“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/

Putting another eucalyptus myth to rest: Lifespan of blue gum eucalyptus

When the native plant movement began in earnest, about 25 years ago, its proponents weren’t expecting blowback from those who value the existing landscape.  As far as they were concerned, the trees had to be destroyed solely because they “don’t belong here.”

When they started destroying our predominantly non-native urban forest, they learned that it wasn’t going to be as easy as they thought.  They began to defend their destructive projects with cover stories to convince the public who didn’t share their devotion to native plants that it is necessary to destroy non-native trees because they are a threat to public safety and to wildlife.

One by one, we have debunked the myths that were used to justify the destruction of our urban forest:

  •  

Great horned owl in eucalyptus. Courtesy urbanwildness.org

About 20 years ago, one of the first myths was that eucalyptus trees kill birds. It is an absurd claim that is completely unsupported by reality.  With a lot of careful research, we were eventually successful in convincing the public that birds are not harmed by eucalyptus.  In fact, many bird species are dependent upon the trees for safe nesting and winter nectar.   That myth is dead.

  • The claim that eucalyptus and other non-native trees are more flammable than native trees was a powerful narrative that was more difficult to kill. As wildfires have increased in frequency and intensity in California, that claim is no longer credible because every wildfire occurs in native vegetation.  Again, this myth was eventually disproved by reality.
  • More recently, we have finally put to rest the claim that “nothing grows under eucalyptus.” This myth was based on a theory that eucalyptus emits allelopathic chemicals that prevent the growth of plants in the eucalyptus forest.  Thanks to a recent, rigorous study done at Cal Poly, we know with confidence that the allelopathy story is another myth.

It was not surprising that the nativists, having run out of bogus justifications, created a new narrative.  In parks that the East Bay Regional Parks District had been planning to thin, we began to see clear cuts.  When we inquired about why it was necessary to destroy ALL of the trees, we were told they were hazardous.  Then, in the minutes of a meeting of East Bay Regional Park District Park Advisory Committee , we saw the claim that eucalyptus lives only 50-60 years.  Simultaneously, this claim was made in San Francisco by proponents of destroying all eucalyptus trees there.

We eventually tracked down the source of that lifespan estimate to a website called SelecTree, which originally said that the longevity of blue gums is only 50-150 years.  We knew that isn’t an accurate estimate because of how long blue gums live in Australia and how long they have already lived in California.  We provided that information to the authors of SelecTree and were able to get the estimate corrected to “greater than 150 years.”  That’s not nearly long enough, but it is the longest lifespan estimate available on that website and it corresponds with many other trees, including native Coast Live Oak.

In the process of researching the lifespan of eucalyptus, we learned several interesting stories about blue gums that have lived in California for 150 years and are still going strong.  We would like to share some of this information with our readers today.

Blue gum eucalyptus lives in Australia 200-400 years

Blue gum eucalyptus and all other species of eucalyptus are native to Australia.  They were brought to California shortly after the Gold Rush of 1849.  Since they haven’t been in California 200 years, we don’t know how long they will live here.  But how long they live in Australia is obviously relevant to answer that question because longevity is specific to tree species.  We can expect some variation by climate, but not much, and the climate of Australia is similar to the climate in California with wet, mild winters and hot, dry summers.

We know that blue gums live in Australia about 200-400 years because Australian scientists tell us that:

Growth Habits of the Eucalypts by M.R. Jacobs, (Institute of Foresters of Australia, 1955, 1986): Blue Gum eucalyptus lives in Australia from 200-400 years, depending upon the climate.” In milder climates, such as San Francisco, the Blue Gum lives toward the longer end of this range.

That reference was corroborated by John Helms, Professor Emeritus of Forestry at UC Berkeley and an Australian who said in response to our question about blue gums in California, “Blue gums would commonly live for 200 – 400 years, although I presume that some might live longer.”

We also asked the Australian National Botanic Gardens.  They said, “It’s possible that the average lifespan of a native species growing in the wild in Australia would differ to the average lifespan of the same species introduced in northern California, since introduced plants can often “escape” their natural predators when such introductions occur.”

In other words, since eucalyptus trees have more predators in Australia than they do in California, we should expect them to live longer here.  This is called the “predator release” hypothesis.  Ironically, that hypothesis is used by nativists to support their claim that eucalyptus is invasive in California.  (California Invasive Plant Council rates the “invasiveness” of blue gum as “limited.”)  It’s only logical to apply that hypothesis to the question of how long blue gums will live in California.

Many healthy blue gums in California are 150 years old

However, using actual experience in Australia to predict the future of blue gums in California requires some speculation.  Therefore, we turned to the question of how long they have lived in California for guidance.  We found several interesting local stories about blue gums that were planted in California 150 years ago and remain healthy and vigorous today.

There are many examples of blue gums being planted as street trees in California about 150 years ago.  One of the most well-known examples is the city of Burlingame on the San Francisco peninsula. When the City was founded in the 1870s, John McLaren was hired to plant trees to provide a much needed windbreak because the City was nearly treeless, as was the entire San Francisco peninsula.  McLaren planted over 500 eucalyptus (blue gum and manna) along the main highway through Burlingame, along with a row of English elms.  John McLaren was subsequently hired by the city of San Francisco, where he planted many more eucalypts while serving as superintendent of the parks department for 53 years.

The eucalypts in Burlingame are still thriving, but the elms have been dead for about 60 years.  SelecTree says the longevity of English elms is “greater than 150 years,” the longest category of longevity published by SelecTree and completely open-ended.

El Camino Real bordered by Eucalyptus trees. Burlingame, SF Bay area, California, USA

The people of Burlingame greatly value their eucalypts and designated them as “heritage trees” in 1975 under a local ordinance.  That local legal status did not protect them from several attempts by Caltrans to destroy the trees.  The people of Burlingame came to the defense of the trees and were eventually successful in getting permanent legal status to protect 2.2 miles of the trees.  That section of El Camino Real in Burlingame lined with eucalyptus was listed on the National Register of Historic Places in 2012.

Caltrans is now working cooperatively with the people of Burlingame to address safety concerns while “also keeping an eye to the prized grove of eucalyptus trees along the street.”  A task force was formed in 2018 to discuss these issues.  The City of Burlingame remains committed to the preservation of these trees, which suggests that they have a future there. (1)

The life span of street trees is generally much shorter than trees planted as forests because they are subjected to more wind and polluted air of heavily traveled roads, such as El Camino Real.  Although blue gums have passed the test of those challenging conditions with flying colors, they have not been planted as street trees for decades.  Their out-sized scale makes them unsuitable for that purpose.  If blue gums can survive as street trees on heavily traveled roads, they can surely survive longer in the protection of their neighbors in forests.

Blue gums at Stanford University

The blue gums on the campus of Stanford University are another example of 150 year-old blue gums that are very much alive.  Although blue gums were included in the campus landscape design of Frederick Law Olmsted in the 1880s, many of the blue gums actually predate his design:  “Several hundred mighty giants on the campus date back prior to 1870 when Leland Stanford acquired several farm properties, one of which already had avenues of gum trees.  They are mostly Tasmanian blue gums and red gums with a sprinkling of manna trees.”

Eucalyptus on Stanford campus

That description of the old blue gums was written in 1971.  The trees are still alive and well.  I worked on the Stanford campus for 10 years and walked among those trees at every opportunity.

