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

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

Study design determines study findings

Million Trees can never resist a response to misinformation we find in Jake Sigg’s Nature News. (In this case, the statement originates with one of Jake’s readers, not Jake himself.)

“This study takes some of the life out of Art Shapiro’s ecological fitting theory:  Non‐native plants supported significantly fewer caterpillars of significantly fewer specialist and generalist species even when the non‐natives were close relatives of native host plants.”  “Non-native plants reduce abundance, richness, and host specialization in lepidopteran communities” by Karin Burghardt, Doug Tallamy, et, al. (Ecosphere, November 2010).

We’ll get to the study later, but first let’s address the statement about ecological fitting.  Ecological fitting is more accurately described as an observation, rather than a theory or hypothesis and it does not originate with Art Shapiro.  The first observation of ecological fitting was recorded by Dan Janzen in 1980 and described by other ecologists as “the process whereby organisms colonize and persist in novel environments, use novel resources or form novel associations with other species as a result of the suites of traits that they carry at the time they encounter the novel condition.” (1) Ecological fitting is an alternative to the view that relationships between plants and insects and parasites and hosts are the result of co-evolution.  It is consistent with the observation that adaptation to new arrivals in an ecosystem often occurs without evolutionary change and can occur more rapidly than co-evolution would require.

The Colorado potato beetle readily devours an introduced relative of its Solanum hosts as a result of ecological fitting.  (Hsiao, T. H. (1978). “Host plant adaptations among geographic populations of the Colorado potato beetle”. Entomologia Experimentalis et Applicata. 24 (3)) USDA photo

Ecological Laboratory Science

The Burghardt/Tallamy study is a laboratory experiment in the sense that it creates an artificial environment by planting a garden in which it chooses the plant species and then inventories the insect visitors to the garden.  In one garden, native plant species were paired with a closely related species of non-native plant in the same genus (called congeners).  In another, distant garden, native plant species were paired with unrelated species of non-native plants.  The insect visitors that were counted are specifically the larvae stages (caterpillars) of lepidoptera (moths and butterflies).  The adult stage of the caterpillars (moths and butterflies) were not inventoried, nor were members of the other 28 insect orders.


The study considers caterpillars “specialists” if they feed on three or fewer plant families.  The authors make this determination based on scientific literature and on observations of their artificially created garden.  Using scientific literature, 30% of visiting caterpillar species to the experimental garden were specialists.  Using actual visits to their experimental garden, 64% of visiting caterpillars were specialists.  The difference is as we should expect because the scientific literature is based on the behavior of caterpillars in the field, but the study confines the choices of the caterpillars to a few specific plant species chosen by the authors of the study.  In other words, caterpillars in the experimental garden had fewer choices of plant species.

The inventory of caterpillars was conducted over two summer months in 2008 and three summer months in 2009.  Findings were very different in the two years of the study:  “We found no difference between the total Lepidoptera larvae supported by native plants and their non-native congeners in 2008, but found over three fold more larvae on natives in 2009.  In 2008 there was no difference in the abundance of generalists on native and non-native congeners, but natives supported more than twice as many generalists as non-natives in 2009.” (2) Similar results were reported for species richness (number of different larvae species).  When paired with unrelated non-native plants, caterpillars showed a significant preference for native plant species, as we should expect because the plants were not chemically similar.

Caterpillar of Anise swallowtail butterfly on its host plant, non-native fennel. Berkeley, California

Although on average, native species attracted more caterpillars than the non-native congener with which they were paired, the strength of that difference varied significantly.  One matched pair attracted eight times as many caterpillars to the native plant compared to the non-native plant.  Another matched pair attracted slightly more caterpillars to the non-native plant compared to the native plant.  

The study authors interpret the significant differences between findings in the first and second years as an indication that caterpillars accumulated more rapidly on native plants than on non-native plants.  They speculate that a longer study would have found even greater preferences for native plants compared to non-native congeners.  Given that adaptation to introduced species occurs over time that is a counter-intuitive prediction.  In fact, many studies find that insects have made a successful transition from native to non-native hosts within a few generations.

