Drought and Wildfires

A high severity blaze on the Boise National Forest. Almost all large fires occur during extreme drought conditions. Photo George Wuerthner.

One continuously hears from the timber industry and its allies that the present occurrence of large wildfires is primarily the result of 100 years of “fire suppression” and thus “abnormal” fuel accumulations. We are told that forests were historically open and park-like, while today’s forests are “overgrown.”

The solution to large fires by proponents of the “fire suppression” mantra is more logging, thinning, and prescribed burning to “reduce fuels” and restore forests to their pre suppression condition.

There are several things wrong with this assessment, but the biggest error is its failure to incorporate historical fire data and climate influences these assertions.

First, there is debate about how dense historical forest conditions. [i] Reviews of historical observations challenge the idea that all forest types were “park-like” and open.

Second, it begs credibility to say that in the early part of the 1900s, men wielding shovels and axes wandering the mostly trailless mountain West on mules or horses were an effective control of fires. The fire statistics challenge this assertion. We should not forget that in 1910 more than 3.5 million acres burned the Northern Rockies in a single week. And during the 1920s-1930s, as much as 50 million acres burnt annually in the western U.S.

Today, 10 million acres charred is a “record year.”

Most advocates of the “fire suppression” paradigm ignore these early decades and point to what they assert was a successful fire control era during the 1940s-1980s when there were fewer blazes and a lot less acreage charred.

This graph shows the acreage burned annually from 1916 to 2007. Note the mid 1900s cooling period. Few large fires occurred during this period of “successful fire suppression.” Maybe Nature is good at suppressing fires.

However, the West experienced a particularly cool and wet period driven by the Pacific Decadal Oscillation during this same period. Indeed, glaciers were growing in the Pacific Northwest during this era, and some climatologists were predicting a return to the Ice Age.[ii]

What happens when you have cool and wet climate/weather? You get fewer ignitions and fires that fail to spread. Hence, I would argue that Nature was pretty good at “suppressing” fires, but human hubris always takes credit for something they had little to do with.

Fire suppression advocates like to suggest forest stands are denser due to the control of blazes. However, another consequence of cool, moist conditions is the higher survival of tree seedlings. These climate conditions would result in denser forest stands. The research suggests that more luxuriant forests actually are less likely to burn due to cooler temperatures, shade, and thus moisture.[iii]

Conversely, opening up the forest stand with logging/thinning increases aridity and wind penetration, leading to higher severity burns and more rapid-fire spread.[iv]

In a sense, the argument that fire suppression is responsible for large fires and denser forest stands ignores the considerable role of climate in wildfire occurrence.

If fuel accumulation drove large blazes, we would expect the most significant fires to occur on the Pacific Coast of Oregon and Washington, where the temperate conifer forests contain the greatest biomass (fuel) of any forest type in the world. But these forests seldom burn. Why? Because they are dominated by cool, moist conditions most of the time, just like the cool, wet 1940s-1980s period.

A further problem with the fire suppression argument is that it only applies, if at all, to low elevation dry pine and other dry conifer trees. Most of the plant associations in the West have naturally long fire rotations, often hundreds of years between significant blazes. This includes spruce-fir, aspen, lodgepole pine, sagebrush, juniper-pinyon, west slope Douglas fir, and many other vegetation communities. Even if fire suppression were successful, it has not existed long enough to seriously influence fire occurrence in these plant communities.

Why is this important? Because many of the blazes across the West we have experienced in the past few decades are occurring in these “other” plant associations, including chaparral, sagebrush, and higher elevation forest types like lodgepole pine, spruce-fir, and aspen, where “fire suppression” has had little to no influence.

Plus thinning and logging won’t reduce fuels in many plant communities. For instance, half of the acreage burned in California in recent years is chaparral.

What drives the large wildfires if fire suppression is not the major influence on fire occurrence?

The short answer is climate/weather. All large blazes are associated with specific extreme fire weather conditions, which include extensive drought, high temperatures, low humidity, and high winds.[v] If you have these ingredients, you get large blazes. If you don’t have these conditions, fire self-extinguish or are easily controlled.

The one thing that has dramatically changed across the West is the influence of drought. A recent analysis found that the period between 2000 and 2021 was the driest period since 800 CE, and at least 19% of this drought condition was due to human greenhouse gas emissions.[vi] When people suggest fire suppression is driving large blazes, they ignore the huge influence of extreme drought and climate warming.

Another recent study found that most wildfires begin on private lands, not public forestlands.[vii] Thus thinning/logging forests in the hopes it will preclude large blazes is also questionable.

All of this suggests that thinning forests to prevent large blazes is a fool’s errand. The best research indicates that reducing the flammability of the home ignition zone is likely to have a far greater impact on communities than logging the forest.

Notes.

[i] https://esajournals.onlinelibrary.wiley.com/doi/pdfdirect/10.1002/ecs2.2325

[ii] http://publications.americanalpineclub.org/articles/12195616200/Recent-Growth-of-Glaciers-in-the-Pacific-Northwest

[iii] https://www.sciencedirect.com/book/9780128027493/the-ecological-importance-of-mixed-severity-fires

[iv] https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecs2.1492

[v] https://johnmuirproject.org/wp-content/uploads/2021/11/ScientistLetterOpposingLoggingProvisionsInBBB_BIF4Nov21.pdf

[vi] https://www.npr.org/2022/02/14/1080302434/study-finds-western-megadrought-is-the-worst-in-1-200-years

[vii] https://www.nature.com/articles/s41598-022-06002-3.pdf

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

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