly proves otherwise.

Vegetation that burned in the North Bay files of October 2017. Source: Bay Area Open Space Council

Recently, nativists have become the victims of their own wildfire cover story as they try to reconcile the contradictions in their hypocritical agendas.  These contradictions are now visible both nationally and locally in the San Francisco Bay Area.  We will tell you about the lie that binds nativism today.

Sierra Club caught in the wringer of its own making

The New York Times published an op-ed by Michael Brune, Executive Director of the Sierra Club, and Chad Hansen, ecologist and member of the Sierra Club Board of Directors.  They informed us of a proposed federal farm bill to destroy trees on thousands of acres of national forests without any environmental review.  The stated purpose of this federal plan is to reduce wildfire hazards.

The national leaders of the Sierra Club emphatically disagree that destroying trees will reduce fire hazards.  In fact, they say “increased logging can make fires burn more intensely” because “Logging, including many projects deceptively promoted as forest ‘thinning,’ removes fire-resistant trees, reduces the cooling shade of the forest canopy and leaves behind highly combustible twigs and branches.”

They point out that climate change and associated drought have increased the intensity of wildfires.  Therefore, they say we must “significantly increase forest protection, since forests are a significant natural mechanism for absorbing and storing carbon dioxide.”  Destroying forests contributes to climate change and climate change is causing more wildfires.

The leaders of the Sierra Club tell us that the most effective way to reduce damage caused by wildfires is to “focus on fire-safety measures for at-risk houses.  These include installing fire-resistant roofing, ember-proof exterior vents and guards to prevent wind-borne embers from igniting dry leaves and pine needles in rain gutters and creating ‘defensible space’ by reducing combustible grasses, shrubs and small trees within 100 feet of homes.  Research shows these steps can have a major impact on whether houses survive wildfires.”

Does that strategy sound familiar?  Perhaps you read that exact strategy here on Million Trees or on many other local blogs that share our view that destroying trees is not the solution to fire hazard mitigation and safety. 

Unfortunately, the Sierra Club continues to talk out of both sides of its mouth.  While the national leadership speaks rationally on the subject of wildfires, the local leadership of the San Francisco Bay Chapter of the Sierra Club continues to demand that all non-native trees in the Bay Area be destroyed. 

The City of Oakland recently published a draft of its Vegetation Management Plan (VMP) with the stated purpose of reducing fire hazards.  The draft plan recommends removal of most non-native trees on 2,000 acres of open space and along 300 hundred miles of roads.  The plan seemed unnecessarily destructive to those who value our urban forest and have a sincere interest in reducing fire hazards, but it was unacceptable to the local chapter of the Sierra Club because it does not go far enough to destroy all non-native trees.  Here are some of the revisions they demand in their public comment (1) on the draft VMP:

  • “…removal of all second-growth eucalyptus trees, coppice suckers and seedlings in city parks…”
  • “…removal of 20-year old Monterey Pine seedlings that were allowed to become established after the original pines burned and were killed in the 1991 fire…”
  • “…identify areas of overly mature and near hazardous Monterey Pine and Cypress trees that could be removed…”
  • “…recommend adoption of specific updated IPM policies for the city to implement that will allow appropriate and safe use of herbicides…”
  • “The Sierra Club has developed the right approach to vegetation management for fire safety…The Sierra Club’s program for vegetation management can be summarized by the Three R’s:”
    • “Remove fire dangerous eucalyptus, pine, and other non-native trees and other fire dangerous vegetation like French and Scotch broom…”
    • “Restore those areas with more fire safe native trees like bays, oaks, laurels and native grasslands…”
    • “Re-establish the greater biodiversity of flora and fauna that results from the return of more diverse habitat than exists in the monoculture eucalyptus plantations…”

The local chapter of the Sierra Club is making the same demands for complete eradication of non-native trees in the East Bay Regional Park District.  The pending renewal of the parcel tax that has paid for tree removals in the Park District for the past 12 years was an opportunity for the Sierra Club to make its endorsement of the renewal contingent upon the Park District making a commitment to remove all non-native trees (and many other commitments).

“…the Sierra Club believes it is critical that in any renewal of Measure CC [now Measure FF on the November 2018 ballot] funding for vegetation management should be increased for the removal of non-natives such as eucalyptus and their replacement with restored native habitat…Measure CC [now FF] funds should not be used to thin eucalyptus but must be allocated to the restoration of native habitat.” (1)

The Sierra Club has endorsed the renewal of the parcel tax—Measure FF—that will be on the ballot in November 2018.  In other words, the Park District has made a commitment to removing all non-native trees on our parks.  We have reported on some of the clear cuts that the Park District has done in the past 6 months.

Sibley Volcanic Reserve. Photo by Larry Danos, March 2018

The national Sierra Club and the San Francisco Bay Chapter of the Sierra Club are at odds on fire hazard mitigation.  The national leadership understands that destroying trees will not reduce fire hazards.  They also understand that destroying trees will contribute to climate change that is causing more destructive wildfires.  The local leadership clings to the cover story that native trees are less flammable than non-native trees.

