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.

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.

“Drought-Adapted Eucalyptus NOT Dying by the Thousand”

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

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

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


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

But he’s mistaken.

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

2015-05-27 ab eucalyptus with epicormic growth wordEUCALYPTUS RESPONSE TO DROUGHT

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

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

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

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

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

bayview-hill-2010 smTHE GIRDLED TREES OF BAYVIEW HILL

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

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

EUCALYPTUS ADAPTS

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

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

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

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

EPICORMIC SPROUTING IS IMPORTANT IN EUCALYPTUS

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

But again, this is not actually true.

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

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

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

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

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

epicormic sprouts on eucalyptus when nearby trees removed

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

MISTAKING DEFENSES FOR DEATH THROES

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

Epicormic sprouting on eucapyptus 2014In some cases, epicormic sprouting may indicate nothing at all, except that the tree is going through a normal growth phase, or changed light conditions following removal of nearby trees.

LIVING WITH A FEW DEAD TREES

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

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

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

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

Jake Sigg closes his “Nature News” blog

Jake Sigg is the most well known native plant advocate in the San Francisco Bay Area.  He was a gardener in San Francisco’s Recreation and Park Department for decades.  He was the leadership of the local chapter of the California Native Plant Society for years and is still active in it.  He was equally active in the California Invasive Plant Council.

He published a blog called “Nature News” since 2011, in which he announced many nature-related events and expressed his opinion on a wide range of topics, some only tangentially related to his primary interest in the preservation of native plants.  His October 30, 2013 edition of “Nature News” was the last he posted to his blog.  He said, This is the last posting to this blog, based on lack of feedback from it, and from the notices I have posted in last two weeks.  Keeping it up takes too much work for me.  I began it in hopes of making life easier for me, but it has had the opposite effect.”   Back issues of his blog are still accessible here.

Jake Sigg continues to write his “Nature News” but now its distribution is to an email list of 2,400 people.  His blog says that people can ask to be added to his email list.

Sorry to see it go

We were saddened by the loss of ‘Nature News’ as a source of information.  We often try to engage native plant advocates in a dialogue, but they are rarely willing to speak with those with whom they disagree.  Therefore, reading Jake Sigg’s “Nature News” was one of the few ways we could learn what was on the minds of native plant advocates.  We often reported to our readers what we learned from the “Nature News” blog because it was available for anyone to read and verify what we were reporting.  Here are a few examples of our articles about Jake Sigg’s viewpoint as expressed on “Nature News:”

Bay Nature honors Jake Sigg

Bay Nature is a quarterly magazine about nature in the Bay Area, as its title implies.  Perhaps to commemorate the end of Jake Sigg’s publically available “Nature News” they have published an interview with him about his publication.  You can read the entire interview here.

We were primarily interested in Jake Sigg’s strange explanation for why he started “Nature News:”

Nature News started in 2002 by accident, when I started an email group to inform people about upcoming public meetings concerning San Francisco’s threatened Natural Areas Program.

In 1997 the National Park Service began to crack down on dogs running off-leash at Fort Funston, but evidently they did so too suddenly, which set off a backlash by the off-leash dog activists, who became an organized force. They attacked not only the National Park Service but the Recreation and Park Department’s infant Natural Areas Program (NAP) as well, telling community groups that the NAP was going to fence off their neighborhood park and people couldn’t use it anymore–and people actually believed this.  By the time we found out about it the damage had been done, and we are still suffering from it”

We have heard Jake Sigg say many times that all criticism of the Natural Areas Program comes from dog owners who are concerned about the loss of their recreational access that has been the result of native plant “restorations” all over the Bay Area.  Fort Funston is just one of many areas in which recreational access has been restricted by these “restorations.”  However, we were flabbergasted that Jake Sigg continues to believe that this is the only issue.

We will let a commenter on the Bay Nature article about Jake Sigg’s interview speak for the critics of native plant “restorations” in the Bay Area.  His list of the many reasons why these projects are controversial looks fairly complete to us:

“The contentious nature of the discussion of San Francisco’s Natural Areas Program seems intractable. Jake Sigg illustrates why it remains so contentious when he continues to say that opposition to the program comes solely from dog owners. Unfortunately, that demonstrates that he hasn’t been listening for ten years. Thousands of people have questioned the program for many reasons, including:

1.            Loss of thousands of trees that people like in their neighborhood parks.

2.            Use of toxic pesticides to kill non-native plants in public parks.

3.            Lack of success. Repeatedly restored areas rapidly become weedy messes.

4.            Green areas are deliberately turned into areas that are brown and dead-looking for more than half the year.

