Wildfires degrade public health across the country

South Moccasin Fire in Montana, October, 2021
South Moccasin Fire in Montana, October, 2021. Photo by Lauren Kokinda, BLM.

By Matt Vasilogambros 

As wildfires continue to burn in parts of the United States, state public health officials and experts are increasingly concerned about residents’ chronic exposure to toxin-filled smoke.

This year has seen the most wildfires of the past decade, with more than 56,000 fires burning nearly 7 million acres nationwide, according to the National Interagency Fire Center. While the total area burned is less than in some recent years, heavy smoke has still blanketed countless communities throughout the country.

Climate change is causing more frequent and severe wildfires, harming Americans’ health, pointed out Dr. Lisa Patel, deputy executive director at the Medical Society Consortium on Climate and Health, which raises awareness about the health effects of climate change.

“The data we have is very scary,” she said. “We are living through a natural experiment right now — we’ve never had fires this frequently.”

Patel sees the effects of wildfires in her work as a practicing pediatrician at Stanford Medicine Children’s Health, treating more women and underweight and premature infants at the neonatal intensive care unit when wildfires rage in Northern California.

As researchers focus on the public health impact of wildfire smoke, state health and environmental officials across the country have had to issue more air quality notices and provide guidance and shelter for residents struggling during periods of heavy wildfire smoke. And as experts have found, this issue isn’t isolated to the West Coast — it hurts more residents in the Eastern U.S.

Studies show that chronic exposure to wildfire smoke can cause asthma and pneumonia, and increase the risk for lung cancer, stroke, heart failure and sudden death. The very old and very young are most vulnerable. Particulates in wildfire smoke are 10 times as harmful to children’s respiratory health as other air pollutants, according to a study in Pediatrics last year.

What concerns experts is particulate matter in the air smaller than 2.5 microns across; there are around 25,000 microns in an inch. People inhale these microscopic bits, which then can embed deep in their lungs, irritating the lining and inflaming tissue. The particles are small enough to get into a person’s bloodstream, which can lead to other short- and long-term health effects.

Forecast for wildfire smoke
Forecast for wildfire smoke at 12:01 a.m. PDT Sept. 1, 2021.

Particulates in wildfire smoke are even hindering national progress on reducing air pollution, after decades of improvement.

The federal Clean Air Act has substantially decreased the level of toxic particles from industrial and automotive pollution across the country since 1970, the U.S. Environmental Protection Agency notes. But air pollution is expected to worsen in parts of the West because of wildfires, some researchers have found. A United Nations report earlier this year warned of a “global wildfire crisis,” saying the probability of catastrophic wildfires could increase 57% by the end of the century.

Researchers are trying to better understand how more frequent wildfires affect human biology.

Keith Bein, associate professional researcher at the University of California, Davis, created a rapid response mobile research unit in 2017 that he deploys when there are fires around the state. He’s like a storm chaser but for wildfires.

With his mobile unit, Bein can measure particulate matter in the air, take samples back to his lab and then determine their toxicology and chemical compositions. When near these fires, he said, the smoke is so bad that it feels like there’s no escaping it.

“The smoke rolls in, and you get that sinking feeling all over again,” he said.

Massive wildfires that tear through communities are becoming more common. The fires aren’t just burning trees but also synthetic materials in homes. And with repeated exposure to different particulates, health risks are more pronounced and can evolve into chronic conditions, Bein said.

Researchers are just beginning to understand how more frequent wildfires in residential areas impact human health, he added.

“It’s happening more frequently every summer,” he said. “The length of the fires is growing. The public exposure to the smoke is also growing. Once-in-a-lifetime events are happening every summer. This is a different kind of exposure.”

In 2020, a study in Environment International found that winter influenza seasons in Montana were four to five times worse after bad wildfire seasons, which typically last from July until September. The findings shocked study lead author Erin Landguth, an associate professor at the University of Montana.

“We know that hospitalizations for asthma and other respiratory conditions spike within days or weeks of wildfires,” she said. “The thought that this could potentially lead to effects later and how that can affect our immune system is really scary.”

Landguth is currently expanding her study to all Western states. She expects to find a similar trend throughout the Mountain West and Pacific Northwest. Monsoon season in Arizona and New Mexico may disrupt the trend there, she said, while air pollution is already so bad in California from smog and other pollutants that it might be difficult to pinpoint how wildfires are harming human health.

