Fire scientist says, “…eucalyptus did not burn with high intensities leading to home destruction”
We have the pleasure of publishing a guest post by a member of the team that is trying to prevent the pointless destruction of the urban forest in the East Bay Hills. This article is an example of the expertise and dedication of our team. It also makes another contribution to the considerable body of evidence that eucalyptus has been inappropriately blamed for the 1991 Oakland fire and that destroying our urban forest will not reduce fire hazards. (emphasis added)
April 24, 2016
Jack Cohen is a fire scientist at the US Forest Service fire lab in Missoula Montana. For decades he has researched fire behavior in the Wildland Urban Interface areas (WUI). His research includes scores of post-fire investigations, as well as controlled experiments in the only forest fire lab in this country. WUI fire poses a unique set of challenges to local fire departments. Mr Cohen’s research has informed nationwide strategies on how to prevent and manage fire in the WUI setting.
He concludes that it is neither desirable nor realistic to attempt complete suppression of catastrophic fires, or to expect fire departments to fully defend WUI areas. We live, after all, in a fire dependent natural environment, and have over the years constructed many combustible structures within heavily vegetated and dry areas. He does believe it is possible to construct and maintain buildings to resist ignition, (by addressing the Home Ignition Zones) and that this effort will do much more towards preserving human life and property than remote fuel treatment, or poorly focused fire suppression efforts.
As part of my work as a building inspector and engineer, I spent 18 years studying, developing and enforcing building codes in the East Bay, including the WUI areas of Berkeley. In years following the 1991 Oakland hills fire, both local and national bodies incorporated the findings of Mr. Cohen’s ground-breaking research into building regulations for new construction. “…destruction in the WUI is primarily the result of the flammability of the residential areas themselves, rather than the flammability of the adjacent wildlands…Research has shown that a home’s characteristic and its immediate surroundings principally determine the WUI ignition potential during extreme wildfire behavior.” (1)
It’s my opinion that the removal of eucalyptus trees from the hills will not advance, and may even worsen, fire hazard mitigation. The trees are not the problem. As for firebrands emitted during a fire, they are generated in all vegetation types. The best strategy to save homes is to harden structures to prevent ignition and maintain surrounding defensible space. Still, I wondered about the often-repeated claim by local officials that these eucalyptus trees are to blame for the 1991 fire, and that they present a major threat to fire safety. So, I asked Jack. Here’s his private email response. He included some photos, worth taking a look at. His website follows, including links to his extensive research: http://www.firewise.org/wildfire-preparedness/wui-home-ignition-research/the-jack-cohen-files.aspx?sso=0
- Elizabeth Reinhardt, Robert Keane, David Calkin, Jack Cohen, “Objectives and considerations for wildland fuel treatment in forested ecosystems of the interior western United States,” Forest Ecology and Management, 256 (2008) 1997-2006.
(Here attach emails, but remove our addresses)
From: “Cohen, Jack -FS”
Date: March 25, 2016 3:38:38 PM PDT
To: Margaret Hall
Subject: RE: 1991 Oakland Hills fire
Thank you for your generous words of support for the research I’ve done!
I did a quick analysis of Oakland Hills as part of an internal effort to better understand the contribution of firebrand ignitions. I used video footage as my window to the event and did not do a site examination. This effort did not generate a written report. However, it became abundantly clear the Oakland residential fire disaster was similar to more recent disasters where eucalyptus is significantly present. I have attached 5 photos (poor quality) showing that the “gasoline” tree remains unconsumed adjacent to/surrounding destroyed houses as with all the other disasters I’ve examined (refer to my reports). The first 2 photos are from the 2009 Melbourne, Victoria fires that destroyed many structures with 173 civilian fatalities in Kinglake and Marysville in the hills north of Melbourne (I did a site visit but these are not my photos). The unconsumed tree vegetation is eucalyptus. The next 3 photos (not mine) are from the 2003 San Diego County fires. All of the destroyed homes and the burning wood roof home have adjacent eucalyptus – not burning in the tree canopy with high intensities. This is consistent with all the disaster examinations I’ve done (internal reports and published) regardless of the tree species. The common characteristics initiating the disastrous losses in high density residential development are extreme wildfire conditions in surrounding wildlands producing firebrand showers that ignite homes directly and surface fuels within the community to produce significant firebrands from burning homes/structures and adjacent trees that were ignited by the burning homes. This indicates that the eucalyptus trees did not burn with high intensities (or any intensity) leading to home destruction. This strongly suggests that eliminating eucalyptus and replacing it with some other vegetation would not prevent future WU fire disasters because the problem was inappropriately defined as a eucalyptus vegetation problem and not a home ignition-home ignition zone problem.
This is my perspective in answer to your question. Hope that helps. If you have further questions please feel free to ask.
From: Margaret Hall
Sent: Sunday, March 13, 2016 3:09 PM
To: Cohen, Jack -FS
Subject: 1991 Oakland Hills fire
Dear Mr. Cohen,
I am a retired building inspector/civil engineer in the SF Bay Area and am familiar with your work on home ignition zones. After the 1991 fire, we (City of Berkeley) adopted a building code ordinance which focused on hardening structures against wild land/urban interface fire. When I began to learn of your research, I realized retrospectively how very helpful that information was in developing our code. Thanks for all your great work!
There is a debate in our community about a plan to remove large quantities of eucalyptus stands in the East Bay hills. Some firefighters remember that the many wood shingle roofs were the primary contributor to the spread of that fire. Other folks remember events quite differently and blame the trees. I’ve got two questions:
- Did you study the1991 Oakland HIlls fire? If so, can I have a copy of your report? (if it’s not in electronic form, I’m happy to pay for copying/mailing as needed)
- Do you have any fire-science based information on the dangers represented by a specific tree species (in this case E globulus) as compared to other vegetation types? Is there any basis in science for calling eucalyptus trees “gasoline trees”?
Full disclosure: I am opposed to this plan. I don’t think it will reduce the fire danger, especially as the goal of this plan is to replace forested areas with very dry ignitable “grasslands and shrubs”. Also, I’m not happy about the prospect of escalating the use of herbicides in heavily used regional parks, herbicides required to prevent the trees from re-sprouting and suppress unwanted vegetation.
Please let me know if I need to file a formal public records request, and if so, in what format you need that. Again, thanks for your great research. I love watching your videos and the way you are able to make geeky fire science accessible to firefighters and to the public.