New Rim Fire Study: Extreme Weather Trumps Fuel Reduction

Rim fire studyA new scientific study on the Rim Fire has just been published. “Severity of an uncharacteristically large wildfire, the Rim Fire, in forests with relatively restored frequent fire regimes” by Jamie Lydersen, Malcolm North and Brandon Collins is available here.  What follows is the abstract, with some emphasis added.


The 2013 Rim Fire, originating on Forest Service land, burned into old-growth forests within Yosemite National Park with relatively restored frequent-fire regimes (P2 predominantly low and moderate sever- ity burns within the last 35 years).

Forest structure and fuels data were collected in the field 3–4 years before the fire, providing a rare chance to use pre-existing plot data to analyze fire effects. We used regression tree and random forests analysis to examine the influence of forest structure, fuel, fire history, topographic and weather conditions on observed fire severity in the Rim Fire, as estimated from an initial fire severity assessment based on the relative differenced normalized burn ratio (RdNBR).

Plots that burned on days with strong plume activity experienced moderate- to high-severity fire effects regardless of forest conditions, fire history or topography. Fire severity was also highly negatively associated with elevation, with lower severity observed in plots over 1700 m.

Burning index (a composite index of fire weather), time since the last fire, and shrub cover had strong positive associations with fire severity. Plots that had experienced fire within the last 14 years burned mainly at low severity in the Rim Fire, while plots that exceeded that time since last fire tended to burn at moderate or high severity.

This effect of time since last fire was even more pronounced on days when the burning index was high. Our results suggest that wildfire burning under extreme weather conditions, as is often the case with fires that escape initial attack, can produce large areas of high-severity fire even in fuels-reduced forests with restored fire regimes. 

10 thoughts on “New Rim Fire Study: Extreme Weather Trumps Fuel Reduction”

  1. Matt,

    In a blow-up, a crown fire, “Extreme Weather Trumps Fuel Reduction” — in some cases. But an overabundance of fuels makes a blowup or crown fire more likely and more intense. Restored stands are vulnerable to crown fires in adjacent untreated stands, but crown fires are less likely to begin in treated stands. The paper’s authors conclude that “Our study suggests that even fire-restored forests may not be resistant to high-intensity wildfire that escapes suppression during extreme weather conditions.” Yep.

  2. Strong plume activity? What does that mean? Firenadoes? Dust devils? Enough energy to penetrate inversion layers? Individual trees exploding in fire with oxygen fed by wind coming from all directions to create circulation, swirling?
    What happens when an inversion layer is penetrated?

    • Hello Richard:

      According to the National Wildfire Coordinating Group’s Glossary of Wildland Fire Terminology (here) a “Plume-dominated Wildland Fire” is a wildland fire whose activity is determined by the convection column.


  3. We all knew something like this would be coming. Any comparison of Yosemite National Park lands to the National Forest portion of the Rim Fire is inapplicable. There are MANY factors that make it an apples versus oranges situation. The Rim Fire was so big that, if you look hard enough, in different aspects, elevations, timber types, brush types, burning times, weather, fuels moistures, etc, etc, you can find evidence that supports anything you want to illustrate.

    With the fire starting in the bottom of the Tuolumne River Canyon, surrounded by digger pines and flammable brush, it’s rapid growth is more attributed to the terrain, fuel moistures, and, especially, the topographic canyon winds that change every night. The Tuolumne River watershed drains a huge portion of the Yosemite High Sierra. At night, the cold air gathers and flows down the deep canyon, causing a persistent cool and dry morning breeze, every morning. Around mid-morning, the warm air is rising and the push goes up the canyon. The length of the canyon became the conduit for wildfire spread. Of course, if you add the fire’s own weather effects, the spread is amplified.

    You cannot simply say that extreme weather, alone, caused the huge size of the Rim Fire. Yes, recent prescribed fires in the Park did mitigate fire intensity but, their Let-Burn and prescribed fire programs haven’t had good results, in the recent past. Multi-million dollar “oopsies” should really come out of their budgets, instead of the General Treasury.

