Journal Article

Prescribed Burns as a Tool to Mitigate Future Wildfire Smoke Exposure: Lessons for States and Rural Environmental Justice Communities

Yantosca, Robert M., Liu, Tianjia, Kelp, Makoto M., Mickley, Loretta J., Carroll, Matthew C., Hockenberry, Heath E.

2023

Overview

Smoke from wildfires presents one of the greatest threats to air quality, public health, and ecosystems in the United States, especially in the West. Here we quantify the efficacy of prescribed burning as an intervention for mitigating smoke exposure downwind of wildfires across the West during the 2018 and 2020 fire seasons. Using the adjoint of the GEOS‐Chem chemical transport model, we calculate the sensitivities of population‐weighted smoke concentrations in receptor regions, including states and rural environmental justice communities, to fire emissions upwind of the receptors. We find that the population‐weighted smoke exposure across the West during the September 2020 fires was 44 μg/m3 but would have been 20%–30% greater had these wildfires occurred in October or November. We further simulate a set of prescribed burn scenarios and find that controlled burning interventions in northern California and the Pacific Northwest could have reduced the population‐weighted smoke exposure across the western United States by 21 μg/m3 in September 2020, while doing so in all other states would have reduced smoke exposure by only 1.5 μg/m3. Satellite records of large, prescribed burns (>1,000 acres, or 4 km2) reveal that northern California and western Oregon conducted only seven such prescribed fires over a 6‐year period (2015–2020), even though these regions have a disproportionate impact on smoke exposure for rural environmental justice communities and population centers across the West. Our analysis suggests that prioritizing northern California and the Pacific Northwest for prescribed burns might mitigate future smoke exposure. Plain Language Summary Catastrophic wildfires pose substantial risk to public health, infrastructures, and ecosystems in the western United States. As these large and costly wildfires become more common, methods to identify locations for prescribed burning are needed to mitigate impacts on affected populations and ecosystems. Here we investigate the effectiveness of prescribed burning for abating potential wildfire smoke exposures in states and rural environmental justice communities across the western United States during the destructive 2018 and 2020 fire seasons. We find that due in part to prevailing wind patterns, wildfires in the coastal states contribute more to overall smoke exposure in the West compared to wildfires in other states in both 2018 and 2020. We show that implementing prescribed burns in the heavily forested northern California and the Pacific Northwest would yield large net benefits for the entire western United States, while doing so in other states would have relatively smaller impacts. Our work suggests that land managers should prioritize northern California, western Oregon, and eastern Washington for prescribed burns to mitigate future smoke exposure as these regions have a disproportionate impact on smoke exposure for rural environmental justice communities and population centers across the West. Key Points The West Coast both experiences the largest smoke exposures and contributes most to the burden of smoke PM2.5 in the western US Applying prescribed burns on the coast yields large benefits for the West, while doing so in other states has relatively smaller impacts Larger prescribed burns may reduce smoke impacts from future large wildfires, but few such burns have occurred in key areas

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Air pollution / Air quality / Burning / Burns / Case studies / Chemical transport / Controlled burning / Distribution / Emissions / Energy consumption / Environmental aspects / Environmental justice / Exposure / fine particulate matter (PM2.5) / Forest & brush fires / Health aspects / Land use planning / Outdoor air quality / Particles / Prescribed burning / Prescribed fire / prescribed fires / Public health / Receptors / Rural areas / Satellites / Smoke / Smoke concentrations / Wildfires