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California’s 2020 fire siege: wildfires by the numbers

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In a year of superlatives, some statistics stand out for California’s 2020 fire year: Four million acres, 112 million tons of greenhouse gases, thousands of lightning strikes, 11 million gallons of fire retardant. And 31 lost lives.

Lea este artículo en  español .

The most telltale number is 4.2 million.

That’s the stop-in-your-tracks figure — the total acreage burned — from last year’s fire siege, the worst year in California’s long history of wildfires.

2020 was a fire year of unforgettable and awful superlatives. In the new world of mega-fires, a series of wildfires exploded late in August with a barrage of lightning and fires that blazed for four months. 

The 4.2 million acres burned last year is equivalent to the entire area of Los Angeles, Orange, Santa Clara and Santa Cruz counties combined.

The state’s first giga-fire — the August Complex — alone consumed one million acres in the northern Coast Range. 

Before the season was over, 31 people, including 3 firefighters, lost their lives.

George Morris III, an assistant regional chief for Cal Fire, dwells on all these numbers. In the middle of last year’s desperate firefight, he was assigned to compile an historical account in part so the agency could learn lessons from the record-breaking season.

Morris wrote a 122-page report that is a compendium of relentless statistics and gripping narratives.

“The number for me is that astonishing 4.2 million acres,” said Morris, who comes from a family of firefighters and who is responsible for six of the state’s 21 fire units. “That is on a scale that has not been experienced in California in at least 100 years. 

“To me, this is the 1910 watershed moment of this century. The Big Burn is what started the wildland fire suppression systems of that century. This one will likely inform the next century.”

The 2020 fire year “is on a scale that has not been experienced in California in at least 100 years.” George Morris III, Cal Fire

The infamous Big Burn was an out-of-control conflagration in the summer of 1910, coalescing thousands of fires that burned 3 million acres in parts of Idaho, Montana, Washington and British Columbia. The fire burned over two days and nights, killed 86 people and ended only with rainfall and snow.

An hour and a half long flight over last summer’s August Complex fire, viewing mile after mile of burned forests, gave Morris a perspective of just how substantial the 2020 fires were. “It was all burning the entire time. Millions of acres,” Morris said. “It’s still hard to believe.”

A hard copy of his Fire Siege report has been placed in every Cal Fire station in the state.

Here are some key numbers pulled from the report:

Something remarkable happened the weekend of August 15, 2020. A storm slammed into central and Northern California, offering fire bosses the hope that the system would produce rain to smother the fire threat in the region.

Quite the opposite occurred. Rather than water raining down on bone-dry forests, the skies lit up with more than 15,000 lightning strikes , sparking  fire after fire. Making matters worse, the dry storm was followed by warm winds, fanning fires in all directions.

“It was a normal fire season until that point,”   Morris said. “Once we hit that lightning siege, it became evident that this was really an historic event.”

Fires grew large and merged into mega-complex blazes, setting up a multi-pronged fire-management nightmare. “Fires were established simultaneously in multiple CAL FIRE Units and national forests,” the report said.

And, in what would become an oft-repeated phrase during the 2020 fire season, “The volume of incidents challenged available resources and immediately strained the California mutual aid system.”

The storm was created by the collision of two powerful weather systems and did produce rain, but high in the atmosphere.

Thunderstorms are not  unusual in California’s mountains, especially during the monsoon season . But thousands of lightning strikes are not common. “It certainly made things difficult,” Morris said.

935 and 193

With fires multiplying and overlapping at an alarming rate, state officials frantically called for help from neighbors. California made 935 requests for assistance; 193 were answered. Not for lack of compassion, but for a dearth of crews and equipment.

California was not alone in experiencing a summer of record fire emergencies. Major wildfires were burning across the West at the same time. Even with the longstanding tradition of mutual aid during emergencies, there was little help to spare .

The report laid out the problem in stark and simple language: “Early in the siege, the demand for resources exceeded supply.”

“After the initial wave of lightning, resources quickly became scarce. Requests outnumbered available resources as initial attack activity outpaced available resources.”

By mid-August, 14,000 firefighters were working in the state, an astounding number but not nearly enough. At the height of the fire siege, 18,500 firefighters battled blazes in California.

Cal Fire scrounged for more people, bringing back retirees and cancelling vacations. “We reached the ceiling of our capacity,” Morris said.

Major fires did not get the personnel they needed, especially in the critical early stages. The “SCU Lightning Complex and CZU Lightning Complex each managed limited resources in the first seven days of the incidents,” the report found. Fire bosses were instructed to do their best with what they had and wait for reinforcements.

Help eventually arrived, with crews driving engines and equipment thousands of miles to get to California fires. Arizona, Idaho, Montana, New Mexico, Texas, Utah, Washington, Kansas and New Jersey sent whatever they could manage.

International fire services sent staff. Fire crews from Mexico, Canada and Israel joined state and federal firefighters, giving relief to those working on fire lines for weeks without a break.

112 million 

Wildfires emit huge amounts of climate-warming gases. In 2019-2020 alone, California fires released an estimated 112 million metric tons of carbon dioxide into the atmosphere, the carbon equivalent of adding 25.4 million cars to California roads. 

Huge clouds of dangerous fine particles, called pm 2.5, also are spewed by wildfires.

The volume of fine particles spewed by California’s wildfires last year was nearly 1.2 million tons, according to the Air Resources Board. That’s more than 120 times the total amount emitted by all of its cars, trucks and buses that same year. 

The volume of fine particles spewed by California’s 2020 wildfires — nearly 1.2 million tons — was more than 120 times the total amount emitted by all of its cars, trucks and buses that year. 

The impact of the smoke is felt far from the flames: It can be seen from space, it blots out the sun thousands of miles away and it is very unhealthy to breathe .

The fine particles can lodge in lungs and have been documented to cause heart attacks and respiratory problems such as asthma attacks. 

Last year’s fires produced the five worst average daily air pollution readings for fine particles ever recorded in California. 

“The simultaneous occurrence of several large wildfires across the State created widespread, long-lasting smoke impacts to the large majority of Californians, regardless of the prevailing wind direction. Maximum fine particle levels persisted in the ‘hazardous’ range of the Air Quality Index (AQI) for weeks in several areas of the State,” the report found.

11 million and 18 million 

California leans heavily on its array of planes, air tankers and helicopters to attack fires, operating the largest airborne civil firefighting fleet in the world .

At the height of the 2020 fire siege, CalFire managed 132 aircraft a day — 44 fixed-wing aircraft and 88 helicopters. The planes delivered 11 million gallons of retardant. The helicopters dropped more than 18 million gallons of water.

The planes ranged from small World War II-era submarine chasers to massive National Guard C-130J cargo-type planes, as well as a DC-10 and a 747 converted passenger jet .

The state also used its new purpose-built Sikorsky S70i Fire Hawk helicopter.  Cal Fire ordered a dozen of the modern fire-fighting helicopters at a cost of $26 million each.

Aviation can be a useful tool in the initial stages of a wildfire. Water drops cool and can slow the progress of the flames. Retardant — colored red or orange so its drop pattern can be easily seen — lays down a chemical perimeter that retards the advancing flames.

 $1 billion

One line in the report stands out as an almost comical understatement: “Unquestionably, the cost of fire protection in 2020 is significantly higher than it was in 1980.”