Local nativists change their tune

There is no history of wildfires in San Francisco and there is unlikely to be in the future because it is foggy and soggy during the dry summer months when wildfires occur.  But the reality of the climate conditions and the absence of fire in the historical record never prevented nativists in San Francisco from trying to use the fire cover story to support their demand that thousands of non-native trees be destroyed. 

Summer fog blanket over San Francisco. Courtesy Save Mount Sutro Forest.

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 that newsletter, he repeatedly claimed that eucalyptus were dying during the extreme drought and had to be destroyed so they would not cause a catastrophic wildfire.  In fact, eucalyptus did not die in San Francisco or elsewhere in the Bay Area during the drought because they are the most drought-tolerant tree species in our urban forest.  More native trees died in California during the drought than non-native trees. 

Jake Sigg made those dire predictions before the native plant agenda was finally approved in 2017 after 20 years of heated debate and before many wildfires in California have established the truth that wildfires start in grass and brush and seldom in forests and in every case in exclusively native vegetation.

So, to accommodate this new reality, Jake Sigg has changed his tune.  He got his wish that thousands of non-native trees be destroyed in San Francisco as well as a commitment to restore the native grassland that he prefers.  Consequently it is no longer consistent with that agenda to claim that there are acute fire hazards in San Francisco, requiring the destruction of flammable vegetation.

The San Francisco Chronicle published an article about the concerns of park neighbors about dead/dying/dormant grass and brush in parks that they believe is a fire hazard and they want the San Francisco park department to clear that flammable vegetation.  Jake Sigg is now quoted as saying that it isn’t necessary to clear that vegetation—which he prefers—because there are no fire hazards in San Francisco: 

“What protects much of San Francisco’s forested area is the city’s famed fog, said Jake Sigg, a conservation chairman of the local chapter of the California Native Plant Society.  While walking on Mount Davidson on a recent afternoon, he said, one area was so muddy from fog that he has to be careful not to slip…’In the past, (fires) haven’t been too much of a concern for the simple reason that we have had adequate rainfall,’ Sigg said.”

According to nativists, the wet eucalyptus forest must be destroyed, but the dead/dried flammable brush and grassland must be preserved because it is native.

Serpentine Prairie restoration. East Bay Regional Park District

The elusive truth

Despite the constantly shifting story, we are not fooled.  The truth is that native vegetation is just as flammable as non-native vegetation and that destroying trees—regardless of their nativity—will not reduce fire hazards.


(1) These letters on Sierra Club letterhead were obtained by public records requests and are available on request.

Digging In: Nativists aggressively defend their use of herbicides

The trial of DeWayne Johnson vs. Monsanto began early in July.  This is the first trial of about 4,000 lawsuits against Monsanto for “product liability.”  Mr. Johnson is dying of non-Hodgkin lymphoma.  He believes that the glyphosate that he sprayed as an employee of the Benicia School District from 2012 to 2015 has caused his terminal cancer.  His lawyer will present evidence at the trial that Monsanto knew the health risks of the glyphosate they manufactured and hid that information from the public. 

This trial could be the turning point that will determine the future of glyphosate in America.  Therefore, this is a suitable opportunity to explain how we got here and why the fate of glyphosate may also determine the fate of the native plant movement.


Update August 10, 2018:  BREAKING NEWS!!!

”A San Francisco jury has found in favor of a school groundskeeper dying of cancer whose lawyers argued that a weed killer made by the agribusiness giant Monsanto likely caused his disease.

“Dewayne Johnson was awarded nearly $290 million in punitive damages and another $39 million in compensatory damages.

“Johnson’s lawsuit against Monsanto was the first case to go to trial in a string of legal complaints alleging the glyphosate-based Roundup herbicide caused non-Hodgkin’s lymphoma.

“He sprayed Roundup and another Monsanto product, Ranger Pro, as part of his job as a pest control manager at a San Francisco Bay Area school district, his attorneys have said.

“He was diagnosed with lymphoma in 2014, when he was 42.

“Monsanto, for its part, vehemently denies a link between Roundup and cancer.

“But jurors at San Francisco’s Superior Court of California, who deliberated for three days, found that the corporation failed to warn Johnson and other consumers about the risks posed by its weed-killing products.

“The outcome of the trial will not have a direct affect on the slew of other Roundup-related suits in state and federal courts. But it could serve as a bellwether for other cases in the queue.”  https://www.nbcnews.com/news/us-news/jury-orders-monsanto-pay-290m-roundup-trial-n899811

This could be the beginning of the end for glyphosate.  There will be many appeals of this decision, but there are also many other lawsuits in line by people who believe they were harmed by glyphosate.  This is a significant step forward.