But wildfires are not just in the West, nor is their health impact geographically isolated. Some fires burn so intensely at such high temperatures that smoke rises into the atmosphere, where strong winds can carry the smoke long distances.

This was glaringly apparent in 2021 when the sun glowed red, and the sky hazed over New York City and throughout the Northeast, as smoke drifted from massive wildfires in California, Oregon and other Western states.

Pine Gulch Fire
Shot from Colorado National Monument August 7, 2020 about 15 miles Southwest of the Pine Gulch Fire. The view is looking towards the northeast and shows some of the explosive activity on the northern front Friday and the huge smoke plume extending to the east. Photo by Jennifer Deering.

That smoke is hurting the health of more people in the Eastern U.S. than it is in the West, said Katelyn O’Dell, a postdoctoral research scientist at George Washington University, who released that finding in a study in GeoHealth in 2021. Wildfire smoke contributed to more asthma-related deaths and hospital visits in Eastern communities than those in the West, she and other researchers found, in part because of higher population density.

The smoke hitting the Eastern U.S. doesn’t just come from the West; there are wildfires and prescribed burns throughout the country, said O’Dell.

“It’s sometimes easy to feel distant from fires and their impacts when you’re far from the flames of these large Western wildfires that are in the news,” she said. “But wildfires impact the health of the U.S.”

The next orange sunset people enjoy should be a moment to check an air quality mobile app, she said.

In Minnesota, the state has issued 46 air quality alerts since 2015, according to the state’s Pollution Control Agency. Of those, 34 were due to wildfire smoke, and 26 of those were issued last year.

That took state officials by surprise, said Kathy Norlien, a research scientist at the Minnesota Department of Health. The wildfire smoke risk is not just coming from the plumes that drift from the West Coast and Canada, but also from wildfires in the Boundary Waters — a lake-filled region in the northern stretches of the state. She expects the problem to worsen in the coming years.

“At this point, we’re planning for the worst-case scenario,” she said. “We have not had the extent that the Western states have had. But with climate change and concern over drought and the dry conditions, planning is of the utmost importance.”

She meets regularly with the Minnesota Pollution Control Agency and other state officials about how to get the message to state residents about the increasing wildfire risk to public health, encouraging residents to sign up for air quality alerts. State officials also have established larger community centers and buildings as safe air shelters.

The public plays an enormous role in both preventing (nearly 90% of wildfires are caused by humans, according to U.S. governmental data) and adapting to wildfires, many experts say.

For people living in fire-prone areas, there are nonflammable building materials for new homes and indoor air purifiers and upgraded HVAC systems. But these solutions may be too costly for some families, said Patel, of Stanford Medicine.

She counsels families about how to affordably stay safe during wildfire season, encouraging the use of N95 and KN95 masks, which were pivotal in combating the spread of the coronavirus. She also shares designs for do-it-yourself air filtration systems.

But she emphasized that wildfires will continue to rage across the country and cause adverse health effects unless climate change is reined in through serious public policy. Until then, climate change will continue to be the biggest threat to public health, she said.

“Summer used to be a time I’d look forward to,” she said, “but now I look at it with dread with the heat and wildfires.”


First published by Pew Charitable Trusts on Stateline. Used with permission.

Drones are playing an increasingly important role in fighting wildfires

drone wildland fire firefighter
A contracted UAS crew with Precision Integrated Programs / Overwatch Aero — Tyler Kock, Daniel Rodriguez, and Cliff Savage — on the Lighting Complex of fires. US Forest Service photo by Andrew Avitt. FVR-90, N170WA.

By Andrew Avitt, US Forest Service, Pacific Southwest Region

Drones – also called UAS or unmanned aerial systems – are playing an increasingly important role in fighting wildfires by supporting operations with aerial ignition and gathering intelligence for firefighters. The greatest benefit drones provide is they can take to the sky when manned aircraft are grounded for pilot safety.

Take, for example the FVR-90, a fixed-wing drone with a 14-foot wingspan capable of traveling at speeds up to 46 mph with a flight time of 8 hours. They are sent airborne just at dusk when other manned flights are grounded. The sky is theirs, and the overhead view they have of the fire is detailed and in real time.

“The way we use UAS now is very much a supplement,” said Justin Baxter, the Forest Service National UAS Operations Specialist. “There are certain times that it’s just not safe for us to utilize manned helicopters or fixed-wing aircraft, like nighttime operations or in thick smoke or high winds.”

drone wildland fire firefighter
USFS photo by Andrew Avitt.

