“San Francisco’s Natural History”: A mixed bag of fact and fiction

Million Trees breaks its self-imposed silence to bring you this book review of San Francisco’s Natural History:  Sand Dunes to Streetcars, by Harry G Fuller.  It was frustrating to read this book because I had high expectations that I would like it and learn from it.  And to some extent, I did.  However, the book also repeats old myths about eucalyptus that have long ago been debunked and fabricates a new myth.  It also supports deadly and dangerous “restoration” projects in the Bay Area without acknowledging the loss of wildlife they cause. On the other hand, historical records of San Francisco’s natural history seem to be accurately reported by Fuller and he paints the picture of pre-settlement San Francisco as drifting sand dunes and treeless grass and chaparral. 

Persistent myths about eucalyptus

Fuller says, “There is evidence…that eucalyptus trees may be deadly to both wintering birds and monarch butterflies…At the same time the trees provide necessary shelter, their chemical make-up and their sticky leaves may prove deadly.”

Hummingbird in eucalyptus flower. Courtesy Melanie Hoffman

Fuller does not provide the “evidence” for this statement, so we must speculate about what he means.  It seems likely that he is repeating the 23-year old claim that eucalyptus kills birds by suffocating them with their sticky nectar when eucalyptus blooms in winter months. (Neither the nectar, nor the leaves of eucalyptus is sticky.)  A local birder reported seeing two dead birds in eucalyptus forest over the course of his long career as a serious birder and parlayed those isolated observations into the generalization that birds are killed by eucalyptus trees.  Decades of research was required to put that accusation to rest. (1, 2) Officially, the myth died when the California Invasive Plant Council updated the classification of eucalyptus in 2015.  The claim that eucalyptus kills birds was deleted from Cal-IPC’s revised classification. It was aggravating to see this claim repeated by Mr. Fuller in his book, which was published in 2017.

Fuller’s claim that eucalyptus is also deadly to monarch butterflies is unprecedented.  I have heard innumerable stories about the bad habits of eucalyptus, but I have never heard that eucalyptus kills monarch butterflies.  You won’t find that accusation anywhere on the internet and you won’t find it anywhere in the scientific literature.  I confirmed with Art Shapiro, Distinguished Professor of Ecology and Evolution at UC Davis and author of Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions, that he had never heard that claim either. 

In fact, available empirical evidence contradicts that claim. Eucalypts are the preferred trees for over-wintering monarchs in California:  “Three types of trees were used most frequently by roosting monarchs:  eucalyptus (75% of the habitats primarily Eucalyptus globulus), pine (20% of the habitats primarily Pinus radiata), and cypress (16% of the habitats Cupressus macrocarpa).  Twelve other tree species were identified…with a combined prevalence of only 10%.” (3)  Monarchs migrate down the coast of California during the winter months, when eucalyptus is flowering at a time when there is little else blooming in California.  They are an essential source of nectar during the monarch migration. 

Fuller says, “The eucalyptus’s natural herbicides prevent many other plants from growing beneath their canopy.”   

This is another accusation that has been repeatedly disproven by empirical research.  The eucalyptus forest is as biodiverse as native oak woodland (4).  The 2015 revision of the California Invasive Plant Council assessment of eucalyptus deleted previous mention of the allelopathic (the scientific term for “natural herbicide”) properties of eucalyptus.  A rigorous study at Cal Poly concluded, “In these experiments, we found that germination and seedling growth of the species tested were not inhibited by chemical extracts of blue gum foliage, either at naturally-occurring or artificially concentrated levels.” (5)  This study was presented by its author at the most recent conference of the California Native Plant Society, which should establish its credibility with native plant advocates.

Presentation at conference of California Native Plant Society

Fuller says in support of his “natural herbicide” theory, “You never see moss or lichen on a healthy eucalyptus trees.”

We don’t see moss or lichen on eucalyptus tree trunks because the thin, papery bark on the trunk sloughs off annually, leaving the trunk bare.  Moss and lichen grow slowly on tree trunks in the bark that remains on the tree throughout the tree’s life.

