The Thinning Trap

Fire suppression effects on fuels are likely exaggerated. Most forests types are well within their historic range of variability.  Most of the acreage burned in fires annually is in forest types that historically experienced moderate to significant stand replacement blazes. Thus the idea that large fires that occur are the result of fire exclusion is inaccurate.

There is new evidence that suggests that even low elevation dry forests of ponderosa pine and Douglas fir occasionally experienced large stand replacement blazes. The old model that characterized such forests as primarily a consequence of high frequency-low intensity blazes that created open and park-like may not be universally applicable.

Thinning won’t significantly affect large blazes because fuels are not the major factor driving large blazes.  Climatic/weather conditions are responsible for blazes.

Large blazes are driven by drought, wind, low humidity, and high temperatures. These factors do not occur in one place very frequently.  That is why most fires go out without burning more than a few acres.

The probability of any particular thinned stand will experience a blaze during the period when thinning may be effective is extremely low.

The majority of acreage burned is the result of a very small percentage of blazes—less than 0.1% of all fires are responsible for the vast majority of acres charred. Most fires go out without burning more than a few acres.

Even if it were possible to limit large blazes, it would be unwise to do so since the large blazes are the only fires that do a significant amount of ecological work.

Large fires are not “unnatural”.  There are many species of plants and animals that are adapted to and/or rely upon dead trees and snags. There would be no evolutionary incentive for such adaptations and life ways if large fires were “unnatural.”

Dead trees are important physical and biological components of forest ecosystems. They are not a wasted resource.  Beetles and wildfires are the prime agents that create dead trees.  Removal of significant amounts of biomass by thinning and/or logging likely poses a long term threat to forest ecosystems. Biomass energy is the latest threat to forest ecosystems.

Logging/thinning is not benign. Logging has many impacts to forest ecosystems including spread of weeds, sedimentation of streams, alteration in water drainage, removal of biomass, and so on.  These impacts are almost universally ignored and externalized by thinning/logging proponents.

Alternatives to logging/thinning to reduce fuels that do not remove biomass and avoid most of the negatives associated with logging practices exist, including prescribed burns and wildlands fire.

Reducing home flammability is the most economical and most reliable way to safeguard communities, not landscape scale thinning/logging projects.

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The rush to formulate new forest legislation that advocates thinning forests, use of biomass for energy production, and the presumption that our forests are “unhealthy” and/or that large fires and beetle outbreaks are undesirable may soon create a new threat to our forests. There are a host of different bills before Congress including legislation introduced by Mark Udall of Colorado, Jon Tester of Montana, Ron Wyden of Oregon, among others that are all predicated upon a number of flawed or exaggerated assumptions.

Some of this legislation is better than others, and some of it even has some very good things in the language and policies that are an improvement over present policies.  Nevertheless, there are many underlying assumptions that are troubling.


There is a circular logic going on around the issue of fuel buildup and fire suppression. Currently the major federal agencies including the Forest Service and BLM generally attempt to suppress fires, except in a few special locations like designated wilderness.  Despite the fact that most agencies now recognize that wildfires have a very important ecological role to play, we are told by managing agencies that they must continue to suppress fires or face “catastrophic” blazes—which they consider to be “uncharacteristic”.

The problem is that thinning won’t solve the “problem” of large blazes because the problem isn’t fuels.  By allowing the timber industry to define the problem and propose a solution we have a circular situation whereby the land management agencies continue to suppress fires, thereby presumably permitting fuels to build up, which they assert thus drives large blazes, creating a need for more logging and fire suppression.  This cycle of fire suppression, logging, grazing, and more fire suppression has no end.

In addition, since thinning reduces completion, opens up the forest floor to more light, thus new plant growth, thinning can often lead to creation of even more of the flashy fine fuels that sustain forest fires. Unless these thinned stands are repeatedly treated, they can actually acerbate fire hazard by increasing the overall abundance of the very fuels which are most problematic—the smaller shrubs, grasses, and small trees that sustain fire spread.

In addition, thinning can increase solar penetration leading to more rapid drying and greater penetration of wind—both factors that aid fire spread.

This is not unlike the approach taken with predator control, whereby agencies for years have shot, poisoned, and trapped coyotes in the belief that they were reducing coyote numbers. But since coyotes respond to such persecution with greater fecundity, predator control becomes a self fulfilling activity whereby predator control begets more predator control.