The story begins

I have followed the native plant movement in California for over 20 years.  I knew that herbicides were used by land managers to eradicate plants they consider “invasive” only because I made the effort to inform myself of what they were doing.  It wasn’t easy to figure out that they were using herbicides because many land managers do not post notices of their pesticide applications and even fewer report their pesticide use to the public.  State law does not require posting of pesticide application notices if the manufacturer claims that the product dries within 24 hours, which exempts most of the herbicides used by land managers, including glyphosate (Roundup) and triclopyr (Garlon).

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

I didn’t know how extensive herbicide use is on our public lands until the California Invasive Plant Council conducted a survey in 2014 of 100 land managers about the methods they were using to kill “invasive” plants. Here’s what we learned from that survey:

  • Ninety-four percent of land managers are using herbicides to control plants they consider “invasive.”  Sixty-two percent are using herbicides frequently.
  • Ninety-nine percent of the land managers who use herbicides, use glyphosate products. Seventy-four percent use Garlon, which is one of the most hazardous herbicides available on the market.  The Pesticide Research Institute says that Garlon “poses reproductive and developmental risks to female applicators.”
  • Foliar spray is the method used most frequently by land managers to apply herbicides.  This method of application has the potential to drift into non-target areas and kill non-target plants.

Chapter Two:  World Health Organization takes a position

In 2015, one year after the Cal-IPC survey was done, the World Health Organization’s International Agency for Research on Cancer (IARC) classified glyphosate as a “probable human carcinogen.”  That decision suddenly and radically altered the playing field for the use of glyphosate, which is the most heavily used of all herbicides.

Since that decision was made, 25 countries have issued outright bans on glyphosate, imposed restrictions or have issued statements of intention to ban or restrict glyphosate-based herbicides, including Roundup.  Countless US states and cities have also adopted such restrictions. Locally, the Marin Municipal Water District made a commitment to not using pesticides—including glyphosate—in 2015.  MMWD had stopped using pesticides in 2005 in response to the public’s objections, but engaged in a long process of evaluating the risk of continuing use that resulted in a permanent ban in 2015.

Chapter Three:  Nativists dig in

The reaction of native plant advocates to this bad news of the dangers of glyphosate has been to dig in and aggressively defend their use of herbicides.

One of the first indications of this reaction was an article about the IARC decision in the Fall 2015 newsletter of the California Invasive Plant Council (Cal-IPC) that concludes:  “In the final analysis, this means that there’s no good reason to stop using glyphosate whether it’s a carcinogen or not.”  If the IARC decision isn’t a good reason, what is?  If the prospect of cancer isn’t a legitimate reason not to use glyphosate, what is?

In its Fall 2016 newsletter, Cal-IPC stepped up the volume.  The Executive Director’s introductory letter stated the highest priorities for Cal-IPC, including, “the increased need for Cal-IPC to publicly support the appropriate use of herbicides.”

That edition of the Cal-IPC newsletter also includes a review of Tao Orion’s book, Beyond the War on Invasive SpeciesTao Orion is a practicing permaculturalist who shares many of the objectives of native plant advocates. Permaculture is committed to conservation, preservation, and restoration, but practitioners achieve those objectives without using pesticides.  They focus on restoring ecological functions by identifying and correcting the underlying causes of change, such as loss of water resources.

Given Cal-IPC’s commitment to herbicide use, it was unable to find value in Orion’s book.  Much of their criticism seemed unfair.  They said that Orion’s recommendations for using restoration methods such as burning or grazing that don’t require the use of pesticides are preaching to the choir.  They claim that native plant restoration projects are, in fact, doing the same thing.  Yet, the survey Cal-IPC conducted in 2014 says otherwise.  Forty-seven percent of land managers said they “never” use grazing to control “invasive” plants, compared to 94% who said they use pesticides.  Burning was not mentioned by any land manager as a method they use.

The survey and accompanying risk assessment of the herbicides used by those who took the survey was presented at the annual Cal-IPC conference in fall 2014.  It was available on the Cal-IPC website until very recently, when it was scrubbed.  The risk assessment is still available on the website of the Pesticide Research Institute, which conducted that evaluation.

In October 2017, Cal-IPC published a position statement regarding glyphosate, “The Use of Glyphosate for Invasive Plant Management.”  Cal-IPC’s “position on the issue” is:  “Cal-IPC supports the use of glyphosate in invasive plant management as part of an Integrated Pest Management (IPM) approach. When using glyphosate according to the label, with appropriate personal protective equipment and best practices, glyphosate is low-risk for wildlife, applicators and the public.”  Their position is primarily based on their belief that doses of glyphosate used in wildland weed management are too low to be a health hazard.

Several new studies, published after the IARC decision, strengthen the case against glyphosate.  New research suggests that glyphosate is a health hazard at low doses considered “safe” by the EPA.  The Global Glyphosate Study is being conducted by six scientific institutions all over the world. This international consortium of scientific institutions recently published preliminary results of their study: “The results of the short-term pilot study showed that glyphosate-based herbicides (GBHs) were able to alter certain important biological parameters in rats, mainly relating to sexual development, genotoxicity and the alteration of the intestinal microbiome, at the ‘safe’ level of 1.75 mg/kg/day set by the U.S. Environmental Protection Agency (EPA).”  In other words, at doses deemed safe by the US EPA, significant negative health effects were found in animals used in testing.