An even older Olmsted design in Oakland

Mountain View Cemetery in Oakland, California was designed by Frederick Law Olmsted in the 1860s.  Like most of the East Bay, the site was treeless.  Olmsted’s design was an eclectic collection of mostly non-native trees, including blue gums.  The cemetery is on steep, windward facing hills, where the windbreak provided by blue gums is particularly valued.

Eucalyptus in Mountain View Cemetery, planted on an unirrigated windward facing hill. 2017

Update:  This venerable old giant was destroyed in September 2018, along with about 150 other trees of different species, including oaks. I did not protest before or after the trees were destroyed because they were on private land and their removal makes way for more grave sites. However, I will mourn its loss.

Olmsted designed a straight avenue through the cemetery lined with magnolia trees.  Many of the magnolia trees have died and those that remain are in poor condition.  SelecTree claims that the life span of Southern magnolia is “greater than 150 years,” which is contradicted by our local experience.

The current owner of the cemetery destroyed many of the blue gums about 5 years ago, in the middle of the extreme drought.  He replaced many of the blue gums with redwoods.  The redwoods are irrigated and are still surviving.  I did not object to the removal of the blue gums because they are on private property.  I confine my advocacy to healthy trees on public land.

Long live the blue gums!

SelecTree has revised its listing of blue gum longevity based on the information we provided.  The myth that our blue gums are dying of old age will not die as easily.  We will have to repeat this information many times and in many different venues, just as we did for every other myth.  If and when that particular myth dies, we can be sure there will be another waiting in the wings.  Ideologies stubbornly persist, despite contradictory evidence.  And yet, we just as stubbornly persist in defense of our urban forest.


(1) Here is the public record, on which my report about the trees in Burlingame is based:

Catalina Island: Island ecology and restoration

Catalina Island is dear to my heart because of several childhood vacations there.  It was thrilling to return after 60 years and find it unchanged from my memories.  Avalon, the small town of about 3,500 people, is still a quaint collection of little wooden shacks, painted bright colors.  But as an adult, my recent visit to Catalina was broader and encompassed the entire island, which was unknown to me as a child.  That broader perspective on Catalina is my focus today. (1)

Avalon Harbor, Catalina Island. Creative Commons

Catalina is one of the Channel Islands off the coast of Southern California.  It rose from the ocean about 5 million years ago as the result of geologic processes lifting the ocean floor as tectonic plates collided.  Like other oceanic islands (as opposed to those that broke off from continents), it was composed of barren rock for thousands of years.  It took thousands of years to build soil needed to support plants.  Then it took thousands of years to establish plants from the seeds blown in the wind from the mainland, brought by birds in their stomachs or adhered to their feathers and feet, or brought by waves carrying plants in storms.  When plants gained a foothold, the island was able to support insects brought by wind and waves.

The process of populating Catalina with plants and animals accelerated with the arrival of American Indians about 10,000 years ago.  Foxes were probably brought to Catalina by the Indians and oaks probably arrived as acorns brought by the Indians.  Archaeological remains of Indian settlements indicate that there were as many as 2,500 Indians living on Catalina, using only the food and materials available on the island or the surrounding ocean.

Most of the plant and animal life on Catalina came from the mainland of California, only 22 miles away from the island.  When plants and animals evolve in isolation from their ancestors, their gene pools gradually drift apart and are eventually distinct species.  That’s why there are about 60 plant and animal species on Catalina that are endemic, meaning that they exist only on Catalina.  This process of diverging evolution from mainland ancestors to unique island species is typical of all island ecosystems.

Europeans arrive on Catalina

Catalina was visited by Spanish explorers for the first time in 1542 and again in 1602.  Although their visit was brief, it was fatal because they brought diseases to which Europeans were immune and the Indians were not.  Most of the Indians on the island were killed by those diseases, a scenario that played out all over the New World in the 16th and 17th centuries.

Europeans tried to establish communities on the island in the 19th century, but their economic ventures were not successful.  They brought sheep, cattle and goats.  But there wasn’t sufficient forage for their herds and supplementing their diets by growing hay wasn’t economically viable.  They tried mining, but found little of value.  They introduced animals for hunting, such as mule deer and pigs.

Towards the end of the 19th century, Europeans made their first attempt to turn the island into a tourist destination.  The first effort ended when the entire town of Avalon burned in a fire in 1915.  That fire set the stage for the final chapter in the development of the island.  William Wrigley Jr. was able to purchase the entire island in 1919 in the “fire sale” that resulted in a bargain price.

The Wrigley Era on Catalina

William Wrigley Jr. made his fortune manufacturing and selling chewing gum.  He had the means to indulge his passion for the island, which he envisioned as a recreational paradise.  He built a magnificent Art Deco casino in Avalon that opened in 1929 and turned the town of Avalon into a famous destination that attracted celebrities as well as one million visitors each year, arriving on the huge steamers Wrigley built to bring them to Catalina.

Bison on Catalina Island. Creative Commons

Many movies were made on Catalina and movie stars were frequent visitors to the island.  One of the movies brought bison to the island to feature in their western themed story.  The bison herd grew and eventually became another challenge to the survival of vegetation on the island.

The conservancy era on Catalina

When William Wrigley died, his heirs changed the direction of the island’s development.  The island could have continued to grow into a tourist destination, but in 1972 Wrigley’s heirs decided that nearly 90% of the island would be turned into a nature reserve.  The Catalina Island Conservancy was born.  Access and development on conservancy land is restricted.

Catalina Island Conservancy land.

The conservancy has made big investments in restoring the island’s ecosystems and protecting endemic plant and animal species.  Sheep and cattle were removed, which wasn’t difficult because those enterprises had largely failed.  Feral pigs and goats were much harder to round up and were killed by hired sharp shooters.  The extermination of the pigs and goats was as controversial on Catalina as it has been on other Channel Islands.  A decade later, “with the quality of the island habitat rebounding and increased ecotourism revenue being realized by island businesses, the bitterness surrounding the pig and goat eradication is subsiding.  Conservation, contrary to popular belief, is not one long group hug.  This stuff can be hard.”  (1) Indeed, “restorations” in the San Francisco Bay Area have caused one pitched battle after another for over 20 years.  They might have been less heated battles if all opinions had been treated with equal respect, as they seem to have been on Catalina Island.

The population of mule deer is being controlled with hunting licenses.  Most of the herd of 600 bison was given to an Indian reservation in South Dakota.  The remaining herd of 150 is being controlled by a contraception program.  Maintaining the small bison herd is considered a concession to their popularity with residents and tourists on the island.

Island fox. Catalina Island fox is a sub-species of the Island fox on other Channel Islands. USFWS

The Catalina Island Fox, an endemic species, was nearly wiped out by distemper virus introduced by a castaway raccoon.  Fortunately, conservancy staff figured out why the population dwindled to only 100 foxes in time to save the foxes from extinction.  A captive breeding and vaccination program returned the fox population to over 1,500 animals in 2011.  A captive breeding program for the island’s bald eagles has also restored their population.

Invasive species

Like most restorations, the Catalina Island Conservancy is concerned about invasive species.  However, their approach to controlling non-native plants is less extreme than many similar projects.  They consider a species of broom (Genista linifolia) their highest priority for eradication.  Although they have tried and will continue trying to control it they acknowledge that it may not be possible.

