This is an extensive excerpt from an article by Peter Gray Scott on the subject of the myths surrounding Eucalyptus and fire [with emphasis added]. It is quoted here with permission.
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One by one, myths about eucalyptus are pitched at us and, one by one, we must knock ’em down. Like the WMD myth, the apparent intent of those who pitch these myths is to keep propping up the fear factor, to support the eucaphobia that unfortunately grips some of our neighbors. Repeat something scary enough times and in some peoples’ minds it becomes fact.
Myth 1: Eucalypts were responsible for, and exacerbated, the ’91 [Oakland, CA] fire.
The truth is that eucs were nowhere near the origin of the fire on Saturday, October 19. The fire started in dry brush, grass and scrub oak on a steep slope above Buckingham Boulevard. There were some pines nearby but the fire did not jump into them. The fire restarted on Sunday, October 20, as flare-ups in dry brush within and just beyond the area that burned on the previous day. It spread first into oak trees. By the time the flames reached the first grove of eucs (1/6 mile away, just above Charing Cross) the conflagration was no longer a vegetation-fueled fire; it was a full-fledged structure-fueled fire that consumed everything in its path.
Myth 2: Blue gum eucalyptus trees are uniquely hazardous because they are oily, and explode in a fire.
Tree experts disagree with this myth. The leaves of blue gum eucalyptus trees contain oil; so do the leaves of bays and many species of chaparral. However, the trunks of eucalyptus trees are described as “fire-resistant (like redwoods).” Their trunks resist ignition, and the leaves are close to 50% water (koalas live off them). When, finally, the tree’s temperature reaches an ignition point, the euc will outgas a flammable haze, producing a sudden bright flare . . . but this is not an “explosion.” It poses no extraordinary risk, and it occurs significantly after other species have already burned.
Myth 3: Eucalypts are responsible for advancing the fire-front by “spotting”—projecting burning bits ahead of the flames.
In the first version of this myth, the leaves were blamed because they were said to be uniquely aerodynamic. However, experiments demonstrated that a) the leaves don’t fly very well, b) they don’t fly at all once burned, and c) they are incapable of maintaining an ember. So that myth was modified. Now it’s claimed that the euc’s bark strips are the culprits. This assertion appears in serious presentations, like Jerry Kent’s history of the hills fires and EBRPD’s Environmental Impact Report, but it is unsupported by any evidence, and it denies common sense and actual experience. Why should eucalyptus bark embers fly but not burning oak twigs, bay branches and coyote brush limbs?
The truth is: all loose material flies in a Diablo wind. During the 1991 fire, a fire-fighting pilot reported seeing a burning sheet of plywood at 2000 feet!
Myth 4: Eucalyptus forests are prone to dangerous crown fires.
The opposite is true. Because the mature trees’ lowest limbs tend to be more than 8 feet above the forest floor, no “fire ladder” sends the flames into the crowns; because the eucalypt’s wood and leaves naturally resist ignition, the underbrush and surface fuel is consumed before the euc reaches ignition temperature. Films of Australian wildfires show the fire sweeping through the understory, but leaving the eucalypts’ crowns green and intact. Photos of the ’91 fire indicate the same fire behavior in Gwin Canyon. The 2006 Broadway Terrace fire demonstrated this same characteristic.
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In conclusion, he points out that “In an effort to forestall climate change, cities and nations around the globe are busy protecting and planting thousands of trees. Ironically, organizations that historically have supported protection of the environment and the health of the planet—the Sierra Club, the Audubon Society and others — are actively supporting tree removal projects. But it is clear they are advocates for a very different agenda: Although they superficially support fire risk mitigation, their true mission is restoration of native plants.”
Mount Sutro Forest That Was 
As the nativists urge us to attend an ecology class, we urge them to read the scientific literature that supports Mr. Scott’s fine article. Here are a few references which support Mr. Scott’s article:
Notes to “Myth 1.” Mr. Scott lived through the 1991 fire in Oakland, although his mother did not survive it. He and his wife also lost their home. He studied the fire and he drew from his personal experience and observations.
Those of us who did not live through the fire can also inform ourselves by reading the detailed technical report of the fire by FEMA. FEMA has no agenda other than to prevent disasters and to deal with their consequences. Their report was done by experts with no vested interest in any particular interpretation of the fire other than a commitment to preventing another.
