The Very Long Life of Eucalyptus Trees

This article is republished with permission and minor changes from Death of a Million Trees, a website that fights unnecessary tree killing in the San Francisco Bay Area.

 

 

PUTTING ANOTHER 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 IN AUSTRALIA LIVES 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

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:

https://burlingameproperties.com/articles/1607-burlingame-s-heritage-trees

https://www.smdailyjournal.com/news/local/future-plotted-for-burlingame-s-el-camino-real/article_a27c43c4-1dd1-11e8-8a5d-b31dfaa94144.html

http://www.burlingamevoice.com/2012/03/nationally-historic-100-years-of-protection-rewarded.html

https://tclf.org/landscapes/howard-ralston-eucalyptus-rows

http://articles.latimes.com/2003/aug/10/local/me-sbriefs10.1

The Myth that Nothing Grows Under Eucalyptus

Eucalyptus haters are fond of saying “Nothing grows under eucalyptus.” This refers to “allelopathy” of eucalyptus trees – a defense mechanism in some plants that uses chemical means to prevent other plants growing in the same area. This is empirically a myth, as laid out in this article: Eucalyptus Myths.

When confronted with the tangles of diverse vegetation thriving in the eucalyptus forests on Mt Davidson and Mt Sutro, they amend it to “No native plant grows under eucalyptus” – assuming that native plants as a class have particular characteristics that make them susceptible.  Recent scientific research shows that’s a myth too

 

ABSTRACT: EVALUATING THE MYTH OF ALLELOPATHY IN CALIFORNIA EUCALYPTUS GLOBULUS PLANTATIONS (NELSON, RITTER, YOST)

Here’s the abstract from a paper presented at recent conference of the California Native Plant Society (Feb 2018):

“14.05 Evaluating the myth of allelopathy in California Eucalyptus globulus (Myrtaceae) plantations
Kristen Nelson, Matt Ritter, Jenn Yost, California Poly, San Luis Obispo, CA

It is widely accepted that allelopathy is not only significant, but more or less singular, in the inhibition of understory vegetation in California Eucalyptus globulus (Myrtaceae) plantations. However, there is no published documentation of allelopathy by blue gums against California native species despite continuous references in the literature since the late 1960’s. Previous studies on allelopathy have been inconclusive and criticized for their lack of meaningful, ecologically relevant controls, test species, and test conditions.

We tested the effect of blue gum soil, volatile leaf extracts, and water-soluble leaf extracts on germination and early seedling growth of five California native species that are common components of native habitats typically found adjacent to blue gum plantations. We conducted greenhouse and laboratory experiments to compare the effect of blue gum extracts to ecologically-relevant controls including water, a non allelopathic native plant control (Quercus agrifolia [Fagaceae]), and a native allelopathic plant control (Salvia apiana [Lamiaceae]).

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. These results are significant because they are the first to test an allelopathic effect of blue gums against ecologically-relevant species. These results may have significant implications for management and restoration of land historically occupied by blue gum.”

In other words – they looked for allelopathy and they didn’t find it.

The picture below, incidentally, shows Pacific Reed Grass – a native plant – growing under eucalyptus. It’s often found growing under eucalyptus because the water precipitated from the fog provides its preferred growing conditions.

 

 

Cutting Down Forests Releases Green House Gases

Eucalyptus forests are exceptionally good at sequestering carbon: They’re big and fast-growing, with dense wood and long lives. The forests store even more carbon in the soil, much of it in the top three feet. This is true of Sutro Forest, of Mt Davidson, of the forested areas of Sharp Park and McLaren Park and Bayview Hill, the forests on Yerba Buena island. All these forests are threatened, and the people who want to cut them down have understated the expected release of carbon once the trees are cut down, the soil churned up, and the chipped trees left to decay.

The article below is specifically about such understatements in UCSF’s Draft Environmental Impact Report for the Sutro Forest Management Plan (that starts with cutting down 6,000 trees in Phase I). But it’s the same story in all the other forests we mentioned: The carbon impacts are ignored or minimized with bad data.

This article is reprinted with permission from SaveSutro.com, a website that advocates for Sutro Forest.

Sutro Forest is an excellent carbon sink: The eucalyptus trees are tall, fast growing and have dense wood. In some parts of the forest, the mid-story of blackwood acacia boosts this carbon storage as well. The understory is lush and evergreen. The forest floor is damp most of the time. It’s practically the perfect carbon forest. It’s also a special ecosystem and excellent wildlife  habitat.


