Yes, properly executed fuels treatments can modify a wildfire’s behavior and reduce intensity

Victoria Prescribed Fire, Black Hills National Forest
Victoria Prescribed Fire, Black Hills National Forest. South Dakota. USFS photo by Matt Daigle. March, 2021.

In recent weeks there have been discussions online about whether or not fuel reduction projects can aid firefighters by reducing the intensity of wildfires. These rumblings are heard from agenda driven advocacy groups including the John Muir Project.

There is no question that properly executed and followed up fuels treatments — mechanical, or prescribed fires — can modify subsequent fire behavior and reduce a wildfire’s intensity. Despite the attention getting efforts of these groups, this has been a settled issue for a very, very long time. Indigenous people no doubt knew this, and in recent decades wildland firefighters do as well.

From an Associated Press article by Don Thompson:

Scientists say climate change has made the American West much warmer and drier and will continue to make weather more extreme and wildfires more frequent and destructive, accelerating the need for more large-scale forest treatments.

Critics say forest thinning operations are essentially logging projects in disguise.

Opening up the forest canopy and leaving more distance between trees reduces the natural humidity and cooling shade of dense forests and allows unimpeded winds to push fire faster, said Chad Hanson, forest and fire ecologist with the John Muir Project.

Such reasoning defies the laws of physics, said other experts: Less fuel means less severe fire. Fewer trees means it’s more difficult for fires to leap from treetop to treetop.

In a tweet that linked to the Associated Press article, British Columbia-based fire ecologist Robert W. Gray wrote:

Another case of false equivalency: weight of published, peer-reviewed fact vs one or two counter factuals published in a single journal known for pushing pseudoscience.

During extreme weather and fuel conditions, such as strong winds and very low fuel moisture, fires can spread very quickly with a great deal of resistance to control igniting spot fires a mile ahead, and in some cases may burn rapidly through or jump across fuel reduction sites, possibly igniting structures. This can illustrate the importance of homeowners making structures fire resistant and reducing flammable material in the Home Ignition Zone.

But in less than extreme conditions, a fire that spreads into a recently completed fuels project will slow, be less intense, and will offer less resistance to control. A recent example of this was when the Caldor Fire in Northern California began to reach the South Lake Tahoe area, allowing firefighters to attack the fire more directly. In a live briefing on September 3, 2021 East Side Incident Commander Rocky Opliger complimented the agencies for the fuel treatments that had been accomplished over the years. He said the 150-foot flame lengths dropped to about 15-feet when the fire entered the treated areas. This allowed hand crews and engines to take an aggressive approach to suppress the fire and prevent structure loss. The video of the briefing is on Facebook; Mr. Oplinger’s comments about the fuel treatments begin at 34:10.

“Science” funded by agenda driven advocacy groups that has not been peer-reviewed should always be suspect. Settled science that has been proven for decades or even centuries, should be respected.

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Author: Bill Gabbert

After working full time in wildland fire for 33 years, he continues to learn, and strives to be a Student of Fire.

6 thoughts on “Yes, properly executed fuels treatments can modify a wildfire’s behavior and reduce intensity”

  1. The main point is that fires are variable as is the forest. Forest and fires that burn them are complex and that is difficult to explain in a short article. The biggest driver of fire is the weather. No fire line or fuels treatment will stop a fire when the wind is blowing 30 mph on a 90 degree day. On the Antelope fire this summer all our big days were driven by the wind. When fire got into heavy fuels (forest service non management area) with the wind it was like a nuclear explosion resulting in total crown fire, treated areas still burned but at much less intensity. Crown fires threw embers over a mile downwind continuing the conflagration. Chad Hansen is addenda driven and never tells the whole story but has a knack for getting press coverage who repeat his half truths. Thinning works and is just one of the tools needed to reduce fuels to allow the forest to survive and thrive under a more natural fire regime

  2. I believe there’s not one right answer, there is no one-stop shopping here, but a need for a holistic and thoughtful multi-faceted understanding.

    So my only contribution is that trees are not static. I read some responses, but I can’t ignore the lack of mention of healthy vs unhealthy vegetation.

