A team of California-based researchers released in September the results of a study they say has succeeded in determining what was fueling deadly US wildfires—at least those in the Sierra Madre mountains—once the fires had ignited. Although the study’s authors acknowledge the role that climate change plays in increasing wildfire intensity, they suggest that two other culprits are mostly to blame.
The first is the actual fuel itself: large trees whose particles were found in the team’s smoke specimens. The second culprit is the forest management practice that allows the accumulation and preservation of larger trees, as well as thick underbrush kindling.
The researchers say their unique method of using a “ground-based mobile laboratory” at the site of the KNP Complex Fire (2021) helped them study the key fuel source that kept the wildfires blazing.
The research team onsite in the mobile lab measured concentrations of “fine airborne PM (PM2.5)” during a 26-hour sampling period on October 2–3, 2021, amid ongoing fires from their outset of September 9. Based on their results, they were able to estimate that the mean age of fuels burned in the KNP Complex Fire was 40 years, with “a range of 29–57 years.”
The authors concluded that their study provides “evidence for emissions originating from woody biomass, larger-diameter fine fuels, and coarse woody debris that have accumulated over multiple decades.” This, they added, matches independent field observations indicating that high fire intensity contributed to widespread death among giant sequoia trees, a revered species within the zone of the KNP Complex Fire (see image above).
Not only did the team succeed in identifying important wildfire fuel sources in the region, but with the employment of prescribed fires in California already planned in the next ten years (to reduce wildfire impacts), they think their unique measurement methodology can potentially provide “regionally integrated estimates” of the effectiveness of future fuel treatment programs.