Disturbing this forest is going to release Green House Gases (GHG), and the Sutro Forest DEIR (where the deadline for comments closed on September 22nd) underestimates how much. Here, we publish with permission the comment from Eric Brooks. He’s the Sustainability Chair, San Francisco Green Party and Campaign Coordinator, Our City SF. [Please note: all the photographs in this article are ours and not part of the comment sent to UCSF.]

##########

Comments To: Draft Environmental Impact Report (Draft EIR) – UCSF Mount Sutro Open Space Reserve Vegetation Management Plan

Fundamental GHG Calculation Flaws & Neglect of Wildlife Habitat Retention Strategy

To all concerned with the Draft Environmental Impact Report for the UCSF Mount Sutro Open Space Reserve Vegetation Management Plan,

I write to raise very serious concerns about very fundamental and deep flaws in the Draft EIR (DEIR) assessment of greenhouse gas emissions from the proposed project and related wildlife habitat impacts.

The assessment has key and deep flaws in its methodology for greenhouse gas assessment, and must be fundamentally changed, and the assessment completely redone.

1) The first deep flaw in the methodology and assessment is the assumption on page 4.7-3 that:

“Forest‐soil carbon is a large, stable pool, accounting for some 50 percent of the total forest carbon and changing very slowly over hundreds of years (Kimmins 1997). For timeframes of 100 years and less, forest accounting can ignore this pool and focus on changes to more labile forest carbon components (i.e., trees, understory, litter).”

This assumption is simply not correct and completely ignores the fact that when forest soils become both disturbed and more exposed to the elements, due to tree and vegetation removal, vast amounts of carbon in the form of CO2 and methane are released *from* the soil. The greenhouse gas emissions calculations and assessment must therefore be completely redone to include soil carbon losses in the calculations.

2) The second deep fundamental flaw in the DEIR greenhouse gas assessment is its reliance on the Significance Criteria under section 4.7.5 on page 4.7-10

This criteria is solely an arbitrary emissions cap and is the wrong criteria. The only proper criteria by which to assess greenhouse gas emissions of a forest is to compare its net carbon sequestration and emissions before disturbance, to its net sequestration and emissions after disturbance, in order to make a comprehensive assessment of its full internal net sequestration and emissions impacts – including all soil impacts and carbon losses and sequestration. It is the percentage net increase of greenhouse gas emissions in any given forest that matter, not an arbitrary cap on a specific emissions number which is not related to the full carbon cycle of that specific forest.

Therefore this assessment must be fully redone to examine solely the correct net sequestration and emissions, from the forest area that will be managed, accounting for all factors, and also accounting for the fact that near term net emissions over the next 20 years are the most significant because it is over the next 20 years that the planet is hitting a wide array of extremely dangerous climate crisis tipping points, and also because that is the proper window in which to analyze the forcing effect of methane (about 87 times higher than CO2 under that time frame).

3) Besides, and partly because of, the completely incorrect omission of soil carbon loss in the assessment, the net sequestration/emissions calculations in section 4.7 are far too optimistic and appear to be incorrect. This section does not properly and fully account for all emissions and sequestration losses, with an eye to new data which shows that after forests are disturbed it takes at least a century, and likely longer, for a disturbed forest to return to net sequestration of carbon. See links below which discuss these dynamics and which can serve as a starting point for redesigning and redoing your greenhouse gas analysis to make it an accurate one.

4) Chipping of felled and downed trees induces them to lose their carbon to the atmosphere much more rapidly. This assessment must be redone to show options for not chipping felled and downed trees at all, and instead leaving these trees intact, and on site, both as snags and downed trees. (See point 5.)

Chipping in Sutro Forest – 2016

5) Removing any vegetation (especially trees, including dead and felled trees) from a forest, drastically reduces the ecological capacity of that forest to uptake, store and retain carbon, and also dramatically reduces the crucial role of intact dead and dying trees to serve as wildlife habitat.

This DEIR contains no management assessment or mitigation plans that would call for a dramatic reduction in tree felling and removals in order to leave the forest and its soils as undisturbed as possible in order to maximize carbon sequestration, and maximize wildlife density and biodiversity through enhanced intact habitat. See the third link below to the report “The Myth of Catastrophic Wildfire” by expert forest ecologist Chad Hanson, PhD, to get a sense of, and some numbers on, the importance of leaving dead and dying trees intact and on site in a forest.