The drones that Baxter and his team fly are equipped with cameras that are not your normal cameras. They have multiple types of sensors, including infrared, that allow the team to see through smoke and, at night, see heat signatures, or thermal-based imaging. This allows the identification of areas where fire is still active and new areas where flames have advanced, such as spot fires.

Spot fires occur when embers from the main fire are thrown into the air and pushed by wind until they fall to the ground, starting a new fire. They are notoriously hard to identify because they are small at first and visibility is diminished by smoke. They may occur in hard-to-reach places difficult for firefighters to patrol, like on steep slopes or down in drainages.

“Drones are changing that labor-intensive process to identify these spot fires, especially when an operational area can span hundreds of thousands of acres,” Baxter said. With drones, fire managers and incident management teams can scan large areas quickly and easily identify spot fires that may be a mile from the main fire. That enables firefighters to get in and suppress those new starts before they grow.

“To give you an idea, this drone can detect a 2-inch by 2-inch spot fire from a half-mile away,” said Baxter as he gestured to the imposing drone just to his left minutes before takeoff to fly around the perimeter of the Six Rivers Lightning Complex Fire near Willow Creek, California.

Baxter said that much has changed since 2015 when the agency began the UAS program.  With each passing year, incident management teams have increasingly incorporated the capability into their strategies.

The communication between the UAS crew and firefighters on the ground flows in both directions. The drone may be flying over and see heat in an area and transmit the information to a hotshot crew. Conversely, the hotshot crew can ask the UAS crew for assistance in exploring an area that they suspect might be active, and then view a feed from the drone of the area in question.

John Crotty served as the air operations branch director with California Interagency Incident Management Team 15 that responded to the Lightning Complex Fire on the Six Rivers National Forest.

drone wildland fire firefighter
A drone equipped for aerial ignition. USFS photo by Mike Yearwood.

Aerial intelligence isn’t new in wildland firefighting, said Crotty referring to the recently retired Cobra helicopter and its Firewatch capabilities. But the implications of unmanned flight— that opens up new possibilities.

“With the Cobra aircraft, we needed a pilot and an interpreter up there to run the camera and talk to the folks on the ground. So, we expose two individuals plus a flight [to risk],” said Crotty, “But what we really needed was the visibility to fly.”

Thick smoke on the fires like the Lightning Complex can ground manned aircraft. That’s where drones come into play and the images it captures can inform firefighters working across a large area.

“The other day I heard from one of the hotshot crews out there. They were in heavy smoke conditions, at night. With the low visibility they couldn’t see if they had a spot fire across the line,” Crotty said. “This tool being up in the air, looking down at that exact area, the UAS crew was able to pinpoint the spot and provide precise coordinates to the firefighters who were able to check it out and put it out. That kind of information we would never have without these unmanned aircraft and that capability. Drones are the future of aviation for not only fire but for aviation in general. It’s a win-win for the agencies to operate under an umbrella of this type of aircraft that can provide precise and timely info to firefighters and incident management teams. And most importantly, we can do it safely.”

Common approach to keeping wildfire smoke out of US homes doesn’t work, study finds

Trend in heavy smoke days
Measurements from satellites indicate rapidly growing exposure to heavy smoke plumes across much of the U.S. Map shows the estimated annual increase between 2011 and 2020 in the number of smoke plumes that NOAA analysts designate as “heavy,” their densest plume classification. Dots indicate EPA ground-based pollution monitors. Credit: Burke et al.

By Josie Garthwaite, Stanford University

When drifting wildfire smoke brings hazardous air pollution to cities and towns across the country, public health officials urge residents to stay indoors, close windows, and use air filters. New research from Stanford University shows Americans are getting the message, yet still rarely succeed at keeping smoke from entering their homes.

Researchers led by Marshall Burke, an associate professor of Earth system science, analyzed data from consumer-grade air pollution sensors in 1,520 single-family homes across the U.S., as well as nearby outdoor air pollution monitors, cell phones, social media posts, and Google searches in English and Spanish between 2016 and 2020.

They found internet searches for air quality information increased on heavy smoke days, regardless of income, while searches for air filters, smoke masks, and other protective measures recommended by health officials rose only in wealthy neighborhoods. Residents of wealthier neighborhoods are also more likely to shelter at home when wildfire smoke pollutes outside air. “People seem to know they’re being exposed. We see a lot of behaviors change even at pretty low levels of smoke exposure, although those responses differ by socioeconomic status,” said Burke.

