Wildfires have memories

wildfire spread mosaic behavior
Photo from the research described below.

Researchers studying how wildfires have burned at a particular location found that subsequent fires have a “memory” that helped to self-regulate fire sizes and fire severity. When historical fires burned unabated, landscape patterns of surface and canopy fuels developed that provided barriers to future fire spread. Those same barriers can continue to influence the spread of additional fires.

Susan Prichard and Paul Hessburg were the principal investigators on the “Reburn Project” for the Joint Fire Science Program. They developed a paper, “Evaluating the influence of prior burn mosaics on subsequent wildfire behavior, severity, and fire management options”.

Here are some additional highlights from their findings:

The Reburn Project was motivated by a need to better understand wildfires as fuel reduction treatments and to assess the impacts of decades of wildland fire suppression activities on forested landscapes. The study examined three areas, located in the inland Pacific Northwest, central Idaho and interior British Columbia. Each area had experienced a recent large wildfire event in montane forests.

Reburn  Highlights

  • Past wildfires generally mitigate burn severity for a time, even under extreme fire weather conditions that are associated with large fires.
  • Since around 1900-1934, fire suppression and not wildfire has been a primary influence on forest and fuel succession. Quantifying the effects of fire suppression on particular landscapes is difficult given the long history and its prevalence across the region. Results from simulation modeling have the potential to illustrate in compelling ways the combined effects of removing fires from landscapes that experienced variable fire severity and spatial extent.
  • The researchers developed a state-transition model that allowed them to simulate the growth and potential severity 20th century ignitions that were suppressed. Fire growth simulations were modeled using the daily meteorology available at the time of the ignitions and the FSPro model. The researchers found that the simulated landscapes were reburn landscapes; i.e., the complexity of forest seral stage conditions and fuelbeds was an emergent property of successive reburning over the centuries, and fuel succession explained most of the severity patterns  observed.
  • Modern-day fire suppression scenarios led to “boom and bust” landscapes, where continuous mature forests developed, that were capable of supporting large fire spread, and were eventually burned with mostly high severity. However, using a variety of historical landscape conditions as an initial basis, in scenarios where most or all fires were allowed to burn, fine- to meso-grained patchworks resulted, and they provided a highly diverse range of habitats and values over time, and landscapes were much less susceptible to large, high severity events. Instead, more typical fire size distributions and more characteristic variation in fire severity were restored.


Finding common ground among fire scientists

A group of people knowledgeable about wildland fire have produced a 52-page document that attempts to assemble and summarize areas of agreement and disagreement regarding the management of forested areas in the western United States. Calling themselves the Fire Research Consensus Working Group, they looked for areas of common ground to provide insights for scientists and land managers with respect to recent controversies over the role of low-, moderate-, and high-severity fires.

Their report is titled, A Statement of Common Ground Regarding the Role of Wildfire in Forested Landscapes of the Western United States.

Here is how they hope their conclusions will be used:

Our hope is that stakeholder groups will avoid the selective use of particular scientific papers to argue for their particular ends. Instead, they will be able to point to key shared assumptions, common understandings considering the entire body of fire science literature, and terminology to support decision-making in constructive ways. In particular, land and fire managers are a key audience for this report, as are other stakeholders and the interested public engaged in discussions about land management.

The “Executive Summary” is 6 pages long. Below is the section about high-severity fire:

“Respondents disagreed about whether large, high-severity fires have increased to a significant and measurable degree in all forest types in comparison to historical fire regimes (i.e., prior to modern fire suppression). There was strong agreement that in dry pine forests at low elevations there has been either an observed increase in high-severity fires or an increase in the potential for fires of elevated severity as the result of increased abundance and connectivity of woody fuels since the late 19th century. There was similar strong agreement about dry mixed-conifer forests in the Inland Northwest, Pacific Southwest, and Inland Southwest (Arizona and New Mexico) that there has been an increase in high-severity fires and an increase in the potential for fires of elevated severity. There was less agreement about the changes in extent, and causes of changes in extent, of high-severity fires in moist mixed-conifer forests. Although there is general agreement that high-severity fires historically played an important role in moist mixed-conifer and cold subalpine forests, there is strong disagreement over the degree of changes in burn severity patch-size distributions and associated successional conditions for these forests between different regions.