Spartina (aka cordgrass) eradication

Ironically, Mr. Fuller prefaces his strong support for cordgrass eradication with this admonition:  “Do not forgive ignorance, please.”  Then, he displays profound ignorance of the consequences of cordgrass eradication in the San Francisco Bay Area.  Fuller is a professional birder, yet he is seemingly unaware of the fact that the eradication of cordgrass has nearly wiped out the population of endangered Ridgway Rail (formerly Clapper Rail) in the Bay Area.  He is also unaware of the huge quantities of herbicide that have been used to eradicate cordgrass.  Elsewhere in his book, he expresses concern about pesticides and other forms of pollution, yet in the case of cordgrass eradication he turns a blind eye.  (6)

Pesticide Application Notice, Heron’s Head, 2012

Eradication of mice on Farallon Islands

Mr. Fuller also supports plans to eradicate mice on the Farallon Islands:  “The latest effort to return the Farallones to a more natural preserve is an attempt to remove all the house mice.”  He is either unaware of plans to aerial bomb rodenticides on the Farallons to kill the mice or he chooses to use the euphemism “remove” to avoid the issue.  Elsewhere in the book, he mentions that rodenticides used in Golden Gate Park to kill rats also killed Great Horned Owls that ate the dead or dying rats.  He seems to understand that non-target birds are killed by rodenticides, yet he apparently supports the use of rodenticides on the Farallons, a national marine sanctuary.  (7)

Farallon Islands, NOAA

A Cautionary Tale

Mr. Fuller displays a sincere concern for the wildlife of San Francisco throughout his book.  He also acknowledges the very real threats of climate change and pollution for the future of the environment in the Bay Area.  I do not doubt his sincerity and I believe he has written a valuable book that is unfortunately damaged by his uncritical acceptance of inaccurate versions of several important environmental issues in the Bay Area.  I believe Mr. Fuller has been a victim of “incestuous amplification” in his acceptance of these myths.  Let that be a lesson to all of us to look deeply at every issue and to verify any tale you are told by an amateur or someone with a vested interest in those issues, such as employment. 

I cannot recommend this book to anyone who is not prepared to read it critically.  If you don’t already have a basic knowledge of the natural history of San Francisco you could easily be led astray by baseless rumors. 

  1. https://milliontrees.me/2013/11/05/eucalyptus-trees-do-not-kill-birds/
  2. https://milliontrees.me/2014/07/26/birds-and-butterflies-in-the-eucalyptus-forest/
  3. Dennis Frey and Andrew Schaffner, “Spatial and Temporal Pattern of Monarch Overwintering Abundance in Western North America,” in The Monarch Butterfly Biology and Conservation, Cornell University Press, 2004.
  4. https://milliontrees.me/2011/02/04/biodiversity-another-myth-busted-2/
  5. https://milliontrees.me/2018/02/06/highs-and-lows-of-the-2018-conference-of-the-california-native-plant-society/
  6. https://milliontrees.me/2014/06/02/spartina-eradication-herbicides-are-their-dirty-little-secret/
  7. https://milliontrees.me/2014/01/10/the-mouse-eradication-project-on-the-farallon-islands-the-con-in-conservation/

11 thoughts on ““San Francisco’s Natural History”: A mixed bag of fact and fiction”

  1. Thank you for the blog. I live in the Chicago area and the presettlement restorationists are thriving due to the Great Lakes Restoration Initiative and other federal grant programs. In my opinion, it’s all about the money and the science is twisted to create a bureaucracy tied to political power brokers.After thousands of trees are cut down, the prairie is built, then the leveled land is ready for development in later years. The Cook County Forest Preserve(Chicago area) is logging  it forests for prairie and campgroundd and I think they are tied in with the for profit lumber industry.Carolyn Marsh

    1. I am familiar with the Chicago projects because the first book I read about “restoration” ecology was about them: Restoring Nature, edited by Gobster and Hull. I published an article on Million Trees about those projects in 2011: https://milliontrees.me/2011/03/05/chicago-another-example-of-destructive-restorations/. The article explains the similarity of the Chicago project with those in the San Francisco Bay Area. I have met some of the opponents of the projects at a conference. You are not alone in your opposition.

