There has been a spate of articles in various newspapers and magazines, asserting that if the Forest Service were following burning practices of Indigenous people, the massive wildfires we have seen around the West would be tamed.
Here are some representative of indigenous burning will save the forest articles.
The October 7th, 2020 article Wildfires has ravaged the Western United States this year. Sending firefighting experts to Indigenous communities for guidance by Jim Cowan in the New York Times is typical of the erroneous assertions about Native American burning and its influence on large wildfires.
“Long before California was California, Native Americans used fire to keep the lands where they lived healthy. That meant intentionally burning excess vegetation at regular intervals, during times of the year when the weather would keep blazes smaller and cooler than the destructive wildfires burning today.”
And the Guardian article, like most of these recent publications, implies that the loss of native burning is contributing to large blazes: “a century of practicing fire suppression over traditional tribal land stewardship has led to larger, more destructive wildfires.”
The idea that tribal burning impacted the broad landscape is asserted by some scholars (Williams, G.W. 2004; Lightfoot, K.G. and R.Q. Cuthrell. 2015) but often with scant evidence to back up these claims except for “oral traditions” of Native people.
Indigenous burning was widespread, but the debate is about the temporal and spatial effect of human ignitions on fire regimes and geographical influence.
1) The indigenous burning precludes large fires feeds into the “fuels is the problem” narrative, which is increasingly discredited as a significant factor in massive wildfires driven by extreme climate weather.
2) All large fires are driven by climate/weather conditions that include drought, low humidity, high temperatures, and high winds. Climate change is exacerbating these conditions.
3) Periodic drought conditions have always existed, and large blazes have always occurred despite Indigenous burning.
4) Indigenous burning resulted primarily in localized fuel reductions but seldom affected the broader landscape.
5) There is historical, scientific, ecological, and evolutionary evidence that challenges the indigenous burning narrative.
6) Large high severity fires are not “destructive” but essential to healthy forest ecosystems.
Implementation of an effective, prescribed burning program has many obstacles.
The way to protect homes is to start from the home outward.
MYTH OF INDIGENOUS LANDSCAPE MANAGEMENT
As Barrett et al. 2005 noted: “For many years, the importance of fire use by American Indians in altering North American ecosystems was underappreciated or ignored. Now, there seems to be an opposite trend…. It is common now to read or hear statements to the effect that American Indians fired landscapes everywhere and all the time, so there is no such thing as a “natural” ecosystem. A myth of human manipulation everywhere in pre-Columbus America is replacing the equally erroneous myth of a pristine wilderness.
We believe that it is time to deflate the rapidly spreading myth that American Indians altered all landscapes by means of fire. In short, we believe that the case for landscape-level fire use by American Indians has been dramatically overstated and overextrapolated.”
Noss et al. 2014 assert: “Despite ample evidence that lightning fire was a primary ecological driver in the NACP [North American Coastal Plain], the myth persists that most fires before the arrival of Europeans were set by Native Americans. For example, Mann (2005; 361) provides a map that shows essentially the entire pre-Columbian NACP, including the lightning-riddled Gulf coast and Florida peninsula, as “dominated by anthropogenic fire” or with “widespread forest clearing for agriculture.” No evidence is offered to support these claims.”
Most “evidence” for the widespread influence of indigenous burning is based on oral tradition, which is notoriously subject to variation of interpretation and misinterpretation.
DID INDIGENOUS BURNING PRECLUDE LARGE BLAZES?
The question is not whether Indigenous burning occurred, but rather to what extent it influenced the landscape as a whole and precluded large mixed to high severity blazes or what some people term “mega” fires. Is it a panacea for thwarting large blazes as implied? Furthermore, it needs into the notion that high severity blazes are somehow “unnatural” and ecologically “destructive.”
The idea that fire suppression has led to some fuel build up in some plant communities is accurate, but fuel build-up is not the primary cause of sizeable high severity blazes. Most of these blazes are burning in plant communities like lodgepole pine, spruce/fire, juniper, and other plant communities that naturally had long intervals between fire events and naturally accumulate fuels. In other words, fuel build up in these plant communities is entirely natural.