While fire suppression (and logging, grazing, and so forth) may be a contributing factor in fire spread in some forest types (primarily ponderosa pine), they are not ultimately what is driving most large fires. Large blazes are almost universally associated with climatic features like severe drought, wind, and ultimately by shift in oceanic currents such as the Pacific Decadal Oscillation. Therefore fuel reductions will not substantively change the occurrence of large blazes.

Even if one wanted to buy into the fuels-is-driving- large blazes story, it would behoove us to rethink the range of solutions.    The National Park Service, the only agency that does not have a commercial logging mandate, has effectively dealt with fuel reductions through wildlands fire and prescribed burning.  At the very least, any fuel reduction that may be needed should be done by prescribed burning.


One of the underlying assumptions of all these pieces of legislation is the idea that our forests are unhealthy and possess unnatural fuel loads due to fire suppression or fire exclusion.  There is, of course, a bit of truth to the generalization that some forest types may have had some fuel build ups as a consequence of fire exclusion, but whether these fuel build ups are outside of the historic range of variability is increasingly under scrutiny.

It’s also very important to note that the majority of all forests/plant types in the West like lodgepole pine, subalpine fir, aspen, juniper, red fir, silver fir, Engelmann spruce, western red cedar, Douglas fir in west coast ecosystems, and many others have such naturally long fire intervals, that suppression, even if it were as effective as some might suggest, has not affected the historic fire frequency.   Indeed, the majority of acreage of forest types burned annually tend to be characterized by moderate to severe fire, and are not the forest types where fuel build up is presumed to be a major problem—namely ponderosa pine forest type.  Yet most people apply the ponderosa pine model of less intense frequent fires to all other forest types and thus assume that fire suppression has created unnatural fuel levels.

In particular the timber industry has adopted the convenient theme that fire suppression has created a presumed “fuel build-up” responsible for large wildfires. (Never mind that there were always large wildfires long before there was any effective fire suppression—for instance, the 1910 Burn which charred more than 3 million acres of northern Idaho and western Montana)

Thus logging proponents have created a “problem” namely fuel build up, and then by happy coincidence, have a solution that just happens to benefit them– logging the forest.

Fire suppression may have influenced some low elevation dry forests like those dominated by pure ponderosa pine, but perhaps not nearly to the degree or over the large geographical area that timber interest and logging proponents try to suggest. Those who want to justify logging try to conflate low elevation forests with all forest types—many of which such as lodgepole pine—are very likely not affected by fire suppression due to the naturally long intervals between fires in these forests.


The emphasis on fuel reductions has obscured the fact that nearly all large blazes are climate/weather driven events. Evidence is building that wet, cool climatic conditions may be more responsible for dense forest stands and/or lack of fires than anything to do with fire suppression. In other words, fire suppression may not be as effective as some suggest and any fuel build up may be within natural or expected range.

In addition, there is also a growing body of scientific analysis that calls into question the very methods and conclusions used to construct fire histories. These analyses suggest that historic fire intervals, even in lower elevation dry forests like ponderosa pine, are biased.  Fire intervals may be far longer than previously assumed. Because of this longer fire interval, dense forest stands may be natural, and/or no different than what existed in the past.  There is also new evidence for mixed “severity” (i.e. moderate change) fires as well as crown fires in these dry forests.  The implications of these findings is that many forests, even low elevation forests, may well be within the historic range of variability.


One of the issues missed by thinning proponents is that the vast majority of all ecological work occurs in a very small number of fires—the big so-called “catastrophic” fires.  Even though most agencies and environmental groups now profess to believe that wildfire is important to healthy forest ecosystems, they are not willing to let fires do the work.

For example, in the years between 1980 and 2003, there were more than 56,350 fires in the Rockies.  These fires burned 3.6 million hectares (8.64 million acres) Most of these fires were small—despite all the fuels that has supposedly made conditions in forests ready to “explode”.  Out of these 56,350 fires, the vast majority of blazes totaling 55,228 fires or 98% of all blazes only charred 4% of the acreage.

On the other hand, a handful of fires—1,222 or less than 2% of the fires accounted for 96% of the acreage burned. Even more astounding is that 0.1% of the fires or about 50 fires charred more than 50% of the acreage burned.

This suggests four things to me. First, fuels are not driving large blazes. There is plenty of fuel throughout the Rockies, but most fires never burn more than a few acres—despite all the fuels that is sitting around.  Fire suppression if it was responsible for a fuels build up doesn’t appear to be creating a lot of big fires.

