California’s “Sustainable Pest Management Roadmap” is a 25-year poisonous pathway

California’s Department of Pesticide Regulation (DPR) has published a draft of a policy that would replace its Integrated Pest Management policy with a Sustainable Pest Management (SPM) policy that is different in name only.  SPM makes a commitment to continue using pesticides in California until 2050, and by implication, beyond.  It makes NO commitment to reduce pesticide use or reconsider the current targets of pesticide applications.  It claims that the health hazards and damage to the environment will be reduced by identifying “Priority Pesticides” for possible substitution or “eventual elimination.”  It doesn’t commit to identifying any specific number of dangerous pesticides nor does it provide specific criteria for selecting these dangerous products.  It claims that increased testing and development of new products will result in safer products and puts these judgments into the hands of “stakeholders” with “experiential and observational knowledge” rather than scientists with expertise in soil science, endocrinology, toxicology, epidemiology, biology, botany, horticulture, etc.  The “stakeholder” committee that wrote the SPM proposal for urban areas included the manufacturer of pesticides and other users and promoters of pesticides. 

That’s not an exhaustive list of the many faults of SPM and the dangers that lurk in it.  I hope you will read it yourself and consider writing your own public comment by the deadline on Monday, March 13, 2023, at 5 pm.  The document is available HERE.  It’s less than 100 pages long and it is a quick read because it is basically a collection of bullet-points.

This is how to comment:  “DPR is accepting public comments to inform the prioritization and implementation of the Roadmap’s recommendations through March 13, 2023 at 5 p.m. Comments can be shared in writing to or by mail to the department at 1001 I Street, P.O. Box 4015, Sacramento, CA 95812-4015.” Please note that Department of Pesticide Regulations is not offering revisions, only “prioritization and implementation.” 

My public comment on California’s “Sustainable Pest Management Roadmap”

 A summary of my public comment is below.  A link to the entire comment is provided at the end of the summary:

Public Comment on
“Sustainable Pest Management Roadmap”
(AKA “Pathway to poisoning the environment for another 25 years”)

My public comment is focused on pesticide use in urban areas because of my personal experience and knowledge of pesticide use where I live.  These are the broad topics I will cover in detail with specific examples later in my comment:

  • Since glyphosate was classified as a probable carcinogen by the World Health Organization in 2015 and the manufacturer of glyphosate settled 100,000 product liability lawsuits by awarding $11 billion to those who were harmed by glyphosate, public land managers have been engaged in the process of substituting other, usually equally or more dangerous herbicides for glyphosate to deflect the public’s concerns.  The Sustainable Pest Management Roadmap (SPM) formalizes this process of substitution without addressing the fundamental problems caused by pesticides. 
  • SPM endorses the status quo that exists now.  Affixing the word “Accelerating” to SPM is an extreme case of double-speak that deliberately obscures, disguises, distorts, or reverses the meaning of words.  SPM ensures that toxic pesticides will be used in California for more than 25 years, to 2050, and likely beyond.  SPM therefore accelerates the damage to the environment that is occurring now.  Given that climate change will enable the movement of more pests into areas where they are now suppressed by weather, greater use of pesticides should be anticipated so long as the underlying issue is not addressed.
  • The underlying issue is that pests have been identified for eradication that in some cases cannot be eradicated and in other cases should not have been identified as pests either because they are innocuous or because of the valuable ecological functions they perform.  The key question that SPM does not address is whether pesticide use is truly necessary in the first place.  Unless we focus on whether a pesticide is actually necessary, all other issues are merely window dressing for perpetual pesticide use. 
  • SPM proposes to identify “Priority Pesticides” for possible substitution without any clear definition of “Priority Pesticides,” a process that is ripe for manipulation. Given the substitutions that are occurring now, we cannot assume that further substitutions would be less toxic. SPM puts the classification of “Priority Pesticides” into the hands of “stakeholders” without clearly identifying who stakeholders are.  SPM says “stakeholders” were involved in the development of the proposed policy.  Those stakeholders included only users and promoters of pesticide use.  There was no representation on the Urban Sub-Group of organizations such as Californians for Pesticide Reform, California Environmental Health Initiative, Beyond Pesticides, Center for Environmental Health, Environmental Working Group, etc.  Nor was there any visible expertise in the fields of science that are capable of analyzing and evaluating the impact of pesticides, such as soil science, endocrinology, toxicology, entomology, botany, biology, or horticulture.  SPM ensures that this exclusion will continue during the implementation phase by suggesting that “experiential and observational” knowledge should be represented on an equal footing with undefined “science.”  The word “science” is being used and abused by advocates for pesticide use who dangle it as a magic talisman, conferring fraudulent credibility. 

My entire public comment is available here:

Pesticide use in public parks in the San Francisco Bay Area

San Francisco Forest Alliance (SFFA) is a 501(c)4 not-for-profit organization with a mission of inclusive environmentalism. SFFA fights to protect our environment through outreach and providing information. SFFA opposes the unnecessary destruction of trees, opposes the use of toxic herbicides in parks and public lands, and supports public access to our parks and conservation of our tree canopy.

With permission, Conservation Sense and Nonsense is republishing SFFAs annual report on pesticide use by San Francisco’s Recreation and Park Department.  The report separates pesticide use in so-called “natural areas” from other park areas and finds that most pesticides are used in “natural areas.”  Conservation Sense and Nonsense is grateful to SFFA for compiling and reporting this important information. 

Conservation Sense and Nonsense follows pesticide use by the East Bay Regional Park District (EBRPD), where the pattern of pesticide use is similar to San Francisco’s Recreation and Park Department.  EBRPD has restricted spraying of glyphosate pesticides in developed areas of the park while continuing to use pesticides in naturalized areas to eradicate non-native plants.  In other words, most pesticide use in the public parks of the San Francisco Bay Area is devoted to eradicating non-native plants.

Conservation Sense and Nonsense

As we usually do, we compiled the pesticide usage data for San Francisco Recreation and Parks Department for 2021.  (We exclude Harding Park – but not the other golf courses – from this analysis because it’s externally-managed under a PGA contract to be kept tournament-ready at all times.) We’re pleased to note that SFRPD has reduced its pesticide usage in comparison to 2020 and 2019. 


But this is not true of the Natural Resources Division (this includes PUC areas managed in the same way – i.e. use of toxic herbicides against plants they dislike). Their usage has risen and is the highest it’s ever been from 2016.

The Natural Resources Department (NRD, formerly the Natural Areas Program or NAP) is the entity that is trying to bring “native” plants to more than a thousand acres of our parks, cuts down trees and restricts access to people and their pets.  NRD, which accounts for perhaps a fourth of the land area, used over 70% of the pesticides measured as active ingredients in fluid ounces.

NRD – and PUC lands that they are managing the same way – continued to increase their use of triclopyr since the new pesticide Vastlan has been designated Tier II (More Hazardous) instead of Garlon, which was Tier I (Most Hazardous). In both herbicides, the active ingredient is triclopyr. They also increased their usage of imazapyr, and continued to use Roundup, though in smaller quantities than before.

Here are the two earlier graphs lined up to show the comparison. The Native Plant areas used more herbicides in 2021 than they had ever used in the last six years – or that the other SFRPD departments together used in the same time. Their failure to reduce usage in 2021 is in stark contrast to the more than 50% drop in the other SFRPD.

SFRPD Other (i.e. other than the Native plant areas) uses mainly Polaris (imazapyr) and Clearcast ( ammonium salt of imazamox). The native plant areas, NRD / SFPUC, use large amounts of triclopyr, (Garlon and Vastlan), as well as some glyphosate (Roundup).


The NRD’s continually growing usage of the herbicides is a sign that this strategy is failing. They have been using hazardous chemicals on some 50 target species of plants year after year. Theoretically, the point of using toxic herbicides on unwanted species is to allow the desired species to replace them.  Instead, the growing usage of these chemicals shows that if anything, the situation is only made worse.

This stands to reason; “invasive” plants are successful because they are better adapted to current conditions. If they are destroyed with herbicides, the replacement is likely to be the next best adapted (thus, invasive) species. Given 50 target species, the bench is deep. This leads to a vicious cycle of hazardous herbicide use, clearly visible in the graph above.


For many years since we started compiling these data, Sharp Park has been off-limits for pesticides. We’ve seen very minimal usage – maybe 3 or 4 times over all the years. It’s home to the red-legged frog, and the San Francisco garter snake.

In 2021, that changed. In the space of one year, pesticides were applied 9 times. We did anticipate this would happen as NRD extended its grip on this park.


San Francisco’s Department of the Environment (SFEnvironment) assigns Tier hazard ratings to the various pesticides it uses. Tier III is Least Hazardous, Tier II is More Hazardous, and Tier I is Most Hazardous.  Over the years we have been following this usage, we have seen various chemicals being moved from one Tier to another. Milestone was moved from Tier I to Tier II; Glyphosate (Roundup, Aquamaster)  from Tier II to Tier I; and triclopyr (Garlon, Garlon 4 Ultra, Turflon, Vastlan) from Tier I to Tier II (for Vastlan and Turflon). Avenger was moved from Tier II to Tier III, which we think makes sense and makes analysis easier. We analyze the usage of Tier I and Tier II herbicides.


SF Forest Alliance has been trying to encourage SFRPD to reduce or eliminate Tier I and Tier II herbicide use. Some years ago, it appeared that pesticide usage was declining, especially after the Roundup revelations. When we wrote our Pesticides report for 2016, the other areas of SFRPD had slashed their herbicide use; the NRD accounted for 74% of pesticide usage. The 2021 data have renewed our hope that SFRPD’s other departments will adopt a cautious approach to the use of toxic herbicides. Unfortunately, this does not appear true of the nativist departments, NRD / PUC.