This assessment must be completely redone to show a management and mitigation option which *only* removes dead and dying trees *which pose a direct threat to human health and safety and property integrity* while leaving all other trees in the forest undisturbed. This assessment must include both net greenhouse gas, and wildlife density and diversity impacts.

References:

Old-growth forests as global carbon sinks – Sebastiaan Luyssaert, et al
(contains extensive data showing that forests store more carbon the less they are disturbed)
https://www.researchgate.net/publication/42089659_Old-growth_forests_as_global_carbon_sinks_Nature

Forest Carbon Basics – Mark E. Harmon, PhD (contains basic numbers for how forest and soil carbon dynamics operate over both short and long term timescales, and shows clearly that disturbed forests store less carbon for a century or longer)
http://our-city.org/Forest_Carbon_Basics-Harmon.pdf

The Myth of Catastrophic Wildfire – Chad Hansen, PhD
(See pages 19, 22 and 23 *and* referenced documents and studies)
http://johnmuirproject.org/wp-content/uploads/2014/12/TheMythOfTheCatastrophicWildfireReport.pdf

Thanks for your attention to this extremely important matter.

Eric Brooks
Sustainability Chair, San Francisco Green Party
Campaign Coordinator, Our City SF

Sutro Forest

Sutro Forest viewed from Forest Knolls

Can The Public Trust the Pesticide Notices in Our Parks?

2016-11-02_mtd-imazapyr-blackberry-thumbnailOne of the main issues the public has with the use of pesticides in our parks is the lack of transparency. There is no way to know in advance where the San Francisco Recreation and Parks Department (SFRPD) plans to use pesticides. The only way to track pesticide use by SFRPD is to do as we do – get the monthly pesticide use reports each month and compile them. This is of course after the fact, sometimes as much as a month or two after the fact. Right now, the latest report we have is for August 2016.

THE FIRST EIGHT MONTHS OF 2016

In the first 8 months of 2016, the Natural Areas Program – now rebranded as the Natural Resources Department (NRD), as though they were handing out mineral rights or something – was the most frequent user of the most hazardous herbicides. They made 87% of the applications, and used 72% of the four hazardous herbicides, though they are responsible for a quarter of our San Francisco parks.  (These are all herbicides the San Francisco Department of the Environment classifies as Tier I, Most Hazardous, or Tier II, More Hazardous) The SFRPD has done an excellent job of reducing the use of toxic herbicides in other sections, but the NRD, the former NAP, has not kept up.

  • Of the 95 applications of herbicides, 83 were by the NRD.  This is important to park-goers because the NRD controls major park areas where people recreate and explore with family and pets, and this frequent use increases the probability of an encounter.
  • The NRD also applied 72% of SFRPD’s total use of the four major herbicides: Roundup (glyphosate); Garlon; Imazapyr and Milestone VM. The first two are Tier I and the second two are Tier II.
  • Though NRD has sharply reduced its use of Roundup, it used more of the other three chemicals in 8 months than it did all year in 2015.
  • In addition to the four major herbicides, SFRPD did use Avenger, an organic – though Tier II – herbicide in the Polo fields and the Golden Gate Park nursery. We are not very concerned because this is a safe organic herbicide.
  • Aside from NRD, the most frequent SFRPD user of herbicides was the nursery, which applied herbicides only seven times in eight months. The nursery is not commonly used by the public and pets .
  • This summary excludes Harding Golf Course, because it’s managed under contract by the PGA Tour and is required to maintain tournament-readiness at all times.

INFORMING THE PUBLIC – A RECENT CASE IN MT DAVIDSON

At the site, SFRPD is supposed to post notices three days in advance of herbicide applications. People have complained that the notices are not very visible. We are also finding they are not always accurate.

This notice on Mt Davidson clearly indicated that Imazapyr was to be used against blackberry. It gave dates and times, and said blue dye would be used to show pesticide use. Okay.

2016-11-02_blackberry-imazapyr-mtd

A couple of walkers saw the actual herbicide activity. Here’s the gist of their report:

Herbicides used on Mt. Davidson today, November 2, 2016.

  • Three RPD trucks, two Shelterbelt trucks.