  4. MatthewK

    Great Post. I have absolutely no disagreement with anything that you have quoted in your opening post – It is exactly right and exactly what many of us have been saying all along. I thank you for this post because I hope that it will be the key to finally get us on the same page.

    Re: “Our results suggest that wildfire burning under extreme weather conditions, as is often the case with fires that escape initial attack, can produce large areas of high-severity fire even in fuels-reduced forests with restored fire regimes.” This is motherhood and apple pie in forestry. It is just one more affirmation of what foresters have known for decades.
    —> The above quote should iron out our differences in the past which have been the result of:
    1) Prior statements by you that fuel reduction is useless whether it is in the form of a non-revenue producing fuels reduction treatment (a type of Stand Improvement in forestry terms) or a Commercial Harvesting operation. Item #2 explains what was missing from your understanding.
    2) What you missed in the past in our rebuttals is that fuels reduction is critical to:
    —– a) Reduce the chance that a fire will “escape initial attack”
    and create its own weather which dries out the fuels in front of the fire which allows it to make a large run and an even larger run with non-fire induced external extreme weather.
    —– b) Increase the chance of stopping the fire sooner when extreme weather conditions take a breather and/or the wind reverses thereby reducing the acreage “of high-severity fire”. I am sure that you can see that the shorter the time that it takes to stop/control a wildfire, the greater the chance that it won’t make another big run when external extreme weather conditions return.

    Thanks for this post

  5. Finally, I’d like to see a study of the recently-thinned plantations, which appear to have mostly low burn intensities. Such a study would better illustrate the value of thinning on reducing fire intensity and forest mortality. A study like this one in the Park seems like it has limited value.

    I guess we’re going to have to shelf our conspiratorial plans to thin our National Parks, due to this study. Soooo, we got THAT going for us. Thanks for protecting our National Parks, Matthew! *smirk*

  6. I found this interesting contrast of management “styles” and their outcomes in the Rim Fire.,-119.9311462,449m/data=!3m1!1e3?hl=en

    While there is a lot of moderate intensity burn in there, the fire looks like it was wind-driven. Even so, there are substantial amounts of survivors, where there are no survivors in the unthinned stands. I do think that the unthinned parcels were partially planted, where the spacing seems uniform. I also see two other areas that were left to be brushfields after the 1971 Granite Fire. I helped flag the unit to the right of the road. There were big bushes of whitethorn and manzanita along those edges. In many cases, you couldn’t walk from A to B, with all that thick and nasty brush. If you’ve ever worked in whitethorn, you know about those needle-like thorns that go through your jeans, deep into your skin before they break off, leaving the tip behind.

    It’s pretty clear to me that there is value in thinning plantations, to mitigate fuels and wildfire effects. Saying that “… strong plume activity experienced moderate- to high-severity fire effects regardless of forest conditions, fire history or topography.” is like saying there are more flood damages, regardless of human structures and mitigation, during a strong tsunami.

    The Groveland RD must be a poster child for the first-world malady of unmanagement. We’re fast-approaching the end of the comment period and I expect that the Forest Supervisor will waste no time in announcing post time for the chainsaw races. I hope they would see the wisdom in getting as much wood on the ground as possible, in the shortest period of time. They should also stall in District Court to give the fallers more time to work, while, at the same time, educating the court about all the complex details of modern salvage logging. Think of it as a sort of filibuster, in the name of Judicial education. *smirk*

  7. Let’s not forget the conclusion where the authors say that fuels management and wildland fires in the same fireshed be integrated. Yep — one DOES affect the other.
    And I caught the same line — initial attack.

  8. And then, there’s THIS! A petition to get Obama to use the Antiquities Act to make the Rim Fire into a National Monument, “protecting” it for eternity.

    “Dear President Obama, Tom Tidwell, Randy Moore and Susan Skalski,

    President Obama, please use your authority under the Antiquities Act to protect the environmentally sensitive Rim Fire Burn Area federal lands for future generations by creating the Rim Fire National Monument on the portion occurring on the Stanislaus National Forest, west of Yosemite National Park. This would:

    • Validate the scientifically-proven restorative power of fire.

