How Effective Is Fire Suppression? Lessons from Yellowstone

One of the often repeated remarks used to explain the large fires we are experiencing around the West is that a hundred years of fire suppression has led to unnatural accumulations of fuels.

Yet such assertions assume that fire suppression was always efficient and effective—a questionable assumption especially in the early days of the Forest Service.

Secondly, it assumes that if fires were not “extinguished” they would have burned massive amounts of forest and fuels.

The first assumption is doubtful. A hundred years ago most of the mountainous parts of the West were still largely inaccessible wilderness. There were fire lookouts to be sure, and young men with shovels and mules trying to put out flames across millions of acres of roadless lands. But the ability of these enthusiastic men working with technologically primitive methods to really influence fire spread across those millions of acres is dubious, especially in light of the failure of modern fire-fighting equipment to do the same with much greater technological advantage.

(Although the grass/forest ecotone at the lowest elevations may have been affected by livestock grazing that eliminated flashy fuels–this still would not affect most higher elevation forests types.)

Effective fire suppression did not really begin until after World War 11 with the advent of helicopters, smoke jumpers, tanker bombers, bull dozers and modern fire weather predicting and so on. This, combined with a massive logging road network that is the result of years of over cutting of national forests, greatly improved access and “may” have improved the ability of humans to control fire ignitions and spread. As we shall see even with this massive technological advantage, fire suppression may not have had as great an influence as commonly assumed.

As I have often argued, weather/climate controls fire ignition and spread more than fire fighters. Weather also largely controls when fires actually are extinguished.

One point to consider is that between the late 1930s and the big fires of 1988 most of the West experienced cooler, moister climatic conditions. Cool, moist weather tends to thwart ignition in the first place, and limits fire spread.

So did fire suppression extinguish flames or did a period of moist, cool weather create conditions that naturally reduced fire ignitions and spread?

Cool, moist conditions also favors greater seedling survival which in turn creates denser forest stands—exactly the conditions some attribute to fire suppression, but is more reasonably explained by climate/weather.

However, since fire suppression is the standard response to nearly all fires, we don’t really have many control areas where we can judge how effective fire suppression has been and how it may or may not have influenced fuel accumulation.

One test did occur, however. Prior to the extensive fires of 1988, Yellowstone National Park had implemented what is sometimes called a “let burn” policy. During the years between 1972 and 1988 there were 235 wildfires that occurred within the 2.2 million acre park. None of the 235 fires were suppressed or fought–they were merely monitored. Most of those fires burned less than a few acres. Only 15 of those 235 fires burned more than a hundred acres and all 235 of them went out on their own without any assistance from humans.

I repeat for emphasis–all of them went out without a single fire fighter, smoke jumper, tanker retardant bombing, and/or helicopter water drop!

If we assume that Yellowstone is not that different from most of the rest of the West’s high country, it is reasonable to assume that the vast majority of fires that fire fighters “control”, “contain” and “suppress” are also destined to self extinguish.

What we see outside of places like Yellowstone is the public perception that fire fighters are putting out most fires–fires that are destined to go out on their own whether we do anything or not. Keep in mind that even with the large amounts of fuels that littered Yellowstone Park in the 1970s and 1980s (there had not been a large fire in several hundred years) nearly all fires went out without burning more than a few acres.

Since the vast majority of all fires go out without burning a significant amount of acreage, it is difficult to argue that fire suppression has significantly contributed to “fuels build up” except perhaps in the lowest driest forest areas dominated by species like ponderosa pine that may have had more frequent fire. However, even within those pine forests you won’t get large fires if the weather is not conducive to fire ignition and spread.

The important point is most forest types in the West are not ponderosa pine. Even if fire suppression has altered these ponderosa pine forests to some degree—an assumption that is increasingly being challenged as well–that does not explain the large fires we are now experiencing around the West.

Blazes occurring in other forest types like lodgepole pine, subalpine fir, and other tree types naturally have long fire rotations and are dominated by mixed to high severity fires that kill a significant amount of the trees.