The few very large fires that everyone is concerned about occur during very special conditions of drought, combined with low humidity, high temperatures and wind. And these conditions simply do not occur very often.  When they do line up in the same place at the same time than you get a large fire—no matter what the fuel loading may be.  My conclusion is that large blazes are climate driven events, not fuels driven.

Finally, the take home message for me is that even if we were successful at stopping big blazes through thinning and/or fire suppression, we would be in effect eliminating fire from the landscape.  Since almost everyone today at least professes to the goal of restoring fire, than we have to tolerate the few large blazes—not try to stop them.  Of course, it appears that despite our best efforts with logging, thinning, and all the rest, we have not had that much influence on eliminating the large blazes.


One of the other major problems I have with the way many organizations have chosen to work on these issues is the way they “frame” the issues. When words like “working landscapes”, “restoration” , “unhealthy forests” “catastrophic blazes” “beetle outbreaks” are used in any discussion related to forests, they solidify in the public’s mind that there is a major problem with our forests, and more importantly that the “cure” is some kind of major invasive manipulation of forest ecosystems.

One must be careful about how you frame this issue. Even though most environmentalists do not support large scale commercial logging of our national forests, and have a lot of sidebars on how any logging should be done to address ecological concerns, when environmental groups say things like “we need to maintain our timber industry to restore the forests” the public just hears that our forests are a mess and the ONLY solution is more logging. I maintain that is not a message environmentalists want to be conveying. The public does not hear the sidebars, nor the cautionary words, rather they hear that we need to log our forests, and do so in a big way or ecological Armageddon is about to befall the West.


There is an important lesson in science called the precautionary principle. In the absence of full understanding of a problem, it is usually best to prescribe the least invasive and least manipulative actions.  Conservation groups would be wise to apply this principle to forest policy.

That doesn’t mean I don’t support some “restoration” activities. To make an analogy, let’s look at the issue of wolf restoration. Putting wolves back on the land restores predation influences, but this is a very different thing than allowing hunters to kill elk. Especially because it allows the wolves, and natural conditions like drought, etc. t o determine what is the “right” number of elk and deer, not some agency with an agenda to sell licenses.   Hunters influence elk differently than wolves and logging is different than say fires.  Just as an elk killed by a wolf leaves behind carrion that other animals can use, a forest with fire leaves behind a lot of biomass that helps to sustain many other functions in the forest. Logging short circuits those ecosystems functions.  As with hunting whenever you have a commercial enterprise involved in natural resource policy, it distorts the conclusions and it’s convenient to ignore anything that suggests the activity—whether hunting or logging is creating problems.


There is a growing challenge to many of the assumptions about fires and its influence on forests. These challenges to assumptions about constitutes forest “health” and the historic role of large blazes and beetle influences  is not unlike the challenges to common assumptions about predators that began with people like Adolph Murie, George Wright,  and other scientists back in the 1930s and 1940s who started to question  predator policy. These early ecologists were not only challenging politicians and citizens, but many other scientists who were advocates of killing predators to create “healthy” populations of deer and elk.

I need not remind many conservationists that there are still plenty of scientists around that will support killing predators like wolves, despite decades of research about the ecological need for top down predators. So assurances that any logging on public lands will use the “best” science are not reassuring to me. When there is a commercial/economic aspect to any management, that tends to distort and often compromise the science and scientists that are consulted.  It would naïve for anyone to believe that this is any difference when dealing with fire and forest policy issues, especially when there’s an economic benefit to some industry and/or individuals for the policy.


There is a growing scientific body of work that is challenging the notion that fire suppression is responsible for dense forests and/or that crown fires, even in low elevation forests consisting of ponderosa pine and/or Douglas fir.  The implications of this for forest policy are significant for if this is correct, our current conditions are not outside of the historical normal range of variability, especially when you consider past climatic conditions that are similar to the current dry, warm conditions.

One can find plenty of scientists who think our forests are out of whack, and prescribe logging to reduce fuels and so forth, however, if one is monitoring the scientific literature  one would find enough evidence here and there to question the current assumptions about “forest health” and the presumed need for logging.

At the very least, it would seem a prudent approach to avoid endorsing logging when there is at least some evidence to suggest that our forests are not as out of whack as previously assumed, and/or that logging cannot do what advocates suggest—like restore the ecosystem or prevent large blazes.