There is ample evidence that Indigenous burning had little effect on large fires on the landscape. Except for some high-use areas, Indigenous burning did not significantly alter fuels across the broader landscape; more importantly, it did not preclude larger blazes.
Large “mega” fires have occurred for thousands of years, and Indigenous burning did not preclude them.
Plus, the idea that low severity fires dominated western landscapes ignores the fact that numerous species depend on the high-severity snag forests that result from sizeable high severity blazes. The second-highest biodiversity after old-growth forests is found in the snag forests and down wood that results from these blazes. These high severity habitats would simply not exist if such Indigenous burning were as successful as advocates suggest.
Indeed, the effectiveness of “one hundred years of fire suppression” can be questioned. For instance, in the early part of the 20th Century, as much as 50 million acres burned annually in the United States during several drought decades.
LIVING WITH FIRE
Cultural burning was done for a variety of other purposes. To create favorable conditions for the growth of specific plant foods that might be favored by fire, create fresh new growth of grasses and other plants favored by wildlife like deer, elk, or bison. Fires were also used in warfare to burn out enemies that might be hiding in dense brush. Native burning was particularly prevalent to maintain natural prairies and travel corridors (Boyd 1999).
Just as today, wildfire was a natural force that influenced where people lived. One of the ways tribal people “lived with” fire was to locally reduce fuels to safeguard their villages, trading centers, and traditional gathering areas from large dangerous blazes.
This is the model that we should be promoting today—working from home outward to reduce local flammability of homes and communities’ edge.
Since most tribal people lived in lower elevation landscapes like valley bottoms with grasslands or dry ponderosa pine forests where a wildfire was naturally more frequent, Indigenous burning likely favored the continued existence and expansion of these plant communities.
It is important to note that these community types are often a small percentage of the landscape. For instance, dry montane forests (chiefly ponderosa pine) make up only 4% of western Montana and northern Idaho.
However, the question remains as to whether this cultural burning was sufficient to change fire regimes across the broader landscape to the point it precluded larger wildfires.
While there is no doubt that Indigenous burning was widely practiced, the idea that cultural burning was a significant influence on landscape-scale fire influences is questionable.
There are multiple lines of evidence to suggest that Indigenous burning likely was local and did affect the broader landscape.
FUELS DON’T DRIVE LARGE FIRES
Perhaps the biggest problem with the “Indigenous burning will preclude large blazes” is that it feeds into the narrative that “fuels” drive the massive fires we see around the West. The problem with this explanation is that large fires are climate-weather driven events-and have always been a consequence of climate-weather. There is abundant coloration between extensive drought and large landscape fires. Conversely, during periods of wet, cool climates, there are fewer large blazes.
If fuels were the primary driver of large blazes, we would expect large mega-fires along the Pacific Northwest coast where forest biomass is the greatest on the continent. Yet these coastal forests burn very infrequently-typically on 500-1000-year rotations due to the cool, moist climate.
If you have severe drought, low humidity, high temperatures, and, most importantly, wind, you get large landscape fires. If you do not have these weather/climate conditions, you get fewer ignitions, smaller fires that mostly self-extinguish.
While Indigenous burning likely did influence fuel loading in some localized areas, it did not change the basic weather/climate ingredients that drive all large blazes (Whitlock, C et al. 2010).
Furthermore, you simply will not get large acreages to burn unless you have these extreme fire weather conditions.
First, most cultural burning, like the prescribed fires set today by state and federal agencies, was practiced in the spring and fall when fire spread was limited by moist fuels, high humidity, cool temperatures, and when winds are calm. High fuel moisture and cool temperatures limit fire spread. In other words, you will not burn much acreage. Under such conditions, most fires simply self-extinguish and are challenging to maintain.
Despite the implied notion in some of the above articles that somehow the Forest Service is ignorance of burning practices, this is the same reason federal and state agencies usually do prescribe burning during these seasons.