Every year, the San Francisco Forest Alliance also makes public comment at the annual review of San Francisco’s Integrated Pest Management program.  Conservation Sense and Nonsense is grateful for SFFA’s vigilance of pesticide use in San Francisco’s public parks.  Below is an excerpt from SFFA’s public comment to the Commission on the Environment regarding San Francisco’s IPM program.

Conservation Sense and Nonsense

Once again we are sending our comments emphasizing the self-evident truth that high toxicity herbicides are dangerous, unnecessary, and should never be used…

Below are the points we have repeated year after year for many years:

  • Herbicidal chemicals are more toxic, more persistent, more mobile and more dangerous than their manufacturers disclose;
  • The aesthetic or ideological “danger” from “weeds” is not a risk to health and welfare;
  • Scientific studies associate exposure to herbicides with cancer, developmental and learning disabilities, nerve and immune system damage, liver or kidney damage, reproductive impairment, birth defects, and disruption of the endocrine system;
  • There is no safe dose of exposure to those chemicals because they persist in soil, water, and animal tissue, so even low levels of exposure could still accumulate and harm humans, animals, and the environment;
  • Especially vulnerable individuals include infants, children, pregnant women, the elderly, people with compromised immune systems and chemical sensitivities;
  • Toxic runoff from herbicides pollute streams and groundwater, and therefore the drinking water sources;
  • Herbicides are harmful to pets and wildlife – including threatened and endangered species, plants, and natural ecosystems;
  • Herbicides are harmful to soil microbiology and contaminate soil into the future, reducing biodiversity in sensitive areas…

San Francisco Forest Alliance, July 11, 2022

Public opposition to pesticide use in our public parks

On November 19, 2015, a visitor to Mount Davidson park in San Francisco video recorded a pesticide application that is available here:

glyphosate spraying on Mt Davidson - nov 19, 2015

One of the people who saw that video reported several concerns regarding that pesticide application to the city employees who are responsible for the regulation of pesticide use in San Francisco.  Here is the email he sent to Kevin Woolen in the Recreation and Park Department and Chris Geiger in the Department of the Environment:

To:  Kevin Woolen

Dear Mr. Woolen,

I understand that you are responsible for the records of pesticide applications on properties managed by San Francisco’s Recreation and Park Department.  I have heard you speak at public meetings, so I am aware that you have some expertise in that area.  Therefore, I am writing to you about a pesticide application on Mt. Davidson on November 19, 2015.  That pesticide application was recorded by this video:

I have several concerns about this pesticide application:

  • One of the herbicides that was sprayed was Stalker with the active ingredient imazapyr. I notice that most of the spraying was done around a tree, which was not a target of the application according to the posted Pesticide Application Notice.  As you may know, imazapyr is not supposed to be sprayed under and around non-target trees according to the manufacturer’s label:  “Injury or loss of desirable trees or other plants may result if Stalker is applied on or near desirable trees or other plants, on areas where their roots extend, or in locations where the treated soil may be washed or moved into contact with their roots”

Here is a newspaper article about unintentional damage done to trees by spraying an imazapyr herbicide beneath them:

  • The Pesticide Application Notice says that the application method will be “spot treatment/daub cut stem.” This does not seem to be an accurate description of the application method on November 19th.  It seems that “backpack sprayer” would be a more accurate description of this particular pesticide application.
  • The Pesticide Application Notice says that Himalayan blackberries were one of the targets of this Pesticide Application. As you know, birds and other wildlife cannot read the signs that are posted to warn the public about these applications.  Can you assure me that the Himalayan blackberries were no longer fruiting?  Does the Recreation and Park Department have a policy against spraying vegetation when there are fruits eaten by birds and other wildlife?  If not, would the Recreation and Park Department consider adopting such a policy?
  • Although Garlon was not used in this particular pesticide application, it is often used in San Francisco’s so-called “natural areas.” Therefore, it is worth mentioning that Garlon is also known to be mobile in the soil and there are documented incidents of it damaging non-target trees when it has been sprayed on the stumps of nearby trees after they were destroyed.

Thank you for your consideration.  I hope you will share my concerns with the staff and contractors who are engaged in these pesticide applications.

Cc:  Chris Geiger

This is not an isolated incident.  Park visitors in San Francisco have been complaining for years about pesticide use in parks that were designated as “natural areas” over 15 years ago.  Ironically, those areas were never sprayed with pesticides before being designated as “natural areas.”  In fact, they really were natural areas prior to being officially designated as such.  Plants and animals lived in peace in those places before being “managed” by people who are committed to eradicating all non-native plants in many of San Francisco’s parks.

What can you do about it?

If you are opposed to pesticide use in San Francisco, or you object to the pointless destruction of harmless plants that are useful to wildlife, here are a few things you can do to express your opinion and influence the public policy that allows pesticide use in the public parks of San Francisco:

  • You can join over 11,000 people who have signed a petition to prohibit the use of pesticides in public parks. The petition is HERE.  The San Francisco Chronicle reported on pesticide use in San Francisco’s parks and the petition against that use.  (Available HERE)
  • You can sign up HERE to be notified of the annual meeting in which pesticide policy in San Francisco is discussed for subsequent approval by the Environment Commission. That meeting has been scheduled in December in past years.  Update:  The annual meeting has been announced.   “Annual Public Hearing on Pest Management Activities on City Properties and San Francisco’s Draft 2016 Reduced-Risk Pesticide List 4:30-7:00 pm
    Wednesday, December 16, 2015 Downstairs Conference Room, 1455 Market St. (near 11th St.; Van Ness MUNI stop)”  The meeting agenda is available HERE.
  • You can apply for one of the two vacant seats on the Environment Commission. These seats have been vacant for nearly a year.  In the past, the Environment  Commission has actively promoted pesticide use in San Francisco’s “natural areas.”  Qualifications and duties of commissioners are available HERE.
  • Appointments to the Environment Commission are made by Mayor Ed Lee. If you don’t want to serve on the Environment Commission, you can write to Mayor Lee ( and ask him to appoint people to the Commission who do not support the use of pesticides in San Francisco’s public parks.

The parks of San Francisco belong to the people of San Francisco.  They have paid to acquire those properties for public use and they are paying the salaries of those who are “managing” the parks.  If you don’t like how parks are being managed, you have the right to express your opinion.  Our democracy works best when we participate in the public policy decisions that affect us.

What does this have to do with the East Bay?

Our readers in the East Bay might wonder what this incident has to do with you.  Parks in the East Bay are also being sprayed with herbicides for the same reasons.  HERE are reports of pesticide use by the East Bay Regional Park District.

Many of the pesticide applications on the properties of EBRPD are done by the same company that sprayed herbicides on Mount Davidson on November 19, 2015.  That company is Shelterbelt Builders.  You can see their trucks in the above video.  Pesticide use reports of San Francisco’s Recreation and Park Department often report that pesticide applications were done by Shelterbelt.

Shelterbelt began the eradication of non-natve vegetation in Glen Canyon in November 2011
Shelterbelt began the eradication of non-natve vegetation in Glen Canyon in November 2011

Shelterbelt Builders is based in the East Bay.  One of its owners is Bill McClung who is a member of the Claremont Canyon Conservancy and a former officer of that organization.  The Claremont Canyon Conservancy is the organization that is demanding the eradication of all non-native trees on public land in the East Bay Hills.  Here is a description of Mr. McClung’s responsibilities on Shelterbelt’s website:

“Bill McClung joined Shelterbelt in 1997 to help refocus Shelterbelt on native plant restoration and open land management/fire safety.  After his house burnt down in the 1991 Oakland Fire, this former book publisher became interested in how wildland and fire are managed in the East Bay Hills.  He became a member of the Berkeley Fire Commission in 1994 and has a strong interest in the vegetation prescriptions of the Fire Hazard Program & Fuel Reduction Management Plan for the East Bay Hills issued in 1995 by the East Bay Hills Vegetation Management Consortium and the East Bay Regional Park District Wildfire Hazard Reduction and Resource Management Plan Environmental Impact Report of 2009/10.  He has managed many properties in the East Bay where wildfire safety and native habitat preservation are twin goals, and continues to work on interesting and biologically rich lands in the Oakland Hills.”

Claremont Canyon Conservancy

The Claremont Canyon Conservancy held their annual meeting on November 15, 2015.  Oakland’s Mayor, Libby Schaaf, was one of the speakers.  Although she took questions at the end of her presentation, one of the officers of the Conservancy called on the questioners.  There were many people in the audience who are opposed to the FEMA projects that will destroy over 400,000 trees in the East Bay Hills and many of us tried to ask questions.  With one exception, the person controlling the questions only called on known, strong supporters of the FEMA project.  Therefore, those who wished to express their opposition to the FEMA projects to the Mayor were denied that opportunity.  Fortunately, there were many demonstrators outside the meeting who could not be denied that opportunity.

Demonstration at meeting of Claremont Canyon Conservancy, November 15, 2015
Demonstration at meeting of Claremont Canyon Conservancy, November 15, 2015

Norman LaForce was the other main speaker at the meeting.  He is an elected officer of the Sierra Club and he identified himself as one of the primary authors of the project to destroy all non-native trees in the East Bay Hills.  (An audio recording of his complete presentation is available here: ) This is the paraphrased portion of his presentation specifically about the herbicides that will be used by the FEMA project:

“Part of the FEMA program will be to use herbicides in a concentrated, careful program of painting or spraying herbicides to prevent the trees from resprouting. It may need to be done more than once but ultimately the suckers give up.   There is no other way to do that cost effectively.

People are saying that glyphosate causes cancer.  Radiation causes cancer but when people get cancer they are often treated with radiation.  Nobody tells them they can’t have radiation because it causes cancer.

There are a lot of people of a certain age in this room who are probably taking Coumadin as a blood thinner for a heart condition.  Coumadin is rat poison.  Nobody tells them they can’t take Coumadin.*

You must take dosage and exposure into consideration in evaluating the risks of pesticides.