Indeed. In the 1979-80 fire season, Cal Fire tapped the state emergency fund for about $12 million dollars. For last year’s fires, that figure was in excess of $1 billion.

That’s the emergency money that fills in after the agency exhausts the millions in its appropriated budget. It’s the sock-drawer cash that’s set aside for a rainy —or smoky — day.

Not only are there more frequent and more intense fires, like everything else in California, it costs more to do things than it did forty years ago. And, in the case of firefighting, there’s so many more ways to spend money.

There are more squadrons of planes and helicopters equipped for fires than could have been imagined in 1980, and more sophisticated and expensive technology assisting fire bosses to predict fire-spread and observe fire behavior in real time.

The state’s firefighting force is larger and better paid than four decades ago, and California requires more help from state and federal partners to fight fires at home. 

Larger mega-fires that burn for months, called ‘campaign fires’, are more common. That requires building large-scale fire camps in backcountry with sophisticated facilities to feed, clean, shelter and tend to firefighters when they are off the lines. And massive supply depots replenish equipment and clothing damaged in the field.

Thirty-one  people lost their lives from California’s wildfires in 2020. It’s not the worst-ever total, but it is the third most-deadly year since 2013.

One fire alone, the North Complex, claimed the lives of 15 of those people. The fire was erratic and moved fast, burning 318,000 acres and destroying nearly 2,500 structures. 

In terms of fatalities associated with a single fire, the North Complex is tied as the fifth most deadly . The 2018 Camp Fire , which destroyed the town of Paradise and killed 85 people, remains California’s most deadly fire on record. The Griffith Park fire in Los Angeles in 1933 killed 29 people and the Tunnel fire in the Oakland Hills in 1991 killed 25. The 2017 Tubbs Fire in Napa and Sonoma County killed 22.

For Morris, who is back on the firelines in what he fears could be another dangerous season, these numbers don’t fade away.

“I never thought I would see four million acres burn, or that at the same time that there was a one million-acre fire and there were two fires of 500,000 acres burning,” he said.

“I never thought I would see that. But unfortunately we may see it again. It’s looking to be another challenging season.”

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Julie Cart Environment Reporter

Julie Cart joined CalMatters as a projects and environment reporter in 2016 after a long career at the Los Angeles Times, where she held many positions: sportswriter, national correspondent and environment... More by Julie Cart

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California’s 2020 Wildfire Season

Report summarizes record-breaking fire year and calls for shift in strategy.

• by Kat Kerlin
• May 04, 2022

Quick Summary

• Nearly 9,900 wildfires burned 4.3 million acres in California 2020, twice the previous record
• 2020 was the first year acres burned came close to burn rates before Euro-American settlement
• Study calls for management shift to reduce fire severity, not acres burned

Just over 9,900 wildfires burned about 4.3 million acres in 2020. That’s more than twice the previous record of acres burned in California. Yet it is about average compared to burn rates likely experienced before Euro-American settlement, according to a study from the University of California, Davis, that summarizes the 2020 fire season and examines its drivers.

The study , published in the journal Global Ecology and Biogeography, said 2020 was the first year in recorded history that burned area in California came close to rates seen before the 1800s, when an estimated 3-4 million acres burned in an average year.

Increased fire severity is the far greater concern, the study said. The authors advise that resource and fire managers working in forests shift their emphasis from reducing burned area to reducing fire severity and fire damage to people and property, and restoring key ecosystem functions after fire.

“Although burned area in 2020 was very high, it is not unprecedented if you take the longer view,” said lead author Hugh Safford, a forest and fire ecologist with the UC Davis Department of Environmental Science and Policy and chief scientist at Vibrant Planet, an environmental public benefits corporation. “ The problem is that much of the burning we are seeing now is not restorative but destructive. The need to shift management goals is key, as is understanding the very important role that fuels play in driving fire severity.”

A new measure of success

California is the most fire-prone state in the United States. For the past century the key measure of success among forest managers has been decreased burned area, but that needs to change, according to the study.

The problem is that much of the burning we are seeing now is not restorative but destructive.” - Hugh Safford, UC Davis

Reducing burned area remains an important goal in ecosystems like chaparral and sagebrush in coastal, lowland and eastern California. In these places, frequent fires lead to ecosystem degradation and threaten human safety.

But over the past 40 years, the increases in burned area in California occurred almost entirely in central and northern California forests and woodlands rather than in southern California chaparral, which used to be the poster child for the California “fire problem.” This is even though climate warming has been more extreme in southern California.

Read more stories on climate science

These forests experienced a naturally high frequency of fire before fire exclusion policies in the late 19th and early 20th centuries restricted burns, including from lightning ignitions and Native American cultural burning. Fire exclusion led to a huge increase in forest density and fuels, driving an explosion in large, destructive fires.

“In these ecosystems, reducing burned area is a cause of the current catastrophic trends, not a solution to them,” the authors said.

Key 2020 wildfire statistics

The authors summarized 2020’s burning conditions, burned area and fire sizes, fire weather, fuel moisture, fatalities, property damage, suppression cost data, vegetation types, fire history and other variables from public data sources.

They found that fires in 2020 followed an accelerating, decadeslong trend of increased burn area, severity, size and costs to society and the economy.

The fires killed 33 people in 2020 with overall economic losses of more than $19 billion and firefighting costs approaching $2.1 billion. The years 2020 and 2021 together burned more area than the previous seven years combined, and only slightly less than the total burned between 1980 and 1999.

Between 2015 and 2020, total insured economic losses were more than $50 billion, and over 50,000 structures — mostly homes — were destroyed.

Air quality and wildfires

More than half of Californians experienced unhealthy, and sometimes hazardous, air quality index levels for a month or more in 2020, the study reports. The state’s worst five days of air pollution in history all occurred in 2020, according to CalFire.

Wildfire-driven air quality in August and September likely also caused 1,200 to 3,000 “excess” deaths among people age 65 or older.

The fires emitted nearly 112 million metric tons of carbon and 1.2 million tons of fine particulate matter (PM 2.5). That’s 120 times more fine particulate matter than California’s vehicles produced in the same year.

‘We can do something about this’

The study also assessed what drove fire severity patterns in 2020. Fire severity is a measure of the impact of burning on an ecosystem, measured in this study by losses in vegetation biomass.

Overall, fire severity was best explained by fuel load-related variables, with dryness and wind also playing key roles. Longer-term drought — including its effects on tree mortality before 2020 — was less important overall except in a handful of fires.

Nearly 60% of the fires were caused by humans through arson, vehicles, power lines, campfires or unknown causes, while lightning sparked the rest. However, the lightning-sparked fires burned more than five times the area burned by human-caused fires.

“Extreme weather conditions are certainly playing a role, but climate change isn’t driving all the change we’re seeing,” said Safford. “Fuel loads played a major role in driving fire severity patterns in forested landscapes in 2020, like in other years. High fuel loads are due mostly to human management decisions over the last century or more, and we can do something about this issue.”

The authors said a recent agreement between the state and U.S. Forest Service that seeks to increase fuel-reduction activities is promising, as is the recent California Wildfire and Forest Resilience Action Plan. But, they add, “there is no time to lose.”

Study co-authors include Alison Paulson of UC Davis and the USDA Forest Service, Zachary Steel of UC Berkeley, and Derek Young and Rebecca Wayman of UC Davis.