“Opinions also vary over the consequences of any increases in fire severity. For most dry forests, although there may be some disagreement about trends in burn severity and their causes, there is broad agreement that under current and projected climate, post-fire forest resilience is less than in the past. Some forest habitats, particularly at drier sites, but also in some moist and cold forest sites, show evidence of converting to more flammable non-forest vegetation or less dense forests following recent fires where large patches burn severely, especially if reburned. Reburn potential may depend on the interaction of vegetation, weather, rate of fire spread, time since prior fire, ignitions and fire suppression. Opinions are varied concerning the ecological consequences of departures from historical patterns of fire severity in various mixed conifer and subalpine forests. For example, one viewpoint supports the historical precedence of mixed-severity fire (including relatively large patches of high-severity fire), and the concept that pyrodiversity begets biodiversity. Another viewpoint asserts that increased woody fuel connectivity in combination with a warming climate trend is setting large areas of landscapes on fundamentally new trajectories, with significant undesirable ecological and societal consequences. Still a third viewpoint emphasizes that climatic changes increasingly are of overriding importance, and that new trajectories are unavoidable and thus may be considered desirable in many cases to incrementally foster necessary ecosystem transitions. The figure below characterizes these divergent viewpoints – typical of many areas of disagreement we addressed – and the potential common ground among them.

common ground wildland fire scientists

“Uncertainties associated with relative proportions of different burn severities and patch-size distributions combine to cloud key points of consensus that have important management implications. We suggest that resolving many fire science disagreements depends on greater consideration of specific geographical context. This may imply that a narrow range of field experience can limit one’s ability to accept findings that depart from that range. A logical way forward is to increase in-depth cross-regional field research experiences of the fire research community. Cross-regional comparisons of top-down and bottom-up determinants of fire activity in similar forest cover types is a fertile area of future research to examine how differences in seasonality, productivity, understory fuels, land use history, and other factors may explain some of the reported geographical differences in historical fire regimes in broadly similar forest types.

“There are several reasons for the disagreements about the amount and roles of past higher-severity fire. Both scientists and managers often transfer concepts and findings from one place to another, yet we know that “no one size fits all” for historical fire regimes, even within the same forest type. Likewise, the extent of change in abundance and connectivity of woody fuels varies across forest types and ecoregions. Some of the disagreement derives from use of different scientific approaches. For instance, there is strong debate about the fire regime inferences made from historical and modern tree inventory data, simulation models, and other approaches. We believe that application of diverse research approaches will be useful going forward. Further, multiple approaches will be useful in “triangulating” interpretations for which there is some scientific consensus (see Topic H). We challenge fire scientists who do not share similar perspectives on historical fire regimes in particular ecosystems to engage in civil discourse to better understand the reasons for their disagreement, and to objectively communicate those reasons to managers and other stakeholders. We are heartened by the positive outcomes achieved by some previous attempts when small or large groups work together to find common ground.”

Moritz, M.A., C. Topik, C.D. Allen, P.F. Hessburg, P. Morgan, D.C. Odion, T.T. Veblen, and I.M. McCullough. 2018. A Statement of Common Ground Regarding the Role of Wildfire in Forested Landscapes of the Western United States. Fire Research Consensus Working Group Final Report.

Thanks and a tip of the hat go out to Ben.
Typos or errors, report them HERE.

Researchers look at how warming will exacerbate the occurrence of wildfires in Mediterranean Europe

wildfire portugal
Wildfire south of Porto, Portugal, September 2, 2012. Photo by Bill Gabbert.

The climate warming that we have been seeing is expected to continue along with the increased risk of larger, more suppression-resistant wildfires. Scientists have examined how this will affect fires in Europe up to a 1.5°C  rise, which is the not-to-exceed target in the Paris climate agreement. Now a study is complete that examines increases of 1.5, 2, and 3°C warming scenarios. Not surprisingly, it found that the higher the warming level, the larger is the increase of burned area, ranging from ~40% to ~100% across the scenarios. Their results indicate that significant benefits would be obtained if warming were limited to well below 2 °C.

wildfires Climate Change Southern Europe
Ensemble mean burned area changes. Burned area changes (%) for a the +1.5 °C case with the stationary model SM (i.e., using Eq. 3), (b) the +1.5 °C case with non-stationary model NSM (i.e., NSM). using Eq. (4), (c) the +2 °C case with SM, (d) the +2 °C case with NSM, (e) the +3 °C case with SM, and f the +3 °C case with NSM. Dots indicate areas where at least 50% of the simulations (1000 bootstrap replications × the ensemble of RCMs) show a statistically significant change and more than 66% agree on the direction of the change. Coloured areas (without dots) indicate that changes are small compared to natural variations, and white regions (if any) indicate that no agreement between the simulations is found. Click to enlarge.