Another unchallenged assumption of those prescribing thinning to protect say old growth ponderosa pine is the idea that somehow without thinning, we would lose all the old growth to fires. However, that ignores the low probability that any particular acre of land will burn in a fire. For one thing, most fires are small as mentioned earlier. They do not burn more than a few acres and go out. The few fires that do grow into large blazes occur under very special climatic/weather conditions of extreme drought, high wind, low humidity and high temperatures. These conditions do not occur that frequently, and to this you must provide an ignition. So even if you have drought, wind, low humidity, etc. you may not get a blaze.

In addition, even big blazes do not consume all the forest. Most large fires burn in a mosaic pattern for a host of reasons, the likelihood that any particular acre of old growth will burn is extremely small.

Finally, since thinning effectiveness even under the best circumstances rapidly declines over time, in order to protect old growth stands, thinning of that particular location in a forest must be very recent otherwise new growth generated by the opening of the forest, reduced competition, etc. often negates any advantage created by forest manipulation (logging).


Even if one disagreed with these new insights and interpretation of forest an ecosystem, and the presumed effectiveness of thinning projects, that doesn’t necessarily lead to logging as the “cure”.  It wasn’t that long ago we heard many groups outlining the many ways that logging created ecological outcomes that were undesirable—the spread of weeds, changes in the abundance of snags, and down wood, that human activity in the woods disturbs and displaces sensitive wildlife, that disturbance of the land and use of logging roads (even temporarily logging roads) adds sediments to our streams, and so forth.  Most of those critiques are still valid today, but we don’t hear that kind of criticism coming from many environmental groups anymore. This silence and unwillingness to continuously remind the public that logging has many, many negative impacts on forest ecosystems has compromised the environmental effectiveness as defenders of our public forests.  After all who is going to assume that role if environmental groups do not continuously remind the public that logging has many unexamined and ignored externalities.


Even if one did not want to challenge the common perception that we have an “emergency” as Senators Wyden, Udall, Tester and others proclaims, logging isn’t necessarily the only or the best way to address this presumed emergency.

The National Park Service does fuels reductions and ecosystem restoration without logging. They have a long track record demonstrating that one can modify fuels and restore the ecological value of wildfire to the landscape without logging, and without jeopardizing communities. Yosemite NP, for instance, does prescribed burning in the crowded Yosemite Valley as does Muir Woods adjacent to Muir Woods, as well as many other national parks.  That is not to suggest that prescribed burning will alleviate all concerns, but at the very least, it should be the approach that environmentalists advocate.  Prescribed burning combined with natural wildfire can “restore” forest resilience as well as reduce fuels.  Such an approach avoids many of the negatives associated with commercial logging, including the need for roads, the disturbance of water drainage by roading, soil compaction, removal of biomass, and so forth.


There is an abundance of evidence to suggest that if community security is a concern, the best way to achieve that is through reduction of flammability of homes and the area immediately around the community, not wholesale logging for the forest ecosystem.  Jack Cohen’s research at the Missoula Fire had demonstrated that thinning the forest is not the best way to protect homes.

Advocating for logging as the “cure” is like suggesting that the best way to reduce elk herds is by hunting, instead of being an advocate of wolf restoration.  Any time you get an economic activity involved in natural processes you compromise the integrity of the goals and measures.


Even if the majority of you believe our forests are out of whack and are unwilling to accept the critiques from those who suggest that our understanding of forest ecosystems may be incorrect, that doesn’t mean one has to be a hand maiden for the timber industry.  Nature does the best management—that is why we all are advocates for wilderness—we believe that allowing wild places to determine what is right for the landscape is the best way to preserve “healthy ecosystems”. If the forests are overstocked as some may want to conclude, than let natural processes select which trees should survive and do any thinning that is necessary using insects, disease, drought, fire, wind storms, and all the other mechanisms that regulate plant communities—and Nature will do a far better job of determining which trees should survive than any forester.

Our role as humans is to get out of the way as much as possible, not to intrude and advocate for invasive solutions like logging. The only role for logging on public lands that I see is to strategic as listed below.


If you must support logging, make sure it is very limited, and framed not in terms of forest health, but as a useful way to reduce human anxiety. Logging around houses and communities to reduce public anxiety over fires may be a political necessity.  A fire break of significant size around the perimeter of a community may reduce public fears about large fires; however, as has been shown in numerous cases around the West fuel breaks alone will not ensure that homes are safe. Flammability of individual homes must be addressed.

GEORGE WUERTHNER is editor of Wildfire.


George Wuerthner has published 36 books including Wildfire: A Century of Failed Forest Policy