The results, published July 7 in Nature Human Behaviour, show that better education and information about health hazards from wildfire smoke are not enough to protect people from the health harms of wildfire smoke exposure. The findings also bolster evidence for nascent efforts to take a more proactive and systematic approach to mitigating public health risks from wildfire smoke, predicted to be one of the most widely felt health impacts of climate change nationwide.

While most current government policies rely on a do-it-yourself approach to avoiding unhealthy air from wildfires, this tactic will have “modest and unequal benefits,” the authors write. Short-term solutions include establishing clean air shelters and providing public subsidies for lower-income households to filter indoor air. “If people can’t maintain good air quality in their homes, they need a place to go where they can breathe clean air,” said Burke, who is also deputy director of Stanford’s Center on Food Security and the Environment. “That’s a great place to start.”

Leaky homes

Overall, the authors found indoor concentrations of the deadliest type of particle pollution, known as PM 2.5, often remain three to four times higher than public health guidelines, and can vary by a factor of 20 between neighboring households during heavy smoke days. “Households that look exactly the same in terms of income, house price, and house size had enormously different indoor air for a given level of outdoor air quality,” said study co-author Sam Heft-Neal, a researcher at the Center on Food Security and the Environment. According to the authors, the most likely culprits are open doors and windows, leaky buildings, and a lack of filtration.

As the number of heavy smoke days in California and the West continue to climb, lawmakers from several western states have introduced bills that would allow the president to declare a “smoke emergency,” provide federal funding to establish clean air shelters and relocate vulnerable populations, and create a grant program for local community planning related to wildfire smoke. None have been enacted.

“To be able to intervene appropriately, we have to be able to measure things, including what people are exposed to in their home and how they’re behaving,” said Burke. That ability is rapidly expanding, thanks to the growing number of people buying relatively low-cost but reliable air quality monitors from PurpleAir, a private company, and agreeing to have the data put on a public website—although households who own the monitors, for now, are overwhelmingly Californian and higher income. “Our ability to precisely measure infiltration at the household level and then relate that to things we observe about the house or the community is new,” Burke said.

In the absence of systematic support at the federal level, a patchwork of local and state mitigation efforts has emerged. Oregon’s environmental agency, for example, has provided a grant for the city of Ashland to set up a free air purifier distribution program for vulnerable residents. In California, where more than half the population experienced a month of wildfire smoke levels in the range of unhealthy to hazardous during the 2020 fire season, the state has launched a $5 million pilot program providing grants for smoke shelters.

Still, most places are no better prepared for unhealthy air this year than they were in 2020 and, as large fires become more frequent, it will become increasingly onerous for people to protect themselves. “We’ve dug ourselves a huge hole in terms of the amount of accumulated dry fuel in our forests. It’s going to require unprecedented levels of investment over a sustained period to reduce fire risk and lower smoke exposures for everyone,” Heft-Neal said. “In the meantime, we have to be prepared for the large wildfires that, unfortunately, we’re going to get. And we have to be ready to deal with the downwind exposures that those wildfires generate.”

California forests hit hard by wildfires in the last decade

About 25 percent of the states’ forestland burned in the last 10 years — more than triple the previous decade

BAe-146 drops Winding Fire
BAe-146 drops on the Winding Fire in Northern California June 18, 2022. InciWeb.

By Jim Schmidt

Of the 32.1 million acres of forestland in California, approximately 2.1 million acres (6.6%) burned in wildfires in the 2002-2011 time period. In the following decade (2012-2021), that figure more than tripled to 7.9 million acres (24.7%).

National Forests in California were particularly hard hit.  10.1% of 12.7 million acres of forestland managed by the USDA Forest Service in California burned in 2002 – 2011 time period.  In the 2012 – 2021 decade that figure increased to 38.8%. Excluding areas that re-burned in the last 10 years, 44.5% of the forestland in California National Forests has burned in the last 20 years.  In contrast, only 22.6% of National Park forestland in the state has burned in the same time period. About 14 million acres of forestland in California are in private hands.  17.0 % of private forestland has burned since 2001.

Forestland acres burned California last two decades
Forestland acres burned by wildfires in California by owner class, 2002 – 2021. Jim Schmidt

The following maps display the forestland areas and the areas that have burned in California in the last two decades. Fires were concentrated in Southern California in the 2002-2011 time period and in Northern California in the last 10 years.