Even if fire suppression were effective as claimed, most of these forests would still not be outside their historic fire regime due to the naturally long intervals where fuels accumulate for decades or hundreds of years in between fire events.

The other thing that the Yellowstone record demonstrates is that it is only a few fires get large when weather/climatic conditions are conducive to burning as in 1988. When those conditions occur, fire fighters are unable to extinguish blazes.

So we have a situation where the vast majority of all fires extinguish themselves and we exaggerate the influence of fire fighters on fire spread, but we take “credit” for  for putting out fires that are going to self extinguish. (And waste a lot of money putting “out” fires that are not going to burn much.)

By contrast, a few fires are impossible to extinguish. We cannot suppress these large blazes even with our massive technological advantage—again wasting large amounts of money in a largely fruitless effort to contain or control them—until the weather changes and puts them out for us.  

These kinds of scientific findings also call into question the common assumption that Native American burning significantly altered fire regimes across the West. Not discounting that the Indian influence around their villages and other high use areas may have seen more fire, one has to remember that you can’t get a fire to burn much, or at all, if the weather/climate is not conducive to ignition and fire spread. And outside of the immediate high use areas that may have burned more frequently as a consequence of Indian ignitions, it is questionable whether Indian burning significantly altered the majority of natural fire regimes across the West.

Most of the forest ecosystems in the West had naturally long fire rotations–often along the lines of hundreds of years–that is not because there was no fuel to burn or even ignitions–there was always lightning. However, you can’t get moist forests to burn. And many of these ecosystems do not dry out sufficiently to carry a large fire except under extreme drought conditions that occurs intermittently over the millennium.

Even with ignition sources, combined with drought, without corresponding low humidity, and wind, you will not get a significant fire. It takes all those things operating in the same place at the same time to get a large blaze. Those particular combinations do not occur very often in any one geographical spot.

Thus there certainly was just as much fuel in Yellowstone in 1986 or 1987 as in 1988. There were lightning strikes. Why didn’t large fires occur in any of those previous years? Simply put, most of the times in the lodgepole pine forests that dominate Yellowstone conditions aren’t conducive for fire spread.

In 1988 all the factors lined up in a row. There was the driest year on record since record keeping in the park began in the 1800s. There was the lowest humidity ever recorded in the park area—some days as low as 5 percent or less. As a result of low humidity the internal moisture of some living trees was less than kiln-dried lumber. And most importantly, you had some strong winds of 50 mph or more on some days that drove the flames through hundreds of thousands of acres.

Finally, despite the 10,000 fire fighters that were attempting to control the blaze, what finally extinguished the fires was snowfall in early September.

Most of the large fires burning across the West in recent decades are not a consequence of fire suppression or abnormal fuel buildup. Rather they are the normal consequence of changing climate and the natural fire pattern found in those forest types.


  1. CodyCoyote Avatar

    Before the GYE fires of 1988, the last great ” Fire Storm ” came in 1910 , when 3 million acres burned in NW Montana north Idaho, and eastern Washington.

    Those fires were amplified by unrelenting hurricane-force winds across the region. It was a fire season that ossified the fledgling Forest Service’s policy of fire suppression for the next 60 years , or more. I recall reporting on Yellowstone’s ” Let Burn ” natural fire policy in 1973 from Cody WY . It caused a great deal of grief in the region …” How can that stupid #$@^ing Park Service even begin to think about letting a forest fire burn ? “was the hue and cry from local governments and state leaders , et al. They didn’t get it. Yet as George points out, the Park had 235 fires come and go between 1972 and 1987. Good to know that number.

    We still have a lot to learn.

  2. HoofHugs Avatar

    There were also a lot more grazing animals in this region as well. Wild horses are native to this area of the West and have existed in these very ecosystems through a variety of climate and weather changes. Although the dry grass might not be their first choice, their digestive system is well suited to it. Removing native species from ecosystems where they co-evolved has left a hole in the environmental niche.