Limitations of laboratory studies

The Burghardt/Tallamy study is often cited by native plant advocates in support of their belief that insects require native plants for survival.  This generalization is not supported by the results of the Burghardt/Tallamy study because:

  • The study results are not relevant to all insects.  The findings apply only to the larvae stages of moths and caterpillars.  The adult stages of moths and butterflies also require nectar and pollen from a much broader range of plants than their host plant, where the adult lays its eggs and caterpillars feed before becoming flying adults.  At the adult stage of their lives, they become pollinators.  Studies of the preferences of pollinators consistently find that a diverse garden that prolongs the blooming period is most useful to them. 
  • The study does not support the claim that caterpillars consistently choose native plants in preference to closely related non-native plants over time.  In fact, other studies find such preferences fade over longer periods of time.
  • Statements made by native plant advocates about the degree to which caterpillars are “specialized” are often exaggerated.  When a diverse landscape is available to caterpillars, scientific literature reports that specialization to a few plant families is found in only 30% of the 72 caterpillar species identified by this study. 
  • The Burghardt/Tallamy study was conducted on the East Coast where the climate is different than California.  It snows in the winter and it rains during the summer, unlike most of California.  Our native plants are therefore different from natives on the East Coast.  The Burghardt/Tallamy study was conducted in the summer months from June to August.  Native plants in California are no longer blooming and many are dormant during summer months unless they are irrigated.  The findings of the Burghardt/Tallamy study are therefore not applicable to California unless they can be replicated here.
This is the Serpentine Prairie in Oakland. It is one of the native plant “restorations” done by East Bay Regional Park District. About 500 trees (including native oaks) were destroyed to return the prairie to native grassland. This is what it looks like in June.

Comparison of laboratory with field studies

The Burghardt/Tallamy study 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.  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. 

Anise Swallowtail butterfly in non-native fennel. Courtesy

The credibility and relevance of Professor Shapiro’s studies are also based on 47 years of visiting his research plots at least 250 days per year, that is, year around.  During that period of time, he recorded his observations and they were statistically analyzed for the study he published in 2003. (3)  His study is of particular interest as the climate changes rapidly because the length of the study also enables us to observe the impact of climate change on our butterfly population in the Bay Area.  In contrast the Burghardt/Tallamy study was conducted in a total of 5 months over a total of two years.  Population trends cannot be determined from such a short study.

Burghardt/Tallamy study is consistent with mission of Million Trees

The Burghardt/Tallamy study does not contradict anything Million Trees advocates for.  Decisions to plant a particular species and the decision to eradicate a particular species are entirely different.  Gardeners should plant whatever they prefer, in my opinion.  When planting decisions are made for public land, I prefer that plants be capable of surviving current local and climate conditions.  When my tax dollars are being spent, I prefer that they not be wasted. Besides, I hate watching plants and trees die in the parks I visit.

This study is consistent with my view that non-native plants don’t threaten the survival of insects unless they replace native plants that insects prefer.  The Burghardt/Tallamy study quite rightly does not say that they do.  Local experience in the Bay Area informs me that they rarely do.  To the extent that they have replaced native plants, they are better adapted to current conditions in a specific location.  Eradicating them rarely results in native plants successfully replacing them.  As the climate continues to rapidly change, the failure of native plant “restorations” is inevitable because vegetation changes when the climate changes.

Site 29 on Claremont Blvd in Oakland is one of the places where UC Berkeley destroyed about 19,000 trees about 14 years ago. Non-native weeds thrive in the sun where trees were destroyed. Poison hemlock and thistle are 8 feet tall where not sprayed with herbicide. Site 29, May 2016.

The Burghardt/Tallamy study does not justify eradication of non-native plants because it does not take into account the damage done by the methods used to eradicate non-native plants.  Since most eradication projects use herbicides, we speculate that more harm is done to insects by herbicides than by the existence of non-native plants.

The decision to eradicate non-native plants must also take into consideration whatever benefit the plants may provide, such as food for wildlife.  For example, even if a plant species isn’t a host plant, it might be a food plant. Butterfly bush (Buddleia) is an example of a plant that is very useful to pollinators, including butterflies, but native plant activists advocate for its eradication. 

Monarch nectaring on butterfly bush.

Many thanks to Jake Sigg for creating this opportunity for dialogue with native plant advocates.  I am grateful for the window into the community of native plant advocates that Jake’s Nature News provides.

