The 2020 Castle Fire and the 2021 KNP Complex were the two worst fires ever recorded in giant sequoia groves. Researchers went back through 26,400 individual trees across 19 groves to ask a specific question: which ones lived [1].
The answer was prescribed burning. Trees that had been through a controlled burn in the previous decade were about four times more likely to survive - a 77 percent reduction in the odds of dying [1].
In absolute terms, the burns that had already been done prevented roughly 1,900 sequoia deaths [1].
The counterfactual is the number that should travel. Had every tree in those groves been treated, the authors estimate about 3,900 more would have lived [1].
These are trees measured in centuries. A sequoia that dies in a 2021 fire is not replaced in any timeframe a person plans around, which is what makes a management practice with an effect size this large worth reporting as news rather than as forestry.
The work used airborne lidar and satellite imagery, was funded by NASA, and involved UC Davis, the USGS Western Ecological Research Center and Sequoia and Kings Canyon National Parks [1].