    1. Immer Treue Avatar
      Immer Treue

      Yes and no. Horses may have evolved here. But long gone prior to Columbus and his fleet of three. So in terms of historic fire affect, equines zero.

    2. SaveBears Avatar

      Horses as we now know them are not indigenous to the region, the current wild horses in the west are European in origin.

      1. CodyCoyote Avatar

        All horses originally evolved in North America from the tiny Eohippus 60 million years ago , fossils of which are found near my town of Cody from the Eocene formatios. The Appaloosa horse of today did in fact evolve in North America according to the fossil record stock. It’s feet-toes are unique. The animal is unique in other ways. But it emigrated back over the Beringia land bridge to east Asia during the interglacial, the last of the horses from the mother continent. All other horses that evolved in North America went extinct here. In fact, all horses were nearly extincted. A few were domesticated in what is the Ukraine about 8,000 years ago and from those all modern domestic horses have been derived. Every Thorobred in America and Europe is descended from just three Arabian stallions and some English mares, for instance. Quarter horse so popular here in the west are a blend of those English Thorobreds bred back to Spanish mustangs.

        The Appaloosa’s homecoming to western North America was a serendipity of cultural circumstance. You do see Arabian lines in them. Off all the types and breeds of horses in the world today , there’s only one specie that remains undiluted genetically: the Przewalski horse, which went extinct in the wild but was restored from zoo populations and returned to the wild in our time I believe. (?) .

        I really do not know how the Appaloosas kept their herd and genetic integrity mostly intact before being reimported back here , but I’m glad they did. So are the Nez Perce.

        1. Ida Lupine Avatar
          Ida Lupine

          This is what I have always heard, or something similar.

  3. Lyn McCormick Avatar
    Lyn McCormick

    Equids evolved on this continent. The most recent evidence of Equid, the one most closely related to the modern equid, was discovered in the the Great Basin in Wyoming, I believe in the Red Desert area. Most likely they were hunted to the brink of extinction except for the few that managed to cross the land bridge. At one point in time when the bison herd numbers were estimated at 50+ million, the Equids are estimated to have numbered 20+ million, however they grazed different ranges and thrived in different ecosystems. See Craig Downer’s discussion of Reserve Design in his book “The Wild Horse Conspiracy”. Also, Andrew Cohen, The Atlantic Monthly, has a well researched series of articles on the Wild Horse issue.

    1. Mal Adapted Avatar
      Mal Adapted

      I downloaded the National Academy of Sciences report that Cohen cites in his Atlantic Monthly article. I haven’t read the whole thing yet, but I’ve got a couple of observations:

      The report discusses (ch. 8), but doesn’t resolve, differing views on whether horses may be considered native to North America. The current scientific consensus as expressed in the NAS’s refereed scientific journal (e.g. here and here) is that all horses were extinct in North America no later than 10,000 years ago, not returning until the early 16th century when introduced by the Spanish conquistadores and colonists.

      The report’s key findings are summarized beginning on page 16. Many of them are critical of the BLM’s management program, to be sure. But they are clear about the need for population management:

      FINDING: The primary way that equid populations self-limit is through increased competition for forage at higher densities, which results in smaller quantities of forage available per animal, poorer body condition, and decreased natality and survival.


      FINDING: Predation [by current predator populations] will not typically control population growth rates of free-ranging horses.

      From my perspective as an advocate for native (i.e. autochthonous) biodiversity, those are the most salient points.

    2. SaveBears Avatar


      As a biologist, I am quite interested in this information and have studied it extensively, I disagree with the assertions made in the information. There has been no definitive proof offered that the current horses are descendants of the historical equid, I have also seen no credible proof that 20+ million on this continent.