Nature Conservancy used glyphosate on the Jepson Prairie.

State Parks used Garlon on Angel Island when they removed eucalyptus.

The European Union says that glyphosate does not cause cancer, so I don’t know if it does.  I’m not going to take a position on that.

Now they are saying that red meat causes cancer.

We need to put aside the question of pesticides.  They will be used properly.  We must proceed in a scientific manner.”

We leave it to our readers to interpret Mr. LaForce’s justification for pesticide use.  He seems to be suggesting that pesticides are good for our health.  There are instances in which pesticides do more good than harm, but using them to kill harmless plants in public parks isn’t one of them, in our opinion.  Since many chemicals accumulate in our bodies throughout our lives, it is in our interests to avoid exposure when we can.  If we must take Coumadin for our health, that’s all the more reason why we should avoid unnecessary exposure to rat poison when we can.

Connecting the dots

We have tried to connect the dots for our readers.  Here are the implications of what we are reporting today:

  • Pesticide applications in San Francisco are probably damaging the trees that are not the target of those applications. The food of wildlife may be poisoned by those pesticide applications.
  • You can influence the public policy that is permitting pesticide use in San Francisco.
  • The same company that is spraying pesticides in San Francisco is also doing so in the East Bay.
  • That company is also actively engaged in the attempt to transform the landscape in the San Francisco Bay Area to native plants. They have an economic interest in native plant “restorations.”
  • The Sierra Club is actively promoting the use of pesticides on our public lands.

*Coumadin is prescribed for people who are at risk of heart attack or stroke caused by blood clots.  Coumadin thins the blood and suppresses blood coagulation.  Rat poison kills animals by bleeding them to death.  There is a fine line between preventing blood clots and bleeding to death.  Therefore, people who take Coumadin have frequent blood tests to check that the dosage is at the optimal level.  Rat poisons are killing many animals that are not the target of the poison.  Animals such as owls, hawks, vultures are often killed by eating dead rodents that have been poisoned.  We should not conclude that rat poison is harmless because humans are using it in carefully controlled doses.  Herbicides being sprayed in our public lands are not being closely monitored as Coumadin use is.


“Five Reasons it’s Okay to Love Oxalis – and Stop Poisoning It”

The San Francisco Forest Alliance has published an excellent article about the pointless and harmful attempt to eradicate oxalis in San Francisco’s so-called “natural areas.”  We are grateful to SFFA for their outstanding research and permission to republish the article. 

The oxalis season is over, and the perky yellow flowers have vanished for another year. These Bermuda buttercups will be back next year to herald the spring, bringing joy to those who love them, irritation to those who hate them, and Tier I herbicides targeted at them in San Francisco’s so-called “Natural” Areas.

oxalis 1


These flowers are so visible in spring that Bay Nature magazine did an article about them in March 2015: A Natural History of the Little Yellow Flower that’s Everywhere Right Now. It quoted Jake Sigg, the retired SF Recreation and Parks gardener who is considered the doyen of San Francisco’s native plant movement. He hates oxalis pes caprae, which he considers extremely invasive. The article quotes him as saying that, without intervention, “in X many years Twin Peaks would just be one solid mass of yellow, and there wouldn’t be any other plants there…” The article suggested that an oxalis-dominated  landscape “drives away coyotes, hawks and owls that feed on grassland foragers, and the situation is especially dire for endangered Mission blue butterflies, which depend heavily on native wildflowers.” Most of those ‘facts’ about oxalis are mistaken as we’ll explain below.

Mr Sigg’s theories align with those of the Natural Areas Program (NAP) of the San Francisco Recreation and Parks Department (SFRPD), which uses the herbicide, Garlon (triclopyr) to battle oxalis despite its dubious efficacy for the purpose.  San Francisco’s Department of the Environment classifies Garlon 4 Ultra as Tier I: Most Hazardous. It’s listed as HIGH PRIORITY TO FIND AN ALTERNATIVE (their caps). Since oxalis is the main reason NAP uses Garlonthe alternative we propose is – don’t use Garlon or anything else on oxalis.

An article on, based on a detailed study by the Marin Municipal Water Department, describes some of the issues with Garlon:

  • Garlon “causes severe birth defects in rats at relatively low levels of exposure.” Baby rats were born with brains outside their skulls, or no eyelids. Exposed adult female rats also had more failed pregnancies.
  • Rat and dog studies showed damage to the kidneys, the liver, and the blood.
  • About 1-2% of Garlon falling on human skin is absorbed within a day. For rodents, it is absorbed twelve times as fast. It’s unclear what happens to predators such as hawks that eat the affected rodents.
  • Dogs  may be particularly vulnerable; their kidneys may not be able to handle Garlon as well as rats or humans.  Dow Chemical objected when the Environmental Protection Agency noted decreased red-dye excretion as an adverse effect, so now it’s just listed as an “effect.”
  • It very probably alters soil biology. “Garlon 4 can inhibit growth in the mycorrhizal fungi…” (soil funguses that help plant nutrition)
  • It’s particularly dangerous to aquatic creatures: fish (particularly salmon); invertebrates; and aquatic plants.
  • Garlon can persist in dead vegetation for up to two years.

Natural Areas Program uses Garlon on oxalis
Natural Areas Program uses Garlon on oxalis

First, a little about the actual natural history of oxalis. This plant doesn’t set seed in California, and spreads entirely by sending out roots and forming little bulbils (like tiny potatoes) underground. It’s usually found where the soil has been disturbed by activities such as road-building, gardening, or trail-building. In some cases, the disturbance comes from landslides or something similar. It can’t stand frost. If we do nothing, it would tend to die down rather than spreading uncontrollably.

In disturbed landscapes, it can spread fast. For this reason it can be a nuisance in gardens. People don’t want to leave their gardens alone for years to let nature take its course with the oxalis, and not every garden design includes brilliant yellow as the dominant color for a few weeks. The only way to eradicate it in the short term is to dig it out carefully every time you see it, and make sure you get most of the bulbils. Or use strong herbicides, which may not work.

In a natural landscape, though, it’s a different story and here’s why.


Honeybee on oxalis flower
Honeybee on oxalis flower

Oxalis is actually an excellent plant for bees and butterflies.  When blooming, it provides “copious nectar.” In fact, it generously gives away its nectar. Since it doesn’t set seed, it doesn’t benefit from pollinators – but it’s a food source for honey bees, bumblebees and butterflies. (You can read a rather technical description of the plant HERE in a 2-page PDF note from UCLA’s Barry A. Prigge and Arthur C. Gibson.)

Bumblebee on oxalis flower
Bumblebee on oxalis flower

In fact, a recent 2014 study shows that plant communities with exotic plants had more plant species as well as more pollinators, that pollinators didn’t prefer native plants, and that even some specialist pollinators depended on introduced plant species.

It’s true the Mission Blue butterfly needs (native) lupine as its nursery plant. (It doesn’t depend on any other native wildflowers – only three varieties of lupine.  Incidentally, one of the key nectar sources for the Mission Blue butterfly is an invasive non-native Italian thistle: Carduus pycnocephalus).

Butterfly on oxalis flower
Butterfly on oxalis flower

Lupine has been planted on Twin Peaks as NAP attempts to reintroduce the Mission Blue butterfly there. But lupine is also a plant of disturbed areas, which means that NAP must maintain it or it will die out as the area stabilizes. They have to keep planting it, weeding, and trimming the grass around the lupine patches to make it attractive to the butterfly. An SFRPD report on the reintroduction project said “unmanaged habitat deteriorates quickly.” Presumably, they don’t use Garlon near the lupine patches, since it would likely kill that too. Despite what is implied in the Bay Nature article, it’s not oxalis that’s the issue. The real problem is another native plant, the coyote bush which takes over grasslands in a natural succession.


Oxalis bulbils are a food source for wildlife. Gophers and other rodents eat them. In fact, the Bay Nature article says, “Their spread is abetted by pocket gophers and scrub jays, which have been spotted carrying the bulbs and caching them in the ground—effectively planting them in new areas.”

Since gophers are a foundation species in the food web, being dinner for predators from hawks to coyotes to great blue herons, these plants actually provide habitat benefits whether or not they’re flowering, because the bulbils are there all year.

oxalis 6

Where there are gophers, the predators follow. Like the coyotes in these pictures, which clearly haven’t been driven away by a landscape dominated by oxalis.

coyote pouncing in oxalis field. Copyright Janet Kessler
coyote pouncing in oxalis field. Copyright Janet Kessler

coyote in oxalis field. Copyright Janet Kessler
coyote in oxalis field. Copyright Janet Kessler


The article says that oxalis leaves “bare ground during the six months of the year oxalis doesn’t flower.” That’s not true either.

oxalis 9

oxalis 10The spectacular yellow bloom of the oxalis – valuable because the mass of color attracts honey bees and bumblebees – gives the impression that it’s the only plant there.  But though it visually takes over the landscape when it’s in bloom, it naturally grows interspersed with grasses and other plants. Like in the picture above.

In fact, oxalis tends to enrich the soil with phosphorus, which is good for grass.

So when it finishes blooming, as it has by now – you don’t get bare ground. The picture below shows the same area as the first picture in this article – but it’s after the oxalis bloom is over. It’s grassland.

oxalis 11


One argument – related  to the ‘bare ground’ argument – is that oxalis takes over grasslands and destroys them, particularly the native grasses. However, grasslands in most of California including San Francisco are dominated by non-native grasses. The change occurred over 100 years ago, when these grasses were planted for pasture. So the grassland that NAP is defending with herbicides is primarily non-native anyway.

oxalis 12

But anyway, what’s the evidence that oxalis is actually damaging native plants?