Media Resources

Media Contacts:

• Hugh Safford, UC Davis Environmental Science and Policy, [email protected]
• Kat Kerlin, UC Davis News and Media Relations, 530-750-9195, [email protected]

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The science behind the West Coast fires

A collection of research and insights from Stanford experts on wildfires' links to climate change, the health impacts of smoke, and promising strategies for preventing huge blazes and mitigating risks.

Wildfires  torched more than five million acres in California, Oregon and Washington in 2020. They killed dozens of people, prompted evacuation orders for hundreds of thousands more and spewed enough toxin-laden smoke to make air conditions hazardous for millions. 

In 2021, wildfires in California alone burned more than 1.7 million acres before the end of August, destroying thousands of structures and forcing mass evacuations.

Tendrils of smoke from fires in the western United States have drifted as far as Europe. As environmental economist Marshall Burke put it in a virtual panel discussion hosted in September 2020 by Stanford’s Woods Institute for the Environment , “This is not just a U.S. West Coast issue, this is a nationwide issue.”

As the fires burn, they are unlocking huge amounts of carbon dioxide from soils and plants and launching it into the atmosphere. 

Six of the seven largest fires on the modern record in California ignited in 2020 or 2021, and most of the largest fires in the state’s history have occurred in the past two decades. Scientists say global warming and decades of fire suppression have helped lay the groundwork for the devastating blazes. One study by Stanford researchers estimated as much as 20 million acres in California would benefit from vegetation thinning or prescribed burns.  Another  found that the risk of extreme wildfire conditions during autumn has more than doubled across California over the past four decades, and human-caused global warming has made the changes more likely.

This collection covers how scientists are unraveling the factors that contribute to wildfire risk, understanding their impacts and developing solutions. Scroll down for wildfire research news and insights related to climate change , health impacts , prevention and mitigation , prediction and modeling and more.

Last updated: August 31, 2021

Climate change

Back to top

Longer, more extreme fire seasons

A study led by Stanford scientists shows autumn days with extreme fire weather have more than doubled in California since the early 1980s due to climate change.

What to expect from future wildfire seasons

The new normal for Western wildfires is abnormal, with increasingly bigger and more destructive blazes.

Wildfire weather

Stanford climate and wildfire experts discuss extreme weather’s role in current and future wildfires, as well as ways to combat the trend toward bigger, more intense conflagrations.

Climate change has its ‘thumb on the scale’ of extreme fire

“Humans are ingenious at managing climate risk, but our systems are built around the historical climate,” climate scientist Noah Diffenbaugh told  The Washington Post .  “Systems that were built for the old climate are being stressed in a new way.”

(Image credit: Sheila Sund / Flickr )

Shifting biomes

“In a changing climate it’s not just about continuing to manage the risk of ignition. We also need to recognize that we are dealing with biome shifts that will occur through time," said Chris Field, director of Stanford's Woods Institute for the Environment . Read more in the National Geographic article, " How much are beetles to blame for the 2020 fires? "

Wildfire emissions

“The forests are alive. They’re growing and dying and regrowing,” says Michael Wara, director of the climate and energy policy program at the Woods Institute for the Environment. “That’s really different than carbon that was buried 50 million years ago under the earth that we are unearthing and burning. I think it’s not helpful to compare the two. It’s a misdirection.”

Wildfire smoke worse for kids' health than smoke from controlled burns

Immune markers and pollutant levels in the blood indicate wildfire smoke may be more harmful to children’s health than smoke from a controlled burn.

California wildfires bring questions about health and climate

What does smoke inhalation do to my health? What’s the evidence that these are caused by climate change? Here is how some Stanford experts answer and continue to tackle these complex concerns.

Wildfires' health impacts

California’s massive wildfires bring a host of health concerns for vulnerable populations, firefighters and others. Kari Nadeau and Mary Prunicki of Stanford’s Sean N. Parker Center for Allergy and Asthma Research discuss related threats, preparedness and ongoing research.

Mask confusion

"Only certain masks are effective during wildfires, while a range of face coverings may help prevent coronavirus transmission," Stanford researchers write in Environmental Research Letters . Drawing on human behavior studies and past responses to epidemics and wildfire smoke, the scientists recommend ways to communicate mask-use guidance more effectively.

An unexpectedly huge toll on America's lungs

As wildfires become more frequent due to climate change, the increasing amounts of smoke may harm Americans nearly as much as rising temperatures, according to a working paper by Stanford environmental economist Marshall Burke and colleagues. “We hadn’t even thought of that as a key part of the climate impact in this country,”  Burke told Bloomberg .

Wildfire smoke is poisoning California's kids. Some pay a higher price.

Marshall Burke, an economist at Stanford, has found that, across California, as the number of smoke days has risen over the past 15 years, it has begun to reverse some of the gains that the state had made in cleaning up its air from conventional sources of pollution.

The shifting burden of wildfires in the United States

Wildfire smoke will be one of the most widely felt health impacts of climate change throughout the country, but U.S. clean air regulations are not equipped to deal with it. Stanford experts discuss the causes and impacts of wildfire activity and its rapid acceleration in the American West.

Tips to protect against wildfire smoke

Warnings of another severe wildfire season abound, as do efforts to reduce the risk of ignition. Yet few are taking precautions against the smoke. Stanford experts advise on contending with hazardous air quality.

Wildfire smoke can increase hazardous toxic metals in air, study finds

Smoke from wildfires – particularly those that burn manmade structures – can significantly increase the amount of hazardous toxic metals present in the air, sending up plumes that can travel for miles, a new study from the California Air Resources Board has suggested. "No one is protected," said Mary Prunicki of Stanford’s Sean N. Parker Center for Allergy and Asthma Research.

How do people respond to wildfire smoke?

Interviews with Northern California residents reveal that social norms and social support are essential for understanding protective health behaviors during wildfire smoke events – information that could be leveraged to improve public health outcomes.

Wildfire smoke exposure during pregnancy increases preterm birth risk

Smoke from wildfires may have contributed to thousands of additional premature births in California between 2007 and 2012. The findings underscore the value of reducing the risk of big, extreme wildfires and suggest pregnant people should avoid very smoky air.

Prevention and mitigation

Setting fires to avoid fires.

Analysis by Stanford researchers suggests California needs fuel treatments – whether prescribed burns or vegetation thinning – on about 20 million acres or nearly 20 percent of the state’s land area.

A new treatment to prevent wildfires

Scientists and engineers worked with state and local agencies to develop and test a long-lasting, environmentally benign fire-retarding material. If used on high-risk areas, the treatment could dramatically cut the number of fires that occur each year.

Wildfire preparedness

Experts with Stanford's Woods Institute for the Environment discuss strategies for managing wildfire risks, including incentive structures, regulations, partnerships and financing.

Mitigating risks with law and environmental policy

"In talking about risks and policy prescriptions, we need to separate out wildfires at the wildland-urban interface – those that put people and communities at most risk – from fires that historically have burned through our remote forestlands," said Deborah Sivas , Director of Stanford’s Environmental Law Clinic. 

Concrete steps California can take to prevent massive fire devastation

"Successful wildfire preparedness begins with a clear strategy and accountability for outcomes," writes Michael Wara, director of the Climate and Energy Policy Program at Stanford's Woods Institute for the Environment.

Are forest managers robbing the future to pay for present-day fires?

"As fires burn with greater magnitude and frequency, the cost of fighting them is increasingly borne by money earmarked for prevention," writes  Bill Lane Center for the American West writer in residence Felicity Barringer.