5.            Loss of public access when fences are erected around native plant gardens and recreational access is restricted to trails in public parks.

6.            Loss of habitat and food resources for wildlife.

7.            Loss of thousands of tons of stored carbon. The carbon released when large trees are destroyed will never be reabsorbed by the grass and scrub that replace the trees.

8.            The misrepresentations of the Natural Areas Program that its supporters offer to the public, e.g. that all destroyed non-native trees will be replaced by native trees. Nothing in the management plan says or implies that; in some areas the plan specifically calls for forest to be replaced by grassland and scrub. These misrepresentations are sometimes deliberate, sometimes because NAP supporters haven’t bothered to read the NAP management plan.

9.            The un-scientific mythology offered by self-styled “ecologists” in support of the Natural Areas Program, e.g. that grasslands store more carbon than forests.

We can’t have fruitful discussions when we refuse to listen to what is said by people who disagree with us. We can’t even learn the many areas of agreement”.

Interior Greenbelt Natural Area, 2010. Courtesy SaveSuro
Interior Greenbelt Natural Area, 2010. Courtesy SaveSuro

The Anthropocene vs. The Doomed Earth

On Saturday, September 14, 2013, The New York Times published an op-ed by Erle C. Ellis entitled, “Overpopulation Is Not the Problem.”  Professor Ellis challenges the conventional wisdom that the future of the Earth is threatened by an inexorably increasing human population.  He tells us that emerging knowledge of the history of human civilizations should reassure us that humans have altered ecosystems for 200,000 years to meet their needs and there is no reason to believe there is a limit to the ability of humans to continue to manipulate our environment as needed to support a growing population.   

Darwin2

Little of human history is recorded.  Therefore, only recent discoveries of archaeologists have informed us of the many technological advances of human civilization that increased food production.  Irrigation and agriculture, for example, is a relatively recent human accomplishment.  In the Old World, humans have supplemented their diets by raising domestic animals in the past 6,000 years.  This knowledge only reached the New World with Europeans in the 16th century. 

Professor Ellis suggests that our appreciation of human adaptability is based on our knowledge of the history of human accomplishment.   That knowledge is not only relatively new, but is not yet widely known by the public.  He admits that he, himself, did not comprehend human adaptability until studying agriculture in China, where human ingenuity has managed to keep pace with the growth of the most populous country on Earth.  His work is now as informed by archaeology, geography, and economics as it is by his original discipline, biology.

We introduced Professor Ellis (University of Maryland, Baltimore) to our readers in an article about the globalization of ecology by humans.  He is one of the proponents of naming a new geologic era, the Anthropocene, to acknowledge the fact that the activities of humans have altered the Earth in significant and profoundly important ways.  He does not find reason to despair about our impact on the Earth:

“The only limits to creating a planet that future generations will be proud of are our imaginations and our social systems.  In moving toward a better Anthropocene, the environment will be what we make of it.”  (1)

At the opposite extreme:  The viewpoint of Jake Sigg

At the opposite extreme of Ellis’ rosy view of the future of the Earth and its human occupants, we turn to Jake Sigg’s “Nature News.”  Regular readers of “Nature News” will find the following example of Sigg’s pessimistic view of the future of the Earth typical of his viewpoint:

“My vision for the world is increasingly apocalyptic.  Lest you think I’m being overly dramatic, with the type of economic/political system we have, things can only get worse, not better, and the horror and chaos of Syria, Egypt, et al could be easily foreseen–not in detail, but in general, as the result of too many competing for space and resources.  I expect lots of horror stories in the future, and I hope I’m dead by the time it hits me directly.  At the pace things are moving, I may not be that lucky.”  “Nature News,” September 7, 2013.

Jake Sigg’s concern about over-population also motivates his extreme opposition to immigration, including legal immigration. 