  1. Agosta, Salvatore J.; Jeffrey A. Klemens (2008). “Ecological fitting by phenotypically flexible genotypes: implications for species associations, community assembly and evolution”. Ecology Letters11 (11): 1123–1134. 
  2. “Non-native plants reduce abundance, richness, and host specialization in lepidopteran communities” by Karin Burghardt, Doug Tallamy, et, al. (Ecosphere, November 2010).
  3. SD Graves and AM Shapiro, “Exotics as host plants of the California butterfly fauna,” Biological Conservation, 110 (2003) 413-433

Butterflies of the Bay Area Region

Our readers may remember Professor Arthur Shapiro as a critic of massive ecological “restorations” that attempt to turn back the botanical clock.   Professor Shapiro is better known in the world of academic science as an expert on the butterflies of California.  His Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions (University of California Press, 2007) reflects a lifetime of observation and study of butterflies.  It is as informative about butterfly behavior and physiology as it is readable and engaging.  This is no dry, academic treatise.  Rather it represents an accumulation of over thirty years of experience, walking on every sunny day amongst the butterflies of California and enjoying every minute of it.

We could choose any number of interesting topics from Professor Shapiro’s guide, but we think our readers will be most interested in learning about the natural history of California and the Bay Area region and how that history resulted in our current butterfly fauna.   It’s not a gloomy story, as you might expect in a place that has changed so radically since it was occupied by Europeans in the 19th century.  Rather it’s a story of change and adaptation to change and therefore very much in tune with the concerns of the Million Trees blog.

Butterflies in the landscape created by humans

This is the reality of which plants are useful to butterflies in the Bay Area and Delta Region of California:

Red Admiral.  public domain
Red Admiral. public domain

“California butterflies, for better or worse are heavily invested in the anthropic landscape [altered by humans].  About a third of all California butterfly species have been recorded either ovipositing [laying eggs] or feeding on nonnative plants.  Roughly half of the Central Valley and inland Bay Area fauna is now using nonnative host plants heavily or even exclusively.  Our urban and suburban multivoltine [multiple generations in one year] butterfly fauna is basically dependent on ‘weeds.’  We have one species, the Gulf Fritillary that can exist here only on introduced hosts.  Perhaps the commonest urban butterfly in San Francisco and the East Bay, the Red Admiral is overwhelmingly dependent on an exotic host, pellitory.  And that’s the way it is.”

Professor Shapiro explains that alterations in our landscape made by humans made it necessary for butterflies to make the transition from natives to non-natives in order to survive:

The explanation for this odd situation can be found in the history of California’s wetlands.  As recently as the early twentieth century, there were extensive fresh water marshes in our area, especially along the east side of the Sacramento Valley.  These wetlands stayed green in the summer and could support multivoltinism because native host plants were available…The draining, diking, and agriculturalization of the wetlands corresponded in time with the widespread naturalization of exotic weeds related to native marshland plants.”

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

Here are a few examples of native butterfly species that made the transition from native to non-native plants when the wetlands were altered by humans:

“What did our Mylitta Crescent feed on before the various pestiferous annual Mediterranean thistles come to California?  Native, mostly wetland thistles, just as it does in mountain bogs today…The Common Checkered Skipper still uses checkerbloom in wetlands where it can find it, but thanks to a weedy species of mallow it is now found in every garden and weedy lot in the northern part of the state.  And the Anise Swallowtail still lays eggs on water hemlock…in marshes, but percentage-wise very few of them.”

San Francisco is a special case for butterflies

San Franciscans know that although their city is very small in size, it is composed of many even smaller microclimates.  Professor Shapiro explains how these microclimates impacted our butterflies:

“The main reason why we have so many federally endangered or threatened butterflies in the Bay Area is that our peculiar geography is predisposed to the fragmentation of populations—particularly in the coastal fog belt.  These local evolutionary experiments may well have been dead ends in the long run…But they were so restricted to tiny chunks of habitat that even nineteenth-century development was enough to spell their doom.”