Genista linifolia is native to the Canary Islands.  It was introduced to Catalina over 100 years ago when it was used to landscape the Saint Catherine Hotel when it was originally built in 1900.  The conservancy launched the Avalon Grasses Initiative in 2016 to prevent similar introductions of grasses that have a high potential to spread on the wind—such as pampas and fountain grass–from gardens in Avalon to conservancy wildlands.  Conservancy staff quietly patrol the gardens in Avalon, looking for these exotic grasses.  When they find them they approach the property owner with their proposal to remove them and replace them with native plants.  The 20 property owners who have agreed to this proposal express satisfaction with the substitution.  This strategy seems to treat the property owners with respect. (2)

Over 200 species of non-native plants live on the island, but the conservancy considers only 35 of the species a problem.  They describe their approach to non-native plants:

“The Catalina Island Conservancy has developed a thoughtful and comprehensive set of strategies for dealing with invasive plants.  First, they realized that not all introduced plants are invasive and some are less likely to outcompete native species.  Those considered invasive were ranked according to the magnitude of the problems they present, including how widespread they are, how fast they can spread and how damaging to the local native species they are.  On the basis of this information, each highly ranked invasive species is being treated with the purpose of reducing its impact on the native communities, reducing its spread or eliminating the threat.” (1)

They acknowledge that “topical chemical treatments” are one of the methods they use to control plants they consider invasive, but details of their pesticide use are not available to me.  The conservancy is a private entity that is not subject to public record laws.

My eucalyptus litmus test

Catalina Ironwood is one of few species of native trees on the Island. It is an endemic species, like most of the native trees on the island.

There are few species of native trees on Catalina Island and their population on the island is also very small.  Therefore, most trees on the island were introduced.  Eucalyptus (mostly Red River gum and blue gum) were introduced to the island in the 1920s by the Wrigley family for a variety of reasons:  aesthetic, shade, wind break, erosion control of road cuts, etc.  Eucalypts are still there and they are the predominant tree species on the island.  Eucalyptus is found throughout the island, including the town of Avalon and several places on conservancy land, where they were planted.

 

The bark of Catalina ironwood is shredded, similar to the peeling bark of Blue Gum eucalyptus

The conservancy does not plan to eradicate eucalyptus on the island:  “The eucalyptus trees…are non-native, but are not highly invasive. Because of their non-invasive growth pattern and their place in the cultural heritage of the Island, they are not targeted for replacement, except when they die of natural causes.” (3)

The myth that eucalypts are highly flammable that is used as an excuse to eradicate them in Northern California is not heard on Catalina Island.  An enormous wildfire torched about 10% of the island in 2007.  The fire started on conservancy land and spread to the outskirts of Avalon where it was finally extinguished after destroying several homes.  The town was evacuated and its residents stood on the beach front watching the fire approach their homes.  The eucalyptus trees that surround Avalon did not burn.  In the conservancy description of the fire, no mention is made of eucalyptus.  Although the fire was started by unsafe use of mechanized equipment, the conservancy describes fire as a natural and beneficial feature of the chaparral ecosystem of the island.

A street in Avalon is named “Eucalyptus Street.” In the background are some of the eucalypts that surround the town of Avalon.

A restoration that makes sense

I have been studying native plant restorations for over 20 years.  I have finally found on Catalina a restoration that makes some sense to me.  The restoration on Catalina Island has been more constructive than it is destructive.  It has killed less and preserved more.  It preserves eucalyptus because they aren’t doing any harm.  It does not fabricate a cover story to justify killing eucalypts just because they aren’t native. 

The conservancy also acknowledges that difficult choices must be made and that differing opinions must be respected.  Recreational interests and aesthetic preferences are not always consistent with the goals of conservation.  The conservancy preserves bison because people like to see them, despite the fact that they are not native to the island. Competing interests must be balanced if the restoration is to be supported by residents of the island:  “We have realized that people are an intrinsic part of the nature of the island—an influential and fundamental component of the conservation effort.”  (1)


Most of this article comes from this book (1) which was written by the leadership of the Catalina Island Conservancy:

  1. Frank Hein & Carlos de la Rosa, Wild Catalina Island: Natural Secrets and Ecological Triumphs, Natural History Press, 2013
  2. “Protecting Catalina’s Wildlands from Invasive Plants,” Catalina Island Conservancy Times, Fall 2017
  3. Catalina Island Conservancy website: https://www.catalinaconservancy.org/

A Milestone for Million Trees

As the Million Trees blog approaches the anniversary of its eighth year, we are celebrating a milestone. Yesterday, Million Trees reached a total of 250,000 individual views of posts on Million Trees.  We now have over 300 subscribers and we are averaging about 150 views per day.  About 25% of our readers are outside the United States.  Since nativism in the natural world is an international fad, we are gratified that Million Trees is being read by people in other countries.  Million Trees is also proud and grateful for the participation of several academic scientists who have written informative guest posts for Million Trees in the past year.  Thank you, Dr. Matt Chew, Professors Mark Davis and Art Shapiro, and Dr. Jacques Tassin for your help!

Our most popular posts have each been visited by over 10,000 readers.  They are, in the order of their popularity:

  • “Darwin’s Finches: An opportunity to observe evolution in action.”  This article about the speed with which adaptation and evolution occur in a rapidly changing environment is the bedrock of the Million Trees blog.  Nativists mistakenly believe that evolution is much slower than it is.  Therefore, nativists believe plant and animal species are nearly immutable and that they are locked into mutually exclusive relationships, which are, in fact, extremely rare in nature.
  • “Nearly a HALF MILLION trees will be destroyed in the East Bay if these projects are approved.” The Million Trees blog was created to inform the public that nativism is destroying our urban forest in the San Francisco Bay Area.  Our urban forest is composed of predominantly non-native trees.  If they are destroyed, we will not have an urban forest because native trees will not survive in our changed and rapidly changing environment.  Non-native trees were planted here because people wanted trees and native trees existed only in riparian corridors where they were sheltered from the wind and there was sufficient water.
  • “Falling from Grace: The history of eucalyptus in California.”  Because people wanted trees, they planted non-native trees that were capable of surviving in the San Francisco Bay Area.  Non-native trees were valued for nearly one hundred years until nativism got a death grip on our public lands. This article on Million Trees tells the history of why eucalypts were planted and why they “fell from grace.”

In the past year, one of the most popular posts on Million Trees was “Krakatoa:  A case study for species dispersal.”  This post has been viewed by over 7,000 readers.  Understanding how plants and animals were dispersed around the world by natural means–such as by birds, wind, and ocean currents—is another way to realize that the concept of “native vs. non-native” is an artificial construct with little practical meaning.  Plants and animals have always moved and they will continue to move.  In fact, as the climate changes, they MUST move if they are to find the environmental conditions in which they can survive.

Million Trees Commitment

Million Trees will continue to advocate for the preservation of our urban forest in the San Francisco Bay Area.  Our strategy is to inform the public of the many projects that are destroying our forests and to describe the damage that is being done by those projects.  We are particularly concerned about the use of pesticides to eradicate non-native plants and trees.  We are equally committed to providing our readers the latest scientific discoveries that relegate invasion biology to a scientific back-water.  We are hopeful that the gap between public policy and the scientific knowledge discrediting invasion biology will eventually be bridged and bring an end to this destructive fad.

Highs and Lows of the 2018 Conference of the California Native Plant Society

I am pleased to publish the following report of one of our readers who attended the conference of the California Native Plant Society in Los Angeles at the beginning of February 2018. 

