I’ve been studying fire ecology for decades, an interest which led to the publication in 2006 of my book WIldfire: A Century of Failed Forest Policy. My interest in wildfire did not end with the book and I have continued to read and digest the fire-related literature, attend conferences, and most importantly visit and observe large blazes around the West.

What I began to question, even when I put together Wildfire,  was the idea that low severity/high frequency fires were the dominant influence upon western dry forest landscapes

Yet the majority of forest service “restoration” is based upon the idea that somehow our forests are out of whack. That fire suppression has created dense stands that have allowed fuel buildup and thus we are experiencing abnormal fires. That is the common story that everyone repeats. The problem is that it is probably not true.

Therefore, all the forest restoration work being done is likely not restoring anything, rather is more an excuse for logging than for anything.

Consider these points.

1. The majority, if not all, low severity/high frequency fires are small. There are tens of thousands of lightning caused fires that occur around the West. But the vast majority (like 99%) burn out before they can char more than a few trees. Even if you totaled up all the acreage burned by these thousands upon thousands of fires, the overall effect on the landscape would be very small because the geographical footprint of each blaze is tiny. I have probably traveled more of the West looking at fires than anyone I know, and I have yet to see a significant area burned as a low severity fire. The reason is that the major factor that determines fire severity, spread and size are burning conditions. You get low severity fires when the conditions for a burn are not favorable for fire spread.

2. The vast majority of the acreage burned in any year is due to a very small number of fires. These blazes occur under highly favorable climate/weather conditions of low humidity, high winds, high temperatures and drought. They have little to do with fuels. Think of this for yourself–there’s more fuel in the Olympic rainforest than anyplace else in the West, but the Olympic forests seldom burn. Why? Because they are too wet most of the time for a fire to get started and even if one does start, to burn much acreage.

3. Most larger landscape scale fires do not burn as a single type of blaze. Rather they are a mixture of low, mixed, and high severity burns. We call some of these “stand replacement” fires meaning that the majority of trees may be killed by fire–but even in stand replacement blazes, it is unusual to get more than a 50% kill of trees within the burn perimeter. Fires burn in a mosaic with patches of fire killed trees, other patches intermixed with live and dead trees, and still other patches where few if any of the trees are killed. So even in a “stand replacement” burn you can easily have 50% of the forest that is either mixed or low severity (or no burn at all).

4. I’ve been re-reading a lot of the fire scar studies that have been done around the West upon which “restoration” is based, and most of them (maybe all of them) are flawed. They all have several statistical and other errors that exaggerate the number of fires.

One flaw is targeted sampling. Basically one goes out and finds trees with fire scars and samples them. But these are not random samples. In other words, one is seeking out trees that are scarred by fire, which means you are ignoring the majority of all trees. But then people try to suggest these fire scar trees represent the condition of the landscape as a whole. It’s like walking in a bar in Dillon Montana and noting that the majority of men sitting there have cowboy boots on, but then trying to suggest that the majority of all men in America wear cowboy boots. Obviously it may be true about bar patrons in Dillon, but not about men in general. Same is true about the results of fire scar reconstructions.

A second flaw is that most fire scar reconstructions use “composites” of the fire scars. In other words, they add all scars together to come up with the “fire interval”. But this is highly biased in a number of ways.

As noted above, most fires affect only a few trees or small acreage. So should they have the same “weight” as say a fire that burns the entire study area? What you find is that the majority of small fires does not affect much area, and probably have little overall influence on the landscape. In other words, you have a thousand acre study area and lightning causes a single tree to burn—should you imply—as most studies do—that this is one “interval”  in the forest burn cycle?

Worse yet, the larger the sample area, the more likely you are to pick up a lot of these single burn trees, so this tends to skew the fire interval to shorter and shorter time frames, giving a false picture of the burn frequency across the landscape. On the other hand, too small a sample size can also skew things since you might miss a large stand replacement event  because the one plot you sampled for whatever reason might have been one of the no-burn or lightly burned sites in an otherwise more severe and widespread fire.

It is the relatively rare, but large fires that do the bulk of the ecological work. In addition, unless you cross date the fires, you can have a lot of single tree scarred trees, but each one due to a different lightning strike, and not related to any other fires in the area and all burning only a tiny fraction of the total landscape.

A third flaw is the way people think about the results. Fires are episodic much like floods on rivers. The vast majority of fires occur in series due to climate/weather conditions. Thus you can have 2-3 fires in one decade, followed by maybe 80 years without any fires, then another decade of drought where you have a series of very large blazes. In other words you could easily have 5 fires in a hundred years which would give you a fire return interval of every 20 years, but this would be deceptive. In reality you had 80 years without a single fire.