By contrast, all our larger landscape fires occur during extreme fire weather conditions, typically in the summer and early fall months. These include severe drought, low humidity, high temperatures, and, most importantly, wind.
Why is this important? Because most fires, even natural fires, are small. Unless you have these extreme fire weather conditions, 97-99% of all fires will burn 1-5 acres even if you don’t suppress them. Whether the ignitions are from lightning or humans, if you don’t have the right weather conditions, you will not burn a significant amount of the landscape.
For instance, 56,320 fires burned over 9 million acres in the Rocky Mountains between 1980-2003. 98% of these fires (55,220) burned less than 500 acres and accounted for 4% of the area burned. By contrast, only 2% of all fires accounted for 96% of the acreage burned. And 0.1% (50) of blazes were responsible for half of the acres charred. (Baker 2009 Fire Ecology in Rocky Mountain Landscapes).
In another example, between 1972 and 1987, Yellowstone National Park did not suppress backcountry fires. During this period, there were 235 blazes. Of these, 222 charred less than 5 acres and most burned less than 1 acre. And all 235 fires self-extinguished.
Then in 1988, more than a million acres burned in Yellowstone. Did fuels suddenly balloon overnight to sustain large high severity blazes? 1988 was the driest year on record since the park was established, with humidity as low as 1-2% and winds exceeding 50 mph.
Thus, it would require setting thousands of these small fires when the climate/weather is not conducive for fire spread to burn any substantial amount of the landscape. So, the idea that Indigenous burning, which can be characterized as primarily low-severity frequent fires, was of sufficient size and scale to affect larger landscapes is questionable based on such ignitions’ timing.
Native people were wise enough to avoid purposely setting fires in the middle of extreme fire weather. Setting a blaze under conditions with variable high winds and drought was a recipe for disaster because it quickly leads to uncontrollable fires threatening villages and lives.
Most of the West’s plant communities tend to naturally have long to very long fire rotations between fires, of many decades to hundreds of years in length. These communities include aspen, most fir species, mountain hemlock, western hemlock, west-side Douglas fir, chaparral, sagebrush, juniper-pinyon, lodgepole pine, white pine, western larch, and various spruce species.
This means wildfire historically did not burn in these communities except at infrequent intervals, almost always dictated by climate/weather.
“During extreme weather conditions, the relative importance of fuels diminishes since all stands achieve the threshold required to permit crown fire development. Weather/climate is important since most of the area burned in subalpine forests has historically occurred during very extreme weather (i.e., drought coupled to high winds). The fire behavior relationships predicted in the models support the concept that forest fire behavior is determined primarily by weather variation among years rather than fuel variation associated with stand age” (Bessie and Johnson 1995).
Many of these species have few adaptations to withstand frequent fires and would simply not exist if tribal burning affected them.
HISTORICAL EVIDENCE FOR LARGE BLAZES
Though most fire ecologists concede that native burning likely declined after European American settlement due to population decline resulting from disease, warfare, and displacement, there is plenty of evidence for large fires before large scale Euro American occupation.
For instance, in Oregon’s Willamette Valley, most large trees were established after large, high severity fires that occurred long before Euro-American influences on native populations. The 1865 Silverton Fire burned more than a million acres of the western Cascades. The 1853 Yaquina Fire burned nearly a half-million acres. Recent records from Washington estimate that a series of large fires in 1701 may have burned between 3 and 10 million acres in a single summer. To quote from a recent article on fires in Washington state: “1701 is given as the best estimate for the last devastating fire that occurred throughout Western Washington, a fire that burned an estimated 3 million to 10 million acres. At the upper end of that range, the area is roughly equal to 10 Olympic National Parks.”
Although individual accounts can vary, the observer’s detail can provide some hint of early accounts’ accuracy. For instance, David Douglas (for whom Douglas Fir is named) traveled from the Hudson Bay Post at Fort Vancouver down the Willamette Valley in 1826, carefully noting the vegetation. Douglas reported seeing burnt patches but indicated that most were small (Knox and Whitlock 2002).