Million Trees


I attended the last conference of the California Native Plant Society in San Jose in January 2015.  It was interesting to note a few significant new themes in the recent conference in 2018.  Both fire and climate change were much more prominent themes in the recent conference.  While both are relevant to the future of native plants, neither seemed to have any effect on the “restoration” goals of the native plant movement.  For example, there were several presentations about massive die offs of native oak trees, resulting from higher temperatures, drought, and disease.  These presentations ended with urgent pleas to plant more oaks.  That seemed a fundamental contradiction and a denial of the reality of climate change.  When the climate changes, the landscape changes, but native plant advocates are not willing to acknowledge that.  In fact, the greater the threats to native plants, the greater the commitment to their preservation and “restoration.”

Beautiful pictures support nativist ideology

The conference began on a low point for me, but a high point for most attendees of the conference.  The keynote speaker was Doug Tallamy.  He was introduced as a “rock star” of the native plant movement, and indeed he is.  His presentation was very effective in delivering his message, which is that most insects are “specialists” with mutually exclusive relationships with native plants that evolved over “tens of thousands of years.”  If you believe that claim, you also believe that the absence of native plants will result in the absence of insects and ultimately the collapse of the entire food web.

Doug Tallamy’s closing photo, CNPS Conference 2018

Most native plant advocates believe that gloomy scenario, but few scientists still do, which creates a tension within this community of native plant advocates composed predominantly of amateur “botanists” and a smattering of academic ecologists.  For example, one of the first presentations after Tallamy’s keynote was an academic ecologist from UC Berkeley who advocated for accommodating the movement of plants outside of historical native ranges to accommodate climate change. (1) He said that restoring only with local natives is “maladaptive” and that a bioregional perspective is needed to create sustainable landscapes.  Allowing Monterey pines to grow in the San Francisco Bay Area, where they have grown in the past and are presently deemed “native” just 150 miles away, seems a good example of such a broader definition of “native.”  An amateur nativist, parroting Tallamy, asked this hostile question: “But if we move the plants how will wildlife survive?”  The academic delivered this tart dose of reality: “There are few mutually exclusive relationships in nature.  Wildlife will also move and will adapt to changes in vegetation.”

Science debunks a myth about eucalyptus

The high point of the conference for me was a presentation by Jennifer Yost, Assistant Professor at Cal Poly, San Luis Obispo.  She and her graduate student studied the claim that nothing grows under blue gum eucalyptus trees because of allelopathic chemicals emitted by eucalyptus that suppress the germination of other species of plants.  Two studies of this hypothesis were done in the 1960s, but the analytical methods used by those studies were misleading.

CNPS Conference 2018

Rigorous methods used by Yost’s team included planting seeds of 5 native plant species in the soil of eucalyptus forests and comparing germination rates of seeds planted in the soil of oak woodlands.  They also tested the effect of blue gum volatile leaf extracts, and water-soluble leaf extracts on germination and early seedling growth.

They 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.” (2)

CNPS Conference 2018

Yost observed that the lack of allelopathic effects of blue gum on the soil implies that blue gum forests theoretically can be successfully planted with native plants after removal of the trees.  However, she cautioned that those who destroy the blue gums should carefully consider what will replace them.  Will an aggressive non-native weed quickly colonize the bare ground?  If so, what is the benefit of destroying the blue gums? 

I had a conversation with one of the most influential nativists in the San Francisco Bay Area after Yost’s presentation.  This new scientific information does not alter his commitment to destroying blue gum eucalyptus in the Bay Area.  After all, there are many more negative claims that remain unchallenged by scientific studies.  For example, there are no studies that prove that blue gums use more water than native trees, as nativists claim.  Nor are there any studies that prove that eucalyptus leaves contain less moisture than the leaves of native oak or bay laurel trees, which theoretically makes eucalyptus more flammable, as nativists claim.  The lack of scientific evidence enables the persistence of speculation justifying irrational fear of blue gum eucalyptus.

Nativism dies hard because of lack of scientific studies

There appeared to be three distinct groups of people in the crowd of about 900 conferees.  There was a large contingent of grey-haired volunteers who are the backbone of every native plant “restoration.”  They are the dedicated weed pullers.  There is an equally large contingent of young people who are making their living writing the “restoration” plans and directing the activities of the volunteers.  The smallest contingent is a few academic scientists who study the underlying issues in their ivory tower.  The goals and conclusions of these three groups are increasingly divergent as scientific studies disprove the assumptions of the citizen “scientists.”

The tension between science and the citizenry is as evident within the native plant movement as it is in American politics at the present time. The general public rejects scientific evidence at its peril.  The rejection of science will not end well.  In the case of uninformed nativism in the natural world, the result will be a barren, poisoned landscape.


  1. “Climate change and open space conservation: Lessons from TBC3’s researcher-land manager partnerships in the San Francisco Bay Area,” David Ackerly1, Naia Morueta-Holme5, Sam Veloz3, Lisa Micheli2, Nicole Heller4 1University of California, Berkeley, Berkeley, CA, USA, 2Pepperwood, Santa Rosa, CA, USA, 3Point Blue Conservation Science, Petaluma, CA, USA, 4Peninsula Open Space Trust, Palo Alto, CA, USA, 5University of Copenhagen, Copenhagen, Denmark
  2. Abstracts of CNPS conference presentations are available here:  CNPS Conference abstracts

Will the real “gasoline tree” please stand up?

The Sierra Club has said many silly things in defense of its lawsuit demanding 100% destruction of all non-native trees on 2,000 acres of public land in the East Bay Hills, and Million Trees has responded to many of them (1).  Now Sierra Club has provided a new batch of ridiculous statements in its “pre-buttal” to the letter from a Chapter member to fellow Chapter members.

The winner of the intense competition for silliest statement

Sierra Club’s silliest statement:  “Eucalyptus trees are called “gasoline trees” in Australia for their tendency to explode in fireballs at very high temperatures.[ii]” (2)

You would not hear such a statement in Australia about ANY tree (eucalyptus or otherwise) because Australians do not use the word “gasoline.”  What Americans call “gasoline,” is called “petrol” in Australia (and Britain, New Zealand, etc.).  (3)

So, the next question is, do Australians call eucalyptus trees “petrol trees?”  The answer is, “NO, they do NOT call eucalyptus trees “petrol trees.”  A Google search for “petrol tree” directs the searcher to an article about a tree that is being grown in Australia as a source of diesel fuel.  The Brazilian tree Copaifera langsdorfii produces “natural diesel.”  Australian farmers have planted 20,000 of these trees with the expectation that “in 15 or so years they’ll have their very own oil mine growing on their farmland.” (4)

The Sierra Club provides a citation for its statement about “gasoline trees.”  The citation is a paper by Carol Rice, the primary author of the East Bay Regional Park District’s “Wildfire Hazard Reduction and Resource Management Plan.”  So, we might expect her to claim that eucalyptus is very flammable and she does.  However, she does not call them “gasoline trees” (nor does she claim that Australians do) nor does she claim that eucalyptus “explodes in fireballs.”

Wildfires in Mediterranean climates

The Sierra Club also provides a brief film clip of a wildfire in Australia.  The film clip is narrated by an American who claims that “firemen call eucalyptus gasoline trees.”  We hear Australians describing the fire, but they don’t say anything about “gasoline trees.”