Another recent study of glyphosate found that the formulated product is considerably more toxic than the active ingredient alone.  US National Toxicology Program recently conducted tests on formulated glyphosate products for the first time. In the past, tests were conducted only on the active ingredient…that is glyphosate alone. The formulated products that are actually applied as weed killers contain many other chemicals, some of which are not even known. The head of the National Toxicology Program Laboratory, told The Guardian newspaper the agency’s work is ongoing but its early findings are clear on one key point. “We see the formulations are much more toxic. The formulations were killing the cells. The glyphosate really didn’t do it,” DeVito said. A summary of the NTP analysis said that “glyphosate formulations decreased human cell ‘viability’, disrupting cell membranes. Cell viability was ‘significantly altered’ by the formulations, it stated.”

Two empirical studies found that low levels of exposure to the weed killer Roundup (glyphosate) over a long period of time can cause liver disease.

Is Cal-IPC aware of these recent studies?  Are the people who apply glyphosate aware of these studies?  Are the employers of these applicators aware of these studies?  Are these applicators the plaintiffs of future product liability lawsuits against Monsanto?

Chapter Four:  California Native Plant Society defends herbicides with fantasies

If you read the publications of the California Native Plant Society (CNPS) or attend their conferences, you know that little mention is made of herbicides by their followers and those who engage in “restoration” projects.  In the past, the best defense was to turn a blind eye to herbicide use.

More recently, the intense opposition to the use of herbicides on public lands seems to have forced CNPS to become actively engaged in the defense of herbicides.  The most recent edition of the Journal of the California Native Plant Society, Fremontia (Vol. 46 No. 1) is a “Special Issue on Urban Wildlands.” The introductory article is illustrated with a photo of Oyster Bay.  I nearly choked on this statement in that article:  “In order to control invasive plants, agencies and volunteers have sometimes resorted to using herbicides as a step in integrated pest control.  While use of herbicides is contentious, the use for spot treatments has enabled small groups of volunteers to successfully eliminate invasive weeds in some areas where future herbicide use will not be needed.” Oyster Bay is being doused with herbicides as we reported in a recent article that is available HERE.

Oyster Bay herbicide applications, May 2018

That same edition of Fremontia also includes several articles in which specific native plant “restorations” are described in detail.  All of the projects use herbicides, often repeatedly and often without successfully establishing native plants:

  • “Bull Creek Ecosystem Restoration Project: Not Quite a Success Story”:  This project began in 2008, after over 10 years of planning.  Bull Creek was reconfigured with bull dozers, eliminating the existing landscape.  Although natives were planted, weeds quickly took over the site.  It was weeded by hand initially and considered a success until the creek bank eroded significantly and the artificial oxbow filled with silt.  But “weeds continued to thrive” because the native plants were irrigated and they resorted to herbicide applications in 2010.  Subsequent failures of native plants were blamed on unauthorized public access and the state-wide drought.  Volunteer weeding has been abandoned.  The future of this project is very much in doubt.
  • “Weed Control Efforts in the Sepulveda Basin”: “Based on more than 20 years of experience with attempting to control various weeds in the Sepulveda Basin, and given the lack of support from the city due to budgetary priorities, it is apparent that without herbicide it will be impossible to control non-native weeds that threaten regional biodiversity.”
  • “Nature in the City: Restored Native Habitat Along the LA River…”:  The site was sprayed with Roundup (glyphosate) several times to remove as much of the non-native seed bank as possible.  Weeding continued throughout the habitat restoration and construction period.”

Did CNPS notice the contradiction between their first article and subsequent articles in the same publication?  Their introductory article claims they rarely use herbicides and when they do it is only temporary.  But subsequent articles about specific projects make it clear that herbicides are routinely and repeatedly used and even then, weeds persist.

Pesticides used in San Francisco’s “natural areas.” Courtesy San Francisco Forest Alliance

In the Bay Area, one of the oldest native plant “restorations” is in San Francisco, where the so-called Natural Areas Program (now called Natural Resources Division) started in 1998.  They have used pesticides consistently since the program began.  The San Francisco Forest Alliance began tracking their use of pesticides in 2008.  In their most recent report, the Forest Alliance informs us that pesticide use in the so-called “natural areas” has increased significantly in the first half of 2018.  This increase was anticipated because the program plan and its Environmental Impact Report were finally approved in spring 2017, after 20 years of being hotly contested.  The approval of the program enabled them to increase the staff of pesticide applicators from one to five.  Most of the increase in pesticide use in 2018 is of Garlon, one of the most toxic pesticides available on the market.  San Francisco’s native plant restorations are a specific example of the long term use of large quantities of herbicide.  You can visit those areas to see for yourself that 20 years of effort and herbicides have not successfully established native plant gardens.

