Misleading 20 Year Study of “Active Management” in Sierra Nevada

A recent study claims active management can preclude large blazes like the Dixie Fire pictured here. Photo George Wuerthner 

A recent paper Forest restoration and fuels reduction work: Different pathways for achieving success in the Sierra Nevada has gotten a lot of press in the California news media.

The researchers claim that “active treatments,” including prescribed burning, mechanical thinning, and burning plus thinning, created forests more “resistant” to wildfire than untreated control.

Throughout California, there have been numerous news articles citing the study with headlines like Forest Restoration Works, 20-year study confirms California forests are healthier when burned or thinned, 20-year study confirms prescribed burning, forest thinning reduce risks of catastrophic wildfire, and others.

The problem is that the study proves no such thing.

Like many papers suggesting that our forest management will “improve” them and make them healthy, the devil is in the details. The researchers continuously assert that fuel reductions equal “restoration” without defining what constitutes “restoration”—merely asserting that logging and burning equals restoration.

Much of the acreage burned in California occurs in non-forested landscapes like chaparrel. Seen here is the aftermath of the Thomas Fire by Santa Barbara. Photo George Wuerthner 

A further problem in terms of public perception is that they make the usual assertion without qualification that fire suppression has led to abnormal fuel accumulations. While this may apply to some dry pine to mixed conifer forests, most wildfire acreage occurs in other plant communities from chaparral to higher elevation forests characterized by long fire rotations of many decades to centuries. Fire suppression has not affected these plant communities.

The overall impression is that the authors lack an ecological perspective. Large wildfires are characterized with pejorative terms like “catastrophic” and a “loss.” There is no indication that the authors recognize that trees killed by wildfire, drought, or insects serve any ecological function after they are dead.

The paper ignores that the snag forests resulting from major wildfires are essential habitat for many wildlife and plant species. Indeed, some ecologists will assert that snags and down wood provide more diversity in habitat than live green trees.

A thinned forest sanitizes the site eliminating snags, down wood, and shrubs critical to healthy forest ecosystems. Photo George Wuerthner 

And like many timber-oriented researchers, they never count the trees killed by chainsaws as a loss nor see any ecological damage from removing trees from a site.

Ironically, figure 2 in the paper shows that the least mortality and greatest overall growth occurred in the control site without manipulation. You would not get this impression from the way the entire paper presents the study results.

But even beyond these problems, nuances in their paper are overlooked in the numerous media headlines proclaiming that thinning and prescribed burning are panaceas for wildfire. The paper assumes that fuels are the reason for large blazes. This ignores that the West has experienced at 23 year mega drought.

The first is that mechanical treatment or what most people call logging, is indiscriminate. All trees vary in their genetic resistance to drought, insects, disease, and wildfire, and indiscriminate tree elimination can remove the very trees best adapted to these stressors.

One of the problems with prescribed burning is that you must repeat the burning every few years–forever-making it impractical to apply on a landscape scale. Photo George Wuerthner 

Second, even prescribed fire is problematic. The researcher reported that many mature trees were killed or made more vulnerable to insect attack, thus increasing mortality. They also acknowledge hidden deep in their paper that prescribed burning is largely ineffective if you do not repeat treatments—forever.

While climate change is mentioned several times, the authors never admit to how their treatments will alter the conditions for major fire – temperature, humidity, wind – under which no treatment works. In other words, we must keep degrading forests forever and keep paying forever.

Naturally, this involves a huge investment over time that is not practical except perhaps on a very small scale. In terms of scaling up to landscape scale burning, such treatments become prohibitively expensive over time.

Not acknowledged in the paper is that even if burning and logging were effective at reducing wildfires and other stressors like drought, insects, and disease, is the probability that any treated acreage will experience, say, a wildfire when it could be effective (about 10-30 years depending on treatment and ecological site conditions is near zero. Vegetation grows back quickly.