This is somewhat like river floods. Despite the name of “Hundred Year Floods” you can have two hundred year floods back to back, followed by 200-400 years without any significant floods. Same with fires. Such a fire temporal pattern would undoubtedly lead to dense forest stands that are occasionally “thinned” by fire, beetles, or disease.

We know from other methods including geo morphic, fire atlases, pollen and charcoal records, and other alternative means of deciphering fire patterns that fires are highly influenced by changing climatic conditions. And these conditions are largely influenced by factors like off shore currents, periodic shifts in solar input, and so on. These large global influences have a lot to do with how much forest burns and under what kinds of conditions. What these studies indicate is that large fires are quite normal–even in so called “dry forests” like ponderosa pine if you view things from the proper temporal and spatial scales.  At least for many forest types we are not likely experiencing larger fires or fires that are outside of the ‘historic” variability if you view them from the proper time and geographical scales.

The other factor is the cultural bias against dead trees. Dead trees are a sign of a healthy forest. We need beetle kill, wildfires and diseases like mistletoe to keep our forest ecosystems functioning. Most forest management is designed to reduce or eliminate these important factors. The way to think about beetles, fires, and disease is like predators. These are the predators that keep a forest healthy, just as wolves keep the elk herd healthy. Trying to limit these natural processes to a small part of the landscape is like saying it’s OK for a few token wolves to kill a few elk, but we don’t want them affecting elk across the state. However, if you have that attitude, then you are effectively eliminating wolf predations as a major ecological factor. Same thing applies to managing forests to reduce the occurrence of fires, disease and beetles.  We need to embrace these forest processes for the critical role they play in maintaining healthy forest ecosystems.

The end result of all this is that the vast majority of forests now being “thinned” for restoration to “restore” their “historic variability” are likely not out of historic variability at all, thus do not need restoration. I would not suggest this applies to every forest stand, but I am willing to bet the vast majority of restoration projects are based on out of date interpretations of past historic conditions.

 
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About The Author

George Wuerthner

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

13 Responses to Challenging the Standard Paradigm for Fires

  1. avatar DB says:

    What about the fires that have been killing large Ponderosa pines that survived periodic fires in the past? Many of these pine grew and survived in Douglas-fir, even Grand fir habitat types, but because of past fires were growing in sparce, shorter understory conditions. The theroy is that with fire supression these understories became denser, taller and when burned, burned hotter reaching the canopies of, and killing, previously fire-tolerant old growth pine.
    Wouldn’t removing these dense understories protect these old growth pine in much the same way rural home owners protect structures by removing flammables adjacent to their properties?

  2. First, the idea fires didn’t kill large ponderosa pine in the past is based upon the myth of low severity fires. And of course, there are undoubtably places where larger fires were almost always rare and suitable for large pine growth.

    However, there is growing evidence that there were always periodic stand replacement fires even in ponderosa pine forests. And hence most assuredly dead pines.

    You have to keep in mind the temporal consideration. Large stand replacement blazes are relatively uncommon and widely spaced in time. So a pine could easily grow 200-300 years without being in a burn. So the presence of large pine on the landscape does not necessarily preclude large stand replacement fires.

    Furthermore, burns as I suggest are a mosaic. So even in a large fire, there are islands where trees survive. Many of our large old growth pine may be survivors of earlier stand replacement fires simply by the fact of where they were growing. They may have been in an island that did not burn or a place where the fire intensity was lower as in a mixed severity blaze and thus survived perhaps several of these large blazes.

    Third, even if large pines were killed, so what? I am not being flippant. The real ecological value of large trees is after they die. Large trees take longer to rot, provide more nutrients, survive longer as standing snags, and are important for wildlife, stream structure, etc. All of these are not “lost” if there’s a fire that kills the pines–other than if the pines are removed by “post fire” logging euphemistally called “salvage logging.”

  3. Excellent post, George. I’ve come to the same conclusion about forests in the southwest. Periodic “catastrophic” fires have been around for centuries, and result in a mosaic of habitats that increase biodiversity at many scales. Trying to restore forests so that they appear like some arbitrary point in the past is just ecological hubris.

  4. One other statistical flaw in the tree ring data is that trees that were totally consumed by the fires are not available for sampling, again leading to a bias to low-severity fires.