      1. Lyn McCormick Avatar
        Lyn McCormick

        Also, Dave Phillips, of ProPublica, has researched and written on the wild horses. Of course, now I can’t remember what the source was for the 20+ million figure and I am sorry, but I will keep looking. I know – the 20+ million figure sounds staggering but I remember reading that and thinking that if it was possible for 50+ million bison to thrive maybe that population size was possible for horses ??????

    3. mikepost Avatar

      The fossil record does not support any large native american horse population in the era being discussed. Nor does the oral history or rock art of native americans from pre-contact with europeans provide any evidence of the presence of native horses.

  4. Ralph Maughan Avatar
    Ralph Maughan

    Thanks for the important article, George. With all the fires, and especially the Rim Fire, there will be a great debate about this as the fire season continues and ends.

    Let’s hope the debate is as well informed as your writing.

  5. Dan Avatar

    The majority of fires wildland firefighters put out you never hear of because it’s a snag or smoldering spot that lightning ignited. George’s assumptions are based on fires that are already large. Fires start at a spot, mostly by lightning. Big fires happen because small fires consume due to super low RH and extremely low moist contents of fuels. Fires suppression does work because the majority of fires, the ones that do not make the news, are stomped out by fire fighters before the conditions(low RH and low fuel MCs) happen that allow them to consume. George is only right on the point that once small fires become huge fires they are extremely hard to put out unless the RH raises dramatically.

    1. JB Avatar

      “Fires suppression does work because the majority of fires, the ones that do not make the news, are stomped out by fire fighters before the conditions(low RH and low fuel MCs) happen that allow them to consume.”

      Query: If you put out the first 3 or 4 or 5 forest fires via suppression, but the 6th one consumes your home (or worse, your whole town), has fire suppression “worked”? Put another way, if you decrease the frequency of ‘large’ fires via suppression efforts, but in the process increase the intensity and extent of the burns that do become ‘large’, can you claim to have effectively dealt with forest fires?

      1. Rancher Bob Avatar
        Rancher Bob

        It appears either you don’t believe George or your not reading him. George claims,”Even if fire suppression were effective as claimed, most of these forests would still not be outside their historic fire regime due to the naturally long intervals where fuels accumulate for decades or hundreds of years in between fire events.” Me, I think George is full of it on most of his points.

        1. SaveBears Avatar


          I think a lot of people like to “read” between the lines.

        2. JB Avatar

          Slow down, Bob, I just asked a question. I don’t claim to know much about forest fires, but I do understand the importance of defining goals. It seems to me that the success (or failure) of fire suppression could be judged in a variety of ways. So when one makes the claim ‘fire suppression does [or does not] work’ they need to be specific about what they mean (i.e., how they define success).

          1. Rancher Bob Avatar
            Rancher Bob

            I was just trying to get your response to George’s article.
            Fire suppression is about goals but those goals should change with location and the person. Locations vary from heavy homes to wilderness. Then we have to look at slope, elevation, aspect, then the regions weather, past weather, current weather and the forecast. All these things effect fire behavior and fuel.
            Then we have to look at the person do they value a log being turned to lumber or would they rather see it in ash and smoke.
            As with most issues here the definition of success depends on the person and where that person lives and the effect on their life style.
            Net effect your above query requires answers to many more factors.

      2. Dan Avatar

        and thus the reason for actuaries……

        when and if the big one is going to happen???

  6. mikepost Avatar

    While I do not disagree with GW, one factor he does not discuss is the misguided rural planning process that allows homes. resorts, etc to be built in and around these forested areas. The Yellowstone example is unique in that no tax paying voter has a house in the middle of the fire prone areas.

    The current Rim Fire in Yosemite is another type of example. It is being fough vigorously because of nearby threatened residential communities AND THE PRESENCE OF WATER AND ELECTRICAL GENERATION SYSTEMS FOR SAN FRANCISCO!