Peter Skene Ogden noted extensive burns in the Blue Mountains of eastern Oregon and attributed it to natives. However, unless one actually observed Natives setting fires, it is difficult to know the source of ignition.
On the other hand, numerous travelers who kept meticulous notes like Lewis and Clark and John Fremont seldom mention encountering Indigenous burning. The absence of evidence is not the same as no evidence; nevertheless, when someone like Lewis and Clark or John Fremont fails to report extensive Indigenous burning, it does raise a cautionary note about interpreting historical accounts.
The other consideration is that Douglas, like most people traveling through the landscape, used the Indigenous trails and natural travel routes. Since human occupation is greatest in such areas, it may provide a biased view of the occurrence of human ignitions. Even today, the majority of wildfires occur near roads. Also, since most of these areas were dominated by grasslands and low elevation dry pines where fire is more frequent even today, it does not support the broader influence of human burning on the landscape.
FIRE STUDY TECHNIQUES GIVE A BETTER LANDSCAPE SCALE PICTURE OF FIRE
Beyond just historical accounts of fires, there is proxy evidence for past fire occurrence. Scientists use various methods to determine the “fire history” of any location.
The scientific evidence for historical fire regimes is based on a few different methods. Each method has its advantages and disadvantages (Whitlock et al. 2004).
The most common method for reconstructing fire history is fire scars, but other ways, including charcoal and pollen studies, among other techniques, result in different perspectives.
When a fire burns through an area at low severity (i.e., typically does not kill mature trees), it can leave a scar in the surviving trees. The scar eventually heals and is “recorded” in the tree rings. By examining tree rings, one can count the years between fires, and in some cases, even determine the season of the burn. This is the most popular method of determining fire histories.
Fire scar in ponderosa pine Oregon. Photo by George Wuerthner
There are, however, some problems with fire scar methods that some researchers believe results in an overestimation of fire frequency and influence (see Baker and Ehle 2001). For more detail on the problems of fire scar historical reconstructions, see (Wuerthner 2018)
There have been numerous studies that have looked at Indigenous burning and its influence on fire regimes. Most work done by fire ecologists who focus on large landscape fires do not find any additive impact from Indigenous burning. Instead, climate/weather appears to control periods of significant wildfire activity (Baker W.L. 2002).
In other words, they find evidence for more frequent fires during major droughts and in the immediate area of villages, along major travel corridors, trading centers, and other high use areas. Still, across the landscape as a whole, they do not find evidence that human ignitions were additive to total landscape acreage charred by wildfire.
In my view, the best way to document whether human ignitions were an important influence for landscape-scale fires is to use charcoal or pollen studies. But other techniques such as air photo, General Land Office (GLO) surveys, and even historical accounts of early Euro Americans can also provide insights.
Charcoal studies are a proxy for wildfires that rely on examining core drillings in lakes and ponds to extract sediments where charcoal from major wildfires are recorded. By reviewing such cores, researchers can document the larger wildfires in a landscape going back thousands of years. Charcoal studies tend to record the larger regional blazes.
Pollen from the same core samples also documents the primary vegetation present in surrounding lands.
For instance, Vachula et al. 2019 studied Yosemite National Park, where historically large Indigenous communities resided. Their research found a direct correlation between climate and the amount of burning on the landscape.
“We analyzed charcoal preserved in lake sediments from Yosemite National Park and spanning the last 1400 years to reconstruct local and regional area burned. Warm and dry climates promoted burning at both local and regional scales… Regional area burned peaked during the Medieval Climate Anomaly and declined during the last millennium, as climate became cooler and wetter and Native American burning declined.”
“Our record indicates that (1) climate changes influenced burning at all spatial scales, (2) Native American influences appear to have been limited to local scales, but (3) high Miwok populations resulted in fire even during periods of climate conditions unfavorable to fires. However, at the regional scale (< 150 km from the lake), fire was generally controlled by the top-down influence of climate.” (Vachula et al. 2019)
Another study in the Willamette Valley found that the mean fire interval in Oregon’s Coast Range was 230 years, and the presence of fire-sensitive species like Sitka spruce indicates a lack of frequent fire (Knox and Whitlock 2002).
