More Fire Factors: Fire Ladders and Embers

Recently, a local news program broadcast an interview about the legal suit filed by the Hills Conservation Network (HCN) against the “Wildfire Hazard Reduction and Resource Management Plan” of the East Bay Regional Park District (EBRPD).  Although both HCN and EBRPD are committed to reducing fire hazard, they disagree about how to achieve that goal.  The spokesperson for HCN said there is no “scientific or factual evidence” that eliminating the canopy of non-native trees will reduce fire hazard.  The spokesperson for EBRPD said the trees will be removed because they “burn intensely” and “loft embers into the wind, causing spot fires downwind” when their crowns begin to burn.  

Is there scientific or factual evidence to support the claims of EBRPD?  Are non-native trees more likely to burn than native trees and if so do they burn more intensely than native trees?  Are non-native trees more likely to loft embers than native trees?  This post will document the answers to these questions:  NO, NO, and NO!

When fire spreads on the ground, through fine fuels such as grass, it bypasses trees unless there is a fire ladder to their canopy.  The fire ladder is composed of low branches that extend from the ground, into the canopy of the tree.  Tall eucalyptus trees usually do not provide such a fire ladder to their canopy.

We see a few of the eucalypts in the distance that EBRPD intends to destroy in Lake Chabot park. We notice that they are very tall and there is no fuel ladder to their canopy. In the foreground, on the right, we see some of the native bay laurels that EBPRD plans as replacements for the eucalypts. We notice that the bays are close to the road and that they grow to the ground, providing a fuel ladder to adjacent vegetation.

When tall trees, such as eucalypts have a fire ladder to their canopy, their lower limbs can be removed without harming the tree.  This method of reducing fire hazard has been used effectively in the Mountain View Cemetery in Oakland.  Obviously, this method of reducing fire hazard is cheaper and less destructive than destroying the trees and then killing their roots with poison.  This was one of the strategies suggested by the Hills Conservation Network during negotiations with EBRPD before they filed suit after negotiations failed.

The fire ladders on these eucalypts have been removed in the Mountain View Cemetery.

In a wind-driven firestorm the fire may rapidly spread high above the ground.  In that case, how likely is the canopy of eucalypts to ignite compared to other trees?  The firestorm of 1991 in the Oakland/Berkeley hills is an example of such a fire.  In our posts “FIRE!!! The Cover Story” and “The Power of a Legend” we have reviewed two official documents and one book about the 1991 fire which contain no evidence that eucalypts were responsible for that fire.   

Please click here to see a picture of an entire neighborhood of homes destroyed by a wildfire in the Scripps Ranch in 2003..  The burned homes are entirely surrounded by tall eucalyptus trees that are untouched by the fire.  Despite this obvious evidence that the eucalypts were blameless in this fire, native plant advocates seized upon this fire to demand that the eucalypts be destroyed.  The residents of Scripps Ranch fought back and for the moment, they have succeeded in preventing the destruction of their eucalyptus forest. 

The National Park Service is one of many managers of public lands that are engaged in massive restorations of native plants that frequently result in the destruction of non-native trees.  And as most managers of public lands, it attempts to justify the destruction of the trees by claiming that they are a fire hazard.  Reading the fine print of its literature about eucalyptus,  we find that their claims are not supported by the evidence.  Studying the table comparing the fuel loads of eucalyptus with native oaks and bays, we find that the table has been carefully constructed to support their case.  If logs–which would take 1,000 hours to ignite*–are removed from this table, the available fuel load of eucalyptus is not greater than that of native oaks.  Also, deeply embedded in the fine print, you find that the park service admits that the leaves of the eucalyptus are resistant to fire (“The live foliage [of the eucalypts] proved fire resistant, so a potentially catastrophic crown fire was avoided.”) 

We conclude that all evidence from past fires indicates that eucalypts are unlikely to ignite in a wildfire.  If they don’t ignite, they obviously will not “loft embers” to spread the fire.  The final question is, in the unlikely event that there is a crown fire in eucalyptus, how likely is it that embers will be produced that spread the fire downwind?  Although we don’t know the answer to that question, we have both scientific and experiential evidence that native trees are also capable of producing embers.

In “Ignition Behavior of Live California Chaparral Leaves,”  Steven Smith, Joshua Engstrom, Jordan Butler, Thomas Fletcher (Brigham Young University, Provo, Utah) and David Wiese (USDA, Forest Service) report the results of laboratory tests on four species of native plants and trees, including oaks.  They find that both native chamise and oaks loft embers absent any wind.  In the case of oaks, they report that “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.” 

The Marin Independent Journal in its report of the Angel Island Fire of 2008 tells us that embers from the burning oaks were responsible for nearly igniting the historic buildings on the island:  “’All the oaks up there were burning,” said the 28-year veteran of the department. “It was an ember shower that just rained on the entire building, and all the vegetation around us was burning.’”  As we reported in our post about the Angel Island Fire, most of the eucalyptus had been removed from the island about 12 years before the fire in 2008.  The fire stopped at the edge of the remaining 6 acres of eucalyptus.

There is overwhelming evidence that eucalyptus is not more flammable than native trees and has not played a role in the many wildfires in California.  The myth that eucalypts are responsible for wildfires is propagated by native plant advocates who use the fear of fire to justify the destruction of eucalypts.  Those who are willing to look closely at the evidence will see through this carefully constructed myth to the reality that destroying non-native trees will not reduce fire hazard.

*For a technical explanation of timelag, we quote from Sugihara’s Fire in California Ecosystems:  “The proportion of a fuel particle that contains moisture is a primary determinant of fire behavior…Timelag is the amount of time necessary for a fuel component to reach 63% of its equilibrium moisture content at a given temperature and relative humidity……1,000-hour fuels reflect seasonal changes in moisture.  The firewood analogy applies here as well.  Your large logs would take several months to dry if left out in the rain for the winter, yet kindling, if brought inside, would dry in a few hours.”