Finding Common Ground

As diametrically opposite as these viewpoints seem on the surface, they actually share common ground.  As Professor Ellis says, “The science of human sustenance is inherently a social science.”  In other words, the famines that humans have experienced were as much a failure of the social system as they were of the physical limitations of the planet to provide adequate food.  Jake Sigg agrees that “our economic/political system” is at least partially to blame for the failure to compensate for inadequate resources. 

For example, the current round of climate change has been caused by the activities of humans, but our social, political, and economic systems are preventing us from responding to it effectively.  Hunger in America will be exacerbated if conservative politicians are successful in their effort to drastically reduce the availability of food stamps to the poor.     

Professor Ellis is confident that human social systems will accommodate population increases.  Mr. Sigg predicts the opposite outcome.  The more likely outcome is probably somewhere in between.  We will probably muddle through with occasional catastrophic famines where physical shortages cannot be mitigated by competent social/political structures. 

Admittedly, this topic is a digression for Million Trees.  It is intended as a reminder that the ecological “restorations” being demanded by native plant advocates should be a public policy decision and the failure to treat it as such has resulted in irreparable harm to our environment.  It is therefore an example of how environmental problems and their resolution are ultimately failures of human social systems.

Update:  Our readers might be interested in Jake Sigg’s very different reaction to Erle Ellis’ op-ed in his latest newsletter (September 17, 2013), available here.  Here is an excerpt from it:

“One of the most discouraging developments of our time is the elevation of opinion to equal status with knowledge in the minds of large numbers.  People who have spent their lives studying and working in a field are on equal footing with someone who hadn’t thought about the matter five minutes ago, and their vote counts just as much.  Not exactly a way to build a lasting, self-perpetuating society.”

In other words, problems are caused by too much democracy, in Sigg’s opinion.  He believes that “experts” should be in charge, of which he—a retired gardener in the Recreation and Park Department– is apparently one and Erle Ellis—Associate Professor of geography and environmental systems at University of Maryland, Baltimore—is not.  In contrast, Million Trees values expertise, but considers the alteration of our public parks a political decision which must be made democratically.  More democracy is needed to resolve these conflicts, not less. 

****************************

Erle C. Ellis, “Overpopulation Is Not the Problem,” New York Times, September 14, 2013.

Can the native plant ideology be defended with name-calling?

On Monday, March 26, 2012, the San Francisco Forest Alliance (SFFA) gave a presentation to a neighborhood association in San Francisco about the Natural Areas Program.   SFFA expressed its objection to the destruction of healthy non-native trees and vegetation which is useful to wildlife, the use of pesticides, and the closure of trails in the so-called “natural areas” as well as the money being spent on these destructive projects. 

Park Bathroom Paradox. Courtesy San Francisco Forest Alliance

Jake Sigg, one of the leading proponents of native plant “restorations” in San Francisco was invited by the neighborhood association to give a rebuttal.  For some reason that remains mysterious, Mr. Sigg chose to speak exclusively about Mt. Sutro which is not owned or managed by the Natural Areas Program.  Therefore, there was a bit of a disconnect in these two presentations, with the common theme being only the destruction of non-native trees for the purpose of restoring native plants.

During his presentation, Mr. Sigg said that SFFA’s presentation was “disinformation” and/or “nonsense.”  However, he provided no specific examples of these misdeeds, so SFFA is unable to respond to these accusations.

The following day, March 27, Mr. Sigg published an exchange about the SFFA presentation with one of his fans on his internet blog, “Nature News from Jake Sigg.”  Mr. Sigg’s fan said he “…was so aghast at this evening’s display of ignorance and mendacity…”  And Mr. Sigg agreed:   “The ignorance and ill will of the Forest Alliance was on full view for anyone caring to look.  The cherry-picking of facts, the distortions and outright lies were transparent.”

The presentation by the Forest Alliance was based on public documents and nothing was said that could not be documented by the public record.  So, naturally SFFA was mystified by these accusations.  SFFA allies wanted to know if the SFFA presentation contained any factual errors, so they asked Mr. Sigg, “What were the ‘outright lies?’”

Mr. Sigg responded to the question, but not with an answer:  “I don’t have any reason for answering this, as I’m time-short…”  In addition to being busy, Mr. Sigg wasn’t really in a position to answer the question because he admitted that he hadn’t listened to the presentation:  “I listened to the presentation for the first five minutes, then decided my time was better spent tightening up my talk outline; there wasn’t enough substance to make listening worthwhile.”

