“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/