The FEMA technical report is available here: http://www.nps.gov/fire/utility/related_items/1991_oct19.pdf. You will find that the eucalypts played little role in the 1991 fire. If the dead leaves and limbs of the eucalypts (and other plants as well) had been cleaned up after the deep freeze the previous winter of 1990, they wouldn’t have played ANY role. There hasn’t been another such freeze for 20 years. If there is another freeze, the cost of cleaning up after it would be miniscule compared to the loss and the cost of eradicating every eucalyptus in the East Bay.
Notes to “Myth 2.” The source of this information about “outgassing” is a book entitled The Tree by Colin Tudge. Mr. Tudge is a fellow of the Linnean Society of London and the author of several natural history books.
I also recommend A Natural History of California, by Schoenherr (UC Press 1992). This is a comprehensive natural history book, written by a respected academic. Here are a few tidbits from that book about the flammability of native vegetation:
Shreddy bark and volatile oils are characteristics of many plants, both native and non-native. They are not characteristics exclusive to eucalypts: “The [chaparral] community has evolved over millions of years in association with fires, and in fact requires fire for proper health and vigor…Not only do chaparral plants feature adaptations that help them recover after a fire, but some characteristics of these plants, such as fibrous or ribbonlike shreds on the bark, seem to encourage fire. Other species contain volatile oils.” (page 341)
Here is an example of a particularly flammable member of the native chaparral plant community from that book (page 344)
“The relationship between fire and Chamise is illustrated by the plant’s tendency to ‘encourage’ burning. A thermometer was placed within a Chamise shrub as a fire approached, and the following changes were documented. At about 200⁰F the plant began to wilt as its temperature approached the boiling point of water. At about 400⁰F the plant began to emit combustible gases such as hydrogen, alcohol, and methane. At about 600⁰F the shrub smoldered and began to turn black. At about 800⁰F the plant burst into flames! This species must have evolved in association with frequent fires to have reached the point where it seems to encourage burning.”
Notes to “Myth 3.” Here is an empirical study done in a USDA laboratory about the ability of several native plants and trees to produce flying embers: “Ignition Behavior of Live California Chaparral Leaves” available here: ams.confex.com/ams/pdfpapers/65289.pdf. Here are a few quotes from that study, done in the lab with NO wind:
“As the chamise burned, occasionally a brand would be lofted off the main stem and float away from the FFB [burning platform]”
“Many of the oak leaves had sharp points (i.e., spines) around the outer edge. The oak leaves would ignite at these points, sometimes accompanied by small explosions of the points that led to the ejection of small brands.”
Notes to “Myth 4.” One of the reasons why we object to the eradication of eucalypts in the East Bay is that it has been attempted several times in the past. Because attempts to poison the trees unto death were unsuccessful, they returned and for many years were immature trees with lower fire ladders than the mature trees that were destroyed. They were therefore more susceptible to crown fires for several reasons: their lower fire ladders, their immature leaves which are more flammable than mature leaves and their greater susceptibility to die back caused by freezes. In other words, eradication attempts in the past failed and resulted in a more vulnerable landscape than what had been destroyed.
Ironically, the source of this information Is the “Wildfire Hazard Reduction and Resource Management Plan” of the East Bay Regional Parks District, which proposes to destroy hundreds of thousands of non-native trees, as well as countless plants, on thousands of acres of park land. While trying to make a case for their plan, they unwittingly document that their plan is unlikely to reduce fire hazard. The plan is available here: http://www.ebparks.org/stewardship/fireplan/plan.
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I hope this will invite a response from our nativist friends. A dialogue has the potential to inform us all.
NatureLover,
See my responses to your additions/responses.
NatureLover // March 3, 2010 at 9:05 am
Those of us who did not live through the fire can also inform ourselves by reading the detailed technical report of the fire by FEMA. FEMA has no agenda other than to prevent disasters and to deal with their consequences. Their report was done by experts with no vested interest in any particular interpretation of the fire other than a commitment to preventing another.
JMC: I doubt they were expert Botanists with extensive experience in either California vegetation or Eucalyptus. And that is besides the point. I can care less about whether it caused the fire or not (not to discount the loss of life and property during that tragedy).