2016-11-02_131027-small

  • Saw 3 notices – two on western slope, one on eastern. All mentioned Imazapyr (Polaris, Stalker) for use on blackberry.

2016-11-02_135834-small

  • Saw an NRD staff person as he pulled up to the top of the mountain in the truck. He said they were daubing (not spraying) cotoneaster and blackberries. The notices didn’t mention cotoneaster.

2016-11-02_mtd-cutting-eucalyptus-herbicide

  • Saw another NRD staff person on the western side, just where the vegetation changes from grass/brush to trees. He was cutting down “a nice-looking small (but over 15 feet tall) eucalyptus tree and applying herbicides to the stump.” He said he was protecting 1000 year old biodiversity by cutting the tree to prevent it from shading the “important” plants.

    “He may have cut more trees,” the observers noted, “But we had to leave and didn’t see how many.”  The notices didn’t mention eucalyptus.

So the notices are incomplete, at best. This one didn’t mention cotoneaster, though the NRD employee said it was being targeted. What the observers actually saw was eucalyptus being cut down, also not mentioned. And unless the herbicide being put on the stump was imazapyr – unusual in this application – then the notices  also omitted the actual herbicide used – generally Roundup or Garlon.

Since the notices and the pesticide use reports are the only primary information source, if these are corrupted, then there is actually no accurate record available.

Three Myths About the Monarch Butterfly

The beautiful Monarch butterfly – possibly America’s best-known butterfly – is being considered for “endangered”status under the Endangered Species Act. Meanwhile, we’re cutting down the trees these creatures depend on. Nativist myths are partly responsible.

There are two migrations of these butterflies: East of the Rockies, these butterflies migrate between Mexico and the northern part of America. On the Western side, they migrate between the interior and the coast. These are the butterflies we see in California.

The Eastern migration is threatened mainly by a lack of milkweed, their nursery plant, as farmers efficiently exterminate the “weed.” But the Western migration is threatened by something different – a steady reduction in wintering sites as the war on eucalyptus trees continues. On Treasure Island, where Monarchs have been known to over-winter in some years, hundreds if not thousands of trees are being cut down.

We think the article  below is an important one. It’s  republished with permission from “Death of a Million Trees.” Recognizing the truth will help us save these beautiful creatures.

MONARCH MYTHS REVISITED by Million Trees

Debunking the myths of nativism—especially those that justify the eradication of non-native trees—is the task we have assigned ourselves, which requires us to revisit a few of the misconceptions about monarch butterflies in California.

Monarch Butterfly. Creative Commons

Monarch Butterfly. Creative Commons

When application for endangered status for monarchs was filed in August 2014, a few new monarch myths emerged and have since been faithfully repeated by native plant advocates who are demanding the eradication of our urban forests.  The monarch migration in California is using predominantly non-native trees, which should afford those trees some protection.  Unfortunately, it has only produced more convoluted theories that deny the value of non-native plants and trees to monarchs.

Myth #1:  The California migration of monarch butterflies prefers native trees for their winter roost. 

Monarch butterflies roosting in eucalyptus tree.

Monarch butterflies roosting in eucalyptus tree.

A study of the trees used by monarch butterflies for their winter roost in over 300 different sites in California reported that the vast majority of monarchs are using eucalyptus:

“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%.” (1)

Unfortunately, this fact has been obscured by a small study of a few selected sites used by monarchs during their migration.  Griffiths and Villanova (2) observed the monarch migration in a few sites in Monterey and San Luis Obispo counties.  They report that the monarchs moved around among three tree species including eucalyptus, suggesting to them that Monterey pine and cypress are equally important to the monarchs.  While we don’t doubt that this may be true, we don’t think we can generalize from this study because it was conducted in the small native range of Monterey pine and cypress.

The California migration of monarchs spends the winter months roosting in tall trees in 17 counties along the coast of California, from Mendocino County in the north to San Diego County in the south. (1) Most of that expanse is outside the native range of Monterey pine and cypress.  Griffiths and Villanova do not acknowledge that both Monterey pine and cypress are being eradicated outside their native range for the same reason that eucalyptus is being eradicated, i.e., they are considered “alien invaders” where they have been planted outside their native range.  Here in the San Francisco Bay area, for example, 500 Monterey pines were destroyed on the Marin headlands a few years ago and an untold number of Monterey pines will be destroyed by the FEMA projects in addition to those that have already been destroyed here.

