Automated workflow demonstrates mixed treatment impacts on burn severity across ecoregion scales

Background Intensifying wildfire activity in western North America has motivated focus on fuel treatments as a tool for moderating fire severity. Treatment effectiveness is influenced by complex interactions among biophysical settings, treatments and weather. Aims This study introduces a standardized, scalable workflow to quantify wildfire-treatment outcomes across diverse landscapes. Methods We evaluated federal fuel treatments across 50 wildfires in southern Oregon and Northern California (2012–2021). We analyzed outcomes across two distinct landscapes: the productive, western Klamath mountains (west) and the more arid southeastern Cascades (east) to predict the probability of high severity fire. Results In the east, treatments reduced the probability of high-severity fire, especially treatments less than 9 years old. Thinning followed by prescribed fire mitigated high-severity effects even during extreme fire conditions. Conversely, in the west, large fire spread days primarily predicted high severity, masking the effect of treatments and other bottom-up drivers. Conclusions In pine systems with low topographic complexity, fuel treatments that remove both canopy and surface fuels from stands lower the likelihood of high severity fire within 9 years of implementation, including under extreme fire conditions. Implications This study proposes an open-source workflow to evaluate the conditions which treatments are effective across large landscapes.