The FEMA technical report is available here: http://www.nps.gov/fire/utility/related_items/1991_oct19.pdf. You will find that the eucalypts played little role in the 1991 fire. If the dead leaves and limbs of the eucalypts (and other plants as well) had been cleaned up after the deep freeze the previous winter of 1990, they wouldn’t have played ANY role. There hasn’t been another such freeze for 20 years. If there is another freeze, the cost of cleaning up after it would be miniscule compared to the loss and the cost of eradicating every eucalyptus in the East Bay.
JMC: But the benefits to removing the Eucalyptus outweigh the cost of removing them, particularly when they are done correctly. The opening of habitat for a wide range of species that prefer their native and more diverse habitat to the substantially reduced diversity offered by the Euc forests.
Notes to “Myth 2.” The source of this information about “outgassing” is a book entitled The Tree by Colin Tudge. Mr. Tudge is a fellow of the Linnean Society of London and the author of several natural history books.
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JMC: Eucalyptus is designed and adapted to burn. The accumulation of bark debris and limbs at the base of the trees is meant to serve as tinder to create a fire hot enough to open the resin coated seed pods. The shaggy bark on the trunks (like shredded paper) is designed to bring the fire to the crown which will help the leaves (and their oil) catch fire and open the pods. Fires are much more frequent in Australia/Tasmania than they are here. This would reduce the fuel load. The cool coastal climate and the lack of lightning we have here doesn’t promote fires that frequently and therefore the fuel loads on the ground in many of these older groves are exceptionally high.
If you want to test for yourself and you have a fireplace, go round up some of the shredded bark off any Euc tree when it is not wet (due to fog or rain) and start a fire with it – it burns fairly easily.
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I also recommend A Natural History of California, by Schoenherr (UC Press 1992). This is a comprehensive natural history book, written by a respected academic. Here are a few tidbits from that book about the flammability of native vegetation:
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JMC: Finally we agree on something. This is an excellent book.
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Shreddy bark and volatile oils are characteristics of many plants, both native and non-native. They are not characteristics exclusive to eucalypts: “The [chaparral] community has evolved over millions of years in association with fires, and in fact requires fire for proper health and vigor…Not only do chaparral plants feature adaptations that help them recover after a fire, but some characteristics of these plants, such as fibrous or ribbonlike shreds on the bark, seem to encourage fire. Other species contain volatile oils.” (page 341)
Here is an example of a particularly flammable member of the native chaparral plant community from that book (page 344)
“The relationship between fire and Chamise is illustrated by the plant’s tendency to ‘encourage’ burning. A thermometer was placed within a Chamise shrub as a fire approached, and the following changes were documented. At about 200⁰F the plant began to wilt as its temperature approached the boiling point of water. At about 400⁰F the plant began to emit combustible gases such as hydrogen, alcohol, and methane. At about 600⁰F the shrub smoldered and began to turn black. At about 800⁰F the plant burst into flames! This species must have evolved in association with frequent fires to have reached the point where it seems to encourage burning.”
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JMC: Yes, exactly. However, two things: chamise is no taller than 6-8 feet in really overgrown areas and generally less than 4 ft. Eucalyptus are >150-200 ft in many locations in California. These forests were largely planted at in the late 1800’s and early 1900’s and have not had their understory cleaned in most cases (Sutro Forest being a prime example).
Also, Chamise does not grow on the SF Peninsula. It is found on my drier south chaparral communities. The native coastal scrub and chaparral to the SF peninsula would support Coyote brush, California sage, bush lupine, poison oak, buckwheats, etc. etc.
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Notes to “Myth 3.” Here is an empirical study done in a USDA laboratory about the ability of several native plants and trees to produce flying embers: “Ignition Behavior of Live California Chaparral Leaves” available here: ams.confex.com/ams/pdfpapers/65289.pdf. Here are a few quotes from that study, done in the lab with NO wind:
“As the chamise burned, occasionally a brand would be lofted off the main stem and float away from the FFB [burning platform]”
“Many of the oak leaves had sharp points (i.e., spines) around the outer edge. The oak leaves would ignite at these points, sometimes accompanied by small explosions of the points that led to the ejection of small brands.”
JMC: Again chamise is the wrong species to use in this argument. Oaks are much shorter and would be restricted to canyons or the east facing slopes of Mount Sutro if at all. Again, oaks are not nearly as tall and frankly don’t accumulate the fuel that Eucalyptus do. See the National Park Service flier on Eucalyptus (contains studies that compare oak woodland vs. Eucalytpus and fire risk…..guess who was worse by a mile….was this in FEMA?)