Grasses and other fine fuels seen here on the Los Padres NF make up the bulk of what burns in a wildfire–while large trees do not burn and reman as snags. Photo George Wuerthner 

Worse if you are trying to preclude wildfire is that the bulk of regrowth tends to be “fine fuels” like grasses, shrubs, and other plants that are more flammable. Large tree trunks—often what is removed by logging operations—do not burn readily, which is why you get snags. The fine fuels that burn in wildfires are needles, small branches, grasses, shrubs, and other materials that easily ignite.

It is important to note that none of the research sites encountered wildfire. Rather, the researchers used modeling to analyze the results of various treatments.

The paper justifies “active management” as a panacea for the 1% of large wildfires that account for the bulk of acreage burned annually.  These large blazes occur during periods of extreme fire weather. Yet, in their calculations, where they claim that active management is successful, they use the 80th percentile of fire weather when there is a far lower chance of crown fires and wind-driven fire spread.  It is climate change, not fuels, that is driving large wildfires.

The Camp Fire that charred Paradise, California burned under extreme weather with high winds that drove fire spread as rapidly as one football field per second. No amount of thinning or prescribed burning is effective under such conditions. Photo George Wuerthner

Nearly all the large blazes that advocates of active management seek to slow or stop occur under the 1-2% extreme fire weather conditions. This includes recent blazes like the Camp Fire that destroyed Paradise, California or the Dixie Fire that charred the northern Sierras or the Holiday Farm Fire that raced down the McKenzie River in Oregon, among many others I could name. These blazes charred areas that had previously experienced extensive logging, prescribed burning, and so-called active management (i.e., fuel reductions) to no avail when extreme fire weather occurs with ignition sources.

Logging removes carbon from the site, and even a severe fire leaves behind the bulk of carbon in snags, roots in the ground, and charcoal. This carbon remains “stored” for decades to centuries. On the other hand, logging releases carbon immediately, adding to the climate warming that is driving wildfire, drought, and other forest stressors.

Finally, they coopt native “cultural burning” as the justification for prescribed burning, never noting that research has demonstrated that Indian set fires typically only influenced a small portion of the landscape. Not to mention that all these plant communities existed for millions of years before the colonization of North America by humans and somehow survived without human manipulation from Native Americans.

In short, the paper is overly optimistic about the ability of active management to mitigate wildfires under current climatic conditions. At the same time, the study ignores the multiple negative ecological impacts associated with active management, including removal of biomass, loss of carbon, and spread of weeds that result from logging operations, disturbance of wildlife, and numerous other effects that are far worse for ecological function than if a site burns.








  1. Edward Heisel Avatar

    “Not to mention that all these plant communities existed for millions of years before the colonization of North America by humans and somehow survived without human manipulation from Native Americans.“

    Hard to fathom how this could have happened.

  2. Jeff Hoffman Avatar
    Jeff Hoffman

    I consider anyone making ANY argument for killing trees to be full of it, without even wasting my time and effort reading or listening to their argument. The ONLY exception would be to replace non-native trees with native ones and/or other native plants. Humans don’t need to manage forests, including by making them more resistant to wildfires. These forests evolved with wildfires for millions of years, and they know how to handle them, thank you.

    If it were shown that human fire suppression caused a forest to be unnaturally dense, that would be a reason for thinning it back to its natural state, but I think that George has shown that these claims are also BS, because human fire suppression has not been substantially effective.

    1. Ida Lupine Avatar
      Ida Lupine

      “without even wasting my time and effort reading or listening to their argument.”

      This is how I’ve begun to feel about certain environmental issues like wolf reintroduction, and ‘forest management. Over the years, I have found that there is just no compromise or progress to be made with these people.

      We cannot afford to lose our trees, especially in a time of climate change.

      This is simply about continuing our own human activities, IMO.

      1. Jeff Hoffman Avatar
        Jeff Hoffman

        As we said in Earth First!, No Compromise in Defense of Mother Earth!

  3. Wayne Tyson Avatar
    Wayne Tyson

    George has hit most of the nails on the head, but far be it from me to reveal any nit-picking details.

    I hope he’ll consider rendering it into a harder-hitting Op-Ed piece of 800 words or less.


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George Wuerthner