The paper, published in Nature, was written by Marco Turco, Juan José Rosa-Cánovas, Joaquín Bedia, Sonia Jerez, Juan Pedro Montávez, Maria Carmen Llasat, and Antonello Provenzale.

University chemist and students take flight with groundbreaking wildfire emission study

A flying laboratory carrying researchers from the University of Montana has the capacity to change what we know about future fires

Above: University of Montana and Colorado State University students in the Aircraft Observations and Atmospheric Chemistry course pose in front of their flying laboratory equipped with state-of-the-art instruments to map the smoke over the western US this past summer. Photo credit: Ali Akherati.

MISSOULA – Most aircraft slicing through the smoke above wildfires either drop water or smokejumpers in an effort to manage fire on the ground. But one plane – a flying laboratory carrying researchers from the University of Montana – has the capacity to change what we know about future fires.

This summer, the four-engine cargo plane spent more than 100 hours slicing through smoke above fires burning in the West, collecting data about the chemical composition of smoke and how it changes over time and travel.

The National Science Foundation National Center for Atmospheric Research C-130 research aircraft was based in Boise, Idaho this summer, but it sampled wildfire plumes in California, Oregon, Washington, Idaho, Nevada and Montana. The results will provide a new understanding of air quality and how it may affect populations downwind.

Assistant Professor Lu Hu from UM’s Department of Chemistry and Biochemistry, along with four UM graduate students, are part of the research team funded to work on the study through a multimillion-dollar collaborative NSF project called the Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption and Nitrogen, or WE-CAN. It is the “largest, most comprehensive attempt to date to measure and analyze wildfire smoke,” according to the NSF.

Hu and his atmospheric chemistry group are leading the investigation into chemistry and emission of organic pollutants from smoke. The team deployed UM’s new mass spectrometer on the C-130 research aircraft.

This instrument provided real-time measurements of volatile organic compounds in wildfire smoke and more insight into organic gas composition than previously possible. The emissions from wildfires are typically toxic, and they can form ground-level ozone and fine particulate matter, which are linked to serious health impacts and regulated by the U.S. Environmental Protection Agency.

“We expect to observe many toxic species from smoke that had been rarely characterized or reported before,” Hu said. “This unprecedented and rich dataset will help us better predict air quality downwind and understand how fire smoke impacts the climate system.”

Back in the lab on campus, Hu and his team focus to interpret how cloud chemistry, aerosol absorption and reactive nitrogen in wildfire plumes affect air quality, nutrient cycles, weather, climate and the health of those exposed to smoke.

The collaborative study includes researchers from Colorado State University, the University of Colorado-Boulder, the University of Wyoming, the University of Washington and the National Center for Atmospheric Research.

As part of this project, Hu teaches students aircraft observations in UM’s new Atmospheric Chemistry course. This educational initiative is co-led by Professor Emily Fischer of Colorado State University and Professor Shane Murphy of University of Wyoming. There are more than 30 students across three universities in the course, including seven students from UM.

The class brings the C-130 flying laboratory into a classroom. Students learn about the aircraft-based mission design and flight planning, and they just planned and executed three flights with the C-130 aircraft in early September. Last week, UM students traveled to Broomfield, Colorado, and visited other state-of-the-science laboratories of NCAR along with their educational flight.

Students will present what they learned from their educational flight later in the semester.

“Bringing cutting-edge research into a classroom is very fun and a great experience for both students and instructors,” Hu said. “Opportunities for aircraft observations being taught and experienced in a classroom are almost zero due to reasons like the limited accessibility and perceived high expense. I am just extremely happy that our UM students are involved in this rare and valuable educational opportunity.”


The course is sponsored by the UM College of Humanities & Sciences Toelle-Bekken Family Memorial Fund Award and the Department of Chemistry and Biochemistry.

