Study Finds Old Growth Forests Burn Slower and Cooler, Preserving Habitat

The following is a press release from the USDA’s National Forest Service:

New findings show that old-growth forests, a critical nesting habitat for threatened northern spotted owls, are less likely to experience high-severity fire than young-growth forests during wildfires. This suggests that old-growth forest could be leveraged to provide valuable fire refuges that support forest biodiversity and buffer the extreme effects of climate change on fire regimes in the Pacific Northwest.

A recent study published in the journal Ecosphere examined the impact of the Douglas Complex and Big Windy fires that burned in the Klamath-Siskiyou region of Oregon during July 2013, a drought year. The fires burned through a long-term study area for northern spotted owls. Using information on forest vegetation before and after the fires, along with known spotted owl nesting areas, researchers had an unprecedented chance to compare the impact of wildfire on critical old-growth nesting habitat.

“On federally managed lands, spotted owl nesting habitat is largely protected from timber harvest under the Northwest Forest Plan, but wildfire is still a primary threat to the old-growth forest that spotted owls rely on for nesting habitat,” said research wildlife biologist Damon Lesmeister. “The loss of spotted owl nesting habitat as a result of severe fire damage could have significant negative impacts on the remaining spotted owl populations as well as a large number of other wildlife species that rely on these old forests.”

Old-growth forests have more vegetation than younger forests. Researchers expected that this meant more fuel would be available for wildfires, increasing the susceptibility of old-growth forests to severe fire, high tree mortality, and resulting loss of critical spotted owl nesting habitat. However, the data suggested a different effect.

Lesmeister and his colleagues classified fire severity based on the percentage of trees lost in a fire, considering forest that lost less than 20% of its trees to fire subject to low-severity fire and those with more than 90% tree loss subject to high-severity fire. They found that old-growth forest was up to three times more likely to burn at low severity—a level that avoided loss of spotted owl nesting habitat and is generally considered to be part of a healthy forest ecosystem.

“Somewhat to our surprise, we found that, compared to other forest types within the burned area, old-growth forests burned on average much cooler than younger forests, which were more likely to experience high-severity fire. How this actually plays out during a mixed-severity wildfire makes sense when you consider the qualities of old-growth forest that can limit severe wildfire ignitions and burn temperatures, like shading from multilayer canopies, cooler temperatures, moist air and soil as well as larger, hardier trees.”

Because old-growth forests may be refuges of low-severity fire on a landscape that experiences moderate to high-severity fires frequently, they could be integral as biodiversity refuges in an increasingly fire-prone region. Leveraging the potential of old-growth forests to act as refuges may be an effective tool for forest managers as they deal with worsening fire seasons in the Pacific Northwest.

The study was a collaboration between researchers Damon Lesmeister and David Bell, USDA Forest Service, Pacific Northwest Research Station; Stan Sovern and Matthew Gregory, Oregon State University; Raymond Davis, USDA Forest Service, Pacific Northwest Region; and Jody Vogeler, Colorado State University.

The USDA Forest Service Pacific Northwest Research Station—headquartered in Portland, Ore.—generates and communicates scientific knowledge that helps people make informed choices about natural resources and the environment. The station has 11 laboratories and centers located in Alaska, Washington, and Oregon and about 300 employees. Learn more online at



  • 🕯🌳Good morning Kelley, nice article and link.

  • Ernie Branscomb

    Also… Fire is critically important to maintain the health of a redwood forest. The duff and other species of underbrush can choke the root systems of the redwood. The flying squirrel that owls hunt and eat live in old growth forests.

    It is big mistake to keep fire away from a redwood forest.

  • It would be nice if commenters would actually read and think about the study before they get all excited with the “I told you so”s. But they won’t.

  • Duh

  • This isn’t new information. I remember similar studies from the PNW forest research station from decades ago, when I was studying forest ecology.

    • Thank you. Yes- we knew this and we know this and yet we keep knocking down old forests. It’s a nice study and all but I don’t have much faith in humans. We keep telling young people to do studies and research but really it’s a lot like fiddling away while Rome burns. We know enough and what is required is direct action. Direct action to reverse our destruction of the forests, rivers and seas. Direct action to check climate change. . The time for scientific studies to help convince agencies and people to change their suicidal habits and desires is over. We need Direct Action. Those who do not understand the extremely dangerous time we are at in our human-driven extinction event will probably never understand. The time is past for pleasantly trying to get them away from their sit-coms and video games and explain to them why they should care. Indeed…the time for pleasant convincing was over 30 years ago.

  • This is what HSU was teaching back in the 80’s when I went there.

  • I worked in the redwood forest for soom years and all you have to do is walk thu the forest to see how mother nature does its work

    • The study did talk about the inherent bias formed when people favored forests with little undergrowth that made getting through them and taking pretty pictures easy. Because such forests are so commonly presented, people tended to think that’s was healthy forests look like. The study mentioned that was not the natural look of the kind of forests common in the west.