Map, California forestland and wildfires, 2002 - 2011
California forestland and wildfires, 2002 – 2011. Jim Schmidt
Map, California forestland and wildfires, 2012 - 2021
California forestland and wildfires, 2012 – 2021. Jim Schmidt

The article was edited September 7 with revised figures to account for areas that reburned, which account for about 5% of the forestland burned on National Forests in the last 20 years.

Jim Schmidt retired from the Stanislaus National Forest where he worked as a GIS specialist.

Remembering Jan van Wagtendonk, who shaped fire management in Yosemite National Park

Jan van Wagtendonk
Jan van Wagtendonk. NPS photo.

From the National Park Service, Yosemite National Park, August 12, 2022:

“We are sad to report that pioneering Yosemite scientist Jan van Wagtendonk died on July 15, 2022.

“Jan was a Yosemite and National Park Service legend: an accomplished scientist, a preeminent fire ecologist, a wilderness advocate, and a beloved colleague. He was an innovative wilderness manager, coming up with the trailhead quota system that we still use today to protect wilderness while ensuring that hikers are free to enjoy that wilderness on their own terms. His impact affects fire policy to this day as one of the authors of the first federal fire policy in 1995. Jan possessed an amazing intellect, deep humility, a sharp wit, and a profound love of Yosemite and the Sierra Nevada.

“Jan was a strong advocate for returning fire to the Sierra landscape. His pioneering use of prescribed fire in the early 1970s in and around the Mariposa Grove started us on the path to reestablishing an ecological balance lost in over 100 years of fire suppression. There is poetry, in the words of Jan’s son Kent, that in Jan’s final days the fruits of those efforts had a direct and dramatic effect in saving the Mariposa Grove from the Washburn Fire, which started just outside of the grove.

“Our heartfelt condolences go to Jan’s family and wide circle of friends and colleagues. He was one of a kind, and will be deeply missed.”


The article below from the US Geological Survey was originally written in 2020, based on an interview with Jan van Wagtendonk in 2019:


The first thing to know about emeritus scientist Jan van Wagtendonk is that he loves trees—always has and always will. As a kid, he looked at trees, inventoried trees, wrote a report on trees. One of his neighbors as a kid described young Jan by saying “I never saw him inside.”

He was a forest scientist before he even knew that was a thing you could be.

At age 13, van Wagtendonk was on two-months long family camping trip when he met a forest ranger. Upon realizing that he, too, could work with trees for a living, van Wagtendonk decided to become a forester. Several years later, he entered the forestry school at Purdue University in Indiana.

Wildfire 101

One day in college, van Wagtendonk found a listing on a campus bulletin board for a summer job on a wildland firefighting crew in Oregon. He applied, got the job, and headed West. It was his first experience with wildfire, the subject that would become his life’s work. Unsurprisingly, he loved Oregon—it had great trees—and ended up transferring to Oregon State University. He would spend several summers on fire crews in Oregon and then Alaska, first mopping up the final embers of wildfires and later working as a smoke jumper. The job was to put the fires out. Years later, his job became more about the opposite—reintroducing fire to Western forests.

Van Wagtendonk claims he “had no inkling about fire ecology at all” at the time, but he thinks that several experiences he had during his smoke jumping days may have shaped his thinking as a forest scientist and led him to fire ecology. In one instance, he was assigned to a put out a fire in a remote part of Alaskan tundra. The landscape was dotted with bird nests. The flames were about two inches high, and the fire crept along at about a foot per minute. Van Wagtendonk was struck by the birds’ seemingly nonchalant reaction to the fire: “the fire would be coming, they’d go up like this”—he mimes a bird flapping its wings and rising into the air a few inches as he tells this story— “fire’d go by, and they’d go right back on the nest.”

Many wildfires, he found, were not destructive. They burned slowly, part of the landscape.

After graduating from Oregon State University, van Wagtendonk served in the army as an officer in the 101st Airborne Division and as an advisor to the Vietnamese army. But after four and a half years, he was ready to move on and applied for graduate school, eventually ending up studying fire ecology under Dr. Harold Biswell at UC Berkeley.

Bringing Fire Back to the Forest

Van Wagtendonk began his study of fire ecology just as it was coming into its own as a field and taking forestry by storm. When van Wagtendonk was an undergraduate forestry major, fire ecology was only obliquely mentioned.