Click to access Eucalyptus.pdf
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Notes to “Myth 4.” One of the reasons why we object to the eradication of eucalypts in the East Bay is that it has been attempted several times in the past. Because attempts to poison the trees unto death were unsuccessful, they returned and for many years were immature trees with lower fire ladders than the mature trees that were destroyed. They were therefore more susceptible to crown fires for several reasons: their lower fire ladders, their immature leaves which are more flammable than mature leaves and their greater susceptibility to die back caused by freezes. In other words, eradication attempts in the past failed and resulted in a more vulnerable landscape than what had been destroyed.
Ironically, the source of this information Is the “Wildfire Hazard Reduction and Resource Management Plan” of the East Bay Regional Parks District, which proposes to destroy hundreds of thousands of non-native trees, as well as countless plants, on thousands of acres of park land. While trying to make a case for their plan, they unwittingly document that their plan is unlikely to reduce fire hazard. The plan is available here: http://www.ebparks.org/stewardship/fireplan/plan.
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JMC: Removing Eucalyptus is the right move for many reasons. 1) It re-establishes habitat for a wider diversity of species…not just butterflies and raptors, but for a whole host of birds, mammals, insects and a wide range of plants that can’t live under the Eucs. 2) It DOES reduce fire hazards compared to oak or bay woodland and “properly” managed chaparral and scrub communities. 3) Studies have confirmed that Eucs absorb more water (groundwater) than native species. Some restoration sites (Colma Creek headwaters on San Bruno Mountain) have witnessed a return of perennial stream flow to small streams once extensive stands of Eucs were removed. Their leaf litter (toxins) reduces in-stream insect production which is critical food resources for fish (i.e. salmonids) and amphibians.
Most progressive ecologist would agree that managing for ecosystem preservation is the way to go. Native plant restoration is key to this.
I thought about one of your responses to my previous email in which you brought up Gould’s views on Native vs Non-native. I do disagree with Gould as I am sure others do as well.
There is a difference between letting nature introduce new species by way of climate change and adaptation as opposed to large-scale human interference. I don’t see the planting of an entire forest thus replacing native pre-existing communities as a good example of land stewardship or for biodiversity. For example, the native species that once thrived on Mt Sutro or in the Presidio had no fighting chance against wide-spread conversion due to forest planting; few remain in small pockets and are hanging on by a thread.
If you still feel that Gould is correct in that trying to stop non-native species then you/we should celebrate the longhorn borer and other pests threatening Eucalyptus. “The ultimate test of whether or not something “belongs here” is whether or not it is surviving here.” Lets join together and cheer on the longhorn borer then….if what you say is true.
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I hope this will invite a response from our nativist friends. A dialogue has the potential to inform us all.
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JMC: It has. I am not opposed to maintaining small groves of Eucs in corners of urban parks here and there, but the last remaining natural lands or open spaces that aren’t ball fields, or cemeteries should be managed for native species first and not invasive/non-natives. This ideology of keeping the forests as an Old Growth ecosystem or a Cloud forest are false and don’t make much sense. Do I think the Eucalyptus forest should be clear cut and replaced over night? Absolutely not. But phased overtime with careful measures in place to minimize erosion, maintain trails, and ensure restoration is moving along with success is very doable. Look at Angel Island, Point Reyes, San Bruno Mountain…these have all been great successes for the return of native ecosystems. I would encourage local schools (K-12) to become involved as part of their science curriculum. Get students out of the class rooms and into the field and connected with their local ecology.
JMC, Thanks for your response. A few replies…..
JMC: “I can care less about whether it caused the fire or not…”
The SaveSutro website was built to respond to UCSF’s application to FEMA to destroy 90% of the eucalypts on 14 acres of Mt. Sutro based on the premise that they are a fire hazard. Whether or not the eucalypts on Mt. Sutro are a fire hazard is therefore the subject of debate here, whether it’s something you personally care about or not. The 1991 fire in Oakland is the primary evidence used by proponents of eradication of eucalypts. Therefore, if eucalypts were not the cause of that fire, the evidence that is used to advocate for their destruction is relevent to the discussion.