      • Forests were managed, not for pretty pictures, but for functionality and longevity. They looked like parks after underbrush was burned and cleared, and this was the ‘natural’ look of forests in both the east and the west, until white people came and killed the people and societies who managed them.

        • That such bs. Native americans only managed tiny areas. The redwood forests the jed smith and josiah gregg expeditions encountered were virtually impenetrable, as were all the forests of the pacific northwest. You have to go much further east to find any semblance of park like forests, east of the cascade crest, and that was not the result of management but less precipitation and more frequent lightning fires.

          • They’ve been discrediting your racist paradigm for years now.

            If you want to learn something, you can always pick up a book. You know, one from less than 50 years ago.

            I ain’t got time to teach you. Got more important things to do like pick cotton outta my belly button.

            • It is comforting to cry racist and then pretend to be above the rest. Saves wear and tear on ego.

            • You could always pick up a book containing the personal observations of members of the Josiah C. Gregg party during their quest for Humboldt Bay. L.K. Wood, in particular. He talks about barely making two miles a day coming down through the Basin, at the headwaters of the north fork of the Mad, and down Little River to the ocean. There were fires that went through there, but it wasn’t park-like.

              Then again, that was untouched old growth redwood forest. There were areas the native people either burned intentionally, or let burn when lightning struck (like they had a choice), but I don’t believe the natives around here had nearly enough manpower (or need) to keep all of the woods, “parklike.”

        • Accoding to the study- no, it never was like that in the western forests at all. Period. It had nothing to do with any supposed superior management of pre columbian humanity. It’s weather and topography that guided how the forests grew in the “good ol’ days.” That idea park like forests is the same Golden Age fantasies that most civilizations create when faced with difficulties. It’s the idea that earlier people were wiser and better than later generations. What makes those fantasies possible is the lack of documentation that contradicts about the real issues that people faced so later generations fill in the gaps in knowledge with the things they prefer to believe about their ancestors. A large scale version of the old person who affirms things were better in “their day” than now, being nostalgic for their youth and strength they no longer have.

  • Not when firefighting contractors whos pay depends on fires burning are shooting flares into the canopy with 15%RH

    • If we harvest the last 10% and then we can start all over again and not have to worry about the old growth loggers can make money for a couple months or so and the environmentalists will have nothing to protect we don’t need future generations do we jobs might be more important after planet starts warming up we’ll just turn on the air conditioner these environmental should get jobs installing air conditioners instead of complaining the future is ours for ruining

      • “future is ours for ruining”

        We’ve got the right “president” for that.

        • Willing to give up a day of pot smoking to save the forests? Oh well. The irrational and abusive left sparring the parnoid and fearful right gave us the President we would elect. Someone who was not Doctor Doom. It wasn’t a particularly high standard.

          “war is peace
          freedom is slavery
          ignorance is strength ” as on the Ministry of Truth.

      • And, outside of complaining, what have you done to make a better life for people without sending them back to subsistence living? Have protests funded by those who have already made their huge piles of money screwing over everyone a long the way?

  • “New findings…” ummmmm… how is this a new finding?

    • Well… since John Muir described old growth forest fires… (150 years ago +-) anyway.

      • Perhaps if Mr. Muir had submitted his observations to the proper authorities the forest management practices over the past 150 years could have been executed with intelligence and forethought.

        • Funniest (dark dark humor) comment of the day!

        • Hmmm… did you live in a house?

          Well… the housing was built on the forests.

          Asphalt and concrete were developed to give roads.
          Water systems developed for the ‘cities’. Iron sewer pipe keep things clean.
          Steel for bridges… cars. Copper for wires, dams, power plants.
          Rare metals were excavated to provide computers… and were used by you to post on this site.

          • What? I’m confused. Does your post mean something.

            “Farce” obviously understood my sarcastic humor… perhaps you should reread.

  • written by a new employee who has very little knowledge of fire behavior in mixed systems with the express intent of keeping a protected bird on ESA

    • Being that the goal was to evaluate habitats survival for the Spotted Owl, that would be the orientation of the study. But, although the data collection was not available for review, there were some interesting comparisons made between the affects of federal versus private lands that had been burned was interesting. The map of types of forests subject to fire was also interesting.

  • how much did this new ‘study’ cost the taxpayers?

  • C'mon 2020 elections

    Probably millions tax payer !!!!

  • California conservative

    With my home adjacent to an old growth Douglas Fir forest, I can observe the reality rather than the hype. Our community has supported the US Forest Service in there plans to reduce the fire danger in this forest. Neighbors who don’t live directly adjacent to this forest have always complained about their efforts and have effectively stalled all efforts. Meanwhile, the trees continue to rot and fall down. Can you imagine the damage when these trees fall a cross my driveway? Of the many trees that have already fallen, thankfully no one has been crushed.
    Healthy old growth forest may be resistant to wildfire, but dying ones create crown fire hazards, leading to fire storms and much death.
    Forests that are dying have no commercial value, no loggers getting rich.

  • Pingback: The Risk of Watching California Burn on TV

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