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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.
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, a time when most fire ecologists assume fire suppression had its greatest influence, much 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 be within 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.
George Wuerthner has published 36 books including Wildfire: A Century of Failed Forest Policy.