Research

More research on less tree growth after fire

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(RJ Sangosti, The Denver Post)

 

 

This article summarizes some recent research on the topic:

Among Stevens-Rumann,’s work was a 2017 study of nearly 1,500 sites charred by 52 wildfires in the U.S. Rocky Mountains. Her research found that lower elevation trees had a tough time naturally regenerating in areas that burned between 2000 and 2015 compared with sites affected between 1985 and 1999, largely due to drier weather conditions.

More recently, a 2019 study written by her colleague Kerry Kemp found that both Douglas fir and Ponderosa pine seedlings in the Idaho’s Rocky Mountains — just south of B.C. — were also struggling in low-lying burned areas due to warmer temperatures, leading to lower tree densities.

Both studies attribute climate change to be the lead cause of why the trees are struggling to grow back in certain fire-scarred areas.

As a result, some ecosystems will no longer be able to support tree species. Instead they may convert to grasslands, she said.

We’ve talked about this before (for example, here).  But I would like to know how this kind of information is being incorporated into long-term planning for timber harvest levels. In accordance with the requirement for sustainability on national forests, we should be assuming forest growth consistent with the natural range of variation, which should reflect the effects of climate change on future forests.  What I would expect to be seeing based on this kind of research is reduced area suitable for timber production because it would become too dry, and reduced volume resulting from reduced density, slower growth rates and more frequent fires.  “Sustained yield” means that projections of lower future timber yields may lead to reduced near-term volume. I’ve looked at the timber volume documentation for a few forest plan revisions, and I haven’t found anything there about climate change (there’s usually an unconnected section on the effects of climate change somewhere).  (Projected timber harvest volumes are not tending to go down in revised forest plans.)  Maybe that just requires digging deeper than the public-facing documents or maybe it’s not happening.   Does anyone know more about this?

Tongass transition to young-growth – are we there yet?

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The Tongass National Forest is being managed under a 2016 amendment to its 2008 forest plan that addresses the Forest’s transition away from old-growth timber harvesting.  The amendment accelerated the transition in the plan from 32 years to 16 years, but there has been continuing controversy over how long that process should take.   Here’s the latest in an extended article from E&E News:

A new complication in the debate over the young-growth transition comes from Catherine Mater, a forest products engineer from Oregon who recently completed an inventory of 43 areas within the Tongass under a contract with the Forest Service’s Pacific Northwest Research Station. There’s enough young growth coming online to provide around 55 million board feet of timber annually for decades, she said, or more than double the total timber volume the service reported cut there in fiscal 2018. Mater found 138,760 acres of young growth — between 55 and 80 years old — suitable for harvest. All of it was within 800 feet of Forest Service roads and away from steep slopes and other environmentally sensitive areas.

Of course there’s still pushback from the “timber companies and industry-friendly politicians, who want more thinning and bigger clear cuts.”

What caught my attention though was these comments from the Tongass spokeswoman:

Forest Service managers stand by their estimates that the young-growth transition won’t be complete before 2033, Fenster said. “If, once the analysis is complete, it shows the projections in the forest plan were not valid, then the Forest Service would have to consider alternatives to incorporating new information into the forest plan estimates,” Fenster said.

The projected volume of young growth was a fundamental assumption in the 2016 amendment, so I don’t think the Forest has the option of ignoring how it could affect the decisions it made in the forest plan.

Research: eastern forest old growth more resilient to climate change

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“Analyzing large amounts of field data from 18,500 forest plots – from Minnesota to Maine, and Manitoba to Nova Scotia – the study identifies priority regions for forest climate adaption efforts.”