For more information on the project, call Hu at 406-243-4231, email lu.hu@mso.umt.edu or visit http://hs.umt. edu/luhu.

Comparing the numbers of human and lightning caused wildfires

During a 21-year period 84 percent of the wildfires in the United States were caused by humans, but the ratio varies greatly across the country.

lighting human caused wildfires

A study published by the National Academy of Sciences looked at the causes of wildland fires, human vs. lightning, and their occurrence geographically and seasonally. The researchers analyzed 1.5 million fire occurrence records from 1992 to 2012.

I was interested in reading the paper after having been attracted to the compelling graphics comparing the numbers of fires caused by humans and lighting, ecoregion by ecoregion over time.

The research was conducted by Jennifer K. Balch, Bethany A. Bradley, John T. Abatzogloue, R. Chelsea Nagy, Emily J. Fusco, and Adam L. Mahood.

lighting human caused wildfires
Frequency distributions of wildfires by ecoregions, ordered by decreasing human dominance. Click to enlarge.

You might have noticed a large short-lived spike in the number of human caused fires in several of the ecoregions around June-July. That represents ignitions caused by fireworks on the Fourth of July.

Below is an excerpt from the research:

“In conclusion, we demonstrate the remarkable influence that humans have on modern United States wildfire regimes through changes in the spatial and seasonal distribution of ignitions. Although considerable fire research in the United States has rightly focused on increased fire activity (e.g., larger fires and more area burned) because of climate change, we demonstrate that the expanded fire niche as a result of human-related ignitions is equally profound. Moreover, the convergence of warming trends and expanded ignition pressure from people is increasing the number of large human-caused wildfires. Currently, humans are extending the fire niche into conditions that are less conducive to fire activity, including regions and seasons with wetter fuels and higher biomass.

“Land-use practices, such as clearing and logging, may also be creating an abundance of drier fuels, potentially leading to larger fires even under historically wetter conditions. Additionally, projected climate warming is expected to lower fuel moisture and create more frequent weather conditions conducive to fire ignition and spread, and earlier springs attributed to climate change are leading to accelerated phenology. Although plant physiological responses to rising CO2 may reduce some drought stress, climate change will likely lead to faster desiccation of fuels and increased risk in areas where human ignitions are prevalent.”

(end of excerpt)

You can download the paper HERE (it is a large 13 Mb file).

Winners announced for contest to build deployable device to monitor wildfire smoke

Wildland fires produce significant air pollution, posing health risks to first responders, residents in nearby areas, and downwind communities.

The existing air quality monitoring hardware is large, cumbersome, and expensive, thereby limiting the number of monitoring stations and the data that is available to help officials provide appropriate strategies to minimize smoke exposure. They can’t be easily moved to the latest areas that are being affected by wildfire smoke.

Last year the Environmental Protection Agency in association with the U.S. Forest Service, National Park Service, and other agencies issued a Wildland Fire Sensors Challenge to spur the development of a transportable device that could measure some of the byproducts of combustion produced by vegetation fires. They offered prizes for the first and second place entries of $35,000 and $25,000.

The goal was a field-ready prototype system that could be set up near a fire that was capable of measuring constituents of smoke, including particulates, carbon monoxide, ozone, and carbon dioxide over the wide range of levels expected during wildland fires. It was to be accurate, light-weight, easy to operate, and capable of wireless data transmission, so that first responders and nearby communities have access to timely information about local air quality conditions during wildland fire events.

The winners have been announced:

Sensor Challenge Winners

Jason Gu of SenSevere/Sensit, a co-developer of the first place winning system, said they have a number of units in the field now being tested under real world conditions. They also want to install them near existing air quality monitoring stations to ensure that the data from the new design is comparable to data from the old-school stationary equipment that has been used for decades. When they are satisfied with the results, manufacturing will be the next step.

smoke monitor air quality sensors

The SenSevere/Sensit unit has a battery that can last for three weeks but will have a solar panel to keep it charged. The device can transmit the data via a cellular connection or a radio. All of the sensors are made by SenSevere/Sensit. Their smoke sensor uses a blower that pulls air through a filter which removes the larger particles, and then a light beam detects the remaining very small PM2.5 particles, the ones that can be ingested deep inside a person’s lungs.

The video below has more information.