Good luck to DeWayne Johnson

It is difficult to understand how nativists can continue to advocate for the use of herbicides.  It is even more difficult to understand how land managers can continue to use public money to spray herbicides on our public parks and open spaces.  Since they are apparently impervious to scientific assessment of the health hazards of herbicides and blind to the failures of their projects, we can only hope that DeWayne Johnson will prevail in his lawsuit against Monsanto.  We would like to see justice for Mr. Johnson and his family and the bonus will be the legal liabilities and associated economic costs of continuing to use a dangerous herbicide that damages the environment and everyone who lives in it.

Putting another eucalyptus myth to rest: Lifespan of blue gum eucalyptus

When the native plant movement began in earnest, about 25 years ago, its proponents weren’t expecting blowback from those who value the existing landscape.  As far as they were concerned, the trees had to be destroyed solely because they “don’t belong here.”

When they started destroying our predominantly non-native urban forest, they learned that it wasn’t going to be as easy as they thought.  They began to defend their destructive projects with cover stories to convince the public who didn’t share their devotion to native plants that it is necessary to destroy non-native trees because they are a threat to public safety and to wildlife.

One by one, we have debunked the myths that were used to justify the destruction of our urban forest:

  •  

Great horned owl in eucalyptus. Courtesy urbanwildness.org

About 20 years ago, one of the first myths was that eucalyptus trees kill birds. It is an absurd claim that is completely unsupported by reality.  With a lot of careful research, we were eventually successful in convincing the public that birds are not harmed by eucalyptus.  In fact, many bird species are dependent upon the trees for safe nesting and winter nectar.   That myth is dead.

  • The claim that eucalyptus and other non-native trees are more flammable than native trees was a powerful narrative that was more difficult to kill. As wildfires have increased in frequency and intensity in California, that claim is no longer credible because every wildfire occurs in native vegetation.  Again, this myth was eventually disproved by reality.
  • More recently, we have finally put to rest the claim that “nothing grows under eucalyptus.” This myth was based on a theory that eucalyptus emits allelopathic chemicals that prevent the growth of plants in the eucalyptus forest.  Thanks to a recent, rigorous study done at Cal Poly, we know with confidence that the allelopathy story is another myth.

It was not surprising that the nativists, having run out of bogus justifications, created a new narrative.  In parks that the East Bay Regional Parks District had been planning to thin, we began to see clear cuts.  When we inquired about why it was necessary to destroy ALL of the trees, we were told they were hazardous.  Then, in the minutes of a meeting of East Bay Regional Park District Park Advisory Committee , we saw the claim that eucalyptus lives only 50-60 years.  Simultaneously, this claim was made in San Francisco by proponents of destroying all eucalyptus trees there.

We eventually tracked down the source of that lifespan estimate to a website called SelecTree, which originally said that the longevity of blue gums is only 50-150 years.  We knew that isn’t an accurate estimate because of how long blue gums live in Australia and how long they have already lived in California.  We provided that information to the authors of SelecTree and were able to get the estimate corrected to “greater than 150 years.”  That’s not nearly long enough, but it is the longest lifespan estimate available on that website and it corresponds with many other trees, including native Coast Live Oak.

In the process of researching the lifespan of eucalyptus, we learned several interesting stories about blue gums that have lived in California for 150 years and are still going strong.  We would like to share some of this information with our readers today.

Blue gum eucalyptus lives in Australia 200-400 years

Blue gum eucalyptus and all other species of eucalyptus are native to Australia.  They were brought to California shortly after the Gold Rush of 1849.  Since they haven’t been in California 200 years, we don’t know how long they will live here.  But how long they live in Australia is obviously relevant to answer that question because longevity is specific to tree species.  We can expect some variation by climate, but not much, and the climate of Australia is similar to the climate in California with wet, mild winters and hot, dry summers.

We know that blue gums live in Australia about 200-400 years because Australian scientists tell us that:

Growth Habits of the Eucalypts by M.R. Jacobs, (Institute of Foresters of Australia, 1955, 1986): Blue Gum eucalyptus lives in Australia from 200-400 years, depending upon the climate.” In milder climates, such as San Francisco, the Blue Gum lives toward the longer end of this range.

That reference was corroborated by John Helms, Professor Emeritus of Forestry at UC Berkeley and an Australian who said in response to our question about blue gums in California, “Blue gums would commonly live for 200 – 400 years, although I presume that some might live longer.”

We also asked the Australian National Botanic Gardens.  They said, “It’s possible that the average lifespan of a native species growing in the wild in Australia would differ to the average lifespan of the same species introduced in northern California, since introduced plants can often “escape” their natural predators when such introductions occur.”

In other words, since eucalyptus trees have more predators in Australia than they do in California, we should expect them to live longer here.  This is called the “predator release” hypothesis.  Ironically, that hypothesis is used by nativists to support their claim that eucalyptus is invasive in California.  (California Invasive Plant Council rates the “invasiveness” of blue gum as “limited.”)  It’s only logical to apply that hypothesis to the question of how long blue gums will live in California.