A study funded by the Forest Service found that older forests in eastern North America are less vulnerable to climate change than younger forests in terms of the sensitivity of carbon storage, timber volume and species richness.  From the abstract (linked to this news release):

We found the strongest association among the investigated ESB indicators (ecosystem services and biodiversity) in old forests (>170 years). These forests simultaneously support high levels of carbon storage, timber growth, and species richness. Older forests also exhibit low climate sensitivity of associations among ESB indicators as compared to younger forests. While regions with a currently low combined ESB performance benefitted from climate change, regions with a high ESB performance were particularly vulnerable to climate change. In particular, climate sensitivity was highest east and southeast of the Great Lakes, signaling potential priority areas for adaptive management. Our findings suggest that strategies aimed at enhancing the representation of older forest conditions at landscape scales will help sustain ESB in a changing world.

Some of this sounds a little contradictory (maybe someone with more expertise and/or who reads the full article could explain), and I wonder if it has any application at all to more fire-prone forests.  But it is a different way of looking at climate change adaptation that could be incorporated into forest planning.

New Forest Service research confirms that today’s wildfires moderate future fires

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“The research results clearly indicate that wildland fire regulated the ignition and spread of later wildfire in all study areas.” This might tend to produce a “duh” response, but apparently nobody had really studied it.  Here is the Forest Service overview of their research project.

Here is what I found most interesting – the Forest Service recognizes that, “Those responsible for managing wildland fires often face extreme pressure to quickly extinguish blazes due to short-term impacts such as smoke pollution or lost timber resources,” and “Parks’ research serves as a reminder that wildland fire, under the right fuel and weather conditions, can act as an effective fuel treatment to improve forest health and prevent future blazes from becoming large, costly and more dangerous” (my emphasis).

It should also be a reminder that when the Forest Service designates an area as suitable for timber production, and bases timber targets on that, it creates an incentive to put fires out, which increases the likelihood of more costly, dangerous fires.  This cause and effect relationship needs to be disclosed in the environmental analysis for forest planning, where the timber suitability decision is made.

Ranchers intimidate science they don’t like

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Data source: “Cattle Death Loss,” a report by the USDA National Agricultural Statistics Service

A wolf researcher at Washington State University has resigned as part of a settlement of a case alleging that the university infringed on his academic freedom.

“Wielgus angered ranchers with his research of wolf behavior. He concluded the state’s policy of killing wolves that preyed on cattle was likely to increase cattle predation because it destabilized the structure of wolf packs.

Ranchers complained to the Washington State Legislature, which cut Wielgus’ funding and demanded he be removed as principal investigator on his ongoing work.”

And they got what they wanted.  So, if you’ve got enough money and political power, not only can you buy your own researchers, but you can silence publicly funded independent research.  Do you suppose they might be able to influence the research conclusions, too?  (Somehow it’s a little hard to see “powerful” environmental groups making this trick work for them.)

 

 

 

Should dry forests be considered suitable for timber production?

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Recent research is showing that lower elevation forests are not regenerating after fires as they have historically.  From the abstract of the research cited in this article:

“Results highlight significant decreases in tree regeneration in the 21st century. Annual moisture deficits were significantly greater from 2000 to 2015 as compared to 1985–1999, suggesting increasingly unfavourable post‐fire growing conditions, corresponding to significantly lower seedling densities and increased regeneration failure. Dry forests that already occur at the edge of their climatic tolerance are most prone to conversion to non‐forests after wildfires. Major climate‐induced reduction in forest density and extent has important consequences for a myriad of ecosystem services now and in the future.”

One of those consequences should flow from NFMA requirements for sustainability and ecological integrity.  To put that in simplistic terms, if the land “wants” to be non-forest in the future climate, we have to let it be non-forest.  And non-forested lands are not suitable for timber production, regardless of whether we could plant and maintain a plantation there.  I don’t recall seeing any discussion of this in forest plan revision material I have reviewed recently.  There is also requirement to use the best available scientific information, so a suitability evaluation of low-elevation forests should go beyond what is currently growing there to address what would be expected there in the future.  Many national forests could end up with fewer suitable acres.