    Trees that are healthy and appropriately hydrated are less easily ignited than trees that are not (too much is as bad as not enough water). Having said that, the best path to healthy, appropriately hydrated trees (water needs vary by species, soil types, and other local / microclimate kinds of conditions) is healthy soil. Removing leaf litter and mulch or whatever decaying organic material naturally occurs is not the way to go unless the layer is excessive. Only excessive material should be removed, the rest is important for healthy soil which is what these trees are living in. They live in the soil, and are depended on it, but what we often pay attention to is above ground. We can’t ignore the soil, and we can’t just treat it like dirt and be surprised when that backfires.

    I can’t imagine a downed log is a bigger threat than deadwood and dehydrated but not-yet-dead foliage & branches that are up at canopy level. Whatever type of tree we are talking about, it needs to be healthy. Even better, it needs to be part of a working plant community. With climate change and so many other environmental stressors, it is harder for individual trees to stay healthy and everything suffers.

    The soil, the moisture in the soil, and the health of trees is dependent on keeping that natural organic material on the ground decaying, feeding the microorganisms that make nutrients and water available to the plants while they also increase soil water holding capacity. Please don’t think that removing this layer is useful, it does more harm than good. Take a look at the mulch flammability studies and see how humus is fire resistant; that’s from decaying organic material, and it’s all kinds of good.

    I am looking for a bridge between these synergies and the suppression experts and managers, etc. I hope for more than a “this is flammable, we must remove it” mindset, I’m looking for a more multi-disciplinary coming together.

    I’m not even going to get into carbon sequestration with healthy soil and the benefits of leaving the soil covered.

  3. Thanks Bill. Lots of misinformation and disinformation on forest and fire management has been polluting the media coverage of the fire issues – offered by self-appointed experts like Hanson. He’s been outed by peer scientists as conducting “agenda-driven ‘science'” which is basically premised by an emotional aversion to active land management. Need to follow the real science that demonstrates conclusively that thinning followed by prescribed fire is absolutely effective in moderating wildfire behavior – even under extreme weather.

  4. Hi Roger,

    I am reasonably sure that you have never actually performed which is a reasoned THOUGHT EXPERIMENT. What Rachel Lee briefly wrote is much more informative. For a critical issue in wildfire management is not the fuel which on the ground. Instead it is the separation between the crowns of the SEPARATED CONIFERS which are composed of NEEDLES instead of LEAVES. These tiny dry, but green, can be easily and quickly ignited with a tiny match. Which is why spot fires can be ignited in the crowns more than a mile ahead of the wildfire

    And clearly it is easy to understand that the localized wildfire is more intense if the density of the trees is greater.

    Have a good day, Jerry

  5. Particle size is very important when it comes to burning.

    Big logs don’t just spring into flame. They catch fire because they are surrounded by smaller pieces of fuel which have the ability to ignite the larger piece.

    For Example … If you work with Aluminum, it becomes very clear, since below a certain particle size, aluminum is Pyrophoric (= Spontaneous combustion).

    For example, cut an aluminum soda can into small pieces, and [ HERE’S WHERE IT GETS DANGEROUS ] put it into a tumbler with the right media to grind it into powder.

    When you start to take the top off the tumbler, all of the oxygen inside the tumbler (if it has a proper rubber seal) will have been consumed by tiny pieces of burning aluminum.

    When you take the top off, at which point you should be surrounded by a large bed of something non flammable like gravel or wet ground or green grass, it starts burning. No separate ignition required !

    The leaves and sticks that light the “big chunks” are not tiny pieces of aluminum, burning.

    But they do have the ability to light the larger logs on fire.

    Since I am time limited in how much time I can spend on wildfire management, one of the easier things that I do is to rake all the leaves sticks etc. away from the bigger logs, so that the bigger logs are just sitting there surrounded by bare forest floor.

  6. Of course, active management of reducing competitive vegetative fuel load will immensely mitigate wildfire extremes and reduce crown fires once rare.

    Rachel Lee Hal for Forest Under Stress (FUS)


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