Study confirms extreme wildfires of 2020 in Western Oregon were not unprecedented

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satellite photo fires smoke Washington, Oregon, and California
GOES-17 photo of smoke from wildfires in Washington, Oregon, and California at 5:56 p.m. PDT Sept. 8, 2020. The photo was taken during a very strong wind event.

By U.S. Forest Service

When the 2020 Labor Day Fires torched more than 300,000 hectares over the span of two weeks in parts of western Oregon and Washington, they devastated communities and put the threat of west-side fires squarely into focus. A new study led by the USDA Forest Service’s Pacific Northwest Research Station examines the context surrounding the fires and offers insight into the historical role of large, high-severity fires—and the future of wildfires—west of the Cascades.

“Without a doubt, the 2020 Labor Day Fires were a significant fire event on many levels, and one that was a wake-up call for the region,” said Matthew Reilly, research forester and lead author of the study, which is published in the journal Ecosphere. “The goal of our study was to help understand how this event compared to past west-side fires so that we can help inform adaptation strategies aimed at preventing or mitigating similar events in the future.”

Drawing from a literature review, extensive historical data, and new analysis, Reilly and his co-authors explored five questions surrounding the 2020 Labor Day Fires: how the 2020 fires compared with historical fires in the region, the role of weather and climate, the effects of forest management and pre-fire forest structure on burn severity, the impacts of these fires on west-side landscapes, and what can be done to adapt to similar fires in the future. Ultimately, they found that the 2020 fires were remarkably consistent with historical fires on the west side, both in terms of their timing and size and the cause of their rapid spread—dry conditions combined with strong east winds.

“Our findings suggest that these severe fires are normal for west-side landscapes when you look at historical fire regimes at longer time scales,” Reilly said. In fact, the researchers identified similarly large historical fires in the early 20th century under similar weather conditions—some even burning right around Labor Day—in some of the same locations that burned in 2020.

Because of the abundant and productive forests characteristic of the west side and the driving role of extreme winds, conventional fire management tools used in dry forests, like prescribed burning and fuels management, will likely be less effective in west-side forests than they are on the east side. This is particularly the case, their study found, when fire weather conditions are as extreme as those witnessed during the 2020 fires.

“Our study indicates we need very different approaches and adaptation strategies in west-side forests compared to those we use in dry forests,” Reilly said.

The study was conducted as part of the Pacific Northwest Research Station’s ongoing West-side Fire Research Initiative, which was launched in 2019 to develop science-based tools to help resource managers respond to wildfire risk in west-side forests. The study’s coauthors are from the Washington State Department of Natural Resources, University of Washington, Oregon State University, and USDA Forest Service’s Pacific Northwest Region.

Highlights

  • The 2020 Labor Day Fires were much larger and more severe than others in the recent record, but they were remarkably consistent with many historical fires. Strong east winds and dry conditions are the common denominators in both large historical fires of the past and the 2020 fires.
  • Forest management and fuel treatments are unlikely to influence fire severity in the most extreme wind-driven fires, like the 2020 Labor Day Fires. Pre-fire forest structure, largely the result of previous forest management activities, had little effect on burn severity when east winds were strong during the 2020 fires.
  • Fuel treatments around homes and infrastructure may still be beneficial under low and moderate fire-weather conditions.
  • Adaptation strategies for similar fires in the future in west-side communities might, instead, focus on ignition prevention, fire suppression, and community preparedness.

More information:

Matthew J. Reilly et al, Cascadia Burning: The historic, but not historically unprecedented, 2020 wildfires in the Pacific Northwest, USA, Ecosphere (2022). DOI: 10.1002/ecs2.4070

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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.

24 thoughts on “Study confirms extreme wildfires of 2020 in Western Oregon were not unprecedented”

  1. While this post seems to suggest that this wildfire was somehow normal, the fact remains that the world’s climate system is no longer normal.

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  2. On first read (at 11p), this study tries to say the large, high severity Labor Day fires of 2020 in OR are not unprecedented and that forest structure or ecological thinning land management don’t matter. The implication being that large, stand replacing fires are inevitable and land management shouldn’t be emphasized.

    I’d note a few shortcomings:

    The study only looks as far back as 1985 for recent (mostly small) fires (Figure 8) and only at five historically large fire events going back to 1850 (Figure 3). All of these events are in the modern era after which European settlement and practices replaced the Native land management practices that kept most of these large tree stands intact and minimized stand-replacing fires. It strikes me as historically-myopic not to look further back at tree-ring data and Native accounts.

    The authors also claim that because the 2020 Labor Day fires burned at high severity across different stand types (Figure 9) that landscape scale treatments won’t be effective in preventing high severity burns during a wind-driven event. This type of simplistic categorization leaves out important factors like the understory composition of large/giant structural class stands in 2020. One wonders whether the more frequent, low-intensity fires set by Natives pre-1850 might have resulted in large/giant class stands with sparse understories and smaller numbers of young trees that burned less severely under similar conditions as the Sept 2020 fires.

    Of course, wildfires can’t really be prevented and there will always be some high severity burn areas, but I’m not ready to write off landscape scale management yet. Native forest management practices are largely unstudied and should, IMHO, be tested. I would like to have seen an analysis of pre-1850 forest stands and fire regimes in the study area and also a better characterization of the forest stands before claiming that land management plays no role in burn severity during wind-driven fire events.

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    1. I think, Ivan, it’s vital to read carefully what the report says and does not say. With long-duration sustained east winds down the river canyons of western Oregon, the pre-fire forest structure (and therefore forestry activities or lack thereof) didn’t much affect the BURN SEVERITY. This doesn’t refer to the size of the fire, the rate of spread, the flamelengths or structures ignited or lost …

      “Pre-fire forest structure, largely the result of previous forest management activities, had little effect on burn severity when east winds were strong during the 2020 fires.” That is a highlight quoted above, but it’s not the whole report. Anti-logging groupies on the westside are already claiming that this report validates their view that all logging and RxFire and other forestry practices should be stopped, because they shouldn’t be “used under the pretense of fire prevention.”