Dr. Harold Biswell (L) and Jan van Wagtendonk
Dr. Harold Biswell (L) and Jan van Wagtendonk
NPS sit against a ponderosa pine near a prescribed fire in 1970 in Yosemite National Park. Van Wagtendonk’s dissertation work on prescribed fire in Yosemite around this time led to prescribed burning guidelines still in use in Yosemite today, and a long career in forest and fire science with the federal government.

At the time, he says, “fire had not been truly accepted as an academic discipline, certainly not something you tell people you’ll set.”

Biswell, van Wagtendonk’s graduate school mentor, was something of an outlier. Biswell would conduct prescribed burns and then take students, scientists, ranchers, land managers, and interested citizens out into the field and show them what he was doing.

Those efforts paid off. By 1968, the year that van Wagtendonk began his doctoral dissertation, lessons from fire ecology were starting to reshape federal fire management policy. The National Park Service, in particular, began incorporating prescribed fire programs in recognition of the ecological role of wildfire; other agencies followed suit in the decade that followed.

Van Wagtendonk’s dissertation research played a major role in this transition. Biswell’s guidance for prescribed burning was based on experience.

“He could go out in the woods and snap a twig and say, okay it’s ready to burn,” as van Wagtendonk tells it. That method wouldn’t do if prescribed burning was to be adopted more broadly. For his dissertation, van Wagtendonk set out to quantify Biswell’s prescriptions. Van Wagtendonk conducted his work at Yosemite National Park after being turned down by the Forest Service. The result? A set of guidelines for prescribed burning that are still in use in Yosemite today.

From Wilderness Management to Megafires: A Career at Yosemite

Soon afterwards, van Wagtendonk was offered a job at Yosemite—and 48 years later, he’s still there, first as an employee and now as an emeritus. The decades have brought changes—to fire ecology, to the park, and to federal government science–and lots of fascinating research about fires, forests, and the way people engage with wild places.

In the 90s, van Wagtendonk moved from the National Park Service to the USGS along with many other federal scientists, keeping his home base at Yosemite. He was among the original scientists of the USGS Western Ecological Research Center that served on the founding Science Council under its first Director, Anne Kinsinger, who is currently the USGS Associate Director for Ecosystems. That Council helped form the Center into the outstanding scientific institution that it is today.

Van Wagtendonk’s research over the years has touched on many aspects of fire science. He has developed methods for mapping fuel types, assessed the effects of fire suppression and fuel treatments like prescribed fire, analyzed patterns of lightning strikes, and studied the influence of fire on owls and small mammals. Over the years, van Wagtendonk has incorporated new technology and methods to the study of fire and wilderness, including GIS, remote sensing, and computer modeling, not only using these tools but also publishing highly-cited guidance on using these tools for fire science.

Van Wagtendonk’s work hasn’t been limited to fire research. Early on in his time at Yosemite, he began to study recreation in the park, especially in its backcountry wilderness areas. Backcountry had increased drastically in the 1960s and ‘70s. Van Wagtendonk described the changes in a 1981 paper, writing that in 1972, managers found trampled vegetation, eroded trails, and up to 200 people camped at popular sites. In the 1970s, the park implemented mandatory permit and quota systems for backcountry use that were informed by van Wagtendonk’s research.

Van Wagtendonk has witnessed Yosemite and fire science shift over the decades. In several publications, he’s traced the history of fire policy and management in Yosemite and beyond. Visitor numbers have skyrocketed at Yosemite, and larger wildfires burn in California as the climate warms. In the past two decades, his research has given more attention to today’s megafires and climate change. There’s still a lot to learn about the future of fire.

It can take a long time for new science to really shape management on the ground, but van Wagtendonk marvels at how far we have come, and how much the still-young field of fire ecology has influenced policy already.

“It has been very gratifying to see my work actually be used in park management and beyond,” he says.

Van Wagtendonk has been in Yosemite for 48 years, and still can’t get enough of it. When he’s not working on his writing and research, he loves to hike and backpack the trails.

“I’ve hiked every trail in the park,” he says. “I’ve been backpacking every summer. . . I’m at the point where I’m going back to places I’ve liked the most . . .but I want to be able to keep doing that as long as I can, do it now before my legs give out.”

Jan van Wagtendonk
Jan van Wagtendonk in the Mariposa Grove, Yosemite National Park, approximately 2019. USGS photo.