It’s true some European studies do suggest that an increase in oxalis is associated with a decrease in native plants diversity –though whether it’s a cause is unclear. It may just be benefiting from human activities that disrupt the landscape. Another study put oxalis head-to-head with a native annual grass, lolium rigidum. The native grass tended to dominate. Their conclusion: “Oxalis is a poor competitor. This is consistent with the preferential distribution of Oxalis in disturbed areas such as ruderal habitats, and might explain its low influence on the cover of native species in invaded sites.

The California Invasive Plant Council rates its invasiveness as “moderate,” considering it as somewhat invasive in sand dunes and less so in coastal bluff areas.

In San Francisco, every place where oxalis grows is already a disturbed environment, a mix of non-native grasses and plants with native plants (some of which have been artificially planted).  Here,  oxalis appears to grow happily with other plants – including, for instance, the native California poppy in the picture above.


Children love oxalis, both for its pretty flower and for the sour taste of its edible stems.

oxalis 13

oxalis 14Even small children love gathering posies of Bermuda buttercups (though picking flowers is technically prohibited in Natural Areas). The flowers are surprisingly hardy for wildflowers, and in a glass of water last quite well as cut-flowers.

The plant is edible, and its tart leaves make a nice addition to salad. People enjoy snacking on its sour stems. Besides Bermuda buttercup, it’s also called ‘sourgrass’ and ‘soursob.’ It does contain oxalic acid (as does spinach, for instance), and so you probably wouldn’t want to make a meal of it. Though in South Africa it’s made into soup.

Adding Garlon to it is probably a bad thing.

Photo credit: Badjonni (Creative Commons – Flickr)
Photo credit: Badjonni (Creative Commons – Flickr)


From our current evidence, there’s no sign that oxalis has a negative impact on wildlife, and plenty of evidence it’s already part of the ecological food web of our city.  The evidence also suggests it’s not having a negative effect on other plants in San Francisco either. Lots of people find this flower attractive; one writer described it as the city smiling with Bermuda buttercups.

In any case, even Doug Johnson of the California Invasive Plant Council doesn’t think it’s worth attacking at a landscape level: the payoff isn’t worth the expense. Removing it from the hundreds of acres in Natural Areas isn’t as simple as eradicating it from a small yard where it’s clashing with the garden design. It requires a lot of work, a lot of powerful herbicides, a multi-year effort – and for what?

The justification for using strong pesticides like Garlon to control it is weak. We call on NAP to stop using Tier I and Tier II herbicides altogether.


2014 Wrap-Up and 2015 Preview

Our last post of 2014 will summarize wins and losses in our effort to save our urban forest and preview the local issues that remain unresolved.  2014 has been a year of many accomplishments, but there have been disappointments as well.

2014 Accomplishments

Good news always comes first!  We are most grateful for the hard work of the San Francisco team with whom we collaborate.  After herculean effort, they completed most of the presentations to the members of the Board of Supervisors about the forthcoming approval process for the Environmental Impact Review of San Francisco’s Natural Areas Program, which has been in the works for eight years…and still counting.  We are advocating for the Planning Commission and the Board of Supervisors to approve the “environmentally superior” Maintenance Alternative, which would enable the Natural Areas Program to maintain the native gardens they have created in the past 15 years, but would prohibit expansion of those gardens.  The Maintenance Alternative could save about 18,500 healthy non-native trees from being needlessly destroyed and significantly decrease herbicide use in our parks.

Because native plant advocates have succeeded in convincing many politicians that their projects are “science-based,” the San Francisco team was particularly glad to have three lectures at the Commonwealth Club by academic scientists, which challenged the unfounded assumptions of the native plant ideology:

These presentations were very well attended, including by native plant advocates.  They were entirely successful from our standpoint, though they seem to have had little influence on the opinions of native plant advocates, many of whom seemed not to understand the scientific information being presented.

The dense and healthy Sutro Forest
The dense and healthy Sutro Forest

 In March 2014, UCSF announced that they have put their plans to destroy most trees on Mount Sutro on indefinite hold.  This decision was made in response to the public’s overwhelming opposition to these plans during the public comment period for the Draft Environmental Impact Report in March 2013.  However, UCSF has destroyed about 1,200 trees during the past 18 months which they claimed would mitigate immediate hazards.  UCSF has also made a commitment to not using herbicides on Mount Sutro.  UCSF has provided no estimated time frame for announcing a new plan. Please visit Save Mount Sutro Forest for a more detailed description of that announcement.  We consider this a “holding pattern” because we know that UCSF is under constant pressure from those who want the Sutro Forest to be destroyed.

Invasion biology is being revised by academic scientists who inform us that empirical studies do not support the hypotheses of invasion biology.  Here are a few of the highlights from the scientific literature:

Likewise, mainstream media has become more even-handed in its coverage of invasion biology and native plant “restorations.”  Here are a few specific examples:

2014 Disappointments

The publication of the final Environmental Impact Statement for FEMA projects in the East Bay Hills was the biggest disappointment of 2014.  There were over 13,000 public comments on the draft and they were overwhelmingly opposed to the proposed projects.  Yet, the projects are fundamentally unchanged by the final EIS, which will be officially approved by a “Decision of Record” on January 5, 2015.  We are grateful to the Hills Conservation Network for their continuing opposition to these projects and we urge our readers to support their effort.

Some of the hundreds of trees destroyed by UC Berkeley in August 2014
Some of the hundreds of trees destroyed by UC Berkeley in August 2014

We were outraged by UC Berkeley’s destruction of hundreds of non-native trees on their property in August 2014, prior to the approval of these FEMA grants.  And we were also appalled by the letters sent to FEMA by elected officials in the East Bay in July, demanding that funding be immediately released and approved for use to destroy all non-native trees on their properties.

In San Francisco, our biggest disappointment of 2014 was the approval of the revised Recreation and Open Space Element (ROSE) of the city’s General Plan, which has committed the city to managing all open space as “natural areas.”  The ROSE defines “natural areas” so broadly that it includes not only areas that currently contain existing remnants of SF’s pre-settlement habitat, but also areas that could support native plants if they were planted there, or, in other words, nearly all open space in SF, including people’s back yards. This policy commits the city to managing nearly ALL open space in San Francisco, including that in private hands, the same way as the Natural Areas Program manages its lands.  As disappointing as that decision was, it was also instrumental in producing one of the biggest accomplishments of 2014.  We were successful in convincing the State of California to decline to fund a grant application which would have implemented the plans to convert all open space in San Francisco to native plant gardens.  That so-called “biodiversity program” continues, but is presumably handicapped by the loss of that fund source.

Looking forward in 2015

In the past six months, the San Francisco team has devoted a great deal of time and effort to influencing the city’s Urban Forestry Council (UFC) to adopt “best management practices” that would discourage the destruction of healthy trees.  The UFC has hosted a “listening series” of presentations by those who advocate for the eradication of eucalyptus forests as well as those who are opposed to that destruction.  Native plant advocates have introduced new justifications for destroying the eucalyptus forests:

  • They claim that eucalyptus forests are dying of disease, drought, old-age, etc. We have sought the advice of many professional arborists and academic ecologists who assure us these claims are inaccurate.
  • They claim that the health of the eucalyptus forests would be improved by radical “thinning.” The scientific literature informs us that mature forests do not benefit from thinning because mature trees are unable to respond positively to increased light and wind.  Thinning is only beneficial to young trees and even then, the disturbance can damage the trees that remain.  Radical thinning of the mature eucalyptus forest is likely to destroy the few trees that will remain.

The UFC has completed its listening series and will probably reach its conclusions in 2015.  Based on the meetings we have attended and the conversations we have had with members of the UFC, we are not hopeful about the outcome.  They seem to be sympathetic to the demands of those who want the non-native forests of San Francisco to be destroyed.   In that case, their “best management practices” could be specifically supportive of the plans of the Natural Areas Program to destroy 18,500 trees in San Francisco and Pacifica.  If you would like to express your opinion to the Urban Forestry Council, you can write to them here:

We also expect the final Environmental Impact Report for San Francisco’s Natural Areas Program to be published in 2015.  We will make our best effort to convince the Planning Commission and the Board of Supervisors to approve the Maintenance Alternative.  However, we should all understand that the lack of an approved EIR does not seem to have prevented the Natural Areas Program from destroying trees whenever and wherever they wish.  Many trees (perhaps a few hundred) in Glen Canyon Park, McLaren Park and Pine Lake in Stern Grove have been destroyed without an approved Environmental Impact Report.  In other words, the Environmental Impact Report seems increasingly irrelevant to what is actually being done in our parks.

A few of the trees destroyed recently in Pine Lake "natural area"
A few of the trees destroyed recently in Pine Lake “natural area”

The President of the San Francisco Forest Alliance, Carolyn Johnston, ran for a seat on the Executive Committee of the San Francisco Group of the Sierra Club.  If you follow the controversy about the Natural Areas Program in San Francisco, you may be aware of the Sierra Club’s role in supporting the nativist agenda (HERE is an example of their role).  Carolyn lost by only 6 votes.  If everyone in San Francisco who abandoned the Sierra Club because of its support for turning urban parks into native plant gardens, would renew their membership, maybe we could win a seat next year.  We are grateful to Carolyn for running.

We also expect a final response from the California Invasive Plant Council to our request that Blue Gum eucalyptus be removed from its list of “invasive” plants.

In summary

Science is rapidly revising the unfounded assumptions of invasion biology and climate change is making the concept of “native” meaningless.  But these realities are having no apparent influence on public policy, which seems to be immune to such facts.  Popular culture always lags behind science.

Million Trees is changing its emphasis in response to these political realities.  In 2015, we will focus on the science that is revising invasion biology because that’s where progress is being made.  This type of research is both difficult and time-consuming for us because we do the background reading to understand the scientific literature and produce accurate reports that are accessible to the layperson.  We therefore expect to publish new articles only once each month in 2015.  As always, we invite guest authors to step forward with news of new developments that we are not covering.

Thank you for your readership in 2014 and for any help you gave us in 2014 on our various initiatives.  We wish you all a Happy New Year in 2015.