Air Pollution from Wildfires compared to that from Prescribed burns

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New research has taken an exponential leap forward in measuring air pollution from forest fires. It confirms the importance of sound forest management in terms of health. To summarize: prescribed burns are significantly more desirable than wildfires. “Researchers associated with a total of more than a dozen universities and organizations participated in data collection or analysis. The scientists published their peer-reviewed results on June 14 in the Journal of Geophysical Research: Atmospheres.” Georgia Institute of Technology was cited as the lead university and Bob Yokelson, a professor of atmospheric chemistry at the University of Montana were specifically mentioned in this article from ScienceDaily.

Some quotes from the article include:

1) “For the first time, researchers have flown an orchestra of modern instruments through brutishly turbulent wildfire plumes to measure their emissions in real time. They have also exposed other never before measured toxins.”

2) “Naturally burning timber and brush launch what are called fine particles into the air at a rate three times as high as levels noted in emissions inventories at the U.S. Environmental Protection Agency, according to a new study. The microscopic specks that form aerosols are a hazard to human health, particularly to the lungs and heart.”

3) “Particulate matter, some of which contains oxidants that cause genetic damage, are in the resulting aerosols. They can drift over long distances into populated areas.

People are exposed to harmful aerosols from industrial sources, too, but fires produce more aerosol per amount of fuel burned. “Cars and power plants with pollution controls burn things much more cleanly,””

4) “”A prescribed fire might burn five tons of biomass fuel per acre, whereas a wildfire might burn 30,” said Yokelson, who has dedicated decades of research to biomass fires. “This study shows that wildfires also emit three times more aerosol per ton of fuel burned than prescribed fires.”

While still more needs to be known about professional prescribed burnings’ emissions, this new research makes clear that wildfires burn much more and pollute much more. The data will also help improve overall estimates of wildfire emissions.”

I feel that the previously expressed concerns by many of us about the impact of wild fires on human populations for a thousand or more miles from a catastrophic fire have been reinforced, once again, by this landmark research. It matters not whether you are for or against human intervention to minimize the risk of catastrophic fires; sound, sustainable, science based forest management to accommodate human health and other needs in harmony with the needs of forests and their dependent species (as a whole system) is in the process of restoring some balance to piecemeal, emotionally driven, faux science and wishful thinking. Save the planet – save our forests – use statistically sound, replicated research validated by extensive operational trials over time and place to make sound environmental decisions.

The response of the forest to drought

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This post provides some on the ground research and consistent but separate modeling results that demonstrate the importance of stand density in coping with climate change and therefore the importance of sustainable forest management. Hopefully this will change some minds on the importance of strategically managing density.

A) The response of the forest to drought: the role of stand density and species diversity This article is an attempt to quantify previously established science.

1) “Droughts affect wood formation through the reduction in photosynthetic rates due to stomatal closure, reducing the amount of carbohydrates available for building new cells.”

2) “used tree-ring data from long-term forest plots of two pine species, ponderosa pine (Pinus ponderosa) and red pine (Pinus resinosa). The experiments were distributed in different geographical areas in the USA and they covered a large aridity gradient. They quantified growth responses at the population level to express both resistance and resilience to drought in relation to the relative tree population density, finding out that reducing densities would enhance both growth responses to drought. Trees growing in denser populations were more negatively impacted by drought and this has been shown in all three biogeographical areas.”
NOTE from “Climate Change Research Focuses on Great Lakes Forests”: “ASCC is monitoring the growth, health and survival rates of the trees in these forests, and focusing on three key qualities: resistance, resilience and transition. Resistance measures a species’ ability to remain stable and productive in a drought situation, resilience is a tree’s ability to return to normal productivity after experiencing an environmental change and transition refers to circumstances that encourage ecosystems to adapt to changing conditions.”

3) “This study confirms once more that the vulnerability of monospecific coniferous forests to increasing drought can be reduced through thinning interventions, which represent a viable adaptation strategy under climate change.”