Then he reminds us what it would take to “restore” the landscapes that supported these rare or extinct butterfly species:

“Had there been an Endangered Species Act in the 1860s, San Francisco would be a very different place.  The “Great Sand Bank” occupying the western third of the city would have been declared critical habitat for any number of plants and animals found nowhere else on Earth—including three butterflies that subsequently went extinct.  We could still have the Xerces Blue, the Pheres Blue, and the Sthenele Satyr, but there would be no Golden Gate Park and no Sunset District.  The reclamation and stabilization of what was seen as a bleak, barren, fog-and-windswept wasteland were hailed at the time as triumphs of civilization.  Now some environmentalists would like to turn the clock back and restore a little of that unique habitat.  But some of its inhabitants, including those three butterflies, are gone, never to return.”

Golden Gate Park and its neighborhood.  Would you trade this for the barren sand dunes that preceded it?  Gnu Free Documentation
Golden Gate Park and its neighborhood. Would you trade this for the barren sand dunes that preceded it? Gnu Free Documentation

 However, the story isn’t entirely of loss in San Francisco:

Gulf Fritillary.  Creative Commons
Gulf Fritillary. Creative Commons

“The Cabbage White…arrived sometime in the late nineteenth century.  The Gulf Fritillary…seems to have become established only in the 1950s.  The Fiery Skipper was unknown…in 1910…Several native species treated as scarce [in 1910] have become commoner due to introduced, weedy host plants.  The Anise Swallowtail and the Red Admiral are prime examples.  The West Coast Lady, most of whose hosts are weedy, was already very abundant in [1910].”

What do butterflies need today?

Professor Shapiro provides a detailed list of the plants used by the butterflies of California.  You will find roughly equal numbers of native and non-native plants on the list of plants they like as well as the plants they don’t like.  This is how he summarizes these lists:  “Most California natives in cultivation are of no more butterfly interest than nonnatives, and most of the best butterfly flowers in our area are exotic.”

What is done cannot be undone

While humans wring their hands about “weeds” and the loss of historical landscapes, butterflies have moved on.  And so they must to survive.  And so should we because these historical landscapes cannot be recreated without abandoning the economic enterprises which feed us or the homes that house us.  We aren’t going to bull doze Golden Gate Park or the residential neighborhoods that surround it.  The least we can do for the butterflies of California is to quit dousing the plants they need with herbicides solely because they are non-native.  We have created the landscape that we need and we should quit destroying the landscape that our butterflies now need.

Professor Shapiro’s Preface is a fitting conclusion:

The changes that humans have wrought on the lives of butterflies are merely the most recent of the many changes they have gone through in their history.  We have no hope of restoring communities to some hypothetical pristine state on any but a miniature scale.  At best we create gardens that more or less resemble what we think those communities looked like at some arbitrary time in the past.  Like all gardens, they require constant effort to keep them from becoming what today’s conditions drive them to become—conditions dominated by what we characterize as “weeds.”  We can, however, try to protect the bits of nature that have survived relatively unchanged despite us, cognizant that larger forces than we control may override our efforts.”

2014 Events for your calendar

The year’s winding down, and many of us are making plans for the next few months. An email from the Commonwealth Club told us of an interesting new series of lectures in January, March and April of 2014. It’s the Science of Conservation and Biodiversity in the 21st Century series, from three professors each giving one talk in San Francisco.

According to the email: “This series of lectures will present a new way of looking at public issues in conservation. The things we’ve assumed as facts often are not. Traditional approaches are losing ground as science illuminates new pathways for framing and achieving conservation goals.”

This is important thought leadership that could shift the way San Francisco manages its wild spaces. A good turnout would encourage the Commonwealth Club to have more such talks. Please do attend if you can.


bumble bee on strawberry tree
Native bumble-bee on non-native Strawberry Tree

Dr Scott Carroll is the Founding Director, Institute for Contemporary Evolution and Department of Entomology at UC Davis. He will talk about Conciliation Biology: An Approach to Conservation that Reconciles Past, Present and Future Landscapes in Nature.

Here’s what the Commonwealth Club website says: Biologists are now considering the “conciliatory approach.” This approach recognizes that mutual adaptation of native and non-native species is changing best practices for promoting biodiversity. Dr. Carroll investigates how organisms respond to human-caused environmental change. Carroll advocates for interdisciplinary solutions to problems of environmental conservation.

Register at the club’s website:


Dr. Arthur M. Shapiro is Distinguished Professor in the Department of Evolution and Ecology, College of Biological Sciences, at UC Davis. He’s speaking on Ecological Communities and the March of Time.

