One Not Very Helpful Report on the Comparison of Wildfire and Prescribed Fire Smoke and Another Helpful One


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).”

2 thoughts on “One Not Very Helpful Report on the Comparison of Wildfire and Prescribed Fire Smoke and Another Helpful One”

  1. WIth 1 out of every 8 acres burned in California in recent years, we’re fast approaching a new era where the amount of acreage that hasn’t burned and still needs controlled burns will continue to dramatically decline.

    It’s also important to not be in denial of the need for limits of air pollution in all aspects of human activities. Portland, Oregon reaching 119 degrees last summer has led to catastrophic damage to tree farms all throughout the landscape. was driving home up the I-5 corridor on Tuesday and once I got North of Portland all the youngest fastest growing trees most commonly seen in tree farms had nearly a foot of almost every branch tip fried orange. The older trees however only had damage on the older leaves, not the new growth.

    In other words, the more we pollute the atmosphere, the more regeneration failure like this is going to get more severe. So we need to think outside the box when it comes to the future of controlled burns being a tool to limit rate of spread during a fire rather than planning controlled burns as a separate additional source of emissions in areas that are not yet directly threatened by an active fire.

    For example, building large amounts of data on surface wind forecasting down the one hectare scale combined with requiring all parcels to be annually prepped for backfires so when a wildfire does begin to make its main run a firefighting commander has the ability to start highly precise backfires during the coolest hours of the day and that can reduce the amount of total acres burned. And when it comes to logistics of doing this on a scale never before seen we already have developed the ability to do this, we just have to ramp up the importance of using thousands of inexpensive drones that cost less than a giant air tanker and doesn’t put firefighters are put at risk:

    “Each of the one-inch spheres, called Dragon Eggs, contains potassium permanganate, and just before they are released they are given a pin injection of anti-freeze. The reaction between the two chemicals ignites the spheres after they hit the ground. The eggs can set fires ahead of an advancing wildfire in hard-to-reach places, denying it fuel. “A bonus is you can do nighttime ops and work in smoky conditions, because if a drone crashes, no one dies,” Weibel notes. At the Point Reyes fire, the drones were “a good safety tool for getting in where it was too thick or too steep for the firefighters,” says Suarez. And the Dragon Eggs they dropped enabled the backfire to cover a strip of land that was 300 to 400 feet wider, which made it a much more effective barrier against the spread of the wildfire.”

  2. I remember a friend telling me about dropping “golfballs” to start backfires. The problem was that they kept exploding when they hit the tree tops and made for instant crown fires.
    Most of the fires in recent history on Forest Service land have actually been large backburns, or controlled burns. The Forest Service maps out the largest area possible and starts lighting fires. They call this full suppression. The fires last till the rains come and large portions of the forest are burned. Some with low intensity burns, some not. This type of fire fighting is burning up an amazing amount of dollars, acreage, and resources.
    The best part for the Forest Service is they just get to do it. No NEPA, long term plans or other bothersome paperwork. They can close all the roads they want and not worry about the smoke. They even harvest danger trees with their BAER funds.
    A friend of mine told me he worked on a Forest Service fire this summer and never made so much money for doing so little. He was a bit upset when his boss told him he really needed him back on the job.


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