Bill Gabbert “took one for the team”- (thank you Bill!) by reviewing a report requested by Ag and Interior of EPA. As reported by Bill on Wildfire Today, it’s kind of embarrassing that the Departments didn’t take a more active role in design of the project (case studies?) and request involvement of key researchers. It seems to me that both departments (Int and Ag) have more than the usual amount of experts themselves- both to focus the questions and pick the right people to get the answers. Perhaps it was a political effort to “get EPA on board” or recognize their air quality authority. If it were me, though, I’d force collaboration on any report between air quality and fire experts in all three departments, and the agencies within each; and clearly define what my questions are. Otherwise to my mind, you are just postponing and possible expanding, Potential Future Interagency Drama, plus wasting money.
The poorly edited report is not light reading and is a slog to wade through the hundreds of pages.
Many of the report’s “key insights” will not be a surprise to land managers (or anyone with a little common sense and exposure to fire management). Here are samples from Chapter 9, “Integrated Synthesis”:
Smaller wildfires produce fewer public health impacts than larger wildfires.
Convincing the public to evacuate or use air cleaners or HVAC filters to decrease exposure to PM2.5 can decrease public health impacts from smoke.
If a wildfire spreads into an area previously treated with prescribed fire it can reduce additional spread of the wildfire.
Smoke plumes that do not intersect with high population areas or last only a few days are less likely to have substantial health impacts than fires affecting larger populations for longer periods.
What was interesting, though, was the information that Bob Yokelson of the University of Montana contributed to Wildfire Today:
We also stress that, despite the evidence for PM evaporation during aging, there are strong data discussed next, supporting the idea that wildfires produce more PM than spring or fall prescribed fires on a per fuel burned or per area burned basis. Liu et al. (2017) reported that EFs for PM1.0 (gPM1.0/kg fuel burned) are almost four times higher in wildfires (27.1 ± 6.1) than spring and fall prescribed fires (7.3 ± 4.2; May et al., 2014). Our 2 year average ΔPM2.5/ΔCO ratio in aged wildfire smoke (~0.117) is ~1.7 times higher than implied for aged, fall western montane prescribed fire smoke (~0.07) based on May et al. (2014, 2015), suggesting that a remnant of the difference in initial PM emissions can survive aging. Fuel consumption in spring/fall prescribed fires at the national level is typically 7.2 ± 2.7 Mg ha−1 (Yokelson et al., 1999, 2013) as opposed to 34.6 ± 9.9 Mg ha−1 on wildfires (Campbell et al., 2007; Santín et al., 2015).
Combining the emissions and fuel consumption differences implies that wildfires emit 18 ± 14 times more PM per area burned. Although prescribed fires cannot simply replace all wildfires (Schoennagel et al., 2017; Turner et al., 2019), their potential to reduce the level of wildfire impacts deserves more attention. In addition, incorporating higher wildfire initial emissions and temperature‐dependent, post emission OA evaporation may improve models of wildfire smoke impacts (Nergui et al., 2017).”