If, in fact, monarchs do have a preference for Monterey pines and cypress for their winter roost, they do not have that option outside of the small native range of those trees in Monterey County. 

For the record, we should tell you that we are just as opposed to the pointless destruction of Monterey pine and cypress outside their small native range as we are opposed to the destruction of eucalyptus.

There is paleontological evidence (fossil cones) that Monterey pines lived in the San Francisco Bay Area several times in the distant past.  That finding was reported (4) in Fremontia, the journal of the California Native Plant Society.  The author asked that Monterey pines be allowed to remain where they lived in the past because the species is threatened in its small native range.  Unfortunately, her advice has been ignored by native plant advocates, who continue to demand that all Monterey pines be destroyed where they have been planted outside their present native range.  This extreme viewpoint is one of the reasons why native plant advocates have earned their reputation as fanatics.

Myth #2:  The California migration of monarch butterflies used exclusively native trees before eucalyptus was planted in California.

Those who wish to discount the value of eucalyptus to overwintering monarchs often assume the California monarch migration predates the planting of eucalyptus in California in mid-19th century.  That assumption supports their claim that all of our eucalyptus can be destroyed without having a negative impact on monarch butterflies.   In fact, there is no historical record of the monarch migration until the mid-19th century.  The historical record of the monarch migration was reported by Vane-Wright (3), who tells us the California monarch migration is probably a 19th century expansion of the range of the eastern monarch migration, from east of the Rocky Mountains to Mexico.  Recent molecular analysis of the monarch migration confirms that the eastern and western migration of monarchs in North America are genetically identical, suggesting that the populations might be dispersing east and west from their Mexican winter roost. (5)

Monarch caterpillar on milkweed. Tilden Botanical Garden

Monarch caterpillar on milkweed. Tilden Botanical Garden

Monarch butterflies are not usually eaten by birds because their host plant contains a toxin that makes birds sick and the monarch’s warning colors broadcast that fact.  The warning colors of butterflies that are toxic to birds are often mimicked by other species of butterflies to confer that protection.  There is a monarch mimic, the Viceroy, in the eastern US, which occurs in California only in a tiny bit of riparian habitat in southeast California.  “The lack of mimics suggests the [monarch] may not have been here long enough for any to evolve.” (6)

Myth #3: Non-native species of milkweed is harmful to monarch butterflies.

Monarch butterflies lay their eggs on milkweed and their larvae, the caterpillar, feeds exclusively on milkweed.  Many native plant advocates believe that the monarch requires a native species of milkweed.  They are mistaken in that assumption.  Wikipedia lists over 35 species of milkweed (genus Asclepias) all over the world and many are known to be used by the widely dispersed populations of monarchs.

The dispersal of monarchs from their original range in North America is approximately 200 years old, according to molecular analysis of populations across the Pacific Ocean (Hawaii, Samoa, Fiji, New Caledonia, New Zealand, Australia) and across the Atlantic (Spain, Portugal, Morocco).  These dispersals are assumed to have been aided by human transportation of both milkweeds and monarchs and extreme weather events.  “For example, monarchs were recorded in Australia in 1870 and were most probably carried there on cyclonic winds from a source population in New Caledonia.” (7)  These populations do not migrate and are therefore genetically distinct from the ancestral population of North American monarchs as a result of genetic drift.

In many of the homes of new populations of monarch butterflies there was no native species of milkweed before being introduced simultaneously with the monarch populations.  Although there are numerous members of the milkweed family native to Australia, monarchs do not appear to utilize the native species, preferring the introduced species of milkweed.

Tropical milkweed (Asclepias curassavica) Creative Commons

Tropical milkweed (Asclepias curassavica) Creative Commons

In California, a tropical species of milkweed is popular with gardeners (Asclepias curassavica).  Unlike the native species of milkweed, tropical milkweed does not die back in winter.  Gardeners therefore tend to prefer the tropical milkweed because it makes a colorful contribution to their gardens year around.

Of course, native plant advocates prefer native species of milkweed and they justify their preference by claiming that tropical milkweed is harmful to monarchs.  They claim that the monarch parasite (Ophryocystis elektroscirrha) can accumulate on tropical milkweed because it doesn’t die back during the winter.  Tropical milkweed is the only milkweed available in winter.  The parasite disrupts some winter breeding of monarchs, but that breeding would not occur in the absence of tropical milkweed.  If more monarchs are the goal, tropical milkweed is making a contribution to the monarch population.