Policy brief

Managing the growing cost of wildfire.

Stanford experts review recent trends in wildfire activity, quantify how the smoke from these wildfires is affecting air quality and health across the U.S. and discuss what policymakers can do to help reduce wildfire risk.

California burning

Heat waves that could melt the fat in uncooked meat until it would “run away in spontaneous gravy.” Forests that turned abruptly into “great sheets of flame.” These are some of the realities of life in California noted by the botanist William Brewer in 1860, and surfaced in an essay for  The New Yorker by Stanford Classics professor Ian Morris about being evacuated from his home in the Santa Cruz mountains.

According to Morris, "Before Europeans came, Native Californians had found ways to cope with this reality. Many moved seasonally, partly to avoid forest fires. As much as one-sixth of the state was deliberately burned each year." Not many people lived in places like the Santa Cruz Mountains until the 1870s. Since then, Morris wrote, the "quiet migration of hundreds of thousands of nature lovers has created one of the most unnatural landscapes on Earth."

Preparing together

"We need programs that emphasize and support herd immunity from fires," Rebecca Miller, a PhD student in the Emmet Interdisciplinary Program in Environment and Resources, told  Mic . Rebuilding efforts after a fire, she added, ought to recognize that once-burned neighborhoods are likely to burn again.

Fire burned the Coffey Park neighborhood of Santa Rosa, Calif. in October 2017. (Image credit: Sgt. 1st Class Benjamin Cosse / California National Guard)

Prediction and modeling

Mapping dry wildfire fuels with ai and new satellite data.

Stanford researchers have developed a deep-learning model that maps fuel moisture levels in fine detail across 12 western states, opening a door for better fire predictions.

Predicting wildfires with CAT scans

Engineers at Stanford have used X-ray CT scans, more common in hospital labs, to study how wood catches fire. They’ve now turned that knowledge into a computer simulation to predict where fires will strike and spread.

Satellite imagery shows hot spots and thick smoke plumes from wildfires burning in Oregon and northern California on Sept. 8, 2020. (Video credit: NOAA)

Stanford Wildfire Research

Find experts, events, information about ongoing research projects and more.

Stanford Wildfire News

Read the latest wildfire coverage from Stanford News.

Media Contacts

Josie Garthwaite School of Earth, Energy & Environmental Sciences (650) 497-0947;  [email protected]

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• Original research
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• Published: 19 January 2024

Air quality and health impacts of the 2020 wildfires in California

• Marc Carreras-Sospedra   ORCID: orcid.org/0000-0001-7038-1468 1 ,
• Shupeng Zhu 1 , 2 ,
• Michael MacKinnon 1 ,
• William Lassman 3 ,
• Jeffrey D. Mirocha 3 ,
• Michele Barbato 4 &
• Donald Dabdub 1  

Fire Ecology volume  20 , Article number:  6 ( 2024 ) Cite this article

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Metrics details

Wildfires in 2020 ravaged California to set the annual record of area burned to date. Clusters of wildfires in Northern California surrounded the Bay Area covering the skies with smoke and raising the air pollutant concentrations to hazardous levels. This study uses the Fire Inventory from the National Center for Atmospheric Research database and the Community Multiscale Air Quality model to estimate the effects of wildfire emissions on air quality during the period from August 16 to October 28 of 2020. In addition, low-cost sensor data for fine particulate matter (PM 2.5 ) from the PurpleAir network is used to enhance modeled PM 2.5 concentrations. The resulting impacts on ozone and PM 2.5 are used to quantify the health impacts caused by wildfires using the Benefits Mapping and Analysis Program – Community Edition.

Wildfire activity significantly increased direct PM 2.5 emissions and emissions of PM 2.5 and ozone precursors. Direct PM 2.5 emissions surged up to 38 times compared to an average day. Modeling results indicated that wildfires alone led to a rise in ozone daily maximum 8-h average by up to 10 ppb and exceeded PM 2.5 air quality standards in numerous locations by up to 10 times. While modeled PM 2.5 concentrations were lower than measurements, correcting these with PurpleAir data improved the accuracy. The correction using PurpleAir data increased estimates of wildfire-induced mortality due to PM 2.5 exposure by up to 16%.

Conclusions

The increased hospital admissions and premature mortality attributed to wildfires were found to be comparable to the health impacts avoided by strategies aimed at meeting ozone and PM2.5 air quality standards. This suggests that widespread wildfire emissions can negate years of efforts dedicated to controlling air pollution. The integration of low-cost sensor data proved invaluable in refining the estimates of health impacts from PM2.5 resulting from wildfires.

Antecedentes

Los incendios de vegetación en 2020 devastaron California, fijando el récord anual de área quemada hasta el presente. Ese año, múltiples grupos de incendios en el norte de California rodeaban el área de la Bahía (Bay Area), cubriendo los cielos de humo y elevando las concentraciones de contaminantes hasta niveles peligrosos. Este estudio usó el Inventario de Incendios de la base de datos del Centro Nacional para Investigaciones de la Atmósfera y del modelo Comunitario Multiescalar sobre la Calidad del Aire, para estimar los efectos de las emisiones de incendios sobre la calidad del aire desde el 16 de agosto hasta el 28 de octubre de 2020. Adicionalmente, el sensor de bajo costo para determinar el particulado fino (PM2.5), tomado de la red PurpleAir, fue usado para mejorar el modelado de concentraciones de PM2.5. Los impactos resultantes en el ozono y PM2.5 fueron usados para cuantificar los impactos en la salud causados por los incendios de vegetación, usando el Programa Beneficios del Mapa y Análisis - Edición de la Comunidad.

La actividad de los incendios incrementaron significativamente las emisiones directas de PM2.5 y los precursores de las emisiones de PM2.5 y ozono. Las emisiones directas de PM2.5 resultaron hasta 38 veces más altas comparadas con un día normal. Los resultados modelados indicaron que los incendios por sí mismos llevaron a un aumento del ozono diario máximo 8 horas en promedio y por 10 ppb, y excedieron los estándares de calidad del aire debido al PM2.5 en numerosas ubicaciones y por hasta 10 veces. Mientras que los valores modelados del PM2.5 fueron más bajos que las mediciones, la corrección de esos valores con el PurpleAir mejoraron su exactitud. Las correcciones usando datos de PurpleAir incrementaron las estimaciones de la mortalidad debida a la exposición de PM2.5 en un 16%.

Conclusiones

El incremento en las admisiones en los hospitales y las muertes prematuras atribuidas a los incendios de vegetación fueron encontradas comparables a los impactos en la salud evitados mediante estrategias enfocadas a alcanzar los estándares de calidad del aire para el ozono y el PM2.5. Esto sugiere que las emisiones generalizadas de los incendios pueden anular años de esfuerzos dedicados a controlar la contaminación del aire. La integración de datos del sensor de bajo costo probó ser muy valiosa para refinar las estimaciones de los impactos en la salud provenientes del PM2.5 resultante de los incendios.

