High-severity blazes are critical to healthy forest ecosystems. Photo George Wuerthner 

I read yet another study circulated by UC Davis and doggedly promoted by the national media, encouraging more prescribed burning, thinning, and forest manipulation to reduce large high-severity blazes characterized as “bad.”

The headline from UC Davis proclaims that scientists have documented, “Unprecedented levels of high severity fire burn Sierra Nevada Forests.” With a sub-title: The “Wrong Kind of Fire Is Burning Compared to Historical Patterns.”

The paper reports that compared to the pre-1850s, there appear to be far more high-severity blazes in the Sierra Nevada today than in the past.

The 2013  high-severity Rim Fire in California burned more than 200,000 acres and created numerous snags and down logs critical to healthy forest ecosystems. Photo George Wuerthner 

That finding may not be inaccurate—though some researchers would question that assertion.

However, since the climate varies over centuries, when in the past you use for your comparison makes a big difference in how you view whether wildfires are “unprecedented” or the “wrong kind of fire.”

The article goes on to suggest that the proportion of “good” fire (low severity where few trees are killed) to “bad” fire (high severity where the majority of trees are killed) is “out of balance.” These statements are human-centric values, and do not reflect evolutionary or ecological perspectives.

Like numerous others I see all the time, the problem with this research and press release is how researchers and the media attribute the observed changes in fire behavior to a host of factors, most of which are insignificant.

The article says: “These modern changes have been driven largely by anthropogenic factors, for example, halting of Native American burning, adoption of fire suppression policies, timber extraction, and forest management practices, changing ignition patterns, and climate change, that have altered the way fire interacts with forests,”

Wind driven fire seen here. Climatic conditions like drought, high temperatures, and high wind are the major factors that drive large wildfires not fire suppression, forest practices or lack of Native American burning. Photo George Wuerthner 

Yet climate change alone probably accounts for 95% of the variation in fire behavior!! By treating the minor influences of forest practices, suppression, and Native American burning as significant drivers, they set up support for greater forest manipulation, including prescribed burning and timber cutting everywhere.

The biggest problem is that “historical patterns” used as the “control” in the study (pre-1850s) depended on a specific climatic condition that no longer exists today. The climate in the pre-1850s was influenced by the Little Ice Age, which span the time from 1300-1850. The Little Ice Age was a particularly wet and cool period. Cold and wet conditions tend to reduce ignitions and limit fire spread.

California is experiencing the worst drought in 1200 years. This fact alone explains the majority of fire behavior. Photo George Wuerthner 

The climate we are experiencing today has no recent precedent. California, for instance, is experiencing the worst drought in over 1200 years. The average temperatures are also reaching record highs. Severe drought characterizes most of the western U.S. at present.

The nearest comparative climatic conditions to today were during the Medieval Warm Spell, which occurred between 800-1300 AD. During this time, there was more fire than today.  As one of the authors of this study noted: “This is one line of evidence that it was very fiery on the western slopes of the Sierra Nevada – and there’s a very strong relationship between drought and fire.”

During that warm, dry period, there were massive wildfires around the West. It is also why the Anasazi Indians abandoned their cliff dwellings, and Greenland was settled by the Vikings (because it was greener in 900 AD).

So, comparing the fire regime of today with a time of glacial formation during the Little Ice Age is comparing apples and oranges.

The press release is full of “pejorative” language that is not ecologically based but rather represents the Industrial Forestry Paradigm that anything that kills trees other than chainsaws is “out of balance” and “bad.”

First, given the climatic conditions associated with global warming, the increase in high-severity blazes may not be “out of balance” at all. On the contrary, more high-severity fires are precisely what you would expect under current weather/climatic conditions.

The greater number of high-severity fires is an example of Nature in “balance” with the current climatic conditions.

The 2021 Dixie Fire burned more than 900,000 acres including many higher elevation fir forests. Photo George Wuerthner

The paper and press release first acknowledge that fire behavior differs in various plant communities but then gives the impression that the same fire regimes apply to all forest types.