New scientific research bebunks the myth that tropical milkweed is harmful to monarchs.  Leiling Tao et.al. (8) studied monarch lifespans when they fed on a variety of milkweed species.  They looked at both resistance to monarch parasite (O. elktroscirrha) infection and tolerance once infected.  They found a complex interaction between species of milkweed the monarchs fed on and the amount of mycorrhizal fungi on the roots of the milkweed.  But one result was clear:  monarchs raised on tropical milkweed (A. curassavica) lived as long, or longer than, monarchs raised on other species of milkweed.  They were less likely to be infected, and once infected, tolerated the infection well.  In short, there is nothing about tropical milkweed as a host that is detrimental to monarch survival in the presence of parasites.

Native plant advocates also speculate that tropical milkweed can disrupt the migratory patterns of monarchs because it is available when native milkweed is not available.  Given that monarchs have persisted for 200 years all over the world, using exclusively non-native milkweed and without migrating, this seems an unnecessarily pessimistic concern.  Neither native milkweed species, nor migration are essential to the survival of monarchs as a species.

Peek under the cover story

As we often do on Million Trees, we have taken a peek under the cover story being used by native plant advocates to justify the eradication of non-native plants and trees.  Once again, we find a lot of pessimistic speculation, but little evidence that eradicating non-native plants will benefit wildlife, or conversely that wildlife can only survive in native habitat.  Yes, it was a tedious journey to that conclusion and we thank you for your patience if you have persevered to our optimistic conclusion that wildlife is far more resourceful and resilient than nativism wishes to believe.

Monarch butterfly in San Francisco. Copyright Janet Kessler

Monarch butterfly in San Francisco. Copyright Janet Kessler


(1) 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.

(2) Jessica Griffiths and Francis Villablanca, “Managing monarch butterfly overwintering groves:  Making room among the eucalyptus,” California Fish and Game 101(1): 40-50; 2015

(3) Richard Vane-Wright, “The Columbus Hypothesis:  An Explanation for the Dramatic 19th Century Range Expansion of the Monarch Butterfly,” in Biology and Conservation of the Monarch Butterfly,Natural History Museum of Los Angeles County, 1993.

(4) Constance Millar, “Reconsidering the Conservation of Monterey Pine,” Fremontia, Vol. 26, No. 3, July 1998

(5) Justine I. Lyons, et. al., “Lack of genetic differentiation between monarch butterflies with divergent migration destinations,” Molecular Ecology, (2012) 21, 3433-3444

(6) Art Shapiro, Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions, California Natural History Guides, UC Press, 2007.

(7) Amanda Pierce, et. al., “Serial founder effects and genetic differentiation during worldwide range expansion of monarch butterflies,” Proceedings of the Royal Society of Britain, 281: 2014.2230.

(8) LeilingTao, et. al., “Disease ecology across soil boundaries:  effects of below-ground fungi on above-ground host—parasite interactions,” Proceedings of Royal Society of Britain, 282: 2015.1993.

San Francisco Fells More Trees – Treasure Island

DSCN0052 - the beautiful trees of Treasure Island San Francisco - soon to be gone 2016

People have started writing to us about hundreds, perhaps thousands, of trees being clear-cut on Treasure Island – beautiful, healthy trees being destroyed. It’s happening right now.

One person wrote: “Over on the area where officers quarters are, there appears to be clear cutting is there any thing that can be done to save the ones left?

Then he sent us these pictures with the note: “Thanks for your attention to these matters. I am just a beer drinking football watching person, but perhaps I am more naive than I thought, because what I saw as represented by these images … was disturbing to a city person like myself.

DSCN0008 trees felled and dumped -Treasure Island san francisco 2016

 

DSCN0021 stumps and piles of mulch are all thats left - treasure island san francisco 2016

“These trees appear to have been just killed and then ground down to saw dust with no thought of conservation, reuse or anything, unconscionable,” he added.  I doubt the proud city of San Fran will ever mitigate the amount of trees they are killing today.”

huge old trees cut down on treasure island san francisco 2016Another person wrote:

“[On Treasure Island] I drove past several spots on the island where eucalyptus have been completely clear cut. I was driving so I couldn’t really get a good estimate, but it looks like many hundreds. Many of the trees were VERY large and healthy looking. They are already being chipped and/or logged…

“The work of the nativists? Looks like it to me. Otherwise why remove entire stands of healthy trees?