Relentless war on eucalyptus

A new front has opened in the relentless war on eucalyptus in California.  The drought has given native plant advocates an opportunity to develop a new narrative to justify their demands for eradication of eucalyptus.  The opening gambit in this new strategy is an item in Jake Sigg’s “Nature News” of May 16, 2014:

“The prolonged drought of the last 2-3 years seems to be taking its toll.  The Tasmanian blue gums in Glen Canyon along O’Shaughnessy Boulevard strongly show drought stress.  The stress is more evident from the high cliffs above O’Shaughnessy than it is at ground level.  Thinning crowns and discolored foliage was striking.  And that was before the recent heat wave.

Barring substantial rains–unlikely, but not impossible–the trees are in serious trouble.  The City could have an emergency situation and no money to address it.”

 Recap of the war on eucalyptus

When public land managers began the war on eucalyptus in the 1980s it did not occur to them that the public would object.  So deep was their prejudice against eucalyptus, that they assumed the public shared their opinion.  The first two massive projects in the 1980s on National Park Service and State Park properties were greeted with angry public protests.  Land managers quickly learned that it was not going to be as easy to eradicate eucalyptus as they had thought.  They developed a series of story-lines to justify their projects, which were designed to convince the public that the eradication of eucalyptus is both necessary and beneficial.  This is a summary of some of their cover stories with links to articles that debunk them:

Based on our experience, we were immediately suspicious of the new claim that San Francisco’s eucalyptus forest is dying of drought.  We know that our predominant species of eucalyptus—Tasmanian blue gum—grows successfully throughout California, all the way to the Mexican border in climates that are much hotter and drier than the Bay Area.  We also know that the central and north coast of California is foggy during the dry summer months, which doubles the amount of annual precipitation in the eucalyptus forest.  All reliable sources of horticultural information describe blue gum eucalyptus as drought tolerant.  Frankly, we couldn’t see how our eucalyptus could be dying of drought.

What is wrong with our eucalyptus forest in Glen Canyon?

 The picture became clearer when Jake Sigg posted the following on his “Nature News” on June 12, 2014:

“The June 10 newsletter [see below*] included an editorial on an evolving catastrophe, mostly involving our numerous plantations of Tasmanian blue gums.  The editorial focused primarily on the plantations on O’Shaughnessy Blvd in Glen Canyon and on Mt Sutro, and included a photo of a grove of Mt Sutro dying trees.  Here is a photo of the Glen Canyon plantation, taken from above the high cliffs on O’Shaughnessy.  The damage is most visible from high, looking down.

The discoloration of leaves was very dramatic, but the foliage color and condition is not fully conveyed in the photograph.  Some trees defoliated entirely in the prolonged winter dry spell.  Look very closely at the juvenile blue leaves of the coppice shoots; anything that appears faintly bluish are new coppice shoots which grew in response to the late rains we had in February and March.  Once you see coppice shoots on old trees you know the trees are in trouble.  These trees are in double jeopardy, as they invested energy in new shoots, but were betrayed by another dry spell which, under normal circumstances, will last until autumn.  Note that you can now see the grassland through the trees; that slope was not previously visible.  Even a casual inspection of these groves reveals dead, dying, and stressed trees, and under normal circumstances we will have four or five months of dry.  The fire situation is serious right now and is likely to become worse.”

View of west side of Glen Canyon Park from Marietta Drive, June 2014
View of west side of Glen Canyon Park from Marietta Drive, June 2014

With more specific information in hand about what Jake Sigg is looking at, we went to see for ourselves.  We could see what he was describing from a vantage point on Marietta Drive, west of Glen Canyon Park.  We could see lighter colored leaves, but they were more localized than Jake Sigg’s description implied.  We didn’t feel qualified to speculate about why the leaves were lighter colored so we recruited an arborist to help us figure out what is happening there.  We were fortunate to enlist the help of a certified arborist who has been responsible for urban forests on public lands in the Bay Area for several decades.  This is what we learned.

Epicormic Sprouts

Looking through binoculars from our vantage point on Marietta Drive, the arborist said immediately, “Those are epicormic sprouts.”  The leaves of epicormic sprouts are distinctively lighter colored than the darker green of mature eucalyptus leaves.  They are also a more rounded shape than the long, pointed mature leaves of eucalyptus.  This is how Wikipedia describes epicormic sprouts:

“Epicormic buds lie dormant 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 plants.”

Epicormic sprouts on trees in Glen Canyon Park, June 2014
Epicormic sprouts on trees in Glen Canyon Park, June 2014

The remaining question was why some of the eucalypts, were producing these epicormic sprouts, when most were not.  We went down to O’Shaughnessy Blvd to get a closer look, hoping to answer that question.  This is what we learned:

  •  The understory of non-native shrubs between O’Shaughnessy Boulevard and the trees with epicormic sprouts has been cleared in the past year.  We could see the dead brush piled up next to the trees.  We had to wonder how people who claim to be concerned about fire hazard could think such huge piles of dead brush were nothing to be concerned about.

Remains of dead non-native brush destroyed along O'Shaughnessy Boulevard, June 2014
Remains of dead non-native brush destroyed along O’Shaughnessy Boulevard, June 2014

  • We could see the stumps of some of the dead brush and we wondered if the stumps had been sprayed with herbicides after they were cut.  Pesticide use reports for Glen Canyon indicate that O’Shaughnessy was sprayed several times in the past year, twice with products containing imazapyrImazapyr is known to be harmful to trees if sprayed in proximity to their roots.  The trees with epicormic sprouts were downhill from the understory shrubs that were destroyed, in the probable direction of water and herbicide flow.
  • We found several trees that had been girdled in the past and are now dead.

Girdled tree in Glen Canyon Park, now dead, June 2014
Girdled tree in Glen Canyon Park, now dead, June 2014

The trees in Glen Canyon Park

Then we walked into Glen Canyon Park from its southern end.  It’s not a pretty sight.  Many huge, old eucalypts have been destroyed.  When they were destroyed, their stumps were immediately sprayed with herbicide to prevent them from resprouting.  The stumps are simultaneously painted with dye so that workers can tell which trees have been sprayed.  The dye is no longer visible, but regular visitors took photos of the painted stumps before the dye faded.  The spraying of the stumps do not appear on the pesticide use reports of the Recreation and Park Department.  We assume that’s because the spraying was done by the sub-contractors who destroyed the trees.

Poisoned and dyed eucalyptus stump, Glen Canyon Park, 2013. Courtesy San Francisco Forest Alliance
Poisoned and dyed eucalyptus stump, Glen Canyon Park, 2013. Courtesy San Francisco Forest Alliance

The arborist who walked in the forest with us said, “The painting of stumps with RoundUp or Garlon in proximity to trees that are being preserved can kill the neighboring preserved tree. Stumps near living, residual (preserved) trees should not be painted with RoundUp or Garlon if the stumps are within 40’ of mature, blue gums that are slated for preservation.”  If the remaining trees are damaged by herbicides, their mature leaves fall and epicormic sprouts will then emerge as the tree recovers.

Some of the stumps of the trees that were destroyed in Glen Canyon Park in 2013. Taken June 2014
Some of the stumps of the trees that were destroyed in Glen Canyon Park in 2013. Taken June 2014

While the trees were being destroyed in 2013, the Natural Areas Program was eradicating non-native vegetation in the Canyon.  They sprayed ivy, blackberry, and valerian with Milestone, which is another herbicide that is known to damage trees if sprayed near their roots.  In addition to these official applications of herbicide in this park, there is a long history of unauthorized, illegal herbicide applications by “volunteers,” more appropriately called vandals.

We saw a lot of epicormic growth in the Canyon, sprouting from stumps that must be cut back and resprayed with herbicides.  It usually takes several retreatments to successfully kill the roots of eucalypts that are destroyed.  We also saw epicormic growth from eucalypts that had been severely pruned and were also exposed to a great deal more light because they had lost the shelter of their neighboring trees.

Epicormic growht, Glen Canyon Park, June 2014
Epicormic growth, Glen Canyon Park, June 2014

Wrapping up

The trees in Glen Canyon are reacting to the traumas to which they have been subjected:  the loss of their neighbors that were either girdled or cut down thereby exposing them to more light and wind, the loss of the shelter of their understory, the application of herbicides known to be harmful to trees.

The good news is that there are still plenty of trees in Glen Canyon that have not yet been destroyed and they are in great shape.  Here is the view of the tree canopy in Glen Canyon taken from the east side of the park near Turquoise Way.  The first picture was taken in December 2012 (before the current round of tree destruction in Glen Canyon Park) and the second picture was taken in May 2014.

Eucalyptus canopy on east side of Glen Canyon Park, taken from Turquoise Way December 2012, before tree destruction began. Courtesy San Francisco Forest Alliance
Eucalyptus canopy on east side of Glen Canyon Park, taken from Turquoise Way December 2012, before tree destruction began. Courtesy San Francisco Forest Alliance

Same perspective of Glen Canyon tree canopy, taken May 2014. Courtesy San Francisco Forest Alliance.
Same perspective of Glen Canyon tree canopy, taken May 2014. Courtesy San Francisco Forest Alliance.

These trees are doing just fine because the Natural Areas Program has not yet gone that deeply into the park.  But NAP intends to destroy many more trees in Glen Canyon (and elsewhere) when the Environmental Impact Report (EIR) for their management plan (SNRAMP) is finally approved.  Then we will see more consequences of the destructive practices of the Natural Areas Program and we will probably hear more bogus explanations for that damage.

We expect the EIR to finally be considered for approval at the end of 2014.  [Update:  now predicted for fall 2015] We will do whatever we can to convince San Francisco’s policy makers that they should approve the “Maintenance Alternative” which would enable NAP to continue to care for the native plant gardens they have created in the past 15 years, but prevent them from expanding further.   We hope that our readers will help to accomplish this important task.