Let’s compare that film clip in Australia with wildfires here in California.  Our most recent local wildfire was in September 2015, in Lake County about 100 miles north of San Francisco.  The Lake County fire destroyed about 1,200 buildings, killed 4 people, and burned over 76,000 acres.  HERE is a film clip of that fire, taken from the dashboard camera of a county sheriff driving through the fire.

Wildfire in California. Bureau of Land Management
“Native” trees burning in a Wildfire in California. Bureau of Land Management.

As we would expect, the Lake County fire looks very much like the fire in Australia because that’s what wildfires look like.  Most start in dry grass and move quickly through the fine fuel.  If it is a wind-driven fire, it will move into tree canopies and it will jump over roads.  The fire in Lake County burned predominantly native vegetation.  You will not see any eucalyptus trees burning in the film clip of the fire.

Wildfire behavior in California and southern portions of Australia are similar because their climates are similar.  They share a Mediterranean climate in which winter rains produce copious herbaceous vegetation that dries out during the long, dry summer months.  The green grass of winter becomes the fine fuel of summer.  It ignites easily and if conditions are right (high winds and temperatures and low humidity) quickly becomes a wildfire in which everything burns.  The native vegetation that survives these conditions must be adapted to periodic fire.  Therefore, native vegetation in California and in Australia are both adapted to periodic fire.  Destroying our non-native vegetation will not reduce fire hazards because native vegetation is equally flammable.

Many native trees are as flammable as eucalyptus trees. The leaves of native bay laurel trees contain twice as much oil as eucalyptus leaves.  A cord of native oak wood contains more BTUs (measure of heat energy) than a cord of eucalyptus wood.  Native redwoods are taller than eucalyptus and are therefore as likely to cast embers over long distances.  There is as much fine fuel in the oak-bay woodland as there is in the eucalyptus forest.

What is a “gasoline tree?”  It is a rhetorical device.

A Google search for “gasoline tree” turns up a mixed bag of American nativists using that term to describe eucalyptus, and sites about tree species being grown for biofuel as a substitute for gasoline.

Calling eucalyptus trees “gasoline trees” is a rhetorical device.  A native plant advocate probably made it up, then it was shared in their closed community until it became a “fact” in their minds.  It is a means of generating fear.  It is a tool used by native plant advocates to support their demand to destroy all non-native trees in California.   Name-calling does not alter the fact that if the trees are removed, the landscape will be much more flammable. They will be replaced by grasses and shrubs that will be easily-ignited fine fuels and result in fast-moving fires.

Preview

This is the second of a series of articles, debunking the latest batch of inaccurate statements made by the Sierra Club in its “pre-buttal” to the letter from a Club member to other Club members.  Stay tuned!


 

(1) https://milliontrees.me/2015/10/09/sierra-club-cannot-hide-behind-its-smokescreen/

https://milliontrees.me/2015/10/30/who-are-the-climate-change-deniers/

https://milliontrees.me/2016/02/12/despicable-behavior-the-sierra-club-sinks-to-a-new-low-2/

(2) http://sierraclub.org/san-francisco-bay/hillsfacts

(3)  Australian dictionary:  http://www15.uta.fi/FAST/US1/REF/aust-eng.html

(4)  http://www.treehugger.com/renewable-energy/the-diesel-tree-grow-your-own-oil.html

 

“Drought-Adapted Eucalyptus NOT Dying by the Thousand”

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

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

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


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

But he’s mistaken.

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

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

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

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

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

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

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

bayview-hill-2010 smTHE GIRDLED TREES OF BAYVIEW HILL

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

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

EUCALYPTUS ADAPTS

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

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

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

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

EPICORMIC SPROUTING IS IMPORTANT IN EUCALYPTUS

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

But again, this is not actually true.

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

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

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

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

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

epicormic sprouts on eucalyptus when nearby trees removed

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

MISTAKING DEFENSES FOR DEATH THROES

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

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

LIVING WITH A FEW DEAD TREES

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

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

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

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

Eucalyptus: A fairy tale

We were browsing in our local used book store when a book caught my eye with the title, Eucalyptus.*  Of course, I had to buy it.  It is fiction, a welcome reprieve from the dry, often dense reading I must do to inform the readers of Million Trees.  Now I have the pleasure of sharing this diversion with you.

A fairy tale told among the trees

Blue gum eucalyptus tree in the Mountain View Cemetery.
Blue gum eucalyptus tree in the Mountain View Cemetery.

We are in post-war Australia.  A young man marries a mail-order bride and soon loses her in childbirth, but not before insuring her life.  With this windfall, he buys a beautiful piece of land beside a river in southeast Australia.  His life is spent collecting and planting hundreds of different species of eucalyptus while raising his daughter.

The hundreds of species of eucalyptus provide what little structure there is to the book.  Chapters are given the botanical names of the great variety of species and their various shapes and characters are described.  Our very own blue gum is mentioned at length:  “The Blue Gum is easily recognizable.  The name E. globulus for the shape of its fruit, now describes the imperial distribution of this majestic tree:  through the Mediterranean, whole forests in California and South Africa, and all states of Australia.”

The farmer is as devoted to his trees as he is to his beautiful daughter, so when the young men start coming around to court his daughter he protects her by devising a scheme that renders her nearly unattainable.  He announces that the man who wins his daughter’s hand must first name every species of eucalyptus on his property.  This proves an insurmountable task, but his daughter is indifferent to the failures of a long line of men who come from all over Australia to see her legendary beauty, but fail over many years to pass the test.

Ghost Gum.  Courtesy Cynthia Clampitt, Waltzing Australia
Ghost Gum. Courtesy Cynthia Clampitt, Waltzing Australia

Finally, a uniquely qualified botanist presents himself to the challenge.  It becomes apparent that he will pass the test.  While the father and this botanist tick off the list of hundreds of eucalypts, a mysterious stranger visits the daughter in the forest.  He tells her stories that charm her.  For the first time in her life, someone interests her.  He brings to her his knowledge of a wide world full of unusual lives and human predicaments.

When the stranger suddenly disappears without explanation, she falls into a deep stupor.  Meanwhile, the botanist passes the difficult test and comes to claim his bride.  But she languishes in despair and he is unable to revive her.

We must leave the story here, because the end is a wonderful surprise of which we do not wish to deprive you.   It was a great pleasure to read about our trees where they are respected and admired, as they deserve to be here as well.


 

*Murray Bail, Eucalyptus, Melbourne, Australia, 1998

Understanding the eucalyptus forest – Professor Joe R. McBride

This article has been republished from the  website of Save Mount Sutro Forest, with permission.


 

Dr. Joe McBride of UC Berkeley spoke at the Commonwealth Club in April 2014 as part of the series “The Science of Conservation and Biodiversity in the 21st Century.” His main message:

  • Eucalyptus groves in California provide habitat for as many native species as do most ‘native’ habitats.
  • They grow well at high densities and an average spacing of 8 feet between trees is quite typical.
  • They have relatively high fuel loads, but the cool and damp dense eucalyptus forests reduce the risk of fire.
  • Eucalyptus is subject to few diseases or pests, and parasitic wasps provide pest control.
  • It provides a host of ecosystem services including carbon sequestration, pollution reduction, slope stabilization, windbreaks, wildlife habitat, and recreational value.