The accusation of lying, and the refusal to be specific about it, is particularly ironic because of Mr. Sigg’s plea during his presentation that “demonizing the other side is not leading to accommodation or understanding.”  On this we can agree.  Calling people liars and refusing to tell them specifically what you think they are lying about, is clearly not leading to “accommodation and understanding.”

Concern about herbicide use: Legitimate or “chemophobia”?

Recently there was a brief dialogue about herbicide use in San Francisco’s so-called “natural areas” in Jake Sigg’s Nature News that was of some interest to those who consider such use a contradiction in a public park designated as a “natural area”:

  •  Jake Sigg:  “Spurious, damaging information being circulated regarding herbicide use in our open spaces:  Mischievous people…are circulating false information…whipping up fears that have no foundation”  (Nature News, February 14, 2011)
  • Reader:  “…Garlon is legally classified as a hazardous chemical.  I am therefore writing to supply you with information from reputable sources.  I ask that in your future communications on this subject, you accurately describe the facts that are known about this chemical.” (Nature News, February 18, 2011)
  • Jake Sigg:  “The chemophobia rampant in this country is primarily based on emotion and anxiety, and does us a great disservice.” (Nature News, February 18, 2011)
  • Jake Sigg:  “The anti-herbicide crazies quickly seize on articles like this NYT one as proof of their contentions…” (Nature News, March 30, 2011)

This dialogue and the positive feedback that Mr. Sigg reported from his readers in support of herbicide use, suggest that herbicides are an important tool for the native plant movement.  They are anxious not to lose this tool in their crusade to eradicate non-native plants and trees.  After researching how much herbicide is being used by the Natural Areas Program, we can understand why they angrily defend its use. 

Herbicide use by San Francisco’s Natural Areas Program

The Natural Areas Program (NAP) reports having used herbicides 69 times in 2010:  36 applications of Garlon, 31 applications of Roundup, and 2 applications of Milestone.  Putting those numbers into perspective, other areas (those not designated as “natural areas”) in the Recreation and Park Department sprayed Garlon, the most hazardous chemical, only a few times in 2010.

 About 20% of these herbicide applications were done by a contractor who was paid $9,000 per application.  The employees of this contractor are therefore equally committed to this source of revenue, contributing to the economic interest that is a motivating factor in the native plant movement.

Not all of the “targets” of these sprayings are identified, but those that are include:  oxalis, blackberry, ivy, fennel, cotoneaster, hemlock, pampas grass, broom, erharta grass, mustard, and thistle.  Blackberry is an important source of food for wildlife in the city. We hope that children in the park do not graze on the blackberries.  Garlon was also sprayed on Scabiosa, which has not been identified as an “invasive plant” by the California Invasive Plant Council.

Glen Canyon, with a creek running through it and a year-around day care center adjacent to that creek, was sprayed 12 times.  Twin Peaks, the watershed to that creek, was sprayed 16 times.  Lake Merced was sprayed 3 times, despite the fact that it has been officially designated as red-legged frog habitat.

What is known about these chemicals?

The City’s policy regarding “Integrated Pest Management” classifies the chemicals used on city properties in terms of the risks associated with their use.  Here is how the City’s policy classifies these chemicals: 

  • Garlon:  Tier I, Most Hazardous.  Use Limitations:  “Use only for targeted treatments of high profile or highly invasive exotics via dabbing or injections.  May use for targeted spraying only when dabbing or injection are not feasible and only with use of a respirator.  HIGH PRIORITY TO FIND ALTERNATIVE.” 
  • Roundup:  Tier II, More Hazardous.  Use Limitations:  “Spot application of areas inaccessible or too dangerous for hand methods, right of ways, utility access, or fire prevention.  Use for cracks in hardscape, decomposed granite and edging only as last resort.  OK for renovations but must put in place weed prevention measures.  Note prohibition on use within buffer zone 60 feet around water bodies in red-legged frog habitat.”
  • Milestone:  Tier I, Most Hazardous

    Spraying Garlon on Twin Peaks without use of the respirator required by City policy, February 2011