*Jake Sigg’s Nature News of June 10, 2014, introduced the theories of Craig Dawson about the health of the Sutro Forest.  Mr. Dawson’s speculations are different from Mr. Sigg’s and we will not address them in this post.  You can find an analysis of Mr. Dawson’s theories on Save Sutro Forest HERE.

Ants used to scapegoat our urban forest


Ants are important members of the ecosystem.  They improve the fertility and consistency of the soil.  They distribute plant seeds.  They are both predators of and food for other insects as well as birds and omnivorous mammals.  Therefore, their abundance in an ecosystem is often considered an indicator of its health.

Today we will report on a study of ant populations in San Francisco’s “natural areas,” parks that were designated over 15 years ago for restoration and preservation of native plants.  This study reaches this conclusion:

“The results of this study indicate that natural areas within urban parks play a critical role in supporting ant biodiversity. Many habitats in the natural areas of San Franciscos parks support healthy, diverse ant communities. Areas of non-native forest, however, reduce this diversity. Maintaining open grasslands, reducing tracts of non-native forest, removing the invasive understory, and thinning forest canopy may all help support a healthier ant community and ecologically valuable parks.”  (emphasis added) (1)

Could this ant study be the first example we have found of evidence that native plants benefit wildlife and conversely that our non-native urban forest is less valuable for wildlife?  We have examined this study to determine how it reached this conclusion.  We have compared this study to similar studies that report different findings.  We reached the conclusion that this study does not support its conclusion that “reducing tracts of non-native forest…may…help support a healthier ant community and ecologically valuable parks.” 

The relationship between ant communities and soil moisture

The ant study used pitfall traps to survey the abundance and diversity of ant populations in 24 “natural areas.”  It also measured the moisture of the soil in proximity of the traps.  The ant study found that soil moisture and ant abundance and diversity were positively correlated at low levels of moisture, but that high levels of moisture found in eucalyptus forest were negatively correlated with abundance and diversity of ants: 

Ant abundance and soil moisture

We will tell you how this ant study used this empirical observation of the relationship between soil moisture and ant populations to reach its conclusion that non-native forests must be “reduced” to achieve “ecologically valuable parks.” 

Generalizing about “urban forests”

This study of San Francisco’s ant population asks us to believe that its negative assessment of San Francisco’s urban forest applies to all urban forests:  “Urban forests are structurally different than natural forests.  Besides being smaller, fragmented, and more isolated than non-urban forests, urban forests also show increased canopy cover, greater disturbances due to human traffic and pollution, and differences in leaf litter accumulation.” (1)

We don’t think it is possible to generalize about all urban forests.  Here are two sources which suggest that the ant study has over-generalized about urban forests and ants found in them:

  • According to the US Forest Service survey of urban forests, San Francisco has one of the smallest tree canopies in the country.  Only 11.9% of San Francisco is covered by the tree canopy, compared to 20.9% of New York City.  According to that survey, San Francisco’s urban forest removes 141 tons of pollutants per year compared to 1,677 tons of pollutants removed by New York City’s urban forest.
  • Ants are found in some urban forests.  A study in Toledo, Ohio and Detroit, Michigan compared ant populations in urban habitats (forests in city parks, community gardens, and vacant lots).  (2) The study found greater diversity of ant species in forests than in other habitat types, but fewer ants.  They found 26 species of ants in the forest, 20 in vacant lots, and 14 in gardens.  They found no correlation between various characteristics of vegetation and ant diversity or abundance.  Soil moisture was not measured by this study.  Generalizations about urban forests derived from one study in San Francisco clearly do not apply to Toledo and Detroit.

More soil moisture in forest with a closed canopy

The ant study in San Francisco predicts greater soil moisture in a forest with a closed canopy and dense understory:

“A combination of high soil moisture, dense canopy cover, and dense understory (habitat complexity) may help explain the lack of ground-foraging ants in urban forests.” (1)  The study associates those characteristics specifically with the eucalyptus forest:  “Within forest types examined, eucalyptus forests contained significantly more soil moisture than other forest types and also had lower ant richness and abundance.”  (1)

We don’t think these generalizations can be applied neither to all eucalyptus forests nor solely to eucalyptus forests:

  • The density of eucalyptus forest in the San Francisco Bay Area varies widely according to data presented recently by Professor Joe McBride to the Commonwealth Club:
Location Average Number of Trees per Acre
Presidio, San Francisco 163
Land’s End, San Francisco 364
Tilden Park, Berkeley 540
East Ft Baker, Marin County 1795

In other words, not all eucalyptus forests have closed canopies.

  • The density of understory in the eucalyptus forests of the Bay Area also varies widely.  One of the densest understories exists on Mount Sutro, which is the location of the Interior Greenbelt, where the ant study reports finding no ants.  In drier locations, such as Bayview Hill, there is little understory in the eucalyptus forest, which may be why the ant study reports finding ants there.  Bayview Hill is on the east side of San Francisco and therefore receives much less fog than Mount Sutro, which is closer to the ocean.
  • Eucalyptus forest is not unique in often having a closed canopy.  Native redwood forest also has a closed canopy:  “Many meters above the ground, the branches of trees, especially those of redwood, merge to form a ceiling, or canopy.”  (3)

Fog and soil moisture

The ant study describes the relationship between fog and soil moisture in San Francisco:  “The increased moisture in eucalyptus is due to the fact that summer fog tends to condense on eucalyptus leaves and branches and drip down to the soil below.  Such fog drip can add as much as 42 cm of water to eucalyptus forest during a single summer.”  (1)

Fog in San Francisco is unrelated to the fact that its forest is predominantly eucalyptus:

  • Redwood forest.  NPS
    Redwood forest. NPS

    Although redwoods did not live in San Francisco when Europeans arrived in 1769, they lived there in the distant past.  Native redwoods now exist only on the coastal fog belt of California.  Fog is essential to their survival:  “During the study period, 34%, on average, of the annual hydrologic input was from fog drip off the redwood trees themselves.  When trees were absent, the average annual input from fog was only 17%, demonstrating that trees significantly influence the magnitude of fog water input to the ecosystem…The results presented suggest that fog, as a meteorological fact, plays an important role in the water relations of the plants and the hydrology of the forest.”  (4)

  • Fog exists along the northern coast of California because the interior is hot and the ocean is cool.  When the cool ocean air meets the hot air from the interior, fog forms.  The existence of fog has nothing to do with the species composition of the forest.  Any tall tree is capable of condensing the fog, which then drips to the forest floor, providing water to both the trees and their understory.  The eucalyptus forest is not to blame for this sequence of events.

The nativity of the urban forest is irrelevant to the ants

The ant study implies that there are few ants in San Francisco’s urban forest because the forest is not native to San Francisco:  “…reducing tracts of non-native forest…may all help support a healthier ant community and ecologically valuable parks.”

Soil moisture is the operative variable in predicting abundance and diversity of ant populations.  The nativity of the vegetation is irrelevant to the ants:

  • If the urban forest in San Francisco was native redwoods, it would precipitate equal amounts of fog, resulting in equal amounts soil moisture.  The ant population would probably be similar.
  • A study of ant populations in the central Appalachian Mountains found the same relationship between soil moisture and ant populations in native forests:  “Fewer ants, lower number of species, and lower ant diversity were found at sites with higher elevation and soil moisture.”  (5)
  • A study of ant populations in Northern California grasslands found that the characteristics of the soil were better predicators of ant populations than the types of vegetation:  “Plants were less important than soil attributes in explaining variation in overall ant species richness and abundance…”  (6) Chemical composition and consistency (sand vs. clay) of soils were evaluated by this study, but not soil moisture

“Science” in the service of nativism

We consider this ant study a classic demonstration of nativism.  In this case, soil moisture was confounded with the non-nativity of forest in San Francisco.  The nativity of San Francisco’s forest is irrelevant to the amount of soil moisture.  Any closed canopy forest of tall trees would precipitate equal amounts of fog and have a similar impact on ant populations. 

The study speculates that the allelopathic properties of eucalyptus may have a negative impact on the ants, but offers no evidence.  We have found no evidence of allelopathic properties of eucalyptus.  Nor do we think that the existence of ants should be the sole criterion for “ecological health.”  Would we demand the destruction of redwood forests so that we could have more ants?  We doubt it.

However, we must also give credit where credit is due.  The ant study reports that the existence of the non-native Argentine ant does not have a negative impact on the populations of native ants.  They report that the Argentine ants occupy the perimeter of the “natural areas” where native ants generally are not found.  This is a refreshing departure from the usual nativist claims that all non-native plant and animal species have negative impacts on native species.

(1)    Kevin M. Clarke, et. al., “The influence of urban park characteristics on ant communities,” Urban Ecosyst, 11:317-334, 2008

(2)    Shinsuke Uno, et. al., ”Diversity, abundance, and species composition of ants in urban green spaces,” Urban Ecosyst, 13:425-441, 2010

(3)    UC Berkeley Botanical Garden, “Plants and Their Environments”

(4)    T.E. Dawson, “Fog in the California redwood forest:  ecosystem inputs and use by plants,” Oecologia, 117-4:476-485, December 1998

(5)    Changlu Wang, et. al., “Association Between Ants and Habitat Characteristics in Oak-Dominated Mixed Forests,” Environmental Entomology, October 2001

(6)    April Boulton, et. al., “Species Richness, Abundance, and Composition of Ground-Dwelling Ants in Northern California Grasslands:  Role of Plants, Soil, and Grazing,” Environmental Entomology, February 2005

Quibbling with Jared Farmer’s “Trees in Paradise”

As we said in our most recent post, we respect Jared Farmer’s comprehensive history of eucalyptus in California as told in his book, Trees in Paradise.  However, we take issue with several of  his assessments of projects that are still on the drawing board.  Since these projects have not yet been implemented and final approval of them is still pending, for the record we will detail our quibbles in this post.