11 thoughts on “More Fire Factors: Fire Ladders and Embers”

  1. Well documented and well-written… but convincing those who refuse to be convinced is tough. Keep it up. The truth will out only if there are those willing to speak Truth to Power.

  2. It is difficult for me to understand how this seems to have become a contest between residents in a fire-prone area who want to preserve eucalyptus trees and parkland managers who want to cut down trees.

    Eucalyptus proponents look at a table from the newspaper ( see “literature about eucalyptus” link above) and ignore the fuel load of peeling bark that is the fire ladder inherent to eucalyptus. The East Bay Regional Park Wildfire Hazard Reduction and Resource Management Plan is shrouded in bureaucratic speak but does not seem (I can’t get through the many segments down-loadable only one at a time) to incorporate the idea of replacing highly flammable eucalyptus with elegant redwoods and sequoias that are the most enduring and least flammable of trees.

    People seem to talk past each other, not with each other.

    1. We agree that more Redwoods in the landscape would be a welcome addition. Unfortunately, they won’t grow everywhere because they don’t tolerate wind and they require a reliable source of water. For example, they are not native to San Francisco, although they grow there now in sheltered areas, ironically in some places where the eucalypts provide a windbreak, such as Stern Grove.

      And as Mr. Gibson has observed, managers of public lands prefer to return landscapes to their historical precedents, which in the Bay Area is predominantly grassland, chaparral, and dune scrub.

      The “literature about eucalyptus” to which Mr. Gibson refers, is a publication of the Natrional Park Service. The table in question claims to include all elements of the trees being compared in the table, including the bark. We can’t verify the accuracy of the table, but since the National Park Service is an advocate for the eradication of eucalypts, we assume that Mr. Gibson would find it a credible source of information.

      We also agree with Mr. Gibson that a respectful dialogue is helpful to understand the issues and reach the desired outcome, which is a fire safe landscape that doesn’t require the use of hazardous methods such as toxic herbicides and polluting, dangerous prescribed burns to maintain.

      1. This is further to comments from Million Trees and others here: There are over 700 species of Eucalyptus and some relatively new hybrids. Reportedly 150 species have been introduced to the Western United States. I am occasionally surprised to find a species in the Bay Area that is new to me. There is a massive such tree in Golden Gate Park just south of the “Polo Field.” It is reminiscent of a Bayan tree. It is surrounded by green grass and few if any others of its species.

        In the Berkeley and Oakland Hills there are extensive forests of a species that grows very tall and is characterised by peeling bark, dangling to the ground. This bark seems a built-in fire ladder for the species. The leaves are six or more inches long, shaped almost like the blade of a scythe. I have seen the leaves, fluttering in the drafts created by a forest fire, several hundred yards from the active conflagation with their singed edges still glowing bright red. The leaves fell into my yard.

        However, I agree with Million Trees that there is danger too from grassland-fire all around the Bay Area. I strongly urge U.C. Berkeley, Oakland Parks and Recreation, East Bay Regional Parks and the City and County of San Francisco to plan for a planting of redwood trees in all the creek beds flowing down from hills into residential or other deveoped areas. Redwoods still dominate many of these areas in the Oakland Hills, but wherever the tall Eucalyptus are removed and water is available, or can be provided to get redwoods started efforts should be made. Ideally, volunteers would be recruited to plant the trees, once any “poisons” have dissipated and in some cases to water trees near their own property lines. Abandoning nearby forest areas to grassland is a hazard, even if the foresters are confident that native Umbellularia californica (California bay laurel) will reclaim the land quickly, and naturally preserve the space for redwood grove expansion. I’d rather be allowed, encouraged and guided to help the process along in Juaquin Miller Park (for example).

  3. Contrary to the unpopular beliefs being expressed here. there is no lack of fuel ladders for eucalyptus.

    Webmaster: Congratulations on the launch of your blog.

    We are not members of the Hills Conservation Network. We are independent of HCN. Dan Grassetti has nothing to do with the content of this blog. He doesn’t subscribe to this blog. So, you are not communicating with him. HCN has its own website and there is an email address on it if you would like to communicate with them.

    You underestimate the size of the opposition to this destructive project. 4,700 people have signed the petition in opposition to this project. The petition in support of the project has less than 500 signatures. Fifty-six people spoke at the public hearing about this project on May 18, 2013. Only 6 people spoke in support of the project.

    1. Your photo of eucalyptus at Alvarado and Claremont Ave appears to be looking to the south across Claremont. Since Alvarado is not visible, it’s hard to tell exactly where along Claremont the trees are. There are two possibilities: 1) The trees are close to Alvarado, and not in the project area, or 2) The trees are in treatment area CC009. In either case, these eucs will not be removed by the FEMA funded projects. (See the map Figure III-7 and the description of CC009 in Table III-2 in the EBRPD DWHR-RMP, July 2009)

      The post you are commenting on is quite accurate about fire ladders. The post does not deny that eucalyptus sometimes has a fire ladder. It says, “The fire ladder is composed of low branches that extend from the ground, into the canopy of the tree. Tall eucalyptus trees usually do not provide such a fire ladder to their canopy.” Your photos support Milliontrees’ statement. They generally show debris on the ground, not low branches that extend from the ground into the canopy. Further, the post says in the very next sentence, “When tall trees, such as eucalypts have a fire ladder to their canopy, their lower limbs can be removed without harming the tree,” and provides a photo to illustrate where this has been done. The East Bay projects claim they are going to limb up oaks and bays to remove fire ladder, where necessary. They could do the same to eucalyptus, where necessary.

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