Federal law also requires that chemicals be evaluated by the Environmental Protection Agency (EPA) before being commercially available to consumers.  The EPA conducts a number of tests of toxicity, reports the results of those tests on a mandated Material Safety Data Sheet (MSDS), and classifies the chemical with respect to its relative toxicity.  Here are a few highlights from the MSDS for these chemicals:

  • Garlon 4 Ultra is defined as a “Hazardous Chemical” according to the OSHA Hazard Communication Standard.  “Material is highly toxic to aquatic species” and “slightly toxic to birds.”
  •  Roundup Pro is defined as a “Hazardous Chemical” according to the OSHA Hazard Communication Standard. Toxicological effects in rats:  “decrease in body weight gain; histopathologic effects.”  “Moderately toxic” to aquatic life.

The Marin Municipal Water District (MMWD) quit using all herbicides in 2005 in response to the public’s protests.  They have been engaged in a process of evaluating herbicides for possible use in the future.  In 2008, MMWD contracted for a risk assessment of 5 herbicides they were considering for possible use.  That risk assessment determined that Garlon 4 Ultra is the most hazardous of the 5 chemicals that were evaluated.    MMWD is not considering the use of Garlon in the future. 

Does NAP’s herbicide use conform to the City’s Integrated Pest Management Law?

 San Francisco’s Integrated Pest Management Ordinance makes the following commitments regarding pesticide use on the city’s properties: 

  • 300a “…the policy of the City..to eliminate or reduce pesticide applications on City property to the maximum extent possible.”
  • “The City…shall assume pesticides are potentially hazardous to human and environmental health.”
  • “The City shall give preference to reasonably available nonpesticide alternatives when considering the use of pesticides.”
  • “Consider the use of chemicals only as a last resort.”
  • “This Chapter applies the Precautionary Principle to the selection of reduced risk pesticides and other pest management techniques.”

The City’s ordinance that obligates the City to follow the Precautionary Principle makes this commitment: 

“A central element of the precautionary approach is the careful assessment of available alternatives using the best available science. An alternatives assessment examines a broad range of options in order to present the public with the consequences of each approach. The process takes short-term versus long-term effects or costs into consideration, and evaluates and compares the adverse or potentially adverse effects of each option, giving preference to those options with fewer potential hazards. This process allows fundamental questions to be asked: ‘Is this potentially hazardous activity necessary?’ ‘What less hazardous options are available?’ and ‘How little damage is possible?’”

We do not believe that herbicide use by the Natural Areas Programs meets the standards of either the City’s ordinance about pesticide use or its commitment to the Precautionary PrincipalThese laws are theoretically rigorous, but the enforcement of those laws is not.  The Natural Areas Program is using an herbicide (Garlon) categorized by City policy as the “Most Hazardous” most of the time.  They are using that chemical in sensitive areas in which water can be contaminated and in which children can be exposed.  Their use of that hazardous chemical has increased over time and they have been using that chemical for at least 5 years, perhaps longer (the 2006 management plan for the Natural Areas Program reports the use of this chemical).  If Garlon has not been capable of eradicating in 5 years, the non-native plants that are the target of the Natural Areas Program, it is not likely to do so in the foreseeable future.  

Legitimate concern or “chemophobia”?

Let the reader be the judge.  Given what we know about these chemicals, the frequency of their use, the length of that use, and the locations of that use:

  • Do you think there is reason to be concerned about the herbicides that are being sprayed on our public parks? 
  • Do you think that places that have been designated as “natural areas” should be sprayed with herbicides which are legally and officially designated as hazardous chemicals? 

Hybridization: “Genetic pollution” or a natural process?

 
Presidio variety of California poppy. NPS photo

The San Francisco Chronicle’s gossip columnist, Leah Garchik, recently published a story about California poppies in the Presidio.  Apparently, someone planted the “wrong” poppy, or it migrated there.  The poppy that is native to the Presidio is small and yellow.  This “alien” poppy is the large orange poppy that most of us consider the classic California poppy.  The historical record indicates that this classic poppy grew elsewhere in San Francisco, but since it didn’t grow in the Presidio it must be removed because the Presidio’s Vegetation Management Plan “contains the requirement to remove any plants that could jeopardize the integrity of the genetics of native plants in the Presidio.” 