San Francisco’s Natural Areas Program

Farmer trivializes the plans of San Francisco’s Natural Areas Program to remove 18,500 trees over 15 feet tall and countless smaller trees on 1,100 acres of park property managed by San Francisco’s Recreation and Park Department.  This is his description of their plans:

“Unfortunately, poor PR and misinformed criticism initially created the impression that the greenery of Golden Gate Park would be clear-cut.  In truth, less than 5 percent of the city’s crown jewel had been rezoned.  Even so, some neighborhood groups opposed any cuts anywhere; they wanted to ‘integrate’ the blue gums instead of “exterminating” them.  (And they didn’t want to give up any place where they could take their dogs off-leash.)

Most of these trees on Mount Davidson will be destroyed if the plans of the Natural Areas Program are implemented.
Most of these trees on Mount Davidson will be destroyed if the plans of the Natural Areas Program are implemented.

Mr. Farmer has not done his homework about San Francisco’s Natural Areas Program.  The disputed tree removals are not in Golden Gate Park.  He’s right that few acres of Golden Gate Park have been designated as “natural areas.”  Most of those acres are oak woodland, which no one would dispute are appropriately designated for preservation of native species.  There aren’t many tree removals planned in Golden Gate Park.  It therefore has not been one of the areas that are disputed by critics of the Natural Areas Program. The most controversial “natural areas” are places like Mount Davidson where the plans propose to destroy 1,600 trees, including many Monterey cypresses, of which even eucalyptus-haters are fond.  Mr. Farmer chooses to defend a “natural area” that isn’t being disputed.

Mr. Farmer repeats one of the accusations of native plant advocates that critics of the Natural Areas Program “oppose any cuts anywhere.”  This is an exaggerated description of most critics of the Natural Areas Program.  Those who have been engaged in the 15-year effort to negotiate for a less destructive program have offered many compromises over the years.  The number of planned tree removals have not been reduced during that long debate.  It would be more accurate to say that supporters of the Natural Areas Program do not want any trees in the “natural areas.”

He also repeats one of the most popular “cover stories” of native plant advocates in San Francisco that all criticism of their plans originates with dog owners.  In fact, NAP is controversial among dog owners and for good reason.  There are only 118 acres of legal off-leash areas in the 3,500 acres of San Francisco’s park land.  The Natural Areas Program claimed 80% of those acres as “natural areas:”  “Approximately 80 percent of the SFRPD off-leash acreage is located within Natural Areas.”  (SNRAMP, page 5-8).  The Draft Environmental Impact Report (DEIR) for the Natural Areas Program proposes to close or reduce the size of several off-leash areas.  The DEIR provides no evidence that these areas have been negatively impacted by dogs.  It also states that all off-leash areas in the natural areas are subject to closure in the future if it is considered necessary to protect native plants.  Since NAP has offered no evidence that the proposed immediate closures are necessary, it is reasonable to assume it will offer no evidence if it chooses to close the remainder of the 80% of all off-leash areas in San Francisco located in “natural areas.”  We know from the DEIR public comments that NAP supporters demand their closure.

There are many reasons why people are opposed to the Natural Areas Program (NAP) and similar native plant “restoration” projects.  The loss of access to parks for walking one’s dog is only one of them.  It is the reason most often cited by defenders of NAP because there is little sympathy for that particular use of parks; it is a way of belittling our concerns.  In fact, this isn’t an issue in some of the most controversial “restoration” projects, such as Mount Sutro where no effort is being made to restrict access to hikers accompanied by dogs.  Yet, opposition to that project is even greater than opposition to NAP because more trees are in jeopardy.

About 50 trees were destroyed in the Interior Greenbelt, the "natural area" on Mount Sutro, in 2010
About 50 trees were destroyed in the Interior Greenbelt, the “natural area” on Mount Sutro, in 2010

The most common reason for opposition to NAP is the removal of healthy trees.  A closely related reason which motivates many others is that large quantities of herbicides are being sprayed in our parks for the purpose of killing non-native vegetation. Herbicides are also needed to prevent eucalypts from resprouting after they are cut down.  Mr. Farmer makes no mention of the huge quantities of herbicides that are required by the “restoration” projects that destroy eucalyptus.  Some critics of these projects are primarily concerned about the loss of habitat for the animals that live in and/or use the existing vegetation.

According to the US Forest Service, San Francisco has one of the smallest tree canopies in the country.  Only 12% of San Francisco is covered by a tree canopy.  Only Newark, New Jersey has a smaller tree canopy.  San Francisco is an extremely cold and windy place.  As Mark Twain famously said, he had never been colder in his life than he had been in San Francisco on a summer day.  Our trees are our protection against that wind.  Destroying them will make San Francisco an even more uncomfortable place.  Trees are an asset everywhere, but in San Francisco they are more than that.  They make an inhospitable climate livable.  The completely artificial landscape of Golden Gate Park would not exist without the windbreak of non-native trees at its Western, windward edge that enabled the transformation of barren sand dunes into a verdant park.

Golden Gate Park in 1880.  The trees are about 10 years old.  In the distance, looking south, we see the sand dunes of the Sunset District.  That's what most of Golden Gate Park looked like before the trees were planted.
Golden Gate Park in 1880. The trees are about 10 years old. In the distance, looking south, we see the sand dunes of the Sunset District. That’s what most of Golden Gate Park looked like before the trees were planted.

Despite Mr. Farmer’s inaccurate assessment of San Francisco’s Natural Areas Program, we consider his chapters about eucalyptus in California very informative and we recommend Trees in Paradise to our readers.  The controversy regarding eucalyptus in California is complex and we cannot expect to agree with everyone about every facet of the issue.  Critics of ecological “restorations” in the San Francisco Bay Area are a broad coalition with a range of opinions.  We welcome Mr. Farmer into our big tent.

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

Professor Joe McBride defends the forest on Mount Davidson

With great pleasure we share with our readers the following letter from Professor Joe R. McBride to Phil Ginsburg, the General Manager of San Francisco’s Recreation and Park Department, expressing his criticism of the plans of the Natural Areas Program to destroy 1,600 trees on Mount Davidson.

 Joe McBride is Professor of Environmental Science in the College of Natural Resources at University of California, Berkeley and an expert on urban forestry in the San Francisco Bay Area and around the world.  He is the author of many studies of urban forests, several of which he cites in his letter to the General Manager.  He is particularly expert on the failure of trees caused by extreme wind conditions. 

Professor McBride kindly accepted the invitation of several neighbors of Mount Davidson to read the plans of the Natural Areas Program (SNRAMP) for Mount Davidson and tour the mountain with them to evaluate those plans within the context of the actual conditions there.  The neighbors and all lovers of the urban forest are extremely grateful to him for his time and willingness to share his expertise and decades of experience with us to help us save this beautiful forest from being needlessly destroyed.


June 29, 2013

Mr. Phil Ginsburg
General Manager
San Francisco Recreation and Park Dept.
San Francisco, CA 94117

Re: Significant Natural Resource Areas Management Plan for Mt. Davidson Park

Dear Mr. Ginsburg,

I am writing to express my concern over the plan for removal of trees on Mt. Davidson.  This concern is based on the historical importance of the trees, their contribution to San Francisco landscape, and several specific aspects of the Significant Natural Resource Areas Management Plan for San Francisco. As a Professor of Urban Forestry at the University of California I have for many years studied plantations of trees in the city and compiled several reports for the U.S. Army, National Park Service, Presidio Trusts, and the Golden Gate Conservancy concerning the condition and management of eucalyptus, Monterey pine, and Monterey cypress stands.  My concern over the proposed management plan for Mt. Davidson is based both on my experience in urban forestry and on my experience as a citizen of the Bay Area who has enjoyed the urban forests of San Francisco for many years.  These concerns are elaborated in the following paragraphs.

The eucalyptus and Monterey cypress on Mt. Davidson were planted under the direction of the former Mayor of San Francisco, Adolph Sutro.  He was also responsible for planting other areas in the city that have subsequently become city parks.  The plantations he established have served to protect park users from the wind, provide wildlife habitat, and in some cases define the visual character of the San Francisco landscape.  They present an important historical heritage that I think should not be discarded lightly.  I found no mention of the historical significance of the Mt. Davidson forest in justification for the proposed management in the Natural Areas Resource Management Plan for San Francisco.  San Francisco might review the vegetation management plan developed by the Presidio Trust for the National Park Service to see the approach taken at the Presidio to maintain and manage historically significant forest plantations.

From a number of vantage points in San Francisco one can see several of the city’s hilltops covered in plantations of eucalyptus and Monterey cypress.  These plantations stand in contrast to the architecture that surrounds them.  They have been part of the San Francisco landscape for over one hundred years.  Eucalyptus plantations are as much a part of the California landscape as the coastal grassland, chaparral, and oak woodland plant communities for many people growing up in the Bay Area.  I did not find the visual value of the eucalyptus and Monterey cypress plantations on Mt. Davidson addressed in the plan.  I was, however, alarmed by the use of the term ”invasive forest” in reference to eucalyptus plantations.  This is a pejorative term that should not be applied to eucalyptus plantations.  I have found little evidence of eucalyptus invading adjacent areas of grassland or other native vegetation types in the San Francisco Bay areas in studies I conducted in open space areas (McBride, Sugihara, and Amme, 1987; McBride, Cheng, and Chorover, 1989; Cheng and McBride, 1992; Russell and McBride, 2003).  Comparison of photographs of Mt Davidson taken in the 1920s and 1950s show no evidence of the eucalyptus invading the adjacent grassland area (Proctor, 2006).  These photographs indicate that a stable boundary exists between the eucalyptus plantation and the adjacent grassland.  I see no justification for the establishment of a stable boundary between the eucalyptus and grassland habitats as called for in the “Site Improvements” section of the Significant Natural Resource Areas Management Plan. Mt Davidson 1885

MD 1927 RPD presentation        MD 2010 RPD

My concerns over the management plan for the eucalyptus and Monterey cypress plantation on Mt. Davidson are based on portions of the Significant Natural Resources Areas Management Plan : 5. General Recommendations, 6.2 Mount Davidson, Appendix F Urban Forestry Statements.  I am concerned with the justification for tree removal and the proposed levels (%) of trees to be removed.