Dr. Joe R. McBride was Professor of Landscape Architecture and Environmental Planning, Department of Environmental Science, Policy, and Management, UC Berkeley. (He has since retired.)

Read on for notes from Dr. McBride’s talk. (There are also links to his Powerpoint presentation.)

—————————————

sutro forest with dappled sunlight

THE HISTORY, ECOLOGY AND FUTURE OF EUCALYPTUS PLANTATIONS IN THE BAY AREA

Notes From a Talk By Dr. Joe R. McBride

Dr McBride’s wide-ranging talk covered a lot of ground. He talked about the ecology of the eucalyptus forest in the Bay Area: its structure, the variety of plants and animals that live within it, its health and the ecological functions it performs; the dynamics within these forest stands; and their invasive potential.

WHY EUCALYPTUS CAME TO CALIFORNIA

Eucalyptus was first planted in California during the Gold Rush, possibly for oil to use in eucalyptus king of the forest smgold-mining and in medicine.

In the 1870s, eucalyptus planting was encouraged for many objectives: to beautify cities, to improve farmland, as windbreaks, and to dry out swamps to combat malaria.

It was grown in woodlots for firewood, but as people switched to natural gas and other fossil fuels this became rare. Later, it was planted for timber – which didn’t work out because the trees were harvested too young; and still later for bio-fuel, which did not become commercially attractive.

By the 1950s, it had become an integral part of the California landscape. Six species were planted, primarily blue gum in Northern California, and red gum and river gum in Southern California. (Worldwide, there are perhaps 640 species.)

Eucalyptus beautifies our cities, and helps stabilize soil on steep hills. The surface area of the leaves, broader than those of conifers, help trap particulate pollution. Unlike deciduous trees, the evergreen foliage of eucalyptus removes pollutants all year long.

HOW DENSE MAKES SENSE?

The density of eucalyptus plantations in Bay Area ranges from 150-160 trees per acre to about 1700 trees per acre. mt davidson understory(The highest density resulted from a freeze in 1970s: trees were cut down because of the perceived fire hazard, but the trees presumed dead later resprouted.) On Angel Island, the normal density was 8ft spacing (about 680 trees per acre) but it ranged to 30 feet between trees.

In the East Bay, 8 ft. x 8 ft. is quite typical eucalyptus plantation density. Left to grow naturally, stands become denser through in-growth, mainly by sprouting and also by sibling establishment.

Is management by thinning necessary for the health of the forest, someone asked, and what density is ideal?

Dr McBride had seen no examples of stands that could be improved by thinning. Eucalyptus grows well with a high density at an average of 8 ft x 8ft spacing between trees. In Australia and New Zealand no one thins; they just harvest the trees and let them regrow from sprouts.

In the US, eucalyptus was not marketable, so there’s no history of managing eucalyptus plantations. Also, until recently there were no diseases or insects. The long-horned borer and the psyllid have now appeared in some places, and thinning is not seen as a solution to these insect problems; they are better controlled by certain predatory wasps.

Logging eucalyptus would mean a lot of ground disturbance and erosion. If the logs are removed, the skid trails can destabilize the soil.

MUCH GROWS UNDER EUCALYPTUS – NATIVE AND NOT

Contrary to popular belief, eucalyptus forests have as many species (or more!) growing in their understory as do oak woodlands. A 1990 survey in Tilden Park found 38 species in the understory of eucalyptus forests (24 native plants; 14 introduced plants), while the oak woodland had 18 species in understory (14 native plants; 5 introduced plants). Only the riparian woodlands in Murray Park are somewhat richer in species than riparian eucalyptus forest (58 species vs 34).  In East Bay eucalyptus forests, California Bay, Coast live oak, poison oak, bedstraw, California blackberry, and chickweed were ubiquitous. The amount of light reaching the ground influences which species can be found in the understory.ferns and blackberry and poison oak

What about allelopathy? Under experimental conditions, eucalyptus litter inhibited germination and growth of cucumber seeds, so eucalyptus litter may be somewhat allelopathic to some plants. But a study from UC Santa Barbara indicates that if eucalyptus litter is removed, within 2 years there’s no inhibitory effect on other plants germinating. And clearly, it isn’t allelopathic to all the species mentioned earlier.

Someone asked whether it would be advisable to “manage eucalyptus stands that have an invasive understory.”

Dr McBride responded: “I have no prejudice against invasive plants. I am an invasive Californian myself.” (There was amused applause.) He continued that each eucalyptus grove is different, so it’s important to look at it on a stand-by-stand basis and measure the fire hazard of eucalyptus plantations against the value of each stand for wildlife habitation, recreation, and wind break functions.

eucalyptus trees in Sutro Forest

In response to a question about whether ivy kills eucalyptus trees, Dr McBride said he has not seen evidence the ivy shades the foliage of eucalyptus trees. He’s seen no evidence of ivy killing eucalyptus, although on Mt. Davidson, he did see ivy growing over trees that had been killed by girdling with an axe or chainsaw.

INSIDE A EUCALYPTUS FOREST

Shading and leaf litter changes the microclimate of a eucalyptus grove. As you move in from the edge to the interior of the forest, conditions change. The species change from the edge to the interior of the forest as the amount of light decreases, so there are different species at the edge of the forest and inside it. A 1980s study in the Presidio compared conditions outside a eucalyptus forest and inside it. It showed:

  • Temperature moderation: Daytime temperature fell an average of 10%, and night-time temperature rose an average of 5%
  • Windbreak: Wind velocity dropped 40%
  • Relative humidity was 5% higher (from the edge to the interior).
  • Shade: Light intensity was 90% lower.
  • Moisture: Precipitation (rain) decreased 12%; but fog-drip (i.e., moisture precipitated from the fog) increased 300%

EUCALYPTUS STORES CARBON

Eucalyptus increases the carbon content in the soil compared to grasslands (Zinke et al, 1988). Its fast growth and large size means it sequesters a lot of carbon in its trunk and root systems.

EUCALYPUS SUPPORTS WILDLIFE

Owlets in an eucalyptus tree nest
Owlets in an eucalyptus tree nest

Again, contrary to belief, eucalyptus provides a good environment for a wide variety of wildlife. A number of studies demonstrate this.

  • A 1970 study showed many birds make “moderate use” of eucs as habitat and a few birds make “great use” of eucs. (Almost all these species are native.) Birds that make most use: mourning doves; Great Horned Owls, whose range has been extended by CA eucalyptus; Stellar’s jays; yellow-bellied sapsuckers; Allen’s hummingbirds; olive-sided flycatchers; brown creepers; dark-eyed juncos; Audubon warblers.
  • Some reptiles make great use of eucalyptus groves: Southern Alligator lizard and the slender salamander. Among mammals, deer mice make “heavy” use of eucalyptus.
  • photo credit: Janet Kessler
    photo credit: Janet Kessler

    Robert Stebbins’ monumental 1978 study on the attractiveness of eucalyptus for habitat in the East Bay found that all species making use of eucalyptus for habitat found eucalyptus about the same as grasslands in attractiveness, but oak/bay woodlands were even more attractive.

  • Monarch butterflies most commonly use eucalyptus trees in state parks. But some of the insects in eucalyptus hurt the trees. One is the eucalyptus long horned borer – but can be controlled by a parasitic wasp. The red gum lerp psyllid is more of a problem in Southern California, which has more red gum. However, it’s part of the food chain: woodpeckers and other bird species feed on their larvae.
  • A study showed that eucalyptus in a riverside environment doesn’t impact species diversity of stream insects or pollution tolerance compared with native riparian environments.