4) “investigated the drought response of 16 individual tree species in different regions of Europe and evaluated if this was related to species diversity and stand density. Based on previous findings indicating that combining species with complementary characteristics is more important than simply increasing species diversity to cope with drought, their results indicate that species growing in a mixture are not always less water stressed than those growing in monoculture.”
See also: a) “Species composition determines resistance to drought in dry forests of the Great Lakes – St. Lawrence forest region of central Ontario” b) “SPECIES RICHNESS AND STAND STABILITY IN CONIFER FORESTS OF THE SIERRA NEVADA” c) “Functional diversity enhances silver fir growth resilience to an extreme drought”

5) “Investigating these effects at the level of species identity (i.e., different combinations of species) is more advisable than doing it at the level of species richness (i.e., abundance of species), because different mixtures respond differently depending on the region. If we consider that different provenances of the same species can show different adaptation strategies to cope with drought, the situation may be even more complex.”

B) Ecosystem services, mountain forests and climate change
Note: This modeling effort passes the #1 smell test in that it agrees with already established scientific principles while adding quantitative measures that support the previously known trend but shouldn’t be taken as absolutes.

1) “it is estimated that about half of the global human population depends – directly or indirectly – on services delivered by mountain forests. It is therefore essential to assess whether multiple ecosystem services can be provided to human societies in the future. Given that climate is changing fast, the consideration of climate change in scientific assessments is a must! Let’s not forget that European forests are managed since centuries (check out this nice book about the history of European forests). Thus, changes in management regimes must be considered as well.”

2) “in the Iberian Mountains their simulation results indicate that forest management, rather than climate change, is responsible for a reduction in carbon storage and biodiversity. On the contrary, in Western Alps changes in climatic regimes could induces large alterations in the supply of several ecosystem services, particularly under the most pessimistic future climate scenarios. In other areas (e.g., in the Slovenian Dinaric Mountains) climate change would strongly affect ecosystem services, albeit differently depending on elevation and stand conditions.”

3) “This confirms that management is a strong driver of forest dynamics in European mountains, and it can highly modify the future provision of ecosystem services (i.e., more than the direct effects of climate change!).”

Inside the Firestorm

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This is for those who insist that we don’t need to use forest management to reduce the risk of catastrophic loss to wildfire. Several people have expressed unscientific views on this site to the effect that ‘Wildfire is climate driven and no amount of controlled burns and or thinning can have any impact on total acreage burned since it is all due to global warming (drought and high winds)’ Hopefully this will bring them to their senses and open their minds to the possibility that they are flat out wrong.

Several of us have tried to explain that global warming only makes the need for managing stand density even more important. We have also tried to explain that what many see as climate driven firestorms are instead micro climate created by the fire. Hence the need to use the appropriate forest management tools to reduce the risk of an ignition spreading at a rate that will create its own weather and to provide opportunities for crown fires to return to the ground in order to allow the fire to be controlled as is appropriate for the specific situation.

I have rightly or wrongly gotten the impression that some here don’t really respect the research done on wildfire for at least the last 80 years. My reason for saying this is the applause they afford to people who come up with conclusions contrary to the science but don’t bother to reconcile their suppositions/theories, based on cherry picked incidents, with the established and well replicated science.

So here is an article that should give you a better understanding of and respect for the work behind the real science and how it corroborates what some of us have repeatedly stated here and elsewhere so, obviously, the principles described here are not new – They are just getting a whole lot more attention as technology has advanced to the point where tools are now available to make precise measurements on what has only been repeatedly observed before. This is a pretty intense read and well worth reading in its entirety.

1) ‘“It looked,” says Kingsmill, “like a nuclear bomb.”
Undaunted, Kingsmill and the pilot decided to do what no research aircraft had done: Fly directly through the plume.’

2) ‘For decades, scientists have focused on the ways that topography and fuels, such as the trees, grass or houses consumed by flames, shape fire behavior, in part because these things can be studied even when a fire isn’t burning. But this line of inquiry has offered only partial answers to why certain blazes, like the Pioneer Fire, lash out in dangerous and unexpected ways — a problem magnified by severe drought, heat and decades of fire suppression.’