Many healthy blue gums in California are 150 years old

However, using actual experience in Australia to predict the future of blue gums in California requires some speculation.  Therefore, we turned to the question of how long they have lived in California for guidance.  We found several interesting local stories about blue gums that were planted in California 150 years ago and remain healthy and vigorous today.

There are many examples of blue gums being planted as street trees in California about 150 years ago.  One of the most well-known examples is the city of Burlingame on the San Francisco peninsula. When the City was founded in the 1870s, John McLaren was hired to plant trees to provide a much needed windbreak because the City was nearly treeless, as was the entire San Francisco peninsula.  McLaren planted over 500 eucalyptus (blue gum and manna) along the main highway through Burlingame, along with a row of English elms.  John McLaren was subsequently hired by the city of San Francisco, where he planted many more eucalypts while serving as superintendent of the parks department for 53 years.

The eucalypts in Burlingame are still thriving, but the elms have been dead for about 60 years.  SelecTree says the longevity of English elms is “greater than 150 years,” the longest category of longevity published by SelecTree and completely open-ended.

El Camino Real bordered by Eucalyptus trees. Burlingame, SF Bay area, California, USA

The people of Burlingame greatly value their eucalypts and designated them as “heritage trees” in 1975 under a local ordinance.  That local legal status did not protect them from several attempts by Caltrans to destroy the trees.  The people of Burlingame came to the defense of the trees and were eventually successful in getting permanent legal status to protect 2.2 miles of the trees.  That section of El Camino Real in Burlingame lined with eucalyptus was listed on the National Register of Historic Places in 2012.

Caltrans is now working cooperatively with the people of Burlingame to address safety concerns while “also keeping an eye to the prized grove of eucalyptus trees along the street.”  A task force was formed in 2018 to discuss these issues.  The City of Burlingame remains committed to the preservation of these trees, which suggests that they have a future there. (1)

The life span of street trees is generally much shorter than trees planted as forests because they are subjected to more wind and polluted air of heavily traveled roads, such as El Camino Real.  Although blue gums have passed the test of those challenging conditions with flying colors, they have not been planted as street trees for decades.  Their out-sized scale makes them unsuitable for that purpose.  If blue gums can survive as street trees on heavily traveled roads, they can surely survive longer in the protection of their neighbors in forests.

Blue gums at Stanford University

The blue gums on the campus of Stanford University are another example of 150 year-old blue gums that are very much alive.  Although blue gums were included in the campus landscape design of Frederick Law Olmsted in the 1880s, many of the blue gums actually predate his design:  “Several hundred mighty giants on the campus date back prior to 1870 when Leland Stanford acquired several farm properties, one of which already had avenues of gum trees.  They are mostly Tasmanian blue gums and red gums with a sprinkling of manna trees.”

Eucalyptus on Stanford campus

That description of the old blue gums was written in 1971.  The trees are still alive and well.  I worked on the Stanford campus for 10 years and walked among those trees at every opportunity.

An even older Olmsted design in Oakland

Mountain View Cemetery in Oakland, California was designed by Frederick Law Olmsted in the 1860s.  Like most of the East Bay, the site was treeless.  Olmsted’s design was an eclectic collection of mostly non-native trees, including blue gums.  The cemetery is on steep, windward facing hills, where the windbreak provided by blue gums is particularly valued.

Eucalyptus in Mountain View Cemetery, planted on an unirrigated windward facing hill. 2017

Update:  This venerable old giant was destroyed in September 2018, along with about 150 other trees of different species, including oaks. I did not protest before or after the trees were destroyed because they were on private land and their removal makes way for more grave sites. However, I will mourn its loss.

Olmsted designed a straight avenue through the cemetery lined with magnolia trees.  Many of the magnolia trees have died and those that remain are in poor condition.  SelecTree claims that the life span of Southern magnolia is “greater than 150 years,” which is contradicted by our local experience.

The current owner of the cemetery destroyed many of the blue gums about 5 years ago, in the middle of the extreme drought.  He replaced many of the blue gums with redwoods.  The redwoods are irrigated and are still surviving.  I did not object to the removal of the blue gums because they are on private property.  I confine my advocacy to healthy trees on public land.

Long live the blue gums!

SelecTree has revised its listing of blue gum longevity based on the information we provided.  The myth that our blue gums are dying of old age will not die as easily.  We will have to repeat this information many times and in many different venues, just as we did for every other myth.  If and when that particular myth dies, we can be sure there will be another waiting in the wings.  Ideologies stubbornly persist, despite contradictory evidence.  And yet, we just as stubbornly persist in defense of our urban forest.


(1) Here is the public record, on which my report about the trees in Burlingame is based:

Nativist fantasies about oaks

San Francisco Bay Estuary Institute is promoting a “restoration” project they call “Re-Oaking California.”  The project is planning to plant oak trees in California cities, in particular.  They have published an elaborate brochure describing their project and they have published a brief description in the quarterly newsletter of California Releaf, the biggest non-profit advocacy organization for California’s urban forest.  Locally, they have made a presentation to Oakland’s Urban Forestry Forum and to the Bay Area Open Space Council.  The Open Space Council convenes meetings of hundreds of public land managers from all over the Bay Area.  In other words, the re-oaking project is being aggressively sold to those who determine the future of our public lands.  Therefore, it is a project that deserves our attention.