    • Protect 50,000 acres of what is known as complex early seral forest habitat, or “snag forest habitat,” a rare and critically important post-fire landscape, with some of the highest levels of species diversity in the Sierra Nevada. Instead of weakening environmental protections on post-fire public lands with standing dead trees or “snags,” and species-rich montane chaparral (native-flowering shrubs), we should appreciate the high ecological value of this habitat.

    • Provide habitat protection for the highly imperiled black-backed woodpecker and the California spotted owl, which thrive in the snag forest. In the first year after the Rim Fire, 70 percent of the historic spotted owl territories are occupied—mostly by pairs. This is higher than the average occupancy rate in unburned mature/old forest in the central Sierra Nevada. Unfortunately, the Forest Service currently plans to nearly clearcut within the occupied California spotted owl territories, which science tells us will eliminate the owls.

    • Stop the Forest Service’s “Rim Fire logging project” that would essentially clear cut about 45,000 acres of ecologically vital snag forest habitat. The Forest Service’s primary stated purpose for this massive post-fire clearcutting project on federal public lands is to generate revenue to pad the Forest Service’s own budget (under an obscure law called the Salvage Sale Fund, the Forest Service keeps 100 percent of the revenue from post-fire logging, creating a powerful perverse financial incentive).

    • Foster and encourage the natural conifer and other regeneration that is already occurring in the Rim fire burn area on the Stanislaus National Forest, and which would be directly killed by the Forest Service proposal to tractor log over thousands of acres of naturally regenerating forest.

    • Require post-fire management focus on activities that benefit forest health, water quality and the many species that depend upon fire for their very existence.”

    Ummmm, yeah, someone wants to fill people’s political mouths with “uninformed opinions” about the Rim Fire. Who knew that light salvage on about 1/8th of the fire, including ample plantation acreage) would generate such controversy? It would be very hard to find someone opposing the salvage who could tell me what the snag requirements are for the project, or what the effects of bearclover are on reforestation, without looking them up. The idea that the Forest Service “… would essentially clear cut about 45,000 acres …” is not based in fact. Survivors don’t get cut and ample snags are left, inside and outside of cutting units!

    Anyone want to pick a bullet point and comment? Any bullet point. *smirk*

  9. Well, people can say whatever they want, whether it’s true or not. In a small community, or even on this blog, you would lose credibility from saying things that aren’t true. I mean at the end of the day, that’s all we have.

    The thing is, the powers that be can ask people who know when the petition comes in. And at the end of the day whether it goes or not probably depends on the politics of it and not false claims. I guess that is encouraging in a way.

    When I worked on projects that were the focus of campaigns of untruths (many) I often thought about the poem by Kipling titled “If”.

    Of course, now that I go to liberal arts school, I understand that Kipling was an imperialist and he was probably a sexist too, given the last line, but I still like the poem.

    If you can keep your head when all about you
    Are losing theirs and blaming it on you,
    If you can trust yourself when all men doubt you,
    But make allowance for their doubting too;
    If you can wait and not be tired by waiting,
    Or being lied about, don’t deal in lies,
    Or being hated, don’t give way to hating,
    And yet don’t look too good, nor talk too wise:

    If you can dream—and not make dreams your master;
    If you can think—and not make thoughts your aim;
    If you can meet with Triumph and Disaster
    And treat those two impostors just the same;
    If you can bear to hear the truth you’ve spoken
    Twisted by knaves to make a trap for fools,
    Or watch the things you gave your life to, broken,
    And stoop and build ’em up with worn-out tools:

    If you can make one heap of all your winnings
    And risk it on one turn of pitch-and-toss,
    And lose, and start again at your beginnings
    And never breathe a word about your loss;
    If you can force your heart and nerve and sinew
    To serve your turn long after they are gone,
    And so hold on when there is nothing in you
    Except the Will which says to them: ‘Hold on!’

    If you can talk with crowds and keep your virtue,
    Or walk with Kings—nor lose the common touch,
    If neither foes nor loving friends can hurt you,
    If all men count with you, but none too much;
    If you can fill the unforgiving minute
    With sixty seconds’ worth of distance run,
    Yours is the Earth and everything that’s in it,
    And—which is more—you’ll be a Man, my son!


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