NATURAL SUCCESSION IN EUCALYPTUS?

Over the next 200-300 years, the eucalyptus forests in the East Bay could gradually – and naturally – shift to oak-bay woodlands. In the East Bay (though not at Mt. Davidson or Mt. Sutro), the eucalyptus plantations have California Coast live oaks and California bay trees in the understory, and they are doing well. The live oaks are “tolerant” of shade and the bays are “very tolerant” of shade. If they aren’t disturbed, the oaks and bays regenerate well in the understory, and being even longer-lived than the eucalyptus trees, they will eventually naturally succeed the eucalyptus. The bay tree is higher in regeneration than the Coast live oak in Tilden Park (McBride, 1990).

WHAT ABOUT FIRE HAZARD?

fog in mt sutro cloud forest sept 2013Eucs support considerable fuel load on the ground because of rapid decay of foliage and shredding of its bark. They have a higher fuel load than California bays or Coast live oaks. They release an aromatic compound that can ignite with sparks, and they burn hot.

However, while the tree density of eucalyptus plantations can mean a greater accumulation of fuel in the understory, the higher density means a cooler, wetter understory that might not dry out as fast. Three risk factors in fire risks of any tree: amount of fuel it produces; tissue moisture content; fuel ladder based on presence of other plants in its understory.

IS EUCALYPTUS INVASIVE?

Under certain circumstances, eucalyptus can spread – for instance, on Angel Island, some stands spread through road cuts and prescribed burns (which destroyed competing vegetation). However, in most cases they don’t: aerial photographs show that boundaries are stable. The eucalyptus forests on Mount Davidson and in Tilden Park show stable boundaries.

mt D comparison 1927 -2010In the Bay Area, Dr McBride found eucalyptus forest area declined between 1939 and 1997. The natural spread hasn’t increased the area of eucalyptus groves.

DO TREES DEPLETE AQUIFERS?

Someone mentioned attending a talk where the speakers said that tree removal would help to replenish aquifers. Was that true? Dr McBride thought it very unlikely; most aquifers are much deeper than tree roots.

WHAT ABOUT PESTICIDES?

Someone speaking for people with disabilities owing to chemicals said herbicide use in these areas violated their right to access, and wondered how “environmental” organizations – like the Sierra Club – could support this. Dr McBride sympathized, said he was also concerned about toxic herbicide use. He mentioned that the East Bay tree-felling project is on hold owing to a number of unanswered questions that would need further research.

Here are links to his Powerpoint presentation in ppt and pptx formats.
PPT: McBride Presentation – Eucalyptus
PPTX: McBride Presentation – Eucalyptus

Here is a link to the audio notes taken by a member of the audience

 

Birds and butterflies in the eucalyptus forest

The deadline for sending comments to the California Invasive Plant Council (Cal-IPC) about their draft reassessment of blue gum eucalyptus is Thursday, July 31, 2014 (send to info@cal-ipc.org).  We are hoping to inspire you to write your own comment by sharing our personal favorites of some of the goofy statements Cal-IPC uses to justify its classification of blue gum as “moderately invasive.”

Eucalyptus trees do NOT kill birds!

Our regular readers have heard the absurd claim that eucalyptus trees kill birds by “gumming” up their noses or beaks with the nectar of the eucalyptus flowers.  We have published detailed critiques of this claim, so we won’t repeat them because you can visit those posts by clicking HERE and HERE.

Of course, all of this detailed information was provided to Cal-IPC when the original request to reconsider their classification of blue gum was submitted in December 2013.  In their draft reassessment, Cal-IPC now sinks to a new low by claiming Ted Williams as the source of the claim that eucalypts kill birds.  Mr. Williams writes an opinion column published by Audubon magazine, which is appropriately entitled “Incite.”  In 2002, Audubon magazine published Mr. Williams’s opinion of eucalyptus, which he called “America’s Largest Weed.” 

Ted Williams is not a scientist or a journalist.  He is a commentator. His column in Audubon magazine is not entitled “Insight,” because it is intentionally inflammatory.  It engages in rhetoric and hyperbole in support of Mr. Williams’s opinion.  In an article in High Country News, Mr. Williams describes “Incite” as a “muckraking column” and he calls himself an “environmental extremist.”  Citing Mr. Williams as a source of information undermines the credibility of Cal-IPC’s draft reassessment.  Quoting Mr. Williams on the subject of eucalyptus is a bit like quoting Rush Limbaugh on the subject of immigration.

But let’s be more specific with examples of the absurd statements Mr. Williams makes and the evidence that these statements are not factually correct.

The truth about Anna’s hummingbirds

Hummingbird in eucalyptus flower.  Courtesy Melanie Hofmann
Hummingbird in eucalyptus flower. Courtesy Melanie Hofmann

Cal-IPC’s draft reassessments says, “Williams reported that PRBO found that 50% of the Anna’s hummingbird nests [in eucalyptus] are shaken out by the wind, while only 10% of nests are destroyed by wind in native vegetation.”

Cal-IPC’s quotes from Williams are not found in any publication of the Point Reyes Bird Observatory (PRBO), which Williams claims as the source of the information.  Statements about the nests of Anna’s hummingbird are explicitly contradicted by Cornell Ornithology Laboratory, America’s preeminent research institution of bird biology and behavior:

  • “In the first half of the 20th century, the Anna’s Hummingbird bred only in northern Baja California and southern California.  The planting of exotic flowering trees provided nectar and nesting sites, and allowed the hummingbird to greatly expand its breeding range.”
  • “Anna’s Hummingbird populations increased by almost 2% per year between 1966 and 2010, according to the North American Breeding Bird Survey…The Anna’s Hummingbird is the most common hummingbird on the West Coast, and it has thrived alongside human habitation.  Its range has increased dramatically since the 1930s, when it was found only in California and Baja California.  Thanks to widespread backyard feeders and introduced trees such as eucalyptus, it now occurs in healthy numbers all the way to Vancouver, Canada.”
  • “Females choose the nest site, usually a horizontal branch of trees or shrubs 5-20 feet off the ground (occasionally higher) near a source of nectar.  They often build nests in oak, sycamore, or eucalyptus trees…”
  • “They [Anna’s Hummingbirds] are notably common around eucalyptus trees, even though eucalyptus was only introduced to the West Coast in the mid-nineteenth century.”

In other words, the nation’s most prestigious ornithological research institution tells us that Anna’s Hummingbirds have benefited greatly from eucalyptus trees, which provide both winter sources of nectar not otherwise available in California as well as safe, secure nesting habitat.  Since Anna’s Hummingbirds nest preferentially in eucalyptus, their populations would not be increasing if 50% of their nests were destroyed, as Mr. Williams claims.

Red-tailed hawk nesting in eucalyptus.  Courtesy urbanwildness.org
Red-tailed hawk nesting in eucalyptus. Courtesy urbanwildness.org

Furthermore, the implication that eucalypts provide a less stable nest site than native trees is also explicitly contradicted by a study that Cal-IPC cites elsewhere in its draft reassessment.  Stephen Rottenborn studied the nesting choices and reproductive success of red-shouldered hawks in Santa Clara County.  He found that the hawks prefer eucalypts to native trees and that their nests were more successful when they made that choice.  He attributes that greater success rate to the fact that eucalypts are “large, sturdy trees” that provide “greater stability and protective cover.”