For example, fire rotation in dry pine forests tends to be more frequent than high elevation forest types like lodgepole pine, fir and spruce forests, and aspen, among others which experience long, often hundreds of years, between significant fire events.

These higher-elevation, moister forest types may not experience significant wildfires for hundreds of years because they require specific climatic conditions of extensive drought, warm temperatures, low humidity, and high winds before they are dry enough to burn. These climatic/weather conditions seldom occur in any location along with an ignition source. When these all align, you get high-severity blazes.

The idea that high-severity fires are “bad” is another example of the derogatory wording in the press release and original research. High-severity fires are always relatively infrequent but tend to be the “norm” for higher-elevation or moister forests.

Research in Sierra Nevada forests suggests that high-severity fire rotations varied between The high-severity fire rotation was 281 years in the northern and 354 years in the southern Sierra.

Since global warming has increased the prerequisite conditions of droughts, high temperatures, low humidity, and wind, we are seeing precisely what you would expect-more higher elevation forests burning. These wildfire fires are not “out of balance” but completely in balance with the prevailing climate conditions.

Furthermore, other research shows that these high-severity blazes are critical to healthy forest ecosystems. Numerous plants and animals depend on the down logs, snags, and decaying wood that high-severity blazes produce.

This is evolutionary evidence that contradicts the proclamation that we see the “wrong kind of fire.”

Logs that fall into stream create good fish habitat. The main source of logs for most drainages comes from high severity blazes. Photo George Wuerthner 

Some studies suggest more plants and animals depend on high-severity blazes for their habitat than low-severity fires. For instance, down logs improve fish habitat. In addition, studies have shown that the more logs in a stream, the more fish. Yet most logs that fall into streams may result from one sizeable high-severity blaze that may only occur once in a couple of hundred years in any drainage.

The input of down wood is episodic, not regular. So you may only have 1-4 such high-severity fires every thousand years.

Beyond these problematic temporal and spatial scale issues, we find that the preferred cure of more prescribed burning and thinning are ineffective because they do not influence the primary driver of significant fires-climate change.

Forest that was thinned six months previous to the  2007 Angora Fire at Lake Tahoe. California that burned at high severity. 

Instead, logging appears to increase the occurrence of high-severity fires by opening up the forest to greater wind penetration and solar drying—both conditions that favor fire spread.

Once again, the forestry industry propaganda is being spewed forth by unwitting media with little scientific ability to judge the nuances in the science.

The bottom line is that high-severity fires are not “out of balance” given the on-going climatic conditions, nor are they “bad” from an ecological perspective. Wildfire, bark beetles, drought, and other sources of mortality is moving the Sierra Nevada vegetation community in balance with the existing and future climatic conditions.

About The Author

George Wuerthner

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

3 Responses to More wildfire misinformation from UC Davis

  1. Chris Zinda says:

    I find it odd that 80+% of wildland fires today are caused by humans, no matter the severity; yet, these kind of papers omit this part of the solution equation entirely. There is nothing natural about that.

    So, logging or not becomes the narrative by the authors and GW as a solution instead of just keeping humans from starting fires – which means decreased unlimited access, especially during extreme fire hazard periods.

    But, nobody wants to address limiting access, right, left or center.

    It’s depressing.

    • Rambling Dave says:

      Yeah, I’ve often wondered why the feds prefer to let boneheads with abandoned campfires and cigarette butts drive their fire policy. A year-round campfire ban on federal lands would likely cut that 80% figure in half. Campfires should just be something that old-timers used to have “back in the day”.

  2. rastadoggie says:

    “Collaborative” groups, in bed with and funded by the Forest Service, are sending the UC Davis findings around. They can no longer say forest fires are bad and can be stopped by logging (our logged areas have readily burned and we’ve had massive grass fires; perhaps we should also mow the prairie). So now they’ve glommed on to the dreaded “high severity” doom to keep the chainsaws humming and prove what groovy environmentalists they all are. Happily, this fine article perfectly refutes.

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

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