Justification for Tree Removal

The primary justification for tree removal in the documents is the restoration of native habitat.  Various statements are made concerning the minimal amount of habitat within the eucalyptus urban forest.  This assumption is not supported by any data or reference to publications on this topic.  Stebbins (1976) concluded that eucalyptus plantations in the East Bay were far richer habitats for vertebrates than either redwood or Monterey forest and that they vie with ‘dry’ chaparral and grasslands in species diversity and ’attractiveness’ to vertebrate species.

The general recommendation to maintain a basal area between 200 and 600 square feet per acre is appropriate.  However, a conflict exists at Mt. Davidson where some stands (MA-1c) within the plantation currently have basal areas less than 200 square feet yet the plan proposes the removal of 82% of the trees.  I think there is a problem with the use of tree density measured in eucalyptus stands in Glen Canyon Park in developing the proposed cutting of trees at Mt. Davidson.  The point-quarter survey mentioned in Appendix F (Urban Forest Statements) of the Significant Natural Resources Areas Management Plan indicates a tree density of 353 trees per acre.  Three eucalyptus plantations measured in the Golden Gate National Recreation Area had tree densities of 50, 98, and 726 trees per acre (McBride, Cheng, and Clausen, 2004).  These numbers demonstrate the wide range of tree densities found within eucalyptus plantations in San Francisco.  I estimated the tree density in stand MA-1c from Google Earth images of Mt. Davidson to range from 24 to 33 trees per acre.  Trees in this stand average about 24 inches in diameter.  Trees of this size with a density of 33 trees per acre would have a basal area of a little over 100 square feet per acre (103.6 square feet).  No trees from the area designated MA-1c could be removed if the basal area recommendation was followed.  The same would apply to stands MA-2e and MA-2c where recommendations are for removal of 23% and 31% respectively.  I think a major shortcoming of the Plan is that lack of stand-specific tree density data.

Various sections of the Significant Natural Resource Areas Management Plan justify tree removal as a means of allowing re-vegetation with native understory vegetation.  Species commonly found in the understories of native forests and woodlands of the Bay Area are adapted to the low light intensity of these forests and woodlands.  Removing the eucalyptus overstory up to 82% as proposed for area MA-1c will expose the ground surface to light levels that most native understory plants will not be able to tolerate.  The management plan also points out that removal of eucalyptus will result in the promotion of growth of existing exotic understory species.  These will no doubt, compete with any native species for the site.  The suggestion that these exotic species will be controlled by manual removal and the use of herbicides indicates the City is prepared for a large investment of time and labor to combat these plants.  Projects to eliminate exotic understory plants at the Presidio after overstories of Eucalyptus and Monterey cypress have been removed have proved to be very expensive and only partially successful.

The Significant Natural Resource Areas Management Plan states that the proposed forest management will not result in long-term changes in recreational use of the natural areas.  I cannot agree with this conclusion.  The proposed cutting of trees will increase the windthrow and wind breakage of the remaining trees.  Trees that have grown up together in a plantation have buffered each other from the wind.  When individuals are exposed by the removal of surrounding trees they are very vulnerable to the wind.  This is well documented in studies of native forests and forests which have been thinned or opened for subdivision development (Franklin and Forman, 1987; McBride, 1999, 2002, 2003; Sinton et al, 2000).  The tree fall and wind breakage hazard to walkers using the Mt. Davidson area after the proposed tree removal and thinning would, I believe, seriously compromise the use of the area for recreational purposes.  The existing forest plantations currently contribute to the use of Mt. Davidson by walkers because of the reduction in wind velocity by the trees.  Forest plantations studied at the Presidio and at Lands End significantly reduce wind velocity and protect people walking from uncomfortable wind chill effects (McBride, 2002; McBride and Leffingwell, 2003).  Choice of coastal bluff trails at the Sea Ranch made by walkers is often dependent on the amount of protective cover from the wind provided by areas planted with Monterey cypress.  The exposure of Mt. Davidson to winds from the ocean will result in a less pleasant recreational experience if trees are removed.

There is an assumption in the Significant Natural Resource Areas Management Plan that minimal impact will occur to species such as hawks and owls as a result of tree removal because the overall acreage of the forest will remain high.  This is not a valid assumption for two reasons.  First, hawks and owls choose specific trees for nesting and perching.  These trees are chosen on the basis of their position in a forest stand and the structure of the tree.  Nests are used by some species year after year so that the removal of a nesting tree can present a major problem for the specific bird using the tree.  Avoiding the cutting of nest trees during the nesting season, but felling of these trees after the nesting season is a major impact that should not be part of the management plan.  It is also important to not remove trees surrounding nesting trees.  Most recovery plans for rare and threatened tree nesting birds require a protected area with a minimum radius of 300’ around a nesting tree.  No trees can be removed within this zone.

In the “Site Improvements” section of the Significant Natural Resource Areas Management Plan it is suggested that the management proposals will improve the health of the eucalyptus forest.  It is suggested that tree thinning will promote a more healthy forest.  This certainly is true in densely stocked forest stands, but I did not observe conditions in the eucalyptus plantations where tree density required thinning.  Several standing dead eucalyptus trees are present at Mt. Davidson, but the standing dead trees I examined had all been girdled.  It was evident that some individual or individuals have had a vendetta against eucalyptus trees and had girdled trees in the past.  I did not see any indication of natural mortality in the overstory of the plantations.  Concern has been raised over the potential for ivy to grow up the trunks and eventually smother the eucalyptus trees.  I have not observed this taking place in eucalyptus plantations in the East Bay.  Ivy (English and Algerian) may climb the trunks of trees, but in my experience it does not have the capacity to grow over the smaller limbs and branches.  There were a couple of eucalyptus snags completely covered by ivy at Mt. Davidson, but these snags were the result of girdling of the trees snags, not the growth of ivy.  The ivy, Cape ivy, and the Himalayan blackberry in the under story of the eucalyptus plantation are restricting establishment of eucalyptus seedlings.  I do not see this as a problem at the current age of the plantation.  Perhaps in another hundred years an examination of the plantation could establish the need for regeneration.  At this time in the life of the Mt. Davidson plantation I do not consider the lack of regeneration a problem.  Removal of the exotic understory species at this time would reduce the habitat quality of the plantation, especially the removal of Himalayan blackberry that provides a valuable food source for many species.

I conclude that the Significant Natural Resource Areas Management Plan for the removal and thinning of different portions of the eucalyptus plantation on Mt. Davidson is not justified.  The plantation serves an important role in the history and visual characteristics of the city.  Trees and the existing understory provide habitat for wildlife and wind protection for walkers.  The justifications for the management prescriptions have not been properly developed.  Furthermore, the cost of removal of the trees seems unjustified in view of other priorities in the San Francisco budget.

Joe R. McBride

CC:  Mayor Edwin M. Lee
City and County of San Francisco Board of Supervisors
San Francisco Recreation and Park Commission
San Francisco Planning Commission
San Francisco Urban Forestry Council
Park, Recreation and Open Space Advisory Committee
Bill Wycko, Environmental Review Officer (Case No. 005.1912E)

Literature Cited

Cheng, S. and J.R. McBride. 1992. Biological Assessment of Mills Creek Riparian Corridor. Report to the California Department of Parks and Recreation. Monterey Co., CA 89p.

Franklin, J. and R.T.T. Forman. 1987. Creating landscape patterns by forest cutting: ecological consequences and principles. Landscape ecology 1:5-18.

McBride, J. R. 1999. Identification of areas of high windthrow potential at the Sea Ranch. McBride and McBride. Consulting Landscape Ecologists. Berkeley, CA.

McBride, J. R. 2002. Presidio of San Francisco Wind Study, First Phase.  Report to the Presidio Trust. San Francisco, CA. 35 p.

McBride, J. R. 2003. Re-evaluation of the windthrow problem at The Sea Ranch. Report to the Planning Department. The Sea Ranch, CA. 6 p.

McBride, J. R. and J. Leffingwell. 2003. Effects of Forest Stands on the Microclimates of the Presidio. Report to the Presidio Trust. San Francisco, CA. 27 p.

McBride, J.R., N. Sugihara and D. Amme. 1987. Vegetation Assessment. In: D. Boyd (Ed.)  Environmental assessment for Eucalyptus Removal on Angel Island. California Dept. Parks and Recreation, Sacramento, CA. pp 23-45

McBride, J.R., S. Cheng and J. Chorover. 1989. Natural Resources Assessment – Jack London State    Park. Calif. Dept. Parks and Recreation. Sacramento, CA. 432 p.

Proctor, J. 2006. San Francisco’s West of Twin Peaks. Charleston, SC: Arcadia Publishing.

Russell, W. H. and J. R. McBride. 2003. Landscape scale vegetation-type conversion and fire hazard in the San Francisco Bay Area open spaces. Landscape and Urban Planning 64:201-208.

McBride, J. R. , S. Cheng, and J. Clausen. 2004. Vegetation management Strategy for Lands End, GGNRA. Report to the Golden Gate National Park Conservancy. San Francisco, CA

Sinton, D. S. et al.  2000. Windthrow disturbance, forest composition, and structure in the Bull Run Basin, Oregon. Ecology 81(9): 2539-2556.

Stebbins, R. 1976. Use of habitats in the East Bay Regional Parks by free-living vertebrate animals. August 1975. In “Vegetation Management Principles and Policies for the East Bay Regional Park District”.  East Bay Regional Parks District. Oakland, CA.