The year 2020 saw the largest area burned due to wildfires in California in recorded history (Fig. 1 ) and included 5 of the top 7 largest wildfires ever recorded in California. More than 1.7 million hectares burned in 8648 incidents, and 33 people perished as a direct result of the fires (CalFire 2022 ). The largest fires started in mid-August, clustering across northern California and around the Bay area, which famously turned San Francisco daylight skies into an apocalyptic orange twilight for several days. Because of the large and widespread fires, the state experienced long episodes of elevated fine particulate matter (PM 2.5 , i.e., particulate matter with diameter smaller than 2.5 micrometers) concentrations (Li et al., 2021 ). Exposure to elevated concentrations of PM 2.5 is linked to increased respiratory and cardiovascular illnesses and can lead to increased mortality (Atkinson et al. 2014 , Brook et al., 2010 ).

Recorded area burned in wildfire events by year in California. (Source: CalFire, 2022 )

Prior research has investigated the effects of recent wildfires on air quality and public health through two primary methodologies. One approach involves employing wildfire emissions and chemical transport models to simulate the contribution of wildfires to PM 2.5 levels, as demonstrated by studies conducted by Shi et al. ( 2019 ) and Lassman et al. ( 2023 ). The other method utilizes direct measurements obtained from ground-based or satellite observations to map pollutant concentrations and subsequently estimates the portion attributed to wildfires, as seen in research by Wang et al. ( 2021 ) and Enayati Ahangar et al. ( 2022 ).

Shi et al. ( 2019 ) specifically examined the impact of wildfires in Southern California in December 2017, utilizing various satellite-based techniques and a chemical transport model to estimate wildfire emissions and their influence on PM 2.5 concentrations and population exposure. Their study revealed that exposure to PM 2.5 induced by wildfires in December accounted for over 40% of the total annual PM 2.5 exposure in certain locations. Lassman et al. ( 2023 ) used a chemical transport model to compare two different wildfire emission schemes that are used by the air quality modeling community: the Fire Inventory from the National Center for Atmospheric Research (FINN, Wiedinmyer et al., 2011 ) and the Surface Fire model (SFIRE, Mandel et al., 2012 ). Although SFIRE provided a more accurate representation of fire location and timing, the resulting PM 2.5 modeling outcomes were only marginally more accurate than those obtained using FINN when compared to measured values of PM 2.5 .

In another study, Wang et al. ( 2021 ) utilized a combination of monitoring and satellite data to map PM 2.5 concentrations in California during the latter half of 2018. This research used low-resolution fire emissions and chemical transport models and assessed the direct and indirect economic impacts and capital losses incurred due to wildfire disruptions.

Enayati Ahangar et al. ( 2022 ) explored PM 2.5 concentration mapping over California's San Joaquin Valley in late summer and fall of 2020, utilizing regulatory monitors and low-cost sensors from the PurpleAir sensor network (PurpleAir, 2022 ). PurpleAir sensors use a low-cost technology to estimate concentrations of particulate matter and data is reported in real time to the PurpleAir website. Enayati Ahangar et al. employed a trajectory model to quantify the contribution of wildfires to total PM 2.5 concentrations, utilizing fire emissions estimates derived from satellite observations. Kramer et al. ( 2023 ) used data from regulatory monitors and PurpleAir sensors and used various interpolation techniques to estimate exposure to wildfire-induced pollution in Northern and Southern California.

The goal of this study is to estimate the impact of wildfire emissions on air quality and public health in California from mid-August to late October in 2020. The methodology in this study integrates two approaches mentioned above. Specifically, it combines a wildfire emissions inventory and a comprehensive chemical transport model with ground-based observations to gauge the influence of wildfires on air pollution. Ground-based monitoring data are employed to refine the PM 2.5 model estimates, thereby enhancing our understanding of the effects of wildfire emissions on PM 2.5 concentrations and population exposure. Furthermore, the air quality impacts resulting from wildfires are assessed in terms of health using the Benefits Mapping and Analysis Program – Community Edition model (BenMAP-CE, U.S. EPA, 2021 ).

2020 fire season

This study focuses on the period between August 16 and October 28, 2020. Initially, this period was marked by a series of wildfires in the northern portion of the state, primarily ignited by lightning strikes. These fires began as small, isolated, and scattered incidents but rapidly evolved into substantial fire complexes that persisted for weeks. The fire complexes, as depicted in Fig. 2 , included the August, Sonoma-Lake-Napa Unit (LNU), San Mateo-Santa Cruz Unit (CZU), Santa Clara (SCU), and the Butte/Tehama/Glenn (BTG) lightning complexes. Among these large wildfires, the August complex became the largest wildfire ever recorded in California. In early September, the Creek fire developed quickly in the Sierras producing a large pyrocumulonimbus cloud that reached altitudes of more than 15,000 meters above sea level. Around the same time, the El Dorado fire broke out in Southern California. At the end of October, fanned by strong Santa Ana winds, the Silverado and Blue Ridge fires ignited. In addition to in-state wildfires, large wildfires that originated in Oregon also contributed to air pollution in California, as satellite images (NASA Worldview 2020 ) showed smoke being transported southwards and reaching the San Francisco Area around mid-September.

Cumulative PM 2.5 emissions from wildfires during the period August 16–October 28, 2020

The modeling framework, illustrated in Fig. 3 , comprises multiple models designed to estimate different factors and processes related to air pollution formation. These models calculate the resulting impacts on both air quality and public health and are described in more detail in this section. In general terms, the framework includes a meteorological model to assess the weather conditions during the modeling period, models to estimate anthropogenic, biogenic, and wildfire emissions, and a chemical transport model to analyze the formation and transport of air pollutants. Additionally, data from PurpleAir sensors are utilized to assess and refine certain correction methods for air pollution estimates. Finally, a comprehensive model is employed to evaluate the health effects of air pollution induced by wildfires. Specific details on each individual model are described below.

Diagram of the modeling setup for this study. Emissions and meteorological inputs are used to run the air quality model. Low-cost sensor data is used to analyze potential correction methods, and adjusted results are used to calculate potential health impacts using the health impact model.

The modeling period spanned from August 16 to October 28, 2020. Meteorology fields for the study period were generated using the WRF model, version 4.2.1 (Skamarock et al. 2019 ). The model was initialized with the National Center for Environmental Prediction Final (NCEP FNL) Operational Global Analysis data (NCEP 2021 ) and was run in nested mode with two domains: the outer domain at a 12-km grid resolution and the inner domain at a 4-km grid resolution. The model was run in staggered periods of 5 days, with modeling being reinitialized by reanalysis data every 3 days. The first 2 days were used for spin-up, and the remaining 3 days were used for air quality modeling. The following physics options were selected: (1) Purdue Lin scheme microphysics (Chen and Sun 2002 ), (2) YSU planetary boundary layer (PBL) scheme (Hong, Noh and Dudhia 2006 ), (3) NOAH land-surface (Campbell et al. 2019 ), (4) Grell G3D cumulus parameterization (Grell and Devenyi 2002 ), and (5) Rapid Radiative Transfer Model (RRTM) longwave (Mlawer et al. 1997 ) with Goddard shortwave radiative transfer schemes (Matsui et al. 2020 ).

Air quality was modeled using the Community Multiscale Air Quality model (CMAQ, Byun and Schere, 2006 ), version 5.3.2. Version 5.3.2 includes minor bug fixes with respect to version 5.3.1, which was documented and validated by Appel et al. ( 2021 ). Initial and boundary conditions were derived from concentration fields from the Whole Atmosphere Community Climate Model (WACCM) configuration of the Community Earth System Model 2 (CESM2) (Gettelman et al. 2019 ).