      Although I agree that money is a factor in the proliferation of these projects, I don’t see development as their ultimate goal. I believe the primary goal is job creation. These projects are now employing about 200,000 people in the US. They create jobs at all skill levels, from highly educated authors of the plans and environmental impact evaluations to low skilled jobs spraying herbicides and killing plants. Virtually all of the money is public money, which means our tax dollars are the source. Until that fund source dries up, these projects will continue because the task is never done. It is essentially a form of gardening, not “restoration.” Gardening is never done.

  2. With you on all points until you got to the Farallons. Remember, island ecosystems are different and operate on different principles than mainland ecosystems. Rodenticide application is a terrible idea on the mainland and causes a great deal of harm, spreading through the ecosystem and accumulating in predators. (The newer generation of rodenticides such as Brodifacoum are worse than the old ones in this regard.)

    On islands, however, it has been repeatedly demonstrated that rodenticide can be used with little ill effect, because the ecosystems usually do not include rodent predators. (Which of course is why the rodents proliferate to such a degree in the first place.) If there are no owls, foxes, etc around to prey on the poisoned rats or mice, then the poison tends not to move through the ecosystem. This isn’t just theory, it has been show to work in several spectacularly successful efforts on remote islands.

    With regard to the Farallons, then, the question is whether that ecosystem presents the conditions that are likely to produce a similarly successful outcome. From what I have read, they do, which is why the program was proposed.

    Like you, I was initially extremely skeptical about this whole idea. Everything I knew about poisoning mammals led me to believe it was always and everywhere a bad idea. But once I looked into the scientific evidence and understood how different an isolated island ecosystem is from a mainland ecosystem, it began to make sense.

    1. Tim says, “….it has been repeatedly demonstrated that rodenticide can be used with little ill effect…” Actually, it has been repeatedly demonstrated that these projects on islands have killed non-target animals and polluted the marine environment. Here are examples of the damage done by these projects:
      1. In the case of Rat Island, off the coast of Alaska, no monitoring was planned after the aerial bombing of 46 metric tons of anti-coagulant rodenticide to kill rats. However, neighbors of Rat Island demanded an investigation when they saw dead birds and animals floating in the vicinity of the island after the project was done. That investigation (https://drive.google.com/file/d/0BwdOUBgcb_baeXlYTzZ0X05hWFU/view) was done by USFWS Law Enforcement. The investigation found that the manufacturer’s recommendations regarding dosage were exceeded, that instructions to collect dead rats so they would not be eaten by birds were not followed, and that hundreds of birds died, including many legally protected bald eagles. The investigation was not done until 7 months after the project was completed. We should assume that the number of dead animals found would have been greater if the investigation had been done promptly after the project was completed.
      2. In the case of Palmyra Island, off the coast of Hawaii, the scientific study conducted after the aerial bombing of rodenticides reported, “We documented brodifacoum [rodenticide] residues in soil, water, and biota, and documented mortality of non-target organisms. Some bait (14–19% of the target application rate) entered the marine environment to distances 7 m from the shore. After the application commenced, carcasses of 84 animals representing 15 species of birds, fish, reptiles and invertebrates were collected opportunistically as potential non-target mortalities. In addition, fish, reptiles, and invertebrates were systematically collected for residue analysis. Brodifacoum residues were detected in most (84.3%) of the animal samples analyzed. Although detection of residues in samples was anticipated, the extent and concentrations in many parts of the food web were greater than expected.” (William Pitt, et. al., “Non-target species mortality and the measurement of brodifacoum rodenticide residues after a rat (Rattus rattus) eradication on Palmyra Atoll, tropical Pacific,” Biological Conservation, May 2015, 36-46)
      Tim says, “…it has been show to work in several spectacularly successful efforts on remote islands.”
      The most damning evidence of all is that after killing untold numbers of animals, including those not meant to be killed, and poisoning the environment with a deadly toxin that bioaccumulates and persists in our bodies, the rat population often returns to pre-project levels within a few years. Here are examples of such failures:
      1. Henderson atoll in the Pacific is an example of such a failure. Eighty tons of rodenticide pellets were aerial bombed on Henderson in 2011. Apparently, at least two rats survived, one presumably male and one presumably female. Within a few years the rat population had returned to pre-projects levels of 50,000 to 100,000 rats.
      2. The failure of the extermination attempt on Henderson is not an isolated incident. (https://www.nationalgeographic.com/news/2016/04/160419-rats-exploded-poison-henderson-island/) Lehua is one of the Hawaiian islands on which extermination was attempted and failed. An evaluation of that attempt was published in 2011 to determine the cause of the failure so that a subsequent attempt would be more successful. That evaluation included this report on the success of similar attempts all over the world: “An analysis of 206 previous eradication attempts against five species of rodents on islands using brodifacoum or diphacinone is presented in an appendix to this report. For all methods, 19.6% of 184 attempts using brodifacoum failed, while 31.8% of 22 attempts using diphacinone failed.” Brodifacoum and diphacinone are both anti-coagulant rodenticides. Diphacinone is considered less toxic and less persistent than brodifacoum.
      Tim says, “If there are no owls, foxes, etc around to prey on the poisoned rats or mice, then the poison tends not to move through the ecosystem.”
      This is not an accurate statement for several reasons. First, owls on the Farallons are the primary targets of the eradication project. Secondly, the dead and dying mice are eaten by some bird species, especially gulls. Thirdly, thousands of pink poison pellets are scattered on the ground and are directly eaten by the birds who do not know that they are poison. Fourthly, the poison pellets often drop in the ocean when aerial bombed from helicopters. Rodenticide is just as deadly on an island and in the ocean as it is on land.
      Tim says he “looked into the scientific evidence.” I suggest he look again. For the moment, the Farallons project is on hold because the California Coastal Commission would not endorse the project after receiving over 600 public comments from many municipalities in California and the Oceanic Society. The project will require many permits in order to implement. For the moment, those permits are in doubt.