First, I must say that I love oaks.  I decided to buy the home I now live in before I stepped inside, because of the beautiful coast live oak in the front yard.  The loss of that tree would be devastating both emotionally and to the value of my home.

However, my opinion of the re-oaking project is based on the reality of climate change and its implications for the future of California’s urban forest.  Although the project brochure acknowledges that Sudden Oak Death has killed many oaks in California, it does not accurately reflect the scale of that epidemic.

Sudden Oak Death

Sudden Oak Death (SOD) killed 5 million oak trees in California from 1994 to 2015, when that number was reported by a study. (1)  The study also said that the SOD epidemic could not be stopped and would eventually kill all oaks in California.  More recent estimates are that 5 to 10 million oaks have been killed by SOD. (2)

Tan oaks killed by SOD. US Forest Service

SOD is caused by a pathogen that is spread by rain and wind.  We had a great deal of rain in 2016 and 2017, which greatly increased the spread of SOD infections.  In the past, SOD has been mostly confined to wildlands.  Now it is found in many urban areas, including San Francisco and the East Bay.  In the most recent SOD survey done in spring 2017, new infections were found on the UC Berkeley campus, the UC arboretum, and the San Francisco Presidio. (2)

The scientist at UC Berkeley who conducts the annual survey of SOD infections reports that “A dramatic increase this year in the number of oaks, manzanita and native plants infected by the tree-killing disease known as sudden oak death likely helped spread the massive fires that raged through the North Bay…” (3)

Brice McPherson, Associate Specialist in Organisms and the Environment at UC Berkeley, has been studying SOD infections in Marin County and the East Bay.  He made a presentation in November 2017 about the current status of SOD infections in East Bay parks.  Wildcat Canyon is the park in which Mr. McPherson has most recently inventoried infected and dead trees.  In 2017, Mr. McPherson found that 16.2% of coast live oaks were infected and 20.5% were dead.  The number of dead and dying oaks in Wildcat Canyon is staggering:  18,750 oaks are infected and 21,360 oaks are dead.  McPherson predicted that 50% of all oaks in East Bay parks would be dead within 20 years, depending upon the amount of rainfall.

Native bay trees are considered the main vectors of the pathogen that causes SOD.  The re-oaking project therefore suggests that SOD infections in urban areas can be avoided if bay trees aren’t planted in proximity to the oaks.  However, the source of the SOD infection recently found in the Presidio in San Francisco is said to have been rhododendrons, which should remind us that bays are not the only vectors of the SOD pathogen.  In fact, the USDA reports 46 confirmed hosts for the SOD pathogen, including both native and non-native shrubs and trees. (4)  Many of the hosts are commonly found in urban gardens.

Climate change kills oaks in Southern California

Sudden Oak Death infections have not been found south of San Luis Obispo.  However, that does not mean that oaks in Southern California are any less threatened by changes in the environment.  Several land managers in Southern California made presentations at the recent conference of the California Native Plant Society in Los Angeles about massive die-offs of oaks in Southern California.  Here is an example from the Santa Monica Mountains:  “Over 9,000 coast live oak and 114,000 riparian trees died from [2014 to 2017]…” (5) These deaths were caused by extremely high temperatures to which the trees are not adapted, associated drought and new insect predators, such as shot-hole borer.

The unsuitable climate conditions in Southern California are the anticipated climate conditions of Northern California.  Carbon storage in our urban forest is one of the few tools we have to combat climate change.  Although coast live oaks store carbon, they are not particularly long lived.  Their life expectancy is from 125 to 250 years in suitable conditions. (6) Planting trees with no long-term future is not a responsible response to climate change.  The US Forest Service predicts coast live oaks will be virtually gone in California by 2060:

Wildlife in our urban forest

Although oaks are clearly useful to wildlife, they are not significantly more useful than other urban trees.  Here are three studies conducted in the East Bay that compare the biodiversity of animal life in oak woodland to other tree species:

Dov Sax (Brown University) studied six forest plots of about 1 hectare each in Berkeley, CA, three of eucalypts and three of native oaks and bays.  The sites were not contiguous, but were selected so they were of similar elevation, slope, slope orientation, and type of adjacent vegetation.  He conducted inventories of species in spring and autumn.  He counted the number of species of plants in the understory, species of invertebrates (insects) in samples of equal size and depth of the leaf litter, species of amphibians, species of birds, species of rodents.  This is what he found:

“Species richness was nearly identical for understory plants, leaf-litter invertebrates, amphibians and birds; only rodents had significantly fewer species in eucalypt sites.  Species diversity patterns…were qualitatively identical to those for species richness, except for leaf-litter invertebrates, which were significantly more diverse in eucalypt sites during the spring.”  (7)