Anthropogenic emissions were derived from the California Air Resources Board’s (CARB) emissions inventory. Area and off-road emissions were spatially resolved using source-specific spatial surrogates developed by CARB. On-road emissions were generated using CARB’s on-road emissions model EMmission FACtor (EMFAC) (EMFAC2017, CARB 2020 ) and spatially allocated using the Emissions Spatial and Temporal Allocator (ESTA) (CARB 2021 ). Dust and biogenic emissions were calculated inline in CMAQ. Inline biogenic emissions were based on the Biogenic Emissions Inventory System version 3.61, which used the Biogenic Emissions Land-use Database (version 3) with 1-km resolution (U.S. EPA, 2016 ).

Fire emissions were developed based on FINN version 1.5 (Wiedinmyer et al. 2011 ). Fire emissions included trace gas and particle emissions from open burning of biomass, which accounts for wildfires, agricultural fires, and prescribed burning. The emissions were estimated using satellite observations of fire detections and vegetation density from the moderate resolution imaging spectroradiometer (MODIS) instruments, land cover data, and emission factors specific for each type of land use/land cover. Resolution of fire emissions is 1 km, and their chemical speciation was converted to the Statewide Air Pollution Research Center (SAPRC)-07 chemical mechanism. The daily average and daily maximum wildfire emissions during the modeling period are shown in Table 1 , along with average and maximum daily anthropogenic emissions. On average, wildfires emitted nitrogen oxides (NO X ) at a comparable rate to that of anthropogenic emissions, whereas reactive organic gas (ROG) emissions from wildfires were more than five times higher than those from anthropogenic sources. NO X and ROG are precursors to ozone formation and secondary PM 2.5 . Wildfires also emitted significantly more PM 2.5 precursors such as sulfur oxides (SO X ) and ammonia (NH 3 ) than anthropogenic sources. Finally, direct emissions of PM 2.5 from wildfires were nearly nine times larger than those from anthropogenic sources. The day with the highest emissions was September 9, 2020, when the August Complex Fire and the Creek Fire were at their peak. In that day, PM 2.5 emissions from wildfires were 38 times the average emissions from anthropogenic sources. Overall, wildfires contributed severely to air pollutant emissions and impacted the air quality across large areas in the state.

The air quality modeling evaluation for ozone and PM 2.5 was based on observations extracted from the Air Quality System (AQS) database. A total of 172 stations measuring ozone and 120 stations measuring PM 2.5 were included in the analysis. The overall model performance is evaluated based on the following statistical parameters: mean bias (MB), mean error (ME), mean normalized bias (MNB), and mean normalized error (MNE). These parameters are defined as follows (Emery et al., 2017 ):

in which P j denotes model prediction on day j , O j denotes observed concentration on day j , and N is the total number of observed data points.

This study used data from PurpleAir sensors, which constitute a large network of low-cost monitors that measure particle pollution, to enhance the modeling of PM concentrations. PurpleAir sensors use laser technology to count suspended particles that range from 0.3 to 10 μm. The particle counts are then processed by a complex algorithm to calculate PM 10 , PM 2.5 , and PM 1.0 mass concentration (PurpleAir, 2022 ). Due to the limitations in low-cost sensor technology, bias in PM concentrations measured by PurpleAir sensors is expected. Previous studies analyzed the performance of PurpleAir sensors collocated with regulatory monitors, and correction factors using ambient meteorological parameters have been proposed. The United States Environment Protection Agency (U.S. EPA) analyzed many complex correction schemes and suggested that a simple linear correction using ambient relative humidity provides a good approximation at a national level (Barkjohn et al. 2021 ). Shulte et al. ( 2020 ) also proposed binning the correction algorithm into two spaces of low and high PM 2.5 concentrations and including seasonality as an additional correction parameter.

This study used data from 5661 outdoor sensors spread throughout California and calculated the correction factors based on daily PM 2.5 observations from 120 reference monitors. Sensors that were within 0.02°radius (~2 km) from regulatory monitors were used to calculate the linear correction parameters following the approach proposed by Barkjohn et al. ( 2021 ) and the concentration binning used by Schulte et al. ( 2020 ) for two models: one for concentrations below 35 μg/m 3 and the other for concentrations equal or above 35 μg/m 3 .

The linear correction scheme obtained using measurements from the period August 16 to October 28 was as follows:

in which PA denotes the PurpleAir PM 2.5 data and RH denotes the relative humidity.

Two approaches were employed to interpolate PurpleAir corrected measurements and to blend them with modeling results: (1) using inverse squared distance weighting for PurpleAir measurements and model gradient adjustment based on the modeled daily PM 2.5 values from the simulation that includes fire emissions and (2) using kriging of the model-to-measured ratios.

Inverse squared distance weighting (ISDW) for PurpleAir measurements with model gradient adjustment

Inverse distance weighting is commonly used as an interpolation method to estimate concentration maps of air pollutants based on monitoring data. For example, inverse distance weighting is used by the Software for Model Attainment Test – Community Edition (SMAT-CE) developed by the U.S. EPA to determine attainment status over unmonitored areas (U.S. EPA, 2022 ). While the recommended exponent of the inverse distance weights can vary depending on the application (de Mesnard, 2013 ), the SMAT-CE model uses inverse squared distance weighting as the default option.

In this study, once all the daily PM 2.5 were corrected, daily PM 2.5 concentration maps were generated using interpolated PurpleAir measurements at the 4 km by 4 km grid level using inverse square distance weighting and gradient adjustment based on the modeled daily PM 2.5 values from the simulation that included fire emissions. The PurpleAir sensors used in the interpolation were limited to the ones within a radius of 40 km from each cell centroid. Modeled values were also included as artificial monitors to constrain grid cells that are far from monitors to concentrations informed by the modeled results. The expression used to calculate the Purple Air concentration maps is as follows:

where C i, fires is PM 2.5 concentration in cell i , D k is the distance of sensor k to cell i , PA k is corrected PurpleAir PM 2.5 concentration from sensor k , and Mod i, fires and Mod k, fires are the modeled daily PM 2.5 concentration in cell i and at sensor location k , respectively. The distance, D k , is expressed in terms of discreet cell lengths, where sensors in cell i have D k =1, and every increment in cell distance is added as integer values.

Kriging of model-to-measured ratios

Kriging is an advanced geostatistical procedure that generates an estimated surface from a scattered set of points by performing a regression that produces a least-squares estimate of the data (Remy et al., 2011 ). Kriging has been used to interpolate measured pollutant concentrations to determine air pollution exposure (Lassman et al., 2017 , Yu et al., 2018 , Kramer et al., 2023 ). Yu et al. ( 2018 ) compared various methods of interpolation for air pollution field estimations and suggested the blending of measured and modeled data by using ordinary kriging of the ratios of modeled-to-observed concentrations. We constructed the experimental semivariogram for each individual day with the ratios of modeled daily PM 2.5 over observed daily PM 2.5 . We tested three different semivariogram models: spherical, gaussian, and exponential. Based on the sum of the squared of the residuals between the experimental semivariogram and the model, the spherical and gaussian models resulted in the best fit.

Conversely, the estimated concentration maps adjusted to PurpleAir data without the impact of wildfires were calculated as follows:

where C i, nofires is the PurpleAir-adjusted concentration without the contribution of wildfires in cell i and Mod i, nofires is the modeled daily PM 2.5 concentration without wildfire emissions in cell i .

