Managing Smoke Risk from Wildland Fires: Northern California as a Case Study

Smoke fine particulate matter (PM_2.5) from increasing wildfires in the western United States threatens public health. While land managers often prioritize reducing wildfire risk in the wildland-urban interface, the impact on regional air quality from mitigating wildfire spread has been less explored. We developed a framework to quantify wildfire contributions to smoke exposure and assess targeted land management strategies. This data-driven approach integrates fire emissions and smoke transport to generate a smoke risk index at 0.25° × 0.25° resolution. We deploy the smoke risk index in an online tool, enabling stakeholders to analyze smoke risk under various scenarios of burned area, fuel consumption, and land management. Using Northern California as a case study, we estimate that in 2020, targeted land management in the 15 highest risk areas (∼3.5% of the total) could have reduced smoke exposure by 17.6%. However, most prescribed burns conducted from 2017 to 2020 did not overlap with these high-risk zones. Our framework also estimates excess deaths from smoke PM_2.5 exposure, attributing ∼36,400 (95% CI: 25,400-47,200) deaths nationally to western US fires in the year following the 2020 fire season. Our adaptable tool can incorporate higher-resolution data sets and help stakeholders prioritize fuel treatment and fire suppression to mitigate smoke exposure risks.