Gulf Fritillary Butterfly emerges on passiflora plant
Gulf Fritillary butterfly breeds on non-native passionflower – wikimedia

From the website: “Ecological communities as we know them are similar to freeze-frames from a long movie. Associations among species are very dynamic on millennial scales, as demonstrated by the evidence since deglaciation 15,000 years ago. Coevolution of species occurs locally in geographic mosaics, and can be extremely dynamic as well. Frederic Clements, the father of American community ecology, had a holistic vision. He saw communities as super-organisms. He was wrong.”

Register at:


ferns and blackberry and poison oak
Eucalyptus forest understory on Mt Sutro

Dr. Joe R. McBride is Professor of Landscape Architecture and Environmental Planning, Department of Environmental Science, Policy, and Management, UC Berkeley. His talk is about The History, Ecology and Future of Eucalyptus Plantations in the Bay Area.

The website says: “McBride will explain the ecology of the eucalyptus forest in the Bay Area. He will discuss its structure, the variety of plants and animals that live within it, its health and the ecological functions it performs. There will be a description of the dynamics within these forest stands (such as whether they are successional or a climax-species that replace themselves over time without human input) and about their invasive potential.”

Register at:


  • All lectures are at the San Francisco Club Office, 595 Market St.
  • The tickets cost $20 to the general public, $8 for members of the Commonwealth Club, and $7 for students carrying appropiate ID.
  • You can register to attend at the links we gave, or call 415.597.6705


This is reprinted from Save Mount Sutro Forest with permission.

Professor Arthur Shapiro’s Review of Emma Marris’ Rambunctious Garden

Rambunctious GardenProfessor Arthur Shapiro is Distinguished Professor of Evolution and Ecology at University of California Davis and a renowned expert on the butterflies of California.  His public comment on the Draft Environmental Impact Report for the Natural Areas Program is one of the most popular articles on Million Trees.

Professor Shapiro has written a review of Emma Marris’ Rambunctious Garden and given us permission to reprint it here.  We share his high opinion of Ms. Marris’ book and we urge you to give it the careful read it deserves.


Rambunctious Garden: Saving Nature in a Post-Wild World by Emma Marris

Review by: Arthur M. Shapiro

The Quarterly Review of Biology, Vol. 88, No. 1 (March 2013), p. 45

Published by: The University of Chicago Press

Stable URL: .

“Several years ago, I attended a seminar on the psychology of the animal-liberation movement. The speaker observed that although very few animal-lib activists were actually religious, most such people scored very highly on the “religiosity” scale in personality inventories. He suggested that animal liberation served the same functions for such people as religion did for many more: it gave life meaning and conferred a group identity centered on shared moral superiority over others. After years of interacting with “weed warriors”—people who spend their free time trying to eradicate “invasive species” from parks and public lands—I would advance the same hypothesis about most of them. They tend to be absolutely convinced of the righteousness of their cause and highly resistant to any suggestion that naturalized exotics might not be all bad. They also tend to be oblivious to the disconcerting degree to which their rhetoric converges to that of racists and xenophobes, and highly defensive if you point that out to them. After all, they are on the “green” side, right?  

In the face of such popular enthusiasm for the alarmist viewpoint on exotics, Emma Marris, a professional science writer, has produced an eminently reasonable, well-researched, and engagingly written defense of the notion that human beings have changed the world and the most sensible way to deal with that is to manage it for the greatest good. She demonstrates very convincingly that communities and ecosystems have always been in flux as the physical world changes around them. The idea of freezing them at some arbitrary moment in time is as wrongheaded as it is impractical. Some naturalized exotics present serious threats to human beings or their support systems: we call them pests, pathogens, and vectors, and they are not what is at issue. Some are such radical ecological gamechangers that they need to be assessed with an eye to the full scope of their impacts (think cheatgrass in the desert and its impact on fire ecology). Most, however, are trivial, and in a world of limiting resources where we must assign priorities to our actions, they do not merit serious attention. But it is not merely a matter of using our management resources effectively. Much of our “invasive species” discourse simply ignores the evolutionary creativity consequent on community reorganization.