The “wrong” poppy

This incident reminded us of an article published in the newsletter of the local chapter of the California Native Plant Society several years ago, entitled “Contaminating the Gene Pool.”  In this article Jake Sigg instructs gardeners to beware of planting the wrong variety of a native plant because it will cause “genetic pollution.”  The California poppy is one of the examples he gives of a variety of California native being planted in San Francisco that doesn’t belong here.  It isn’t sufficient in his opinion, to plant a California native if that specific variety of the species didn’t historically occur in San Francisco.  He asks gardeners to “think in terms of preserving the genetic integrity of the local landscape.”  And he speculates many negative consequences of selecting the wrong variety, such as “genetic swamping, you’ve got all these foreign genes that are going to overwhelm the native population.”  We were reminded of Mr. Sigg’s vocal opposition to human immigration. 

For the benefit of our readers who aren’t gardeners, we should explain what Jake Sigg and the Presidio are worried about.  In a word, they are worried about hybridization, defined as “to breed or cause the production of a hybrid,” which is defined as “the offspring of two animals or plants of different breeds, varieties, or species.”  Hybridization is as likely to occur between two native plants as two non-native plants, but native plant advocates are concerned about the possibility of a native and a non-native plant producing a hybrid variety that is distinct from the native plant.  Hybridization is not inevitable, but it does occur naturally as well as through human manipulation.  The “From the Thicket” blog recently told the fascinating story of the development of a valuable garden cultivar variety of a favorite California native, ceanothus or California Lilac. 

Aside from the unpleasant association with eugenics, Mr. Sigg’s advice raises several practical questions.  How is the gardener supposed to know exactly which variety of a native plant “belongs” in San Francisco or even in a specific neighborhood within San Francisco, such as the Presidio?  And, in the unlikely event that gardeners might have such esoteric knowledge, where would they get the seeds of this specific variety?  Jake Sigg acknowledges this practical obstacle, but advises gardeners to get their seeds and plants only from the annual plant sale of the local chapter of the California Native Plant Society.  One wonders how many gardeners will follow this rather restrictive advice.

However, the more important question is the scientific question.  Is hybridization an inherently harmful process that always reduces species diversity?    We turn to Mark Davis for a less gloomy view of hybridization.  Like most scientific questions, there is evidence of both positive and negative effects of hybridization on species diversity.  Since you’ve heard the negative view from Mr. Sigg, we’ll let Mark Davis speak for the positive view.  Professor Davis reports in his book Invasion Biology* that “the fossil record generally shows that following the invasion of new species, the number of species resulting from adaptive radiations and evolutionary diversification exceeds the number of extinctions.”   And he concludes his discussion of hybridization and evolution by saying, “…a fair appraisal must also acknowledge that species introductions can enhance diversity as well, through hybridization, and the creation of new genotypes.”

The native plant movement has a narrow view of nature, which we do not share.  Their ideology is based on dire predictions of ecological disaster if we don’t follow their restrictive advice.  And when the managers of public lands choose to follow their advice, the consequences are usually the destruction of plants and animals that we value, in this case a field of California poppies. 


* Mark Davis, Invasion Biology, Oxford University Press, 2009, page 78-82.

“Mother Nature’s Melting Pot”

The Sunday New York Times of April 3rd published an op ed in defense of non-native plants.  In “Mother Nature’s Melting Pot” Professor Hugh Raffles (New School) reminds us that our country was built by immigrants.  Despite our origins, we also have a long tradition of opposition to immigration.  As each generation becomes established, it wishes to pull up the welcome carpet to new immigrants.  During times of economic crisis this anti-immigration sentiment is particularly strong.

Professor Raffles notes the extension of this anti-immigration sentiment to non-native plants and animals.  Just as immigrants have contributed to the dynamism and creativity of our society, non-native plants are contributing to our natural world as, “They arrive unannounced, encounter unfamiliar conditions and proceed to remake each other and their surroundings.” (1)

He provides many examples of non-native plants and animals that benefit both humans and native animals, including several examples that are locally relevant.  He reminds us that the eucalyptus is a rare source of winter nectar for the honeybees that were imported in the 1600s and now pollinate about one-third of our food crops.  He also reminds us that ice plant can stabilize sandy soils that might otherwise inundate our roads and neighborhoods as they shift in the wind.