Regarding Indigenous ignitions in the Willamette Valley, Whitlock notes: “The idea that Native Americans burned from one end of the valley to the other is not supported by our data,” says Whitlock. “Most fires seem to have been fairly localized, and broad changes in fire activity seem to track large-scale variations in climate,” she says. (Fire Science, 2010).
In another charcoal study of Washington’s Battle Ground Lake, Megan Walsh (Walsh et al. 2008) concluded that Fire frequency was highest during the middle Holocene when oak savanna and prairie were widespread near Battle Ground Lake. She suggests: “The vegetation and fire conditions were most likely the result of warmer and drier conditions compared with the present, not from human use of fire” (Fire Science 2010).
The authors (Walsh et al. 2008) concluded that wildfires were: “mostly large or high-severity fire episodes. The fire history at Battle Ground Lake was driven by climate, directly through the length and severity of the fire season, and indirectly through climate-driven vegetation shifts, which affected available fuel biomass.”
To give another example, one can show that Indigenous burning was more frequent in the Yosemite Valley where tribal people resided much of the year, but no evidence for wide-spread human burning in the majority of what is now Yosemite Valley or the Sierra Nevada Mountains as a whole (Vale 1998).
Hoffman et al. 2016 looked at Indigenous burning influence in coastal British Columbia and concluded: “fires. At the decadal scale, fires were more likely to occur after positive El Niño-Southern Oscillation and Pacific Decadal Oscillation phases and exhibited 30-year periods of synchrony with the negative phase of the Arctic Oscillation. Fire frequency was significantly inversely correlated with the distance from former Indigenous habitation sites.”
The Karuk and other tribes in northern California’s Siskiyou Mountains assert that their traditional burning precluded large fires, and that fire suppression of native burning practices contributed to the sizeable high severity blazes now burning the region.
Columbaroil and Gavin (2002) documented that large fires always occurred in the Siskiyou Mountains, primarily due to climate/weather, even during the pre-European period. “ Fire is a primary mode of natural disturbance in the forests of the Pacific Northwest. Increased fuel loads following fire suppression and the occurrence of several large and severe fires have led to the perception that in many areas, there is a greatly increased risk of high-severity fire compared with presettlement forests. To reconstruct the variability of the fire regime in the Siskiyou Mountains, Oregon, we analyzed a 10-m, 2,000-y sediment core for charcoal, pollen, and sedimentological data. The record reveals a highly episodic pattern of fire in which 77% of the 68 charcoal peaks before Euro-American settlement…”
Odion et al. (2004) (Conservation Biology), conducted in a 98,814-hectare area burned in 1987 in the California Klamath region, found that the most fire-suppressed forests in this area (areas that had not burned since at least 1920) burned at significantly lower severity levels, likely due to a reduction in combustible native shrubs as forests mature and canopy cover increases: “The hypothesis that fire severity is greater where previous fire has been long absent was refuted by our study…The amount of high-severity fire in long-unburned closed forests was the lowest of any proportion of the landscape and differed from that in the landscape as a whole (Z = -2.62, n = 66, p = 0.004).”
Early timber surveys also record sizeable high severity fires (Leiberg, J. B. 1903).
Contrary studies that presume to substantiate a significant influence of Indigenous burning tend to focus on major village sites, foraging areas, and other areas of high human use where no doubt Indigenous burning was “additive” to the background fire regime.
Unfortunately, this evidence of increased burning is then extrapolated to the broader landscape where human activities were less frequent. A good example is a study by Kimaszewki -Patterson (2019), who looked at Indigenous burning in a meadow of the southern Sierra Nevada, and then inferred this represented the fire regime of the southern Sierra Nevada.
This is the same error made by William Cronon in his book Changes in the Land (Cronon 1983) about Indigenous burning in New England.