Yet we know both in theory and from the fossil record that precisely such creativity is essential for long-term survival in a changing physical context. Ecotypes or ecological races arise in response to novel challenges, both biotic and abiotic. The future of endangered species is likely to depend on such processes. Failure to appreciate this is the single biggest flaw in the “climatic envelope” or “niche modeling” approach to conservation biology. Much of California’s lowland butterfly fauna is now dependent on nonnative larval host plants. When I tell garden clubs—or public land managers—that successful eradication of invasive “weeds” would drive their beloved backyard butterflies to extinction, they stare at me in disbelief. But it is true and emblematic of the larger problem explored very well in this volume.

Shortly after Marris’s book appeared there was a flurry of articles in the professional literature advancing precisely the same ideas. Among the best are by Carroll (2011. Evolutionary Applications 4:184–199) and Thomas (2011. Trends in Ecology and Evolution 26:216 –221). But Marris got there first, and with luck her wise words will be read and acted upon far and wide.”

Arthur M. Shapiro, Center for Population Biology, University of California, Davis, California

Professor Arthur Shapiro’s comment on the Environmental Impact Report for the Natural Areas Program

Mission blue butterfly Wikimedia Commons

With permission and in its entirety we are publishing the comment of Arthur M. Shapiro.  He is Distinguished Professor of Evolution and Ecology at UC Davis and a renowned expert on the butterflies of California.  We hope that you will take his credentials into consideration as you read his opinion of native plant restorations in general and the Natural Areas Program in San Francisco in particular.  We hope that Professor Shapiro’s comment will inspire you to write your own comment by the deadline,  which has been extended to October 31, 2011.  Details about how to submit your comment are available here.


October 6, 2011

Mr. Bill Wycko

San Francisco Planning Department

                              Re: DRAFT EIR, NATURAL AREAS PROGRAM

Dear Mr. Wycko:

Consistent with the policy of the University of California, I wish to state at the outset that the opinions stated in this letter are my own and should not be construed as being those of the Regents, the University of California, or any administrative entity thereof. My affiliation is presented for purposes of identification only. However, my academic qualifications are relevant to what I am about to say. I am a professional ecologist (B.A. University of Pennsylvania, Ph.D. Cornell University) and have been on the faculty of U.C. Davis since 1971, where I have taught General Ecology, Evolutionary Ecology, Community Ecology, Philosophy of Biology, Biogeography, Tropical Ecology, Paleoecology, Global Change, Chemical Ecology, and Principles of Systematics. I have trained some 15 Ph.D.s, many of whom are now tenured faculty at institutions including the University of Massachusetts, University of Tennessee, University of Nevada-Reno, Texas State University, and Long Beach State University, and some of whom are now in government agencies or in private consulting or industry. I am an or the author of some 350 scientific publications and reviews. The point is that I do have the bona fides to say what I am about to say.

 At a time when public funds are exceedingly scarce and strict prioritization is mandatory, I am frankly appalled that San Francisco is considering major expenditures directed toward so-called “restoration ecology.” “Restoration ecology” is a euphemism for a kind of gardening informed by an almost cultish veneration of the “native” and abhorrence of the naturalized, which is commonly characterized as “invasive.” Let me make this clear: neither “restoration” nor conservation can be mandated by science—only informed by it. The decision of what actions to take may be motivated by many things, including politics, esthetics, economics and even religion, but it cannot be science-driven.

In the case of “restoration ecology,” the goal is the creation of a simulacrum of what is believed to have been present at some (essentially arbitrary) point in the past. I say a simulacrum, because almost always there are no studies of what was actually there from a functional standpoint; usually there are no studies at all beyond the merely (and superficially) descriptive. Whatever the reason for desiring to create such a simulacrum, it must be recognized that it is just as much a garden as any home rock garden and will almost never be capable of being self-sustaining without constant maintenance; it is not going to be a “natural,” self-regulating ecosystem. The reason for that is that the ground rules today are not those that obtained when the prototype is thought to have existed. The context has changed; the climate has changed; the pool of potential colonizing species has changed, often drastically. Attempts to “restore” prairie in the upper Midwest in the face of European Blackthorn invasion have proven Sisyphean. And they are the norm, not the exception.

The creation of small, easily managed, and educational simulacra of presumed pre-European vegetation on San Francisco public lands is a thoroughly worthwhile and, to me, desirable project. Wholesale habitat conversion is not.