      1. Nobody argues these projects are risk-free. The question is whether the potential ecosystem benefits justify those risks.

        An 80% success rate doesn’t sound that bad, especially when you consider the consequences of just letting the rodents have their way: extinctions.

        The basic assumption is that it’s worth killing some non-target animals (species that are not at risk) in order to prevent the extinction or extirpation of endangered species. Do you challenge that assumption?

        1. There are no rats on the Farallons. The project proposes to eradicate mice that are not eating birds, chicks, or eggs. The project blames a small group (8-10) of burrowing owls for eating the chicks of Ashy storm petrel. The project claims that the burrowing owls will quit visiting the Farallons if their preferred prey—mice—are eliminated. The owls are more likely to be killed by the poisoned mice. If they aren’t killed, they are likely to eat even more chicks if that’s the only available food.

          Both burrowing owls and ashy storm petrels are a threatened species. They are not endangered. They are equally rare.

          Letting the mice “have their way” will not kill more birds or marine mammals. Dumping 1.4 tons of rodenticides will undoubtedly kill birds and animals that are not presently in danger. Therefore the “potential benefits” do not outweigh the risks. Yes, I do challenge your assumption that risks are outweighed by benefits in this project.

          1. OK, fair enough – that assumption should always be challenged. (To be pedantic, it isn’t _my_ assumption; it’s what I perceive to be the underlying assumption behind all such proposals.) Scientists should always explicitly state all assumptions and provide justifications for them, so they can be challenged like this.

            Perhaps I misunderstood – I thought you were against all such projects. If that’s not the case, then I apologize for arguing with you. I don’t have a strong opinion either way on this particular proposal. The Farallons are neither remote nor isolated and are famous for the diversity of birds that stop there during migration, conditions that would seem to increase the risks.

          2. Thank you. I hope our dialogue will help readers get the point of the article on which you have commented. The cautionary tale is that we owe it to ourselves, the environment, and the animals who live in it to critically examine proposals to kill plants and animals with poisons. Is the project necessary? Is it more beneficial than the damage it will do?

            We are living in an era in which sound and fury obscures truth. Environmental policy is not immune from the extremism that pervades civic discourse.

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