  5. avatar rork says:

    Thanks for this article. There is not lots of talk out east about these matters, and I fear many people have bought in to a demonization of fire (helped by daily propaganda at certain points in past national administrations).
    In Michigan, we have to debate about historic fire regime being to a small or great extent thanks to humans of long ago. We have little pre-human data. Natural doesn’t automatically mean best in the sciences I’m used to (humans,cancer), but it is often a touchstone. Not normative maybe, very instructive always. Still I’m at a bit of a loss. After being a former skeptic, I’m now favoring more prescribed burns near me, after I’ve helped in a few and seen many other times that it does help with invasives (e.g. the damned autumn olive and common buckthorn which have made some woods you could jog through into a vicious fight where you see nothing more than 10m away – the woods have radically changed recently). It also has the chance to keep or get some areas into stands of large oaks, and nothing looks as good to my eyes as fairly pure stands of fat white oaks and their occupants (which look like they are set to be replaced with new understory stuff like maples unless we get some fires). Historically, that might have been how things were, thanks in some degree to fire-setting humans, but whether it is good or even natural, I don’t know. Due to the new species plaguing us, and the succession I don’t like, I’m thinking it really might be good. Obtaining relevant data might take a very long time I’m afraid.

    • avatar Ida Lupine says:

      I know – I have mixed feelings about some of the invasives. Autumn olive smells magnificent in spring, and you can eat the fruit. I wonder if we can eliminate entirely all of the invasives we have brought in when and if they are beneficial, or if we should, or if it is even possible to return areas to their prior state. 🙂

    • avatar Immer Treue says:

      Rork,

      That European Buckthorn is a plague. If memory serves me correct, from a terrestri ecosystems class, it is believed some oak (reds)have actually developed an evolutionary strategy of not dropping their leaves until Spring. This contributes to dry ground cover. Ground fire comes in and burns competition.

  6. avatar Barb Rupers says:

    This was written by Dr. Jerry Franklin, University of Washington, regarding proposed salvage of timber on the 500,000 acre Biscuit Fire in southwest Oregon that burned in 2002.

    LSR (late successional reserves); NSO (northern spotted owl)
    “A summary is provided at the beginning of these comments. I would conclude that the salvage activities proposed within the boundaries of the LSRs as part of the Biscuit Fire Recovery Plan are inappropriate. Salvage would be completely antithetical to the goals of reestablishing late successional forest habitat. Retention of the large snags and logs are essential to natural recovery processes and none of this material can be viewed as in excess to ecological needs.” “Tree planting may be appropriate in some locations to provide seed sources for a variety of tree species but in moderation and, above all, in irregular patterns and with variable density. Establishment of large areas of homogeneous stands, even at low density, is inappropriate within the LSRs. Current knowledge
    regarding the ecology of the NSO should be considered during revision of the DEIS.”
    http://www.orww.org/Wildfires/Biscuit/References/Franklin_2004.pdf

  7. avatar DB says:

    I’m skeptical of “the myth of low severity fires.” I think the author’s assertion requires at least some documentation. And I doubt that fire intervals are determined eronously simply by saying that a single scar implies a fire interval over a broad area. I think there is research that shows that fire scars have been linked by year of burn over broad areas and indicate rather frequent intervals of low severity fire accross portions of the landscape.

    I don’t doubt that some forest restoration work is a rationaliztion for logging, or make-work where no commercial product results. But at least it returns some stands to densities and species compositions that existed prior to immediate fire supression in all forest types whether or not fire was historically frequent in some of those types.

    This may be ecological hubris but some sort of management is required and will happen (FLMPA and NFMA). It only seems smart to return some dry forest types back to those conditions that burned more frequently and with less severity. And these are often the types in the urban interface where so much money is spent to protect.

  8. avatar Mal Adapted says:

    George,

    I just ordered the last, used copy of your book from Powell’s. I have read the work of Agee, Swetnam and other fire ecologists, and I’d like to know their reaction to your ideas. Based on my reading, and my own observations in eastern Oregon and northern New Mexico, it’s clear that fire history has been determined by conditions specific to different areas, and I’m not ready to say that the importance of frequent, low-severity fire is a myth in every case.

    I know that some merchantable-timber sales are disguised as forest “restoration” projects, and that many others are ineffective at best. That doesn’t mean that the very idea of trying to safely restore fire to its natural role in forest ecology is wrong.

    I’m not optimistic I’ll ever see the idea successfully implemented, though. It seems more likely that historically open forests of 300-yr-old ponderosa pine, now choked with dog hair, will continue to be erased by conflagrations like the Las Conchas blaze in New Mexico’s Jemez Mts. two years ago. What a world!

  9. avatar Rancher Bob says:

    George
    I really like the part where you tell us that your the only person that travels the west looking at fires.
    7 Billion people in the world and you believe your the only person studying western fires.
    My suggestion is call you doctor and have your hormone replacement medication reduced your ego is off the charts, and that can be dangerous.

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‎"At some point we must draw a line across the ground of our home and our being, drive a spear into the land and say to the bulldozers, earthmovers, government and corporations, “thus far and no further.” If we do not, we shall later feel, instead of pride, the regret of Thoreau, that good but overly-bookish man, who wrote, near the end of his life, “If I repent of anything it is likely to be my good behaviour."

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