3) ‘“The plume is orders of magnitude harder to study than the stuff on the ground,” says Brian Potter, a meteorologist with the Pacific Wildland Fire Sciences Laboratory in Seattle who sometimes works with Clements. Indeed, it took a global conflagration much darker than any forest fire to even begin laying the foundations of this work. Kingsmill’s observation about the bomb, it turns out, isn’t far off.’
–> Here the article dives off into the beginning of fire study as it began in the early ’40’s in preparation for the British bombing of Hamburg, Germany on July 27, 1943 when ‘42,000 people died, and another 37,000 were injured’

4) ‘these old experiments, finished by 1970, are still a key source of knowledge about extreme fire behaviors. Until recently, technology was simply too limited to reveal much more about the specific mechanisms by which a fire plume might feed a firestorm, let alone how beasts like fire tornadoes and fireballs form.’

5) ‘His instrument towers, deployed in carefully controlled fires, provided yet more unprecedented and precise measurements: how winds accelerate and draft into an advancing flame front, the heat and turbulence above the flames, and the speed of the rising hot air.’

6) ‘Clements wanted to capture the whole phenomenon — to look inside the opaque mass of an entire fire plume from a distance, and see all of its parts swirling at once. In 2011, he found his lens: a technology called Doppler lidar.’

7) ‘The team’s insight about the Bald and Eiler fires has implications for predicting smoke and air quality — a constant concern for communities near large fires. It also impacted the fires themselves. Even though both fires existed in the same atmospheric environment of pressures and winds, and burned across similar terrain, they were spreading in opposite directions that day — Bald to the south, and Eiler to the north. This denser current of cold air and smoke was actually pulling the Bald Fire in the opposite direction of what was predicted based on wind alone.’

8) ‘Coen works at the National Center for Atmospheric Research in Boulder, Colorado, where she studies fire’s inner workings. In September 1998, she spent several hours aboard a Hercules C-130 aircraft as it circled over Glacier National Park. The McDonald Creek Fire was marching up a steep slope at roughly three feet per second. Its smoke obscured the advancing flames, but infrared video cameras mounted outside the plane recorded what was happening underneath. It was only later, as Coen looked through individual frames of that video, that she noticed something strange: At one point, a jet of flame seemed to shoot ahead of the fire. It lasted only a second or two, but left a trail of newly ignited vegetation in front of the fire. Not until Coen calculated the size of the pixels and the time between frames could she appreciate its true significance.
The jet had surged 100 yards ahead of the fire’s front, advancing 100 mph — “like a flamethrower,” she says. It was 10 times faster than the local wind — generated, somehow, by the fire’s own internal tumult.
Coen called it the “finger of death,” and for her it brought to mind the unconfirmed reports of fireballs that occasionally circulated among firefighters.
She had never seen such a thing, but as she examined footage of other fires, she was surprised to find fire jets again and again.’

9) ‘Finney’s slow-motion videos show that these rolling eddies exist in pairs within the fire. They roll in opposite directions, coupled like interlocking gears. Their combined motion periodically pushes down on the advancing front of the fire, causing flames to lick downward and forward, ahead of the fire.
Finney believes that these forward flame-licks are scaled-down versions of the “fingers of death” that Coen has seen in wildfires — possibly even related to the fireballs said to have shot out of buildings during the 1943 Hamburg firestorm.
Coen has actually documented similar flame-rollers in real wildfires using infrared video. But she believes that the finger of death also requires another factor. As bushes and trees are heated by an approaching fire, their decomposing cellulose releases hydrogen, methane, carbon monoxide and other flammable gases in a process called pyrolysis.
Coen and Shankar Mahalingam, a fluid-dynamics engineer at the University of Alabama in Huntsville, believe that rolling currents can mix these flammable gases with oxygen-rich air. “The dangerous situation is when the fire is going up on a hill,” says Mahalingam. “Maybe there are pyrolysis products that have accumulated” in front of the fire and mixed with fire-boosting oxygen. As the flame licks forward into this invisible tinderbox, it ignites a blowtorch. … These same buoyant gases also supply the momentum that drives a fire whirl to spin once it is triggered. And on a much larger scale, they are what pushes a fire plume ever higher in the sky, powering the in-drafts that keep the fire burning below.’