“I, for one, am sick and tired of this disgusting, unsupportable destruction that has no scientific or practical basis. These actions go beyond normal landscaping or aesthetic decisions. The city will suffer the effects of these actions for decades to come.

“Frankly, I’m also disappointed that the main opposition relies so heavily  on scientifically unsupportable counter-arguments. It makes it very hard to find effective ways to combat the destructive philosophy that has taken over Parks and Rec.”

DSCN0020 stumps and piles of mulch are all thats left - treasure island san francisco 2016

The huge eucalyptus trees of Treasure Island are among the sites where Monarch butterflies have been known to overwinter. Eucalyptus trees are great at sequestering carbon because of their dense wood, their fast growth, their huge size, and their long lives… if they’re not cut down like these trees here.

  • How many tons of sequestered carbon are now being released?
  • How much monarch butterfly over-wintering habitat has been destroyed?
  • How much tree cover for birds and animals has been removed?

How can San Francisco call itself a green city with this tree canopy shrinkage going on in these times of global warming?

monarch butterfly in a San Francisco eucalyptus tree - copyright Janet Kessler

Season’s Greetings with Monarch Butterflies

Monarch butterfly in San Francisco - copyright Janet KesslerIt’s a lovely coincidence that here in California, the holiday season is Monarch butterfly season. We bring you this post (partially based on a post from SutroForest.com, used with permission) to celebrate the season with butterflies.

We wish all our readers and supporters a wonderful holiday season, and a happy and fruitful year in 2016.

THE WESTERN MIGRATION OF THE MONARCH BUTTERFLIES

Unlike the Monarchs east of the Rockies (which migrate from Canada to Mexico and back), the butterflies in the West migrate between the interior and the coast. The butterflies east of the Rocky Mountains go south to Mexico in winter. The butterflies on the Western side come to the California coast in search of warmer, milder weather than the inland winters.

From November to February, monarch butterflies gather in thousands in tall trees by the coast.

fallmigrationmap usfws

One of the wonderful things eucalyptus trees do is provide wildlife habitat. In particular, they are crucial to supporting the Western Migration of the the Monarch butterflies, by providing a roost for the butterflies to spend the winter. A study by Dennis Frey and Andrew Schaffner of 300 over-wintering sites showed that three-quarters of them were in eucalyptus trees. In fact, there’s some evidence that the butterflies’ Western migration exists because of the eucalyptus trees.

Most winters, you can see the butterflies at Natural Bridges State Park, about an hour and a half south of San Francisco. Some years they’re even found right in San Francisco, in places like the Presidio and Treasure Island. This is one of those years: The Monarch butterflies came to San Francisco and also to Oakland’s Aquatic Park.

MONARCH BUTTERFLIES IN SAN FRANCISCO IN 2015

Janet Kessler visited the Presidio and took these lovely pictures of Monarchs on the eucalyptus trees there. They’re published here with permission.

monarch and shadow on eucalyptus copyright Janet Kessler

monarch butterfly in a San Francisco eucalyptus tree - copyright Janet Kessler

Monarch butterfly on eucalyptus leaf - copyright Janet Kessler

CHILDREN DRAW MONARCHS

Also in celebration, we’re proud to publish these pictures from Girl Scout Troop #61902, sent in by Alma Sorenson, Troop Leader:

Grace-'Untitled' sm

Monarch Butterfly – by Grace M.

Addy-'The Monarch in Golden Gate Park' sm

The Monarch in Golden Gate Park – by Addy

Emma-'Take Flight' smm

Take Flight – by Emma

Angelina-'One Monarch in a San Francisco Eucalyptus Tree' sm

One Monarch in a San Francisco Eucalyptus Tree – by Angelina S.

Lindsey-Monarch Butterflies Love Eucalyptus Trees' sm

Monarch Butterflies Love Eucalyptus Trees – by Lindsey D.

 

Troop 61902 Sign sm

Girl Scouts: Building girls with courage, confidence, and character who make the world a better place

From Ms. Sorenson:

“We are a troop of twelve 4th and 5th grade Juniors from five different San Francisco schools focused on learning and earning Girl Scout badges, and on serving our community.

“We have our donated time and our cookie money to My New Red Shoes, the SFSPCA, and Project Open Hand. This year we will continue our theme of helping kids in need and on the environment.