Parshall and Forester 2002 challenged Cronon’s conclusions. ”The major factor influencing the distribution of fire across New England is climate, which has a direct effect on the physical conditions conducive to fire ignition and spread and an indirect effect on fire through its control on the distribution of vegetation at this spatial scale. We find evidence that other factors exert some control over local fire regimes, including landforms and their impact on vegetation composition, firebreaks, and prevailing winds. Native Americans likely influenced the local occurrence of fire, but their impact on regional fire regimes in New England is not apparent from this or other studies….”
A more recent review of the evidence by David Foster of the Harvard Experimental Forest concluded that Native American burning was localized (Oswald et al., 2020). The researchers conclude: “Our new research, published in the journal Nature Sustainability, tests this human-centric view of the past using interdisciplinary, retrospective science. The data we collected suggest, in New England, this assumption is erroneous….
Our study (Oswald et al. 2020) contradicts the theory that people had significant ecological impacts in southern New England before European arrival. Instead, it reveals that old forests, shaped by climate change and natural processes, prevailed across the region for thousands of years….”
Matlack (2013) wrote: “Prescribed burning is increasingly being used in the deciduous forests of eastern North America. Recent work suggests that historical fire frequency has been overestimated east of the prairie–woodland transition zone, and its introduction could potentially reduce forest herb and shrub diversity…. Thus, it appears that the majority of forests of the eastern United States were little affected by burning before European settlement.”
Russell (1983) also challenges the notion that Indigenous burning influenced large landscapes: “The historical evidence for the Indians’ burning the northeastern United States forests is reevaluated. Of 35 documents that describe vegetation or Indian life in the 16th or 17th centuries, only half mention any use of fire except for cooking. Only six purportedly first-hand accounts might refer to purposeful, widespread, and frequent use of fire. These six are all consistent with use of fire only locally near camps or villages or with accidentally escaped fires. It is concluded that the frequent use of fires by the Indians to burn the forests was probably at most a local occurrence. The Indians’ presence in the region and their use of fire for many purposes did, however, increase the frequency of fires above the low levels caused by lightning, and thus had some effect on the vegetation: for example, grasses characterized the ground cover at small, local, frequently burned sites.”
“Although in some specific areas of particularly high human populations such as the southern California coastal areas, Indian burning may have expanded natural grasslands at the expense of natural chaparral vegetation (Keeley 2008). However, this must be considered the exception more than the rule given the extremely high human populations and the general dry Mediterranean climate.
Benix (2002), writing about the southern California chaparral region, concluded: “It would be reasonable to summarize the impact of native Californian fire in the following terms: a variety of Native cultures made sophisticated use of fire, both to favor edible species and to facilitate ( directly or indirectly) hunting. The scale of fire use was so limited, however, that the bulk of the chaparral as we know it evolved under a natural, lightning-dependent fire regime. Undoubtedly, anthropogenic fire did have some ecological impacts, but those impacts were spatially limited to the immediate surroundings of population centers and to the preexisting (i.e., quasinatural) ecotones. Because of the limited spatial extent of anthropogenic burning, the overall chaparral environment was unchanged by the cessation of native burning, as evidenced by the static nature of the stratigraphic record. It would be reasonable to summarize the impact of native Californian fire in the following terms: a variety of Native cultures made sophisticated use of fire, both to favor edible species and to facilitate ( directly or indirectly) hunting. The scale of fire use was so limited, however, that the bulk of the chaparral as we know it evolved under a natural, lightning-dependent fire regime. Undoubtedly, anthropogenic fire did have some ecological impacts, but those impacts were spatially limited to the immediate surroundings of population centers and to the preexisting (i.e., quasinatural) ecotones. Because of the limited spatial extent of anthropogenic burning, the overall chaparral environment was unchanged by the cessation of native burning, as evidenced by the static nature of the stratigraphic record.”
The conclusion from nearly all of these charcoal/pollen studies has several implications for the question of Indigenous burning and its influence. A good example is a 14,000-year study from western Washington, which covers the entire time of Indigenous occupation. Given the abundance of food resources (like salmon) and mild climate, western Washington supported some of the densest native populations in western North America. If native burning were a significant influence on the landscape, this is where one would expect to document it.