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      1. @kelly – Yes, it’s the potential for mis-use by the “touch nothings” that I’m concerned about. The simplified characterization of the landscape (simply looking at the structure class of the standing trees) is most problematic in my view, especially when making the claim that landscape-scale *ecological* treatments are unlikely to be effective.

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  3. 300,000 hectares=750,000 acres. Not sure why they refer to hectares unless trying to spin something as here in the USA I believe we almost exclusively use acres for land area measurement.

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    1. I’ve been playing around with the Calculations for “Hiroshima Equivalent” fire loads, based on dry (dead) fuel loads of 100,000 pounds per acre.

      Last time I did it, it was 85 acres @ 100,000 pounds per acre, based on 4 Gigajoules per ton of TNT, and 20 million BTU’s per cord of mixed oak/ madrone/ pine for the dead & rotten wood that comprises the fuel load … if I remember correctly.

      But that of course implies that 8.5 Million pounds of dry mixed dead wood, has as much energy as 30 Million pounds of TNT, 15 Kilotons. Which doesn’t sound quite right … but I don’t have that paper in front of me.

      Perhaps for any international audience, both Hectare and Acre units should be used. Friends in New Zealand always speak of Hectares.

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  4. How many studies does it take to confirm that the goal in fire management has to be preventing fires? Human caused fires are by far the majority of fires.
    Thank goodness the Forest Service has stopped “prescribed burns” which have not only gone wild but have fouled the air 11 months a year. Is that like prescribing cigarettes for lung cancer patients? We cannot continue to pollute the air in the vain hope that will prevent fires. Doesn’t work. Pollutes the air. Releases tons of carbon. Goes wild.
    Stop allowing fires of any type on public lands. Get a camp stove.

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    1. Fires are as natural as rain. We won’t prevent them. Nature depends on it to thrive. Sorry but smoke will remain in the air either way.

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    2. That smoke really ties the room together Martha. Don’t like a little smoke in the air ? I here Iowa is nice …..

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      1. Suppressing and preventing wildfires is a very complicated case, Martha. Lotta ins, lotta outs, lotta what have yous, lotta strands to keep in my head, man.

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    3. What you do not hear about is all the 1000’s of successful RX burns and thining projects. Both which have been used to assist with containment of large fires and limited growth small fires. Good news does not sell papers or generate ad revenue.

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    4. This aggression will not stand.
      You can’t just be a conscientious objector and stand by while people lay face down in the muck…or smoke.
      Mark it 8

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    5. Martha – you miss the point on so many parts. Fire is a force of nature like earthquakes, floods and tornados. The issue is people and where they build, what lifestyle they chose, and then learning how to live with fire, not exercise an effort in futility to try and exclude it.

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  5. That matches up with the large fires in northeast California the last few years. Not much correlation between pre-fire fuel loading and burn severity. The drivers have been fuel moisture and wind events.

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  6. While living through and experiencing those fires (I was Forest Fire Chief on the Umpqua NF) was very difficult and challenging, we knew the wind event was coming, and we also knew that those East wind events had happened historically (I remember reading about the devastating Tillamook Burn of 1933). Notable differences that contributed to the situation in 2020 were power lines strung extensively throughout the forested areas and expansion of the WUI. Conversely, now we also have better notification systems and more firefighters (though there really wasn’t much firefighting those first couple of days as conditions were too extreme), and those factors made the difference in not having far more fatalities than we could’ve. I’m still very proud of the UPF and DFPA firefighters who safely evacuated hundreds of residents that day.
    Quite the event upon which to end my FS career that following December.

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    1. Today 7/23/22 In the Pacific northwest we will be experiencing the East winds again also known as a Foehn (fern) wind/East wind- If you studied the Synthesis of Knowledge of Extreme Fire Behavior: Volume 1 for Fire managers page 37-41. This publication came out in 2011 any NW fire manager or any fire manager for that matter- should read this book from cover to cover. This is trend that is developing more from global warming. East winds were recognized as a fire problem west of the Cascades from the beginning of fire weather research. (Beals 1914), and Joy (1923) noted that large fires west of the Cascades were caused by strong east winds that were usually hot and dry for that area. They also noted that these strong winds occurred when there was a high pressure east of the Cascades and low pressure west of the cascades. This pattern typically occurs during September and early October and often represents the peak of the fire season west of the Cascades.(USDA Synthesis of Knowledge of Extreme Fire Behavior) all cited et al. 2011

      https://www.fs.fed.us/pnw/pubs/pnw_gtr854.pdf

      here is a copy enjoy

      Also I grew up in Tillamook Oregon, and had a old man neighbor that witnessed the destruction of the Tillamook burns 1933, 1936, 1939. They started up near Gales creek or Portland and burned to the east or to the coast in a day or two approximately 80 miles. Logs on fire the size of Volkswagen’s were dropping on navy warships in the Pacific ocean onto their decks 400 miles west of the coast of Oregon. We need to learn from the past and realize this is a repeat of the history books. We should have more information on these extreme weather patterns and prepare the forest and communities for fire coming from ever direction with high intensity. Teach your folks and read the literature.
      period.

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  7. Thanks for the head’s up on this, Bill. I’d like to see a study comparing the acreages of flash fuels like weedy grasses (and fuels <0.5" dia) over time, with ignition location, spread rate differences, density, distribution, and packing ratios for ground fires on and off pre-burned areas at various wind speeds and vegetation type mixes.

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