Fast Fire

As Westerners cope with the smoke and flames of another record-setting fire season, the media serves up dramatic videos of various active wildfires. Much of this footage focuses on dramatic images of crown fires burning through forest canopies, suggesting these fires pose the biggest threat to our communities. But according to former wildland firefighter Dr. Timothy Ingalsbee, the media perspective skews toward “hype.” To counter this dominant media narrative, which he believes “is a harmful influence on forest policy in the U.S.,” Ingalsbee wrote A Reporter’s Guide to Wildland Fire, which states that crown fire “is the most popular image shown on television newscasts, yet it is the rarest type of fire. Crown fires are normally fast-spreading and high-intensity fires. … They are also the fires that are near impossible to humanly contain and control.”

For land-management agencies, this type of media footage has proven effective at instilling fear that can be used to rally support for industrial tree-thinning. On the one hand, as Ingalsbee observes, crown fires are relatively rare; on the other hand, they are virtually impossible to control. From a forest management perspective, the essential question becomes, “Should we spend billions of taxpayer dollars based on the idea that forest-thinning will protect lives and communities by reducing the threat from crown fires?”

A research team led by University of Colorado Professor Jennifer Balch examined the most destructive fires from 2001 to 2020 and published its findings in 2024. It turns out fast-spreading crown fires represent a small fraction of the most destructive fires, which are characterized by “extremely rapid growth.” The Balch report cites three examples:

• The 2018 Camp Fire in California, which burned 52,000 acres the day it started, killing 85 people and destroying 16,000 homes.
• The 2021 Marshall Fire, the most destructive wildfire in Colorado history, was driven by winds in excess of 100 mph and traveled 3 miles within the hour it started, burning over 1,000 homes.
• The 2023 Lahaina Fire in Hawaii killed 101 people and destroyed more than 2,200 structures when a small brush fire escaped containment and burned through the town to the shore in 2 hours.

Of these three examples, only one, the Camp Fire, involved forested land, much of which had been thinned or clear-cut.

The researchers analyzed fires “in the context of their speed and damage to homes … exploring the maximum single-day fire growth rate.” Their report asserts, “Speed fundamentally dictates the deadly and destructive impact of megafires, rendering the prevailing paradigm that defines them by size inadequate. Fire speed matters more for infrastructure risk and evacuation planning…. Further, we know that fast fires occur when it is hot, dry, and windy…. Most of the area burned in extremely large events is from the growth on a single day, which is driven by extreme fire weather.”

The report cites fundamental changes to fire-evolved ecosystems since colonial times — “fire suppression policies, logging, the proliferation of invasive species, climate change, and anthropogenic [human] ignition patterns.” Exacerbating the problem, residential development “has placed tens of millions of homes squarely into this contemporary fuel matrix … the wildland-urban interface (WUI). The rapid expansion of this footprint has occurred largely without regard for wildfire risk, either through building policies or comprehensive community planning.”

Other scientists, like Dr. Becky Kerns, are also weighing in on the risks from fast fire. Kerns is a research ecologist at the Forest Service Pacific Northwest Research Station in Oregon. As a subject-matter expert, she participated in a Fire and Fuels Deep-Dive Science webinar hosted this spring by the Forest Service Rocky Mountain Research Station.

All five experts on the panel emphasized the importance of performing long-term maintenance to address revegetation in treatment areas. Fuel treatments, they agreed, are never a one-off event, and failure to perform regular fuel-reduction maintenance often leads to an increased level of fire hazard at former treatment sites.

“You may have a system where you do a really good job of reducing crown-fire potential or you’ve really altered the overstory,” Kerns said, “but now you have a lot of finer fuels that are coming in. So, you’ve lowered crown-fire potential, but now you have fine fuels…. The classic example, of course, is an invasive annual grass coming in after your fuel treatment.”

Kerns noted that fuel treatments in piñon-juniper forests are especially concerning, given the likelihood of post-treatment infestation from invasive annual grasses. “Any sort of treatments or fuel breaks where you start having a lot of invasion … can create a fast-fire situation…. Even though you might actually bring fire down to the ground and not have a crown fire, it could just rip through that break or that treatment if you have a lot of invasion…. The issues around invasives, particularly annual grasses, are really concerning around WUIs because it’s a fast-fire issue. You’re just going to bring that fire potentially up to the WUI, and that is concerning.”

As the Balch report demonstrates, the “lack of attention to fire growth is a critical risk assessment gap, particularly given the rapid expansion of the WUI into areas with the greatest probability of wildfire and the mechanisms by which most homes burn. We know that the primary mechanism for home ignition is firebrands propelled ahead of the flaming front that land on flammable materials attached to, on, or inside the structure and ultimately consume it.”

The authors emphasize three implications of their work:

• They define what constitutes “fast fire.”
• They demonstrate that fires are growing ever faster, particularly in the Western U.S.
• They show that grassland fires are particularly dangerous.

Based on their definition of fast fire, the authors “delineate a new class of the fastest growing and most destructive fires” based on a growth rate of 4,000 acres or more per day.

Fires that grow this quickly destroy most of the structures lost to wildfire each year (78%) and generate the highest suppression costs (61%). The authors determined, “There is a strong relationship between growth rate and burned area; growth is the fundamental mechanism driving final event size.” The authors also “quantify that the fastest-growing fires are in grassland systems, where more homes have been destroyed relative to forest wildfires.”

In summary, fast fires are the biggest threat to lives and communities, and the fastest-growing fires occur in grasslands. Therefore, the small percentage of forest wildfires that produce crown fires is rarely, if ever, a legitimate rationale for wildfire-mitigation logging.

Featured photo caption: Brushfire.