JMC: “But the benefits to removing the Eucalyptus outweigh the cost of removing them, particularly when they are done correctly”
This is your opinion. It is not shared by those who do not believe that using toxic herbicides for 10 years after the removal of the eucalypts to prevent their regeneration is a benefit to the people or the animals on Mt. Sutro.
JMC: “Eucalyptus is designed and adapted to burn. The accumulation of bark debris and limbs at the base of the trees is meant to serve as tinder to create a fire hot enough to open the resin coated seed pods. The shaggy bark on the trunks (like shredded paper) is designed to bring the fire to the crown which will help the leaves (and their oil) catch fire and open the pods.”
The phrase “designed…to burn” is a bit mysterious, but leaving aside for the moment what you might mean by that, the native landscape of grassland and dune scrub is equally adapted to periodic burns. The seeds of some native plants germinate only in response to the heat of a fire or in the ash that remains after a fire. There are native trees and plants that are equally oily, such as bays and coyote brush which are considered very flammable.
JMC: “Fires are much more frequent in Australia/Tasmania than they are here. This would reduce the fuel load.”
I recommend that you acquaint yourself with the research of Jon E Keeley, a scientist of California fire ecology who now works for the US Geological Survey. He has written many articles and books and is often cited by other scientists working in this field. His view of wildfires in the wildland urban interface (WUI) is radically different from our local “experts” who are advocating for the destruction of non-natives.
The conventional wisdom in the San Francisco Bay Area is that modern wildfire hazard is caused primarily by accumulated fuel loads resulting from fire suppression policy. Keeley challenges this theory. His research of fire frequency in the WUI correlates population growth with fire frequency. From 1900 to 2000 increased population in the WUI is correlated with more fires.
His research also indicates that fire frequency is unrelated to the age of the native vegetation. Coastal sage and chaparral burn less frequently after 30, 40, and 50 years without fire, than they do after 20 years without fire.
These observations, lead to his conclusion in “Fire Management of California Shrublands” http://www.werc.usgs.gov/seki/pdfs/Fire%20Management%20of%20California%20Shrublands%202002.pdf: “These findings strongly support fire management strategies that emphasize fire prevention and vigorous fire suppression, and raise questions about prescribed burning programs that intensively treat landscapes with the goal of creating fire mosaics.”
JMC: “Finally we agree on something. This is an excellent book.”
It’s interesting that you respect this source of information, yet you seem not to have actually read the quote from it in which Schoenherr describes the flammable characteristics of native plants, including their “shreddy bark” and “oily resins.” These are not just characteristics of eucalypts. They are also characteristics of native plants according to a source of information that you say you respect.
JMC: “chamise is no taller than 6-8 feet in really overgrown areas and generally less than 4 ft. Eucalyptus are >150-200 ft in many locations in California.”
The height of the eucalyptus does not make it more flammable. In fact, the shorter a tree or shrub the more of a fire ladder to its crown it provides. Tall trees with little undergrowth and limbs at least 10 feet above the ground are unlikely to burn in a wildfire.
JMC: “Chamise does not grow on the SF Peninsula.”
Chamise grows in the East Bay where hundreds of thousands of eucalypts are in jeopardy of being eradicated by native plant advocates based on the bogus premise that they are more flammable than the native landscape they prefer.
JMC: “Oaks are much shorter and would be restricted to canyons or the east facing slopes of Mount Sutro if at all.”
Yes, and because the oak is prostrate—that is, low to the ground—it provides a fire ladder to its crown and is therefore more likely to burn in a wildfire than the mature ecualyptus. It is also equally likely to produce the fire brands that spread a wildfire.
JMC: “See the National Park Service flier on Eucalyptus…”
I have read this NSP flier about eucalypts. Here is a quote from it: “The live foliage [of the eucalyptus] proved fire resistant, so a potentially catastrophic crown fire was avoided.” http://www.firescape.us/coastliveoaks.pdf
JMC: “It re-establishes habitat for a wider diversity of species…not just butterflies and raptors,”
We use butterflies and raptors only as examples of the biodiversity that exists as a result of the existence of non-native species. There are many birds that are here because of non-native species. There are many other insects that have adapted to existing vegetation. If non-native species are eradicated, there will be less diversity of species, not more.