  7. Larry Avatar

    Each fire has its own characteristics. We can not use a broad brush with regard to suppression because suppression is driven by human fear or the perception of that. I do note that it is interesting with regard to news interviews how many times a fire boss is interviewed and says, “The only thing that will put this fire out is winter snows”. While that is much more true than most people think it is the proximity to man’s habitat that drives all the money spent on suppression. And then with that in mind it is the timber companies and their lobbies that hitch a ride on that premise and try to use fire as an excuse to open up more logging in the pristine back country far away from man’s artificial habitat. It is a little like home burglary, the closer it is to our home the more we worry and take certain actions. If it is our home we throw a lot of money at a cure and it’s mostly out of fear.

  8. Felice Pace Avatar

    Here in the Klamath Mountains no large fire – at least as far back as 77 when i began studying and walking the big fires – has been successfully “suppressed” – it has taken fall rain and snow.

    In the early days of suppression around here, they loaded the mules, hiked and rode for a day or more, and then put out burning stumps and snags for a week or so.

    Supression became effective in the Klamath Mountains with expansion of the road system in the 60s and 70s and the coming of helitac – I’m thinking in the 80s. But the big factor which has changed in recent years (since OSHA got tuned in after that Colorado fire) is the amount of acreage and % of the “wildfire” as mapped which is actually not natural wildfire but rather what I call “discretionary suppression burns.” Since you can’t safely fight a hot fire directly in the Klamath Mountains, they back way off, build line (with dozers if they can get them there), make it black to the line, and then, cause they are waiting for the natural fire which may never come, they are tempted to burn out between the line and the natural fire. These burnouts can get very large (we documented one of 23,000 acres in 99) and may be a factor in findings that western wildfires are gettiong larger…not the only factor, but significant.

    One thing is clear – we will never get back to fire as a natural part of the ecosystem with the suppression poilicies and practices we have today.

  9. Rancher Bob Avatar
    Rancher Bob

    I have been part of the local initial wildfire attack team for over 10 years. I have many problems with George’s article he bases the article on the thought that we should assume Yellowstone’s weather matches closely with the rest of the west. Anyone who has lived in this area for over a year could tell you that Yellowstone gets more snow and rain and has cooler summer temperatures. Which means it’s a great place for a let burn policy. If we adopt a let burn policy for the rest of the west well we had better get use to breathing smoke, carbon emissions off the chart and stream sediment greater than all the logging roads. Think of all the money we could save though, and who needs a job.

  10. Leslie Avatar

    As the West is adapted to fire, I would suppose all those lightning strikes that barely ignite or don’t cause large fires, as George suggests, burned as ground fires and/or smoldered along for a long time, clearing underbrush.

    In August 1971 I took the train from Banff to Vancouver. The train, that then cost $30 and now costs an arm and a leg, traveled through the rugged mountains of BC at night. That fall evening I saw over 200 lightning fires burning the forests, yet none of them were epic.

    Coastal redwoods are adapted to fire as they have no significant pitch in their bark. The fire scars on ancient living trees have been studied and indicate that fires went through the redwoods every 50-100 years, clearing the forest floor of fungi and brush so redwood seedlings could emerge. More frequent fires would be low fuel fires, essentially ground fires.

    It is sad to me that I will never see a large old growth forest in the lower 48. I have been to old growth protected areas, like Muir Woods or the Charlotte Islands, but all our forests have been so altered with logging and logging roads, as well as fire suppression, that we cannot really know what they did look like pre-Columbus.

  11. Michael Avatar

    GW: I would like your take on the role logging roads and fire trails play in the spread of wildfires. It would seem to me that old growth forests are very closed areas, with little room for flames to penetrate. Whereas wind-whipped fires would more likely find roads and trails to be natural pathways.

    I note the aggressive policies that have been proferred for cutting yet more roads through otherwise untouched remnants of our forests. The rationale, of course, is to provide access for firefighters. Would it not be useful to provide a memorandum to the USFS on the folly of this practise? Or has this already been done, many times?


George Wuerthner is an ecologist and writer who has published 38 books on various topics related to environmental and natural history. He has visited over 400 designated wilderness areas and over 200 national park units.

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George Wuerthner