Painted Lady butterfly on ice plant. Bug Squad, UC Davis

He notes that attempts to eradicate non-native plants and animals are often futile once the species become firmly established and that attempts to do so often harm the environment.   Here in the San Francisco Bay Area we are acutely aware of the harm being done by attempts to eradicate non-native plants.  We witness hundreds of thousands of healthy, mature trees being needlessly destroyed.  We see acres of park land being sprayed with toxic herbicides.  We watch precious recreational space being fenced off for “restorations” in places that are completely artificial, yet also entirely natural in the sense that they are sustained without being actively gardened.

The most recent example is the announcement that the Albany Bulb (in Albany, CA) will soon be transformed into a native plant garden.  The Albany Bulb is composed of landfill that was used for decades as a city dump and is now a heavily used park, populated by art created from the junk that remains from the dump.  Non-native plants and trees thrive there without any care.  It is pointless to destroy this valuable artistic and recreational resource, yet native plant advocates demand its “restoration.” 

Wild radish (non-native), “junk” art on Albany Bulb

Professor Raffles makes the logical connection between anti-immigration sentiment and the native plant movement’s commitment to the eradication of non-native plants and animals.  This connection is relevant in the Bay Area because a prominent leader of the native plant movement here is strongly opposed to immigration.

Jake Sigg has been an officer in the local chapter of the California Native Plant Society for many years.  He was a gardener in San Francisco’s Recreation and Park Department for 31 years.  He was awarded the “Jake Sigg Award for Vision and Dedicated Service” by the California Invasive Plant Council in 2003.  This award was named for him, “For years of tireless service and leadership on invasive plant issues in California.”

For many years, Mr. Sigg has published a “Nature News” newsletter several times each week.  This newsletter is widely distributed throughout the Bay Area and is a valuable source of information about nature-related activities.  It is also Mr. Sigg’s podium from which he expresses his opinion on a range of topics.  In most issues, he expresses his deep concern about immigration, both legal and illegal.

“Virtually All Of California’s Problems Can Be Traced Back To Too Many People…Virtually All Of California’s Population Growth In The Last 10 Years Was Due To Immigration…If We Don’t Do Something About Immigration, Our Problems Will Get Much Worse.”  April 2, 2011, Nature News

He is equally concerned about related issues such as granting visas to workers with unique skills and granting citizenship to children born to undocumented immigrants.

“The Ever Expanding Pool of Cheap Labor and the Case For Fewer Visas By Joe Guzzardi”  January 25, 2011, Nature News

“Current U.S. policy results in over 300,000 additional citizens from anchor babies each year.  The demographic impact is far greater because their families stay and bring in additional relatives. Anchor babies are eligible to sponsor their illegal alien parents and other relatives when they turn 21. Moreover, taxpayers pick up the tab for the medical costs and subsequent welfare outlays because of the child’s citizenship status. ACTION NEEDED  Please ask your Congressional representative to co-sponsor HR 140.”  January 13, 2011, Nature News

And so, we conclude that Professor Raffles is not making an idle philosophical connection between the native plant movement and anti-immigration sentiment.  There IS a connection because we see it discussed repeatedly by a prominent voice in the community of native plant advocates.  Occasionally, one of Mr. Sigg’s allies challenges his opinion on this subject.  However, such a debate is apparently rare in his community of interests.

We thank Professor Raffles for making explicit what is implicit in the native plant movement.  We believe that the connection between the eradication of non-native plants and animals and opposition to immigration should be acknowledged and discussed.  The desire to be rid of immigrants—both plants and animals, including humans—is grounded in a need to find someone or something to blame for problems that we are unprepared to face or are powerless to change. 

In the case of human immigration, our living standards are declining primarily because of the globalization of the economy.  Building a wall around our country will not isolate us from the fact that developing countries with lower standards of living are presently more economically competitive.

Likewise, eradicating non-native plants and animals will not prevent the climate change and associated changes in air and water quality that make those newcomers more competitive than the natives that thrived in a different environment, one that is gone and is unlikely to return.    In fact, the destruction of healthy, mature non-native trees is exacerbating the climate change that will ultimately exterminate many species of native plants and animals.(2)


(1) Hugh Raffles, “Mother Nature’s Melting Pot,” New York Times, April 3, 2011

(2) “Multitude of Species Face Threat of Warming,” New York Times, April 4, 2011