JMC: “If you still feel that Gould is correct in that trying to stop non-native species then you/we should celebrate the longhorn borer and other pests threatening Eucalyptus…. Lets join together and cheer on the longhorn borer then….if what you say is true.”
This is a non sequitur, in my opinion. Gould was not “celebrating” (nor am I) non-native or native species. He was saying that from the standpoint of evolutionary theory, one cannot be presumed to be superior to the other.
If I remember correctly, the particular insects you mention are predators of the eucalyptus in Australia. If I am correct in that memory, these particular insects are not found in the United States (with a few isolated exceptions) because the eucalyptus was imported here as seeds, not as plants according to Doughty in The Eucalpytus (page 148).
Thanks again for your response. I look forward to further dialogue with you.
I hoped JMC would engage in a dialog that might inform us. He did not. He didn’t respond to any of Mr. Scott’s points. He quibbles with NatureLover’s researched evidence in support of Mr. Scott, without offering any evidence of his own. Mr. Scott debunked some common myths about eucalyptus propagated by native plant enthusiasts like JMC, and his debunking stands, unchallenged by JMC.
Myth 1: Eucs were responsible for the ’91 Oakland fire. JMC offers no evidence to support that myth and says he doesn’t care whether eucs caused the fire or not. So Myth 1 remains a myth unsupported by evidence.
Myth 2: Blue gum eucs are uniquely hazardous because they are oily and explode in fire. JMC offers no evidence to support the “oily and explode” myth. Myth 2 remains a myth unsupported by evidence.
Myth 3: Eucs are responsible for advancing the fire-front by “spotting.” JMC says nothing about fire spread by spotting. Myth 3 remains a myth unsupported by evidence.
Myth 4: Euc forests are prone to dangerous crown fires. JMC says nothing about crown fires. Myth 4 remains a myth unsupported by evidence.
Does JMC acknowledge that these myths are just myths? He doesn’t say.
JMC goes on at length, repeating his myth-filled opinions about eucalyptus and native plants, establishing only that he doesn’t like eucalyptus trees. He throws in more unsupported statements, e.g. that “fires are much more frequent in Australia/Tasmania than they are here.” That sounds like a statement of fact. If it were a fact, it should have some evidence behind it, considering we already know wildfires are frequent in California. JMC should follow the example of NatureLover, who cites and quotes his sources. But self-styled “expert Botanists(sic)” and “progressive ecologist(s)” appear to work without data or evidence.
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Oh so ironic that someone with a title of “naturelover” would prize an invasive species above species in our native food web which evolved over thousands of years between native California flora and fauna. No one here mentions that the only benefit provided by eucs is aesthetic, which should never outweigh safety or wildlife habitat considerations. They do not provide a single meaningful habitat benefit function (hawks sitting in them every once in awhile does not count). Studies have documented that California native pollinators do not prefer to use non-native plants. Eucs drop limbs without warning. They poison soil because their oils are allelopathic and prevent anything from growing around them. Anyone who has walked through a grove of eucs will notice that fewer that 5 species will be noted growing around them (also mostly nonnative species). Anyone who thinks biodiversity is important should despise eucs.
[Webmaster: Actually, though widely believed, most of those things are myths. Take a look here: https://sutroforest.com/eucalyptus-myths/ ]
Finally, the eucs that are here were planted by a businessman hoping to get rich by selling lumber. There is no noble cause here… they were planted for profit based on ignorant beliefs not supported by evidence.
[Webmaster: That’s not entirely true either; they were planted for a host of reasons, including their beauty.
See https://sutroforest.com/a-historic-forest/ ]
Doesn’t this make anyone else just a little bit sick?
[Webmaster: Nature comes in many forms, and what makes us a little bit sick is the destruction of existing established eco-systems and habitat for native plant restoration. See:
https://sutroforest.com/2011/03/24/habitat-destruction-with-sutro-stewards/ and this:
https://sutroforest.com/2011/01/24/sutro-forest-ecosystem-and-wildlife-habitat/ ]
I love snow leopards. I think they’re beautiful, and they’re globally rare. But they don’t belong in California. Any nature lover should be able to understand that.