Thanks and a tip of the hat go out to Jim, Gerald, and Kelly.

Western wildfire smoke plumes are getting taller

Larger plumes send more smoke higher into the atmosphere where it can spread farther

Pyrocumulonimbus cloud Bootleg Fire Oregon
Pyrocumulonimbus cloud over the Bootleg Fire in Oregon, July 14, 2021. InciWeb.

By Paul Gabrielsen
Science writer, University of Utah

In recent years, the plumes of smoke crawling upward from Western wildfires have trended taller, with more smoke and aerosols lofted up where they can spread farther and impact air quality over a wider area. The likely cause is climate change, with decreased precipitation and increased aridity in the Western U.S. that intensifies wildfire activity.

“Should these trends persist into the future,” says Kai Wilmot, a postdoctoral researcher in the Department of Atmospheric Sciences at the University of Utah, “it would suggest that enhanced Western U.S. wildfire activity will likely correspond to increasingly frequent degradation of air quality at local to continental scales.”

The study is published in Scientific Reports and supported by the iNterdisciplinary EXchange for Utah Science, or NEXUS, at the University of Utah.

Smoke height

To assess trends in smoke plume height, Wilmot and University of Utah colleagues Derek Mallia, Gannet Haller and John Lin modeled plume activity for around 4.6 million smoke plumes within the Western U.S. and Canada between 2003 and 2020. Dividing the plume data according to EPA ecoregions (areas where ecosystems are similar, like the Great Basin, Colorado Plateau, and Wasatch and Uinta Mountains in Utah) the researchers looked for trends in the maximum smoke plume height measured during August and September in each region in each year.

In the Sierra Nevada ecoregion of California, the team found that the maximum plume height increased, on average, by 750 ft (230 m) per year. In four regions, maximum plume heights increased by an average of 320 ft (100 m) per year.

Why? Wilmot says that plume heights are a complex interaction between atmospheric conditions, fire size and the heat released by the fire.

“Given climate-driven trends towards increasing atmospheric aridity, declining snowpack, hotter temperatures, etc., we’re seeing larger and more intense wildfires throughout the Western U.S.,” he says. “And so this is giving us larger burn areas and more intense fires.”

The researchers also employed a smoke plume simulation model to estimate the mass of the plumes and approximate the trends in the amount of aerosols being thrown into the atmosphere by wildfires . . . which are also increasing.

The smoke simulation model also estimated the occurrence of pyrocumulonimbus clouds—a phenomenon where smoke plumes start creating thunderstorms and their own weather systems. Between 2017 and 2020, six ecoregions experienced their first known pyrocumulonimbus clouds and the trend suggests increasingly frequent pyrocumulonimbus activity on the Colorado Plateau.

Taller plumes send more smoke up into higher elevations where it can spread farther, says John Lin, professor of atmospheric sciences.

“When smoke is lofted to higher altitudes, it has the potential to be transported over longer distances, degrading air quality over a wider region,” he says. “So wildfire smoke can go from a more localized issue to a regional to even continental problem.”

Are the trends accelerating?

Some of the most extreme fire seasons have occurred in recent years. So does that mean that the pace of the worsening fire trend is accelerating? It’s too early to tell, Wilmot says. Additional years of data will be needed to tell if something significant has changed.

“Many of the most extreme data points fall within the years 2017 -2020, with some of the 2020 values absolutely towering over the rest of the time series,” he says. “Further, given what we know of the 2021 fire season, it appears likely that analysis of 2021 data would further support this finding.”

In Utah’s Wasatch and Uinta Mountains ecoregion, trends of plume height and aerosol amounts are rising but the trends are not as strong as those in Colorado or California. Smoke from neighboring states, however, often spills into Utah’s mountain basins.

“In terms of the plume trends themselves, it does not appear that Utah is the epicenter of this issue,” Wilmot says. “However, given our position as generally downwind of California, trends in plume top heights and wildfire emissions in California suggest a growing risk to Utah air quality as a result of wildfire activity in the West.”

Wilmot says that while there are some things that people can do to help the situation, like preventing human-caused wildfires, climate change is a much bigger and stronger force driving the trends of less precipitation, higher aridity and riper fire conditions across the West.

“The reality is that some of these [climate change] impacts are already baked in, even if we cut emissions right now,” Wilmot adds. “It seems like largely we’re along for the ride at the moment.”