Leveraging wildfire to augment forest management and amplify forest resilience

Successive catastrophic wildfire seasons in western North America have
escalated the urgency around reducing fire risk to communities and
ecosystems. In historically frequent-fire forests, fuel buildup as a
result of fire exclusion is contributing to increased fire severity, but
the probability of high severity fire can be reduced by active forest
management that reduces fuels, prompting federal and state agencies have
committed significant resources to increase the pace and scale of fuel
reduction treatments. However, wildfires also have the potential to act as
“treatments” in areas that burn at lower severity, but even catastrophic
fires with large areas of high severity can still have substantial area of
lower severity fire that may be improving forest conditions. We quantified
active management and wildfire severity across yellow pine and mixed
conifer forests (YPMC) in the Sierra Nevada of California over a 22-year
period (2001-2022). We did not detect clear increases in the area treated
through time but the area of beneficial wildfire (low to moderate
severity) increased substantially, exceeding active treatment area in 9 of
22 years. Overall, beneficial wildfire treated ~20% more area than all
treatments combined, and nearly seven times more area than fire-related
treatments alone. We then used disturbance history to evaluate resistance
to high severity wildfire and forest loss across the YPMC range. Of the
2.3 million ha that were YPMC forests in 2001, 19% lost mature forests due
to high severity fire by 2022, nearly half of all YPMC area burned. Most
of the landscape (47%) remains at risk of high severity fire because it
had no restorative disturbances, but 33% of the study area has some level
of resistance to high severity wildfire. In these areas, resistance will
need to be enhanced and maintained over time via active management or
managed wildfire. These treatment needs will likely outpace capacity even
under optimistic implementation scenarios. Given limited resources for
implementing active management and the likelihood of a more fiery future,
incorporating beneficial wildfire into landscape-level treatment planning
has the potential to amplify active management treatments, expanding the
forest area that is resistant to high severity wildfire.