The pollen record is also of importance. If Indigenous burning were so widespread to influence landscape-scale vegetation, we would expect to find abundant pollen from species favored by frequent, low-seity fires. For the most part, except in the immediate area around villages, this evidence does not exist.
OTHER EVIDENCE FOR MIXED TO HIGH SEVERITY BLAZES
The second line of evidence is the use of General Accounting Office (GLO) land surveys. These surveys were often done in advance of major settlement. In other words, before there was significant logging, livestock grazing, fire suppression, or any other factor commonly used to “explain” why “fuels” built up during the 20th century.
When doing a GLO survey, notes are made of all vegetation encountered along the survey line. This includes notations on tree species, size, and condition (i.e., a significant patch of burnt timber would be noted). Also, every mile of these surveys, a “corner” was located to make the location. As part of this corner marking, “bearing trees” were noted, recording the species, size, and distance to the corner.
An advantage of land surveys is that they are linear, random surveys of the vegetation at that point in time. We don’t have to “interpret” the vegetation, density of vegetation, or lack thereof, as people who use fire scars must do.
These land surveys tend to draw different conclusions about historical vegetation and fire influence that fire scar studies. They tend to document denser forests and plant species favored by more massive, high severity blazes instead of low severity, frequent fires.
The idea that most wildfires in all plant communities were low severity is inaccurate. Mixed-intensity Fire, Including Patches of High-Intensity Fire, Is Natural: Mixed-intensity fire is not limited to true fir and lodgepole pine; mixed-intensity fire, including a significant proportion of high-intensity fire and occasional large high-intensity fire patches hundreds or thousands of acres in size, is also a natural condition in ponderosa-pine/Jeffrey-pine and mixed-conifer forest, and generally dominated pre-fire suppression fire regimes historically in these forest types.
For example, Baker, W.L. 2012, using GLO records, found that in dry mixed-conifer forests of the eastside of the southern Cascades, historic fire was 24% low-intensity, 50% mixed-intensity, and 26% high-intensity.
Similarly, Hessburg et al. 2007 using air photo interpretation, came to similar conclusions: “Historical mixed-conifer forests of eastern Oregon Cascades were mainly mixed- and high-intensity, and were dominated by dense, early- and midsuccessional forests regenerating from past higher-intensity fire, rather than by open and park-like old-growth forests.”
And these results were found in a wide variety of geographical locations and forest types, including ponderosa pine forests across the West.
Shinneman D.J. and W.L. Baker, 1997, looked at pine forests in the Black Hills of South Dakota. It concluded that high-intensity fire patches many thousands of acres in size occurred in the Black Hills’ ponderosa pine forests in South Dakota before fire suppression and logging.
ECOLOGICAL AND EVOLUTIONARY EVIDENCE
Another line of evidence that frequent, low severity blazes were not the rule in most plant communities based on evolutionary evidence.
For instance, sagebrush ecosystems once covered 150 million areas of the American West—the same geographic location utilized by numerous tribal groups. Because sagebrush was so prevalent, multiple species are obligate sagebrush species, which include ferruginous hawks, burrowing owls, loggerhead shrikes, sage sparrows, Brewer’s sparrows, sage thrashers, greater sage grouse, long-billed curlews, sagebrush voles, Merriam’s shrews, pygmy rabbits, Washington ground squirrels, black-tailed jackrabbits, sagebrush lizards, and striped whipsnakes and many plant species ( Rowland 2011). More than 350 associated plant and animal species are at risk of local or regional extinction due to the decline of sagebrush (Thompson 2007).
Most sagebrush species have no adaptations to fire. Indeed, the fire rotation for sagebrush species varies from 50 to more than 400 years (Baker 2006). If IIndigenous burning were occurring annually or at least every few years, sagebrush simply would not survive. Therefore, we simply would not have sagebrush, and there certainly would not have been the evolution of species like sage grouse.