In 1975, Professor Robert Stebbins (UC Berkeley) was hired by East Bay Regional Park District to conduct a survey of vertebrate animals living in several parks (Sibley, Chabot, and Tilden). The forest types that Professor Stebbins studied were redwood, Monterey pine, eucalyptus, and oak-bay woodland as well as grassland and dry chaparral. Here is how he described his findings:

  • “Redwood and Monterey pine habitats are notably depauperate in vertebrate species.
  • “Eucalyptus habitat is far richer in vertebrates than either redwood or Monterey pine and vies with ‘dry’ chaparral and grassland in species diversity and ‘attractiveness.’
  • “Oak-bay woodland is the richest in both species and ‘attractiveness.’
  • “Grassland is a little less rich in species and ‘attractiveness’ than the other native habitats, but only slightly richer than eucalyptus habitat.” (8)

A wildlife study of Angel  Island prior to the removal of most eucalyptus trees found:

“The total number of birds observed in native stands was similar to that observed in eucalyptus stands…Few small animals were caught in any stand; captures were in native stands five Norway Rats…in eucalyptus stands one Norway Rat…in grassland one Norway Rat and six California Voles…about three times as many salamanders were located in eucalyptus stands compared to native stands.” (9)

As David Ackerly said in response to a question at the recent conference of the California Native Plant Society, “There are few mutually exclusive relationships in nature.”  It is a risky evolutionary strategy.  If an animal is dependent upon a single plant species, it won’t survive in the absence of that plant species unless it is capable of adapting to available vegetation.  Despite the handful of examples given in the re-oaking brochure, wildlife in California is using non-native vegetation as often as native vegetation.

California’s urban forest is not native

The suggestion that California’s cities could be “refugia” for our threatened oaks is wishful thinking.  As Matt Ritter tells us in his book about California’s trees (A Californian’s Guide to the Trees Among Us), only 6% of California’s urban trees are native to California.  Thirty-three non-profit tree advocacy organizations in California (including California Releaf) told us why in their letter to California’s Natural Resource Agency about the Urban Greening grant program:  “Native trees are generally not suited to urban conditions.  They have difficulty adapting to the urban environment, thereby substantially reducing survivability…As an example, the approved list of street trees for the City of San Francisco includes no trees native to San Francisco.  In Oakland, two of the 48 allowed species are native.”

The future of California’s urban forest

So, what is the future of California’s urban forest?  Scientists with sufficient knowledge of trees are trying to answer that question and we would be wise to pay attention to their advice.  Greg McPherson gave a presentation in Davis on March 10, 2018 about “Growing Resilient Forests.”  McPherson’s research at the US Forest Service about the economic value of ecosystem services provided by urban trees (carbon storage, reduction of energy use for heat/cooling, increased property values, removal of particulate pollution, etc.) has been vital to those who defend our urban forest.

McPherson lives in Davis, where he is conducting a 20-year study about the urban forests of the future, i.e., those that will survive predicted changes in the climate. Three years into the study, his research team has made some preliminary recommendations for the trees that are likely to survive anticipated changes in the climateNone is native to Northern California. Most are foreign, particularly Australian.  (10)

Nativists deny reality of climate change

When the climate changes, the vegetation changes, moves, or dies.  That has been one of the few axioms in nature since life has existed on Earth and we would be wise to assume that it will continue to be true.  The future of California’s urban forest depends on our willingness to plant trees that are adapted to the climate and to the anticipated climate.  Climate change is killing California’s trees and nativism is preventing us from replacing them with suitable trees.


  1. https://www.sciencedaily.com/releases/2016/05/160502161111.htm
  2. “Disease killing oaks spreads,” East Bay Times, October 24, 2017
  3. “Disease in trees pointed at in fires,” San Francisco Chronicle, October 20, 2017
  4. http://www.aphis.usda.gov/plant_health/plant_pest_info/pram/downloads/pdf_files/usdaprlist.pdf
  5. http://www.rcdsmm.org/wp-content/uploads/2016/04/Drought-and-Invasive-Beetle-impacts-RCDSMM-1.2.18.pdf
  6. http://ucanr.edu/sites/oak_range/Californias_Rangeland_Oak_Species/Coast_Live_Oak/
  7. Dov Sax, “Equal diversity in disparate species assemblages:  a comparison of native and exotic woodlands in California,” Global Ecology and Biogeography, 11, 49-52, 2002. http://elkhornsloughctp.org/uploads/files/1109813068Sax2002.pdf
  8. Robert Stebbins, “Use of Habitats in the East Bay Regional Park by Free-living Vertebrate Animals,” August 1975. In “Vegetation Management Principles and Policies for the East Bay Regional Park District,” June 1976 (this unpublished study is available on request)
  9. “Focused Environmental Study, Restoration of Angel Island Natural Areas Affected by Eucalyptus,” California State Parks and Recreation, July 1988, pg 96-97.
  10. http://climatereadytrees.ucdavis.edu/