Unprecedented Levels of High-Severity Fire Burn in Sierra Nevada Forests
by Kat Kerlin, UC Davis
January 20, 2023
High-severity wildfire is increasing in Sierra Nevada and Southern Cascade forests and has been burning at unprecedented rates compared to the years before Euro-American settlement, according to a study from the Safford Lab at the University of California, Davis, and its collaborators. Those rates have especially shot up over the past decade.
For the study, published in the journal Ecosphere, scientists analyzed fire severity data from the U.S. Forest Service and Google Earth Engine, across seven major forest types.
They found that in low- and middle-elevation forest types, the average annual area that burned at low-to-moderate severity has decreased from more than 90% before 1850 to 60-70% today.
At the same time, the area burned annually at high severity has nearly quintupled, rising from less than 10% to 43% today. (High-severity burns are those where more than 95% of aboveground tree biomass is killed by fire.)
Lead author and UC Davis project scientist John N. Williams said this ratio is severely out of balance.
“We’re seeing more ‘bad fire’ and less ‘good fire,’” said Williams, who is the coordinator of the California Prescribed Fire Monitoring Program. “Any consolation we’d get from the idea that, ‘At least we’re burning more than we used to,’ isn’t really a consolation because it’s often coming in the form of the wrong kind of fire.”
Read the Ecosphere paper: https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecs2.4397