Similar evolutionary evidence for the occurrence of large, stand replacement blazes, despite Indigenous burning, also exists. Hutto reports numerous bird species that are most abundant in high severity fires. Species like the black-backed woodpecker are massive fire obligates (Hutto 2007, Hutto 2008). Other species like morel mushroom, for example, a culinary treat, thrives after intense fire (Fire Science Brief 2009)
PROBLEMS WITH IMPLEMENTATION OF PRESCRIBED BURNING
There is no doubt that there were extensive wildfires in prehistory. It is estimated that wildfire (of all severity) charred between 4 and 12 million acres of California annually.
For instance, Stephens et al. (2007) estimated, approximately 1.8 million ha burned (5 million acres) annually in California prehistorically (pre 1800). Stephens suggested: “Our estimate of prehistoric annual area burned in California is 88% of the total annual wildfire area in the entire US during a decade (1994–2004) characterized as ‘‘extreme’’ regarding wildfires. Skies were likely smoky much of the summer and fall in California during the prehistoric period.”
Whether we even have fewer human ignitions may be questioned. Approximately 84% of all ignitions are human (Balch et al. 2017).
Even if prescribed burning could reduce large blazes (which would not be good for forest ecosystem health), there are multiple problems If prescribed burning were to ramp up significantly. A recent article in Atlantic points out the fact that burning would have to be ramped up across many more millions of acres of land to have any influence on fire spread.
First, we would still have smoke in the summer months, but a significant increase in prescribed burning would generate almost year-round smoke. Furthermore, since prescribed burning occurs when fuels are moist, and most smoke is water vapor, per acre of fire, more smoke may violate air quality regulations and harm human health.
There is also the potential for prescribed burns to escape control. Perhaps the most notable of such incidents was the 2000 Cerro Grande Fire, which began in early May as a prescribed fire at Bandolier National Monument in New Mexico but escaped to become a 19,000 ha wildfire. The Cerro Grande Fire consumed 235 homes  and subsequently shut down nearly all federal prescribed burning in the US for several months.
Not the least of which is that there are many more permanent habitations in these same locations. Also, to burn enough of the lower elevation areas to reduce fuels across the landscape significantly would create a condition of nearly continuous smoke. Between prescribed burning in the spring and fall, combined with the natural wildfire occurrences resulting in the summer months, would create a pall over the West’s valleys.
Nevertheless, as shown by the numerous long-term studies, large blazes have always occurred despite Indigenous burning. As Reinhardt et al. 2008 concluded: “The majority of acreage burned by wildfire in the US occurs in very few wildfires under extreme conditions (Strauss et al., 1989; Brookings Institution, 2005). Under these extreme conditions, suppression efforts are largely ineffective.”
Furthermore, Reinhardt goes on to determine: “Extreme environmental conditions, overwhelmed most fuel treatment effects. . . This included almost all treatment methods, including prescribed burning and thinning. . .. Suppression efforts had little benefit from fuel modifications.”
More than 200 preeminent scientists signed a letter to Congress to find that proposed solutions to wildfire like thinning forests are ineffective and short-lived.
To quote from the scientists’ letter: “Thinning is most often proposed to reduce fire risk and lower fire intensity…However, as the climate changes, most of our fires will occur during extreme fire-weather (high winds and temperatures, low humidity, low vegetation moisture). These fires, like the ones burning in the West this summer, will affect large landscapes, regardless of thinning, and, in some cases, burn hundreds or thousands of acres in just a few days.”
Plus, the likelihood that a fire will encounter a prescribed burn during the period when it might be useful at slowing a fire is minimal (Rhodes and Baker 2008).
Prescribed burning can increase flammable materials by favoring regrowth of grasses, shrubs, and other fine fuels.
Thus maintenance burning must be done regularly to reduce fuels, and to do this over any significant acreage is problematic.
Baker and Ehle, 2001. Uncertainty in Fire History and Restoration of Ponderosa Pine Forests in the Western United States USDA Forest Service Proceedings RMRS-P-29. 2003.
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