BenMAP-CE version 1.5 was used to estimate the increase incidence of health end points due to wildfires (U.S. EPA, 2021 ). BenMAP-CE converts air pollutant concentration increments into health impacts with the use of concentration-response (C-R) functions. C-R functions are derived from epidemiology studies and provide the relation between a change in pollutant concentration and an increase in the incidence of a given health impact indicator from a baseline incidence rate. Baseline incidence rates for this study are based on values developed in earlier analysis for Southern California (South Coast AQMD 2017a ) and later used to determine the health and economic impacts from California fires in 2018 (Wang et al. 2019 ). Information on the concentration-response functions used in this study are summarized in Table 2 and their respective function forms are described in Table 3 . In general, the functions depend on population ( P ), rate of incidence of a particular health end point ( I ), change in concentration of a pollutant ( ΔC ), and fitting parameters A and β . The baseline function represents the reference value of incidence of a particular health end point (e.g., hospital admission, death) with a zero change in air pollutant concentrations. The concentration-response function calculates an increase in incidence of a particular health end point due to a change in pollutant concentration (Δ C ).

Air quality modeling results and model performance

Model performance is presented in Table 4 . The model overestimated ozone concentrations, most notably along coastal stations, with better performance in stations in the eastern portion of the Los Angeles Basin and in the Central Valley, where ozone concentrations are typically the highest (Fig. 4 a). Generally, PM 2.5 concentrations were underpredicted throughout the state, in part possibly due to the model inability to capture fully the effects of wildfires. As shown in Fig. 4 b, the largest PM 2.5 underpredictions occurred east of the San Francisco Bay Area, which was highly impacted by wildfire smoke throughout the wildfire season.

Mean normalized bias (MNB) during the modeling period for a daily maximum 8-h ozone (DMAO 3 ) and b daily PM 2.5 . Values are normalized with observations, as described in Eqs. 3 – 4 .

Results presented in this study for PM 2.5 are consistent with the negative biases reported for CMAQ version 5.3.1 for California (Appel et al., 2021 ). Appel et al. ( 2021 ) reported model performance of CMAQ version 5.3.1 for the continental US in 2016 at 12 km resolution. Although in 2016 only moderate wildfire activity was recorded in California, the model performance was characterized by biases contained between +4% and −8% for ozone and consistently negative and as low as −30% for PM 2.5 , like the biases shown in the present study. It is also likely that the exceptionally high wildfire activity recorded during the modeling period considered in this study may have negatively affected CMAQ’s ability to reproduce observed PM 2.5 concentrations.

An alternate method to evaluate model performance is to determine the model capability to predict exceedances with respect to U.S. EPA’s national ambient air quality standards (NAAQS). Fig. 5 presents scatter plots of modeled versus observed concentrations for daily maximum 8-h ozone and daily PM 2.5 . The lines indicating each respective standard delineate four quadrants that define the model fitness to predict exceedances. Each subfigure in Fig. 5 shows from top right and clockwise: true positive, false negative, true negative, and false positive. The true positive rate (TPR) is the ability of the model to detect exceedances compared to observations. Conversely, the true negative rate (TNR) is the ability of the model to detect concentrations below the standard. The false negative rate (FNR) and the false positive rate (FPR) are the complementary values of TPR and TNR, respectively. In general, the model performed better when predicting exceedances for ozone, with TPR = 55%, than for PM 2.5 , with TPR = 46%, in part because the model showed a positive bias for ozone and a negative bias for PM 2.5 .

Comparison of observations and modeled concentrations for a daily maximum 8-h average of ozone and b daily average PM 2.5 . Diagonal shows the 1:1 modeled vs. observed ratio, and the vertical and horizontal lines show the National Ambient Air Quality Standards level for daily maximum 8-h average of ozone (70 ppb) and daily average PM 2.5 (35 μg/m 3 ). The true positive rate (TPR) is the ability of the model to detect exceedances compared to observations. The true negative rate (TNR) is the ability of the model to detect concentrations below the standard. The false negative rate (FNR) and the false positive rate (FPR) are the complementary values of TPR and TNR, respectively.

Contribution of wildfire emissions to air pollution

An additional air quality model simulation without including wildfire emissions was conducted for the same period between August 16 and October 28, 2020, to quantify the impact of wildfires on ozone and PM 2.5 . Figure 6 shows the overall increase in daily maximum 8-h ozone and daily PM 2.5 attributed to wildfire emissions during the modeling period and the relative increase with respect to the simulation without wildfire emissions. The impact of wildfires was localized over the northern half of the state, near the location of the wildfires in Northern California. On average, daily maximum 8-h ozone concentrations increased by up to 10 ppb, and many of the largest increases occurred in areas where ozone concentrations are typically high. In relative terms, daily maximum 8-h ozone concentrations increased on average by up to 20% in some northern California locations. Some stations experienced increases in daily maximum 8-h ozone of over 70 ppb in the third week of August, which suggests that wildfire emissions alone led to exceeding the ozone standard. On average, the daily PM 2.5 concentration increased by up to 39 μg/m 3 , which for some stations represented an increase of more than 400% over normal average values. For instance, some stations experienced increases of over 350 μg/m 3 during the third week of August. Thus, considering that the NAAQS for daily PM 2.5 is 35 μg/m 3 , on average, many stations exceeded the daily PM 2.5 due to wildfire emissions alone, and stations experienced daily PM 2.5 over ten times higher than the daily PM 2.5 standard during several days.

Overall contribution of wildfires during the modeling period to a increase in daily maximum 8-h ozone (DMAO 3 ), b increase in daily PM 2.5 , c percentage increase in DMAO 3 , and d percentage increase in daily PM 2.5 with respect to the case without fires.

Figures 7 and 8 show the daily variation in PM 2.5 emissions, the observed and modeled daily PM 2.5 concentrations, and daily contribution of fires to total daily PM 2.5 for the periods of August 16–September 21 and September 22–October 28, respectively. PM 2.5 concentrations were particularly underpredicted during the period of September 10–16, trailing the days with the highest emission increases due to wildfires. In addition, based on satellite images, that period was affected by wildfire smoke that originated from wildfires in Oregon, which were not included in the modeling setup. As a result, the impact from wildfire emissions is believed to be underrepresented in the second week of September, and overall, modeling results suggest that the effects of wildfires on daily PM 2.5 presented here are underpredicted.

Contribution of fires to daily PM 2.5 by day (August 16–September 21): a total daily PM 2.5 emissions from wildfires from FINN, b observed and modeled daily PM 2.5 concentrations, and c modeled contribution of fires to total daily PM 2.5 . Whisker/box plot shows the minimum, 1st quartile, median, 3rd quartile, and maximum. Markers show outliers, which are defined as points that are more than 1.5 times the interquartile range (IQR, namely the height of the box) away from the top or bottom of the box.

Contribution of fires to daily PM2.5 by day (September 22–October 28): a total daily PM 2.5 emissions from wildfires from FINN, b observed and modeled daily PM 2.5 concentrations, and c modeled contribution of fires to total daily PM 2.5 . Whisker/box plot shows the minimum, 1st quartile, median, 3rd quartile, and maximum. Markers show outliers, which are defined as points that are more than 1.5 times the interquartile range (IQR, namely the height of the box) away from the top or bottom of the box.