A significant reaction against the excesses of the “native plant movement” is setting up within the profession of ecology, and there has been a recent spate of articles arguing that hostility to “invasives” has gone too far—that many exotic species are providing valuable ecological services and that, as in cases I have studied and published on, in the altered context of our so-called “Anthropocene Epoch” such services are not merely valuable but essential. This is a letter, not a monograph, but I would be glad to expand on this point if asked to do so.

I am an evolutionary ecologist, housed in a Department of Evolution and Ecology. The two should be joined at the proverbial hip. Existing ecological communities are freeze-frames from a very long movie. They have not existed for eternity, and many have existed only a few thousand years. There is nothing intrinsically sacred about interspecific associations. Ecological change is the norm, not the exception. Species and communities come and go. The ideology (or is it faith?) that informs “restoration ecology” basically seeks to deny evolution and prohibit change. But change will happen in any case, and it is foolish to squander scarce resources in pursuit of what are ideological, not scientific, goals with no practical benefit to anyone and only psychological “benefits” to their adherents.

If that were the only argument, perhaps it could be rebutted effectively. But the proposed wholesale habitat conversion advocated here does serious harm, both locally (in terms of community enjoyment of public resources) and globally (in terms of carbon balance-urban forests sequester lots of carbon; artificial grasslands do not). At both levels, wholesale tree removal, except for reasons of public safety, is sheer folly. Aging, decrepit, unstable Monterey Pines and Monterey Cypresses are unquestionably a potential hazard. Removing them for that reason is a very different matter from removing them to actualize someone’s dream of a pristine San Francisco (that probably never existed).

Sociologists and social psychologists talk about the “idealization of the underclass,” the “noble savage” concept, and other terms referring to the guilt-driven self-hatred that infects many members of society. Feeling the moral onus of consumption and luxury, people idolize that which they conceive as pure and untainted. That may be a helpful personal catharsis. It is not a basis for public policy.

Many years ago I co-hosted John Harper, a distinguished British plant ecologist, on his visit to Davis. We took him on a field trip up I-80. On the way up several students began apologizing for the extent to which the Valley and foothill landscapes were dominated by naturalized exotic weeds, mainly Mediterranean annual grasses. Finally Harper couldn’t take it any more. “Why do you insist on treating this as a calamity, rather than a vast evolutionary opportunity?” he asked. Those of us who know the detailed history of vegetation for the past few million years—particularly since the end of Pleistocene glaciation—understand this. “Restoration ecology” is plowing the sea.

Get real.


                                     Arthur M. Shapiro

                                     Distinguished Professor of Evolution and Ecology

Professor Arthur M. Shapiro, at work, UC Davis

A dialogue about insects and non-native plants

We received a comment on our “Wildlife” page from “entomologist” that deserves a comprehensive response. 

 Conversation with “entomologist”

 “entomologist:”  “Adaptation to exotic species by specialist herbivores is unusual.  Those butterflies that switch to exotics tend to be generalists already.”  

Webmaster:  “Entomologist” is mistaken that the butterflies now using non-native plants are generalists, by which we assume he means that they use many plants, rather than a specific species.  According to Professor Art Shapiro (UC Davis), 26 of the 82 species of California butterflies now feeding on exotic plant species, are using only one plant species.  In other words, nearly one-third of California butterflies presently using exotic plant species are not generalists.(1)  When butterflies have made the transition from a native to a non-native plant, the plants are usually chemically similar. 

Anise Swallowtail, Sutro Forest
Anise Swallowtail, Sutro Forest, March 2010

The Anise Swallowtail is a conspicuous example of a California butterfly that is now dependent upon a particular exotic plant, fennel. This relationship between a specific native insect and a specific non-native plant is one of the reasons why the Million Trees blog was created.  Non-native fennel is being eradicated by every native plant “restoration” in the Bay Area.   

Over ten years ago, a park advocate in San Francisco became enraged by the eradication of fennel in his park because he was aware of the dependence of the Anise Swallowtail upon the fennel.  He made every effort to convince the so-called Natural Areas Program to stop destroying the fennel in his park.  He enlisted the help of Professor Art Shapiro in that effort. His efforts were ultimately unsuccessful.  The Natural Areas Program considered the non-native origins of the fennel sufficient reason to eradicate it, regardless of the needs of a native butterfly.  They continue those eradication efforts to this day. 