10) ‘what drew Potter’s interest was the water. Concentrations of water vapor rose 10 to 20 times higher than the surrounding air.
Water is a major product of combustion, second only to carbon dioxide. It forms as oxygen binds to the hydrogen atoms in wood, gasoline or just about any other fuel — creating hydrogen oxide, otherwise known as H2O. Burning four pounds of perfectly dry wood releases a pound or two of water. …
And yet water vapor fuels the strongest updrafts in nature, says Potter, from thunderstorms to tornadoes to hurricanes. As moist air rises during these storms, the water vapor condenses into cloud droplets, releasing a small amount of heat that keeps the air slightly warmer than its surroundings, so it continues to rise. “Water,” he says, “is the difference between a weak updraft and a really powerful updraft.”’

11) ‘He believes that water was pivotal in fueling the firestorm that swept through the suburbs of Canberra, the Australian capital, on Jan. 18, 2003.
The fire consumed 200,000 acres of drought-stricken territory that day, isolating the city under a glowing haze of Halloween orange. Remote infrared scans suggest that during a single 10-minute period, it released heat equivalent to 22,000 tons of TNT — 50 percent more than the energy unleashed by the atomic bomb dropped on Hiroshima.’

12) ‘When N2UW flew through the plume of the Pioneer Fire in 2016, its instruments registered updrafts of 80 to 100 miles per hour. Yet at that elevation, 8,000 feet above the flames, the interior of the plume was only 3 to 6 degrees Fahrenheit warmer than the surrounding air, meaning that its buoyant stampede through the atmosphere was powered by a density difference of just about 1 percent.
In other words, given the right atmospheric conditions, a few degrees of warmth and extra buoyancy could spell the difference between a plume that pushes 40,000 feet up, into the stratosphere, powering a vicious blaze on the ground — as Pioneer did — and one whose smoke never escapes the top of the boundary layer at 3,000 feet, leaving the fire stunted, like a weather-beaten dwarf tree gasping for life at timberline.’

13) ‘Clements’s trained eye began to pick out some basic structures: a 40 mph downdraft next to a 60 mph updraft signified a turbulent eddy on the edge of the plume. Hot air pushing up past cooler, stationary air had set in motion a tumbling, horizontal vortex — the sort of thing that could easily have accounted for the plane’s brief freefall. Those blotchy radar pictures may finally allow us to see through wildfire’s impulsive, chaotic veneer’

Yes, professional wildfire researchers, the in air observations of pilots of spotters and retardant dropping planes and the on the ground observations of fire crews that point the researchers in various directions all deserve our respect. They actually put their lives on the line as opposed to those who disdain their commitment and repeatedly validated science.

Contact the author if you want references or check back in some previous postings on this site for some related references. I post this without references because it jives with the known and validated science that I have critically studied since I first started my forestry education in 1963.

The Impact of Sound Forest Management Practices on Wildfire Smoke and Human Health

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– Some would have us turn our forests back to a time before any of mankind inhabited North America.
– Some suggest that we should limit our management of forests to that done by native Americans pre European times.
– Some of us see a problem with limiting ourselves to these past practices because of the current population level.
– Some of us even see that properly validated forest science carried out in environmentally sound ways can improve the sustainability of our forest ecosystems and all of the species that depend on them for habitat, store carbon and reduce our dependence on the use of non-renewable, environmentally unfriendly resources which are being extracted from their long term, safe, natural storage underground.

