Quantifying fire-specific smoke severity

Abstract

Rapidly changing wildfire regimes across the Western US has driven more frequent and severe wildfires, resulting in wide-ranging societal threats from the wildfires themselves and the smoke that they generate. However, common measures of fire severity focus on what is burned and do not account for the societal impacts of the smoke generated from each fire. We combine satellite-derived fire scars, air parcel trajectories from individual fires, and predicted smoke PM2.5 to link source fires to resulting smoke PM2.5 experienced by populations in the contiguous United States from April 2006-2020. We develop a new metric of fire-specific severity based on the cumulative population exposed to smoke PM2.5 over the duration of a fire. This measure is only weakly correlated with common measures of wildfire severity, including burned area, structures destroyed, and suppression cost. We find that while recent California fires contributed nearly half of the country's experienced smoke severity during our study period, the most severe individual fire was the 2007 Bugaboo fire in the Southeast. We estimate that a majority of experienced smoke PM2.5 comes from sources outside the local jurisdictions where the smoke is experienced, with 87% coming from fires in other counties and 60% from fires in other states. Our approach enables broad-scale assessment of whether specific fire characteristics affect smoke toxicity or impact, informs assessment of the cost-effectiveness of how suppression resources are allocated, and helps clarify the growing transboundary nature of local air quality.

Health Effects of Wildfire Smoke Exposure

“…Historically, efforts have focused on quickly suppressing fires, with suppression activity and costs focused on preventing incursion of fires into human inhabited areas. Wildfires near urban areas undoubtedly threaten lives, but fires distant from inhabited areas can generate large downwind smoke exposures that also threaten lives; these more distant fires may receive less suppression effort, even if they are potentially more costly from a public health perspective (78). There is also growing recognition that low-intensity fire, when left to burn or-in the case of prescribed firepurposefully ignited, plays a critical ecological function and can reduce the likelihood of future extreme wildfire.…”

Quantifying fire-specific smoke exposure and health impacts

“…The code and data to replicate the results and figures in the main text and SI Appendix will be made available upon publication at https://github.com/jeffwen/smoke_linking_public ( 74 ).…”

Health effects of wildfires

“…these more distant fires may receive less suppression effort, even if they are potentially more costly from a public health perspective. 109 There is also growing recognition that low intensity fire, when left to burn or -in the case of prescribed fire -purposefully ignited, plays a critical ecological function and can reduce the likelihood of future extreme wildfire. Formally quantifying these trade-offs is a critical area for future work.…”