“Fourteen of 27 nests in 1994 and 38 of 58 nests in 1995 were in exotic trees, predominantly eucalyptus.  Nesting and fledging success were higher in exotic trees than in native trees in both years, owing in part to greater stability and protective cover.  Most nest trees in upland areas were exotics, and even in riparian habitats, where tall native cottonwoods and sycamores were available, Red-shouldered Hawks selected eucalyptus more often than expected based on their availability.  Of the habitat and nest-tree variables measured at each nest, only nest-tree height and diameter were significantly associated with reproductive success, suggesting that large, sturdy trees provided the best nest sites.  Red-shouldered Hawk populations in the study area have likely benefited from the planting of exotic eucalyptus and fan palms.” (1)

 Magic!  Turning 2 dead birds into 300

Cal-IPC’s draft reassessment says, “Stallcup reported finding two dead warblers and ‘about 300 moribund warblers with eucalyptus glue all over their faces’ over the years, including ‘a large number of gummed-up Townsend’s warblers, yellow-rumped warblers, ruby-crowned kinglets, Anna’s and Allen’s hummingbirds, and a few Bullock’s orioles. Anyone who birds around eucalyptus trees sees it all the time’ (Williams 2002).”

This particular quote from Ted Williams is easily discredited because Rich Stallcup published his theory about birds being harmed by eucalyptus trees (available HERE).  In this publication, Mr. Stallcup reports seeing just two dead birds (one hummingbird and one ruby-crowned kinglet) in the eucalyptus forest during his long, illustrious career as an amateur birder.  He says nothing about seeing “300 moribund warblers” in his publication.  A small measure of common sense enables the reader to evaluate Mr. Williams’s claim:  If Mr. Stallcup had seen 300 dying birds, why would he say he had only seen 2 dead birds in his published article in which he is trying to make the case for removal of eucalyptus?

Overwintering monarch butterflies use predominantly eucalyptus

Monarch butterflies roosting in eucalypus tree.
Monarch butterflies roosting in eucalypus tree.

Cal-IPC’s draft reassessment says, “Natural experimental evidence from mixed stands (native trees mixed with eucalyptus) show that Monarchs do not consistently cluster preferentially on eucalyptus, and at times, appear to prefer native trees in some seasons and locations. (Griffiths & Villablanca 2013)”

This is a misleading statement because it implies that monarchs have the option of overwintering in native trees.  In fact, the reference cited by Cal-IPC is speaking specifically of three species of native trees with small native ranges:  Monterey pine, Monterey cypress, and redwoodsThe study is reporting observations of monarchs within the native ranges of these three tree species.  These tall trees provide a similar microclimate to overwintering monarchs.     However, the native ranges of these tree species are small.

Monterey pines are native in “three disjunct populations in San Mateo and Santa Cruz counties, Monterey County, and San Luis Obispo County.  The native population of Monterey cypress is significantly smaller:  “The native range of the species was confined to two small relict populations, at Cypress Point in Pebble Beach and at Point Lobos near Carmel, California.” Where Monterey pine and cypress have been planted outside their native range, they are being eradicated by the same public land managers who are eradicating eucalyptus.

For example, when UC Berkeley destroyed approximately 18,000 non-native trees over 10 years ago, many were Monterey pines.  Their plans to eradicate 80,000 more trees include all Monterey pines in the project area.  In San Francisco, the plans (SNRAMP) of the Natural Areas Program propose to destroy many Monterey cypresses on Mount Davidson.  The GGNRA has destroyed about 500 Monterey pines on Hawk Hill in Marin County and many Monterey cypresses throughout their properties.

Furthermore, both Monterey pine and Monterey cypress have much shorter lives than eucalyptus.  Monterey pine lives at most 150 years and Monterey cypress about 250 years, compared to E. globulus, which lives in its native range from 200-500 years.  Therefore, even where they are not being eradicated, they will die long before E. globulus and are unlikely to be replanted outside their small native range by public land managers who are committed to a “natives-only” policy.

We are unaware of any attempts to eradicate redwoods outside their native range, in the few locations where they still exist. They seem to have escaped the wrath of nativism. However, the range of redwoods is very narrow:  “The redwoods occupy a narrow strip of land approximately 450 miles (724 km) in length and 5 to 35 miles (8-56 km) in width.  The northern boundary of its range is marked by two groves…within 15 miles (25 km) of the California-Oregon border.  The southern boundary of redwood’s range is marked by a grove…Monterey County, California.”

Although native plant advocates may be willing to plant redwoods outside their native range, they do not have that option because of the horticultural requirements of redwoods.  Redwoods require more water than Monterey pine and cypress and they do not tolerate wind, which prevents them from being successful in many coastal locations, where monarchs overwinter.  Redwoods cannot be successfully grown south of Monterey County where the climate is warmer and drier than its native range.

In other words, monarchs do not have the option of roosting in native trees in most of the places in California where they overwinter.  This is a more accurate description of the behavior of overwintering monarchs and the alternatives that are available to them in about 300 locations along the entire coast of California, where they have overwintered in the past:

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 Cupressus macrocarpa).  Twelve other tree species were identified…with a combined prevalence of only 10%…The negative sign for this indicator means that habitats had smaller populations when the roosting tree type was a species other than eucalyptus, pine, or cypress…our long-term analysis showed that abundance has historically been greater at habitats dominated by eucalyptus, pines, or cypress than at those with ‘other’ species.  Stands of these three signature taxa may be more likely to produce a community structure and associated microclimate that increases the residence time of monarchs.  Furthermore, these taxa may produce a more attractive landscape architecture in terms of sensory cues to migratory monarchs arriving in a certain region.” (2)

For the record, we will add that we would be happy to have more Monterey pines and cypress and if public land managers would quit destroying them, we would consider them attractive alternatives to eucalyptus.  However, for the moment, we must assume that the crusade against all non-native trees will continue unabated.

What is your personal favorite?

We have shared our personal favorites with you, but everyone comes to this issue from a different place.  We have been flabbergasted by the unfounded claims that the eucalyptus forest is devoid of life.  We wonder if the people who say that, really believe it.  Or is it just one of the many strategies used to justify their demands that our non-native landscape be destroyed?

Please choose your own personal favorite and write your own comment by Thursday, July 31, 2014.  Are you primarily concerned about the herbicides that are needed to prevent the trees from resprouting when they are destroyed?  Are you concerned about the loss of your protection from wind or noise?   Or do you value eucalyptus as a sight screen or for shade in an otherwise treeless environment?  Are you concerned about the carbon loss that will contribute to climate change?  Please help us to save our urban forest from being needlessly destroyed by telling Cal-IPC why they should take blue gum eucalyptus off their “hit list.”

Thank you for your help to save our urban forest.

Update:  On March 13, 2015, the California Invasive Plant Council published its final reassessment of Blue Gum Eucalyptus (available HERE).  Cal-IPC has downgraded its rating of invasiveness and ecological impact from “moderate” to “limited.”  Although the detailed assessment is less than perfect, the over all rating itself is an improvement.  Thanks to those who sent comments to Cal-IPC.


(1)    Stephen Rottenborn, “Nest-Site selection and reproductive success of urban red-shouldered hawks in Central California,” J. Raptor Research, 34(1):18-25

(2)    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.