This article (J. For. 115(●):000–000 http://dx.doi.org/10.5849/jof.16-042
Copyright © 2017 Society of American Foresters) “fire & fuels management Aligning Smoke Management with Ecological and Public Health Goals” seems to me to be a good starting point for a much neglected discussion on why mankind has to manage our federal forest better just from the point of protecting human health.

A) Motivation for the study comes from:
1) “mismatches between the scale of benefits and risks make it difficult to proactively manage wildland fires to promote both ecological and public health.”
2) “A recent update to wildfire smoke policy proposed by the US Environmental Protection Agency (US EPA) recognized the need to restore and maintain more frequent fire regimes through intentional use of fire, while asserting that protecting human health remained the agency’s “highest priority” (Office of the Federal Register 2015). Therefore, addressing both forest restoration and air quality objectives remains a central challenge.”
3) “Hurteau et al. (2014) found that under a business-as-usual climate scenario, this escalation in fire potential is likely to increase wildfire emissions in California by 50% by the end of this century unless agencies take a more proactive approach to fire use.”
4) “… current policies have permitted regulators to curtail fires intentionally managed for resource objectives in response to nuisance complaints by a few individuals, despite the potential for such
fires to have long-term collective benefits (Engel 2013). Because the impact and likelihood of smoke increase the longer that fire is kept out of the system, extensive fire suppression can result in a vicious cycle that becomes more and more costly to escape until the system fails, as represented by extreme
wildfires (Calkin et al. 2015).”
5) “Smoke and wildfires can impact public health in ways other than particulate pollution, including ozone pollution, increased stress during and after wildfires, and strains on medical services and communication systems (Fowler 2003, Kumagai et al. 2004, Finlay et al. 2012). Despite these broader
considerations, public health regulations for smoke typically focus on a 24-hour average of PM2.5. Values that exceed 35ug/m3 are considered unhealthy for sensitive groups, which include pregnant women, young children, elderly individuals, smokers, and people with chronic respiratory problems such as asthma (Delfino et al. 2009, Kochi et al. 2010, Moeltner et al. 2013).”

Please note that this study was not offered as a be all and end all study. In my opinion, the main objective was achieved. That objective being to give order of magnitude numbers to justify further research and further stimulate the process of rethinking current regulations and forest management policies.

B) Known Facts:
1) California: “The wildfire emissions in 2008 represented 68% of all PM2.5 emissions in the state, and they caused notable public health impacts (Wegesser et al. 2009, Preisler et al. 2015)”
2) “An important spatial mismatch results from the fact that large wildfires can create smoke impacts on distant urban populations. The risk to urban populations from regional-scale smoke impacts has increased as California became the most urbanized state in the United States, with 90% of its population residing within cities that have more than 50,000 people and another 5% living in smaller urban clusters (US Census Bureau 2015). Many of those urban areas are situated in valleys or basins that have poor air quality due to human activities as well as natural conditions that often trap pollutants (Ngo et al. 2010, Nakayama Wong et al. 2011). For example, the four metropolitan areas in the United States with the highest levels of particle pollution are all located in California’s Central Valley (American Lung Association 2015). Because many urban populations already experience poor air quality during the summer, they are particularly vulnerable to health impacts from wildfires (Delfino et al. 2009, Cisneros et al. 2014)”
3) “Within the study area, daily emissions from both prescribed burns and resource objective wildfires remained well below 500 tons PM2.5 , whereas the Rim Fire had 20 days exceeding that threshold (nearly half of its entire period of active fire growth) and peaked at nearly 11,000 tons PM2.5 /day on Aug. 26, 2013 (Figure 2). During the late summer, air quality is already problematic in downwind areas such as the Lake Tahoe Basin and San Joaquin Valley”
4) “Ground-level monitoring indicated that these large smoke plumes coincided with highly polluted days in Reno, which occurred on August 23–25 and again on August 28–29, when PM2.5 values exceeded the “unhealthy for all populations” standard (55.5ug/m3) (Figure 4F). Such high levels are such a serious health concern that people are advised to avoid going outdoors. Navarro et al. (2016) reported that very unhealthy and unhealthy days occurred at 10 air monitoring sites in the central Sierras, northern Sierras, and Nevada during the Rim Fire.”

