When one read papers about the effectiveness of fuel reductions to limit or control wildfires,  there are several points to keep in mind. Many papers suggest that fuel treatments are effective–but under what conditions is critical. See comments below.
First, keep in mind that most researchers are looking for success. So they tend to focus on evidence that suggests fuel reduction work and ignore or do not report the failures.
Second, fuel reductions vary in effectiveness both due to what is done (thinning, burning, or both) as well as where they done. Thin and burn is far more effective than thinning alone, burning is better than thinning in most studies, yet the FS emphasis is on logging/thinning. The majority of thinned forest stands are not burned–at least that is what I have seen around the West.
Third, Fuel effectiveness varies in effectiveness over time. So while a thinned and burned plot might be effective in the first couple of years after treatment, it declines quickly over time. Most studies suggest that if these treatments are not repeated within ten years, you might as well not do them at all. In fact, thinning, in particular, by removing competition for light, water, etc. can induce rapid growth of smaller trees, grass and shrubs which are good fine fuels that can increase fire risk. While the FS has money and political support to log it doesn’t do the follow up maintenance. The money isn’t usually there. In fact, in most cases they don’t even burn a thinned stand once, much less come back in 4-5 years to repeat it. Mind you to maintain effectiveness, you have to do this indefinitely. I.e. you have to reburn over and over again. Where is the money for this in FS budgets.
Fourth, many forest types naturally do not burn frequently. Their normal mode of growth is to accumulate fuels and then burn at mixed to high severity. For instance, lodgepole pine in the Rockies, spruce fir almost everywhere, etc. So fuel treatments are not “restoring’ these forests, but degrading them. Fuel accumulation is normal and natural. But even among dry forests, there is debate about the extent they burned occasionally at high severity. One does not preclude the other. You could have multiple low severity fires and then every hundred years or so have a high severity fire. This is the pattern that has been found in almost all ecosystems where they have bothered to look.
Firth, because of the long fire return interval, the chances that a fire will actually burn through a treatment when they are effective is small to zero. Even in ponderosa pine, Rhodes and Baker showed that only a fraction ( 1-2% of fires if I recall correctly) actually encounter fuel treatments during the time when they were effective. The probably is much less for higher elevation moister forests since fires are typically decades or even hundreds of years apart.
Sixth and probably the most important from a policy perspective is that the majority of our fires are small to moderate size. This is not because of a lack of fuels in most cases, simply because all fires are controlled by weather/climate. If the weather is not conducive to fire spread, it doesn’t matter how much fuel you have. Conversely fires burning under less than extreme weather conditions can be contained with normal fire fighting equipment and effort, and most actually would go out without any control at all whether there were fuel reductions or not.
But the very small number of large fires burning under extreme fire weather conditions are the ones that grow to large blazes like the Biscuit Fire. These are wind driven blazes. Under these extreme conditions–nothing works–yet these are the fires that agencies and politicians are seeking to control and stop.
The bulk of all studies show that even if fuel treatments work under moderate conditions, they do not work under extreme fire weather conditions.
So this raises the very idea of whether all of this money spent on fuel treatments–particularly logging–is worthwhile. Especially when you consider the collateral damage from logging–roads, sedimentation, weeds, removal of biomass, etc.and that most lose money too. I’m less opposed to prescribed burning since it more or less mimics natural conditions, but one has to recognize that even prescribed burning has its limitations.
Seventh, logging is not the same as natural thinning agents. Beetles, wildfire, disease etc. “select” different trees for removal. It is like the documented difference between the animals that wolves remove from an elk herd and the ones that hunters take. Wolves improve the herd, while hunting degrades it. It can be argued that logging is degrading the long-term resilience of the forest ecosystem.
To give only one example, some lodgepole pine are more resistant to bark beetles due to the fact that they have more resin ducts. A forester wandering through a lodgepole stand marking trees cannot tell which of the trees have this genetic trait. And not all trees may have it. So it’s entirely possible that thinning might remove this feature from a significant number of trees, reducing the forest’s ability to cope with beetles. Ditto for all kinds of other traits whether is it resistant to fires (thicker bark perhaps), drought, cold, etc. etc. etc.
Furthermore, there is a philosophical bias against large fires. Most assume that reducing high severity fires is a worthwhile goal, when in fact, one could argue that we need more high severity fires.  Such blazes are the major source of dead wood input into the forest ecosystem.Some argue that the snag forest resulting from wildfires is the most rare habitat out there and short-lived since vegetation usually grows back quickly.
Eighth, if you are going to do fuel treatments at all focus it on the edge of communities and homes. All the studies show that you need not treat areas more than a couple of hundred feet from homes and communities. So all these fuel treatments miles from towns are essentially a waste of time for a host of reasons.
 
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About The Author

George Wuerthner

George Wuerthner is an ecologist and former hunting guide with a degree in wildlife biology

3 Responses to How to think about fuel reduction effectiveness at controlling wildfire

  1. avatar Patrick says:

    Succinct commentary George. I agree with your points…there is not a lot of political will to conduct prescribed burning in forests in the west due to the risk of escape. I think though since we don’t have the continuum of fire frequency/intensity that we used to have, prescribed fire is more important to provide transition zones of habitat to promote biological diversity, which I think in turn, helps promote forest health and resilience.

  2. avatar Real Nice Guy says:

    And on cue, Sen McCain calls for more forest thinning in light of the Arizona Tenderfoot wildfire.

  3. avatar Calamagrostis says:

    A great book is Fire in the Sierra Nevada Forests by George E. Gruell. He compares early landscape photos of Sierra forests with modern photos to show how dense and overgrown these forests are today. What we see in the old photos is a landscape of large scattered trees with large areas dominated by shrubs or grasses, in other words a much more diverse community of plants.

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