Tucson Standard

Contrary to common perceptions, North American forests are experiencing fewer wildfires than in the past, according to a new study published in Nature Communications. The research suggests that this trend may contribute to more severe fires.

Donald Falk, a fire ecologist and professor at the University of Arizona, co-authored the study with alumni from U of A and researchers from the USDA Forest Service's Rocky Mountain Research Station. Falk noted, "What we see in the record is that widespread wildfires were happening very frequently, about every 10 to 20 years in many areas." He explained that these historical fires were typically mixed-severity and surface fires over large areas, unlike today's severe wildfires.

The study was funded by the John Wesley Powell Center, an Earth science research initiative of the U.S. Geological Survey. Researchers aimed to understand historical fire patterns better. Falk emphasized that fire has historically played a crucial role in maintaining forest ecosystems by naturally reducing underbrush and controlling tree density. However, the absence of frequent fires has disrupted these cycles, resulting in denser forests and more destructive wildfires.

"As a result," Falk stated, "today's extreme wildfires are more likely to harm people and communities while exposing forests to damaging effects on soils and natural vegetation."

Researchers used data from fire scars—marks left on trees after being exposed to heat—to determine historical wildfire frequency. This data comes from the North American Tree-Ring Fire Scar Network developed at U of A's Laboratory of Tree-Ring Research.

Sean Parks led the study as a research ecologist at USDA Forest Service Rocky Mountain Research Station. He remarked on recent wildfire events: "In recent history, between 1984 and 2022, wildfires in 2020 seemed like they were unprecedented... but historically speaking, they were not." Parks pointed out that although recent fires have significant adverse impacts on communities and forests, there have been periods between 1600 and 1880 with greater burned areas.

The fire scar data spans over 1,800 sites across North America with diverse forest types. It was also used in another study led by Ellis Margolis that found connections between wildfire activity and climate patterns such as El Niño.

Falk concluded by highlighting the importance of understanding historical fire patterns: "Our forests are overgrown now due to 140 years of fire exclusion... but the more we can do to make our forests more resilient...the better off we're going to be."