C) Data – Smoke Plume data was used to “compare differences in smoke impacts between resource objective wildfires and full-suppression wildfires within the San Joaquin River watershed in California’s Sierra Nevada, the Sierras that burned between 2002 and 2013, including 10 resource objective wildfires (totaling 20,494 acres), 17 prescribed fires (totaling 6,636 acres), 4 small wildfires (totaling 12,025 acres), and the exceptionally large Rim Fire (257,314 acres). … the limited availability of smoke monitoring data, particularly before 2007, requires a focus on modeled emissions.”

D) Findings: Reasonable Expectations from the use of increased forest management to reduce the impact on human health of catastrophic wildfires include:
1) “Our results indicate that the 257,314-acre Rim Fire of 2013 probably resulted in 7 million person-days of smoke impact across California and Nevada, which was greater than 5 times the impact per burned unit area than two earlier wildfires, Grouse and Harden of 2009, that were intentionally managed for resource objectives within the same airshed.”
2) “The combination of a warming climate and accumulation of forest fuels ensures a future with more large fires and smoke in dry western US forests. We have outlined framework to more directly account for regional-scale smoke impacts from these events using surface monitoring and satellite observations of smoke. Managing large fires for resource objectives can shift the release of inevitable emissions to conditions that minimize large-scale smoke impacts, by controlling fire spread based on available dispersion and monitored impacts and creating anchors for containing future hazardous fires. When well supported by firefighting, air quality monitoring and modeling, and public communications resources, this approach can overcome existing disincentives for achieving ecological and public health goals.”
3) “August 31 … Altogether, medium- and high-density HMS smoke from the Rim Fire on that day covered a large area (251,691 mi2) with a population of 2.8 million people, more than 2 million of whom resided below high-density smoke … In contrast, the Grouse and Harden Fires burned slowly over the early summer of 2009, with very modest emissions until the last week of June … Our analysis of HMS maps indicated that there were only 2 days when medium-density plumes overlaid substantial populations in California and Nevada, amounting to 25,000 person-days”
4) “the Rim Fire burned 55 times more area (257,213 acres) than the combined footprint of the Grouse and Harden Fires (4,695 acres), but our analysis suggests that it had at least 275 times greater impact in terms of persondays, or 5.5 times greater impact relative to area burned.”
5) “Our analyses help to illustrate and begin to quantify many of the potential benefits of resource objective wildfires compared with those of extreme fires:
– 1. Reduced fuels and reduced consumption. … We accounted for this effect within the 10,385 acres of the Rim Fire’s footprint that had experienced prescribed fires or resource objective wildfires since 2002 by changing “typical” fuel loads to “light,” which reduced estimated emissions in those areas by 53%.
– 2. More favorable dispersion and potential for less ozone. As maintenance burns reduce fuel levels over time, managers may be able to burn more safely earlier in the summer and or later in the fall, when dispersion is often more favorable and ozone concentrations are lower (Jaffe et al. 2013). Fires managed for resource objectives are less likely to result in the greater lofting and concentrations of smoke reported from extreme fires, which often deliver pollution to distant, large urban populations in lower-elevation valleys (Colarco et al. 2004, Peterson et al. 2015).
– 3. Greater ability to regulate fire spread. Because wildfires would be managed for resource objectives when weather and fire behavior conditions are more moderate than under extreme wildfires, their slower fire spread can curb daily emissions. In addition, managers can employ the push-pull tactics burn described for the Grouse Fire to regulate daily emissions based on monitored concentrations fire will become increasingly important for reducing the likelihood and extent of large-scale, extreme fires like the Rim Fire (Westerling et al. 2015).”