[We don’t believe anyone is trying to introduce snow leopards to California. But in an increasingly globalized world, the concept of what belongs is getting broader all the time. Native species and non-native species are interwoven in the food web… including the one we human beings are in. We couldn’t survive without non-native species. Practically *everything* we eat is non-native, and California’s agriculture is based almost entirely on non-native species. If we had to elminate non-native species, we’d have to live on acorn flour and fish. ]
I notice that the linked page is permeated by “myths” labeled “partly true” and “mostly false”. There’s nothing like hedging around science to accomplish the objectives you want, I guess. Opinion and anecdotal evidence do not stand up to scientific observation. Sorry to break this to you.
[Webmaster: Hmm. And here we thought we were providing a better level of accuracy than merely a dichotomy. Anecdotal evidence can be used to disprove a case. If you said “all swans are white” then only a few black swans would disprove the theory. So we do try to provide evidence and sources.]
Here is the link to the study that bees use but do not prefer alien plants.
[Webmaster: Thanks for the link. It says that in the study areas in New Jersey, bees (which are presumably non-native honeybees, though the abstract didn’t say) appeared indifferent between native flowers and non-native flowers. We agree; we’ve seen the same thing both with bumble-bees and honeybees. They visit oxalis and clover and ceanothus and California poppies. Non-native flowers are important because they’re abundant, and are around longer. Eucalyptus especially flowers nearly year-round, so it provides food at a time when native flowers aren’t blooming. ]
The same applies to birds. Of course a bird will “use” a tree. Trees in general are habitat for birds. I do not disagree with this because it’s a fact. However, some trees are better habitat than others. A lot of birds “use” concrete too, but this does not make concrete acceptable habitat. And honestly, how many bird species have you seen waiting by a roadside for cars to run over eucalyptus pods? All of our wrens, kinglets, warblers, creepers, and flycatchers are insectivorous. They forage mainly by hovering around the new tips of branch growth and picking off small insects. Implying that native birds can effectively use euc seeds as foraging habitat is misleading and insidious. http://en.wikipedia.org/wiki/List_of_birds_of_California
[Webmaster: Actually, we don’t think we suggested that euc seeds are the primary food source. It’s the whole forest ecosystem — including insects. See our posts
https://sutroforest.com/2010/03/29/sutro-forest-birds/ and https://sutroforest.com/2010/07/08/more-sutro-forest-birds/ for birds that actually live in this forest. And a study in the Berkeley, California, found little difference between the number of species in an oak forest and a eucalyptus forest.]
Here is a link to a study that finds that in drier climates eucs are proven to inhibit the growth of other species.
[Webmaster: Again, thanks for that link. The 1990 Australian stud, An Assessment of the Allelopathic Potential of Eucalyptus, used rye-grass, duckweed and acacia in a lab study to see if eucalytus inhibited their growth. It found the fresh leaves didn’t, but if they chopped up the leaves it did. And they also found bark litter, leaf litter and “stemflow” had the effect of inhibiting growth, but cautioned that “It is apparent that allelopathy must be considered in relation to rainfall and the soil water balance.” It didn’t prove that eucalyptus had an allelopathic effect on rye-grass and duckweed and acacia, but the study’s authors thought it had potential to do so: “…allelopathy is likely to be a cause of understorey suppression by Eucalyptus species especially in drier climates.” In Sutro Forest, which is very wet, there is no understorey suppression, and in fact acacia is one of the major sub-canopy species. In the East Bay, a study showed that eucalyptus forest had as many species as native oak forests.]
Finally, of course no one is proposing to introduce snow leopards to California. I use this analogy as a means to demonstrate that simply because something non-native is beautiful does not mean it belongs in a foreign place. California is a biodiversity hotspot. Encouraging invasive species actively diminishes the potential for our native species to survive. This is not opinion; it is a fact.
[Webmaster: If it’s not an opinion, but is fact, could you cite your sources? Though we’ve heard that statement frequently, we haven’t seen any substantiation.]
As I said before: anyone who appreciates the diversity of our native species should encourage native habitats over introduced species, no matter what they are.
[Webmaster: We think it’s not so simple. Native and non-native are now ecologically interwoven in ways that cannot be disentangled. If the forest is destroyed, so will be many of the birds and animals that live there… even though they’re native. We don’t live in a world of “native habitats” any more, especially not in the Bay Area. The habitats are all mixed, and the creatures that depend on them have adapted to form new, unique and — to us — interesting and beautiful ecosystems.]
Hi K! Thanks for the discussion and the links. We’ve embedded our responses in the comment above.
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