It is such mindless destruction of non-native plants, regardless of their benefit to fauna (or other benefits) that has made the Natural Areas Program so unpopular with people with a broader view of nature. We value the Anise Swallowtail butterfly as much as any theoretical benefit from eradicating a non-native plant.

“entomologist:”  “This idea that exotic plants are as good for wildlife as natives is just plain pathetic, especially for anyone who knows about herbivory  patterns on native and exotic plants.”

Webmaster:  By “pathetic” we assume “entomologist” means that he does not believe that insects eat non-native plants.  He is mistaken that insects do not eat non-native plants.  Returning to Professor Shapiro, he reports that 82 of 236 (35%) total species of California butterflies feed on non-native plants

Professor Dov Sax (Brown University) compared insects living in the leaf litter of the non-native eucalyptus forest with those living in the native oak-bay woodland in Berkeley, California.  He found significantly more species of insects in the leaf litter of the eucalyptus forest in the spring and equal numbers in the fall.(2)  Professor Sax also reports the results of many similar studies all over the world that reach the same conclusion.

The California Academy of Sciences finds that several years after planting its roof with native plants, it is now dominated by non-native species of plants in the two quadrants that are not being weeded, replanted and reseeded with natives.  Their monitoring project recently reported that there were an equal number of insects found in the quadrants dominated by native plants and those dominated by non-native plants. 

Damselflies (probably Common Blue) mating on non-native ivy in Glen Canyon Park.

We also use our eyes when we walk in our parks.  We often find insects in non-native plants.  Those non-native plants are often targets for eradication.  The damselflies in a San Francisco park are another example of the contradictory strategies of the Natural Areas Program.  They have made several attempts to reintroduce the rare Forktailed Damselfly to one of the parks in San Francisco.  Although those attempts have not been successful, we see other species of damselflies in that park, using the non-native plants that are repeatedly sprayed with herbicides by the Natural Areas Program.  We wonder if the herbicide use in that park is contributing to the failure of attempts to reintroduce the Forktailed Damselfly. Does the right hand know what the left hand is doing?

“entomologist:”  “Insects eating plants are at the base of the food chain and native plants have more insect herbivores and support more native birds.”

Webmaster:  We can agree that many birds eat insects and those that do are likely to benefit from greater populations of insects.  But, there is substantial evidence that insects are as likely to be found in non-native plants as in native plants and we trust that the birds know where to find them.  However, unlike “entomologist” we are as interested in the welfare of non-native birds as we are in native birds. 

“entomologist:”  “Doug Tallamy’s work shows this in the eastern US conclusively.”

Webmaster:  Professor Tallamy’s (University of Delaware) publications do not seem to be available on-line, which prevents us from reading his publications.  However, since he studies the insects on the east coast we don’t think whatever he reports trumps the studies that we have cited of insect populations here in the Bay Area. 

“entomologist:”     “I certainly feel for the loss of trees, but the alternative is that we accept a homogenized set of urban-tolerant plants and wildlife.  Maybe that’s ok if you don’t know the difference, but for those of us who actually pay attention it is profoundly sad.”

Webmaster:   We don’t see the logic of “entomologist’s” vision of a “homogenized” ecology.  If we destroy non-native plants and animals, our ecology will be less diverse.  And we hope that the readers of Million Trees will agree that we are, indeed, “paying attention.” 

 The Big Picture

 We suggest that “entomologist” and other native plant advocates step back from their deeply-seated prejudices against non-native plants and consider the big picture.  The fact is that insects are particularly vulnerable to climate change because they live in relatively narrow temperature ranges. (3) Although they are adjusting well to changes in vegetation, they are not likely to be able to make an equally successful adjustment to changes in temperatures.  Therefore, if our top priority is insects, we would be wise to reconsider destroying millions of non-native trees that are sequestering millions of tons of carbon, contributing to greenhouse gases and thereby to climate change.    


(1) Arthur M. Shapiro, “Exotics as host plants of the California butterfly fauna,” Biological Conservation, 110, 413-433, 2003

(2) 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.

(3) “Mountain plant communities moving down despite climate change, study finds,” Los Angeles Times, 1/24/11