A study led by the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder and the U.S. Forest Service’s Rocky Mountain Research Station has compared wildfire frequency between two time periods: 1984 to 2022 and 1600 to 1880.
The study used tree-rings and fire scars to determine the wildfire frequency and how this impacts the ongoing risk of forest fires.
Fewer wildfires burn in North American forests today than in previous centuries, increasing the risk of more severe wildfires, according to research published in Nature Communications.
The findings may seem counterintuitive, but frequent low-lying surface fires often maintain balance in forests by reducing fuel sources across large areas.
Scientists analyzed 1,850 tree-ring records in historically burned areas and compared them to maps documenting the perimeters of modern fires across Canada and the United States.
The findings show modern-day fires are much less frequent than they were in past centuries, despite recent record-breaking fire years, such as 2020.
The results also reveal that much of the continent is in a substantial “fire deficit,” experiencing about 20% as much fire as in the past.
According to the research, on average, larger areas of land burned from fires each year before 1880 compared to 1984–2022. This deficit allows fuel to build up over time, creating conditions for more severe fires.
Chris Guiterman, a CIRES Research Scientist and member of NOAA’s National Centers for Environmental Information (NCEI) Paleoclimate team said: “It’s a harbinger for far more bad fires to come unless we can get more beneficial management fires on the landscape.”
Even though a much larger portion of the forest burned in fires in the 18th and 19th centuries, those fires were less devastating: the trees that recorded those fires survived and continued to grow.
Modern fires, in contrast, are so severe they often leave forests barren and speckled with dead trees.
A study by the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder and the U.S. Forest Service’s Rocky Mountain Research Station found a decrease in modern forest fires compared to previous centuries, all by using tree rings and fire scars.