Biomass burning modeled in this study is a major source of atmospheric organic aerosol, typically referred to as brown carbon. Wildfires and brown carbon contribute to the planetary radiative balance and to the formation of secondary organic aerosol, although there are still model limitations in our understanding of the atmospheric transformations of brown carbon (Wong et al. 2019 ). Figures 9 and 10 present modeled daily concentrations of organic matter (OM) with and without the contribution from wildfires for the periods of August 16–September 21 and September 22–October 28, respectively. They also show that, on average, secondary OM corresponds to more than 90% of the total OM, although the percentage of secondary OM in wildfire-driven OM is slightly smaller than that without the presence of fires because of the large contribution from direct OM emissions. Overall, results suggest that wildfires more than doubled the fraction of OM in aerosol, and the overall OM contribution to total PM 2.5 during fire events was over 80%.

Comparison of daily OM concentrations without and with the contribution of wildfires (August 16–September 21): a modeled daily average secondary organic aerosol concentrations, b modeled contribution of secondary organic aerosol to total OM, and c modeled contribution of OM to total PM 2.5 . Whisker/box plot shows the minimum, 1st quartile, median, 3rd quartile, and maximum. Markers show outliers, which are defined as points that are more than 1.5 times the IQR away from the top or bottom of the box.

Comparison of daily OM concentrations without and with the contribution of wildfires (September 22–October 28): a modeled daily average secondary organic aerosol concentrations, b modeled contribution of secondary organic aerosol to total OM, and c modeled contribution of OM to total PM2.5. Whisker/box plot shows the minimum, 1st quartile, median, 3rd quartile, and maximum. Markers show outliers, which are defined as points that are more than 1.5 times the IQR away from the top or bottom of the box.

Enhancement of PM2.5 modeling with low-cost sensor data (PurpleAir)

The use of PurpleAir adjustment improved model performance with respect to observations. Pure modeling results have an R 2 value of 0.27 with respect to PurpleAir observations, whereas the R 2 values for ISDW and ordinary kriging with a spherical model are 0.74 and 0.76, respectively. Even though the gaussian model for kriging showed similar fitting to the experimental semivariogram, the R 2 for the modeled adjusted values was less than 0.2. Consequently, ISDW and ordinary kriging with a spherical model, in addition to direct model outputs, were used to determine the health impacts from wildfires during the period of study.

Figures 11 and 12 show two samples of PurpleAir-adjusted daily PM 2.5 concentration fields for two high PM 2.5 events on August 22 and September 10, respectively. In general, PurpleAir-adjusted concentrations were higher than unadjusted model output concentrations. As shown in Fig. 7 , the model grossly underestimated PM 2.5 in those events, and thus, the use of PurpleAir correction reduced substantially the negative bias of the modeled PM 2.5 .

Example of PurpleAir-adjusted daily PM 2.5 concentrations on August 22, 2020: measured PurpleAir concentrations (top left), modeled concentrations (top right), PurpleAir-corrected model concentrations using ISDW interpolation (bottom left), and PurpleAir-corrected model concentrations using kriging (bottom right).

Example of PurpleAir-adjusted daily PM 2.5 concentrations on September 10, 2020: measured PurpleAir concentrations (top left), modeled concentrations (top right), PurpleAir-corrected model concentrations using ISDW interpolation (bottom left), and PurpleAir-corrected model concentrations using kriging (bottom right).

• Health impacts

Table 5 shows the health impacts related to increase in ozone and PM 2.5 concentrations resulting from wildfires. PM 2.5 impacts were calculated using both direct model outputs and PurpleAir-adjusted PM 2.5 concentrations. While ozone contributed to increased hospital admissions and mortality, PM 2.5 is the major pollutant of concern regarding health effects. Using unadjusted model data, wildfires caused an additional 1391 hospitalizations and 466 deaths. While these figures constitute a small fraction of California’s total hospitalizations and deaths, it is important to note that annual air pollution-related deaths in the state are estimated at around 40,000 (Wang et al., 2019 ). Consequently, wildfire-induced pollution estimated in this study accounts for a 1% rise in air pollution-related mortality. However, as discussed before, due to the negative bias of the air quality model with respect to PM 2.5 , health impacts using direct model output likely represent an underestimation of the wildfire impacts. The correction using ISDW of PurpleAir data increased the estimated hospital admissions by 35% and the estimated increased deaths by 16%, whereas the correction using kriging of model/PurpleAir ratios increased the estimated hospital admissions by 10% and estimated deaths by 9%. Since air quality models tend to show negative bias for PM 2.5 , as reported by Appel et al. ( 2021 ) and previously discussed, the use of monitor-based corrections implemented in this study potentially improves the estimates of air quality and health impacts. Given that the performance of ISDW and kriging are very similar, health impact estimates from both methods are considered comparable within the uncertainty bounds.

Distribution of health impacts was skewed towards counties with the largest population density, as shown in Fig. 13 . In previous studies, it was shown that higher PM 2.5 concentrations during the 2020 California wildfire season were also positively correlated with poverty and housing inequities (Kramer et al. 2023 ). While the largest fires occurred in the northern half of the state, the highest mortality was estimated to occur in Los Angeles County, which suffered a moderate impact from wildfires but houses one fourth of the state’s population. Figure  14 shows the impacts of PM 2.5 using PurpleAir-adjusted concentrations. Estimated county-level average changes in PM 2.5 increased over the northern half of the state, whereas the incidence of mortality increased the most over the Central Valley.

Overall impacts of wildfires on air quality and mortality by county using direct modeling results: a average increase in daily maximum 8-h average of ozone, b increased mortality due to ozone increase, c average increase in daily average of PM 2.5 , and d increased mortality due to PM 2.5 increase.

Overall impacts of wildfires using PM 2.5 adjusted with PurpleAir data on air quality and mortality by county: a average increase in daily average of PM 2.5 using ISDW, b average mortality due to PM 2.5 increase using ISDW, c average increase in daily average of PM 2.5 using kriging, and d average mortality due to PM 2.5 increase using kriging.

Discussion and limitations

The increase in hospital admissions due to wildfires is comparable to the potential health impacts of air pollution in the South Coast Air Basin of California (SoCAB), which houses 17 million people out of the total 40 million in California. It is estimated that the drastic emission reductions needed to attain the ozone and PM 2.5 NAAQS in the SoCAB (South Coast AQMD 2017b ) would reduce the number of hospital admission by numbers similar to those corresponding to the increase due to wildfire emissions during the modeling period for 2020. Also, the impact of wildfires on premature deaths due to air pollution significantly offsets the premature deaths avoided by the drastic air pollution control strategies that are needed to attain the ozone and PM 2.5 NAAQS.

This study is based on wildfire emissions from the FINN database, which estimates daily emissions from satellite products that include MODIS fire detection and land cover classification. Dispersion and transport of air pollutants and smoke from fires is driven by meteorology, whereas secondary formation of air pollutants—ozone and secondary PM 2.5 —depend on atmospheric physicochemical processes that transform primary pollutants. Hence, the results presented in this study depend on the ability of the used models to represent fire emissions, meteorology, and atmospheric chemistry. Moreover, this study demonstrates the use of low-cost sensor data as correction for the negative bias that the air quality model typically displays for PM 2.5 concentrations.

FINN database includes information of daily emissions and starting time of the fire but does not include hourly variation of emissions. For this study, emissions were assumed to be at a daily constant rate since the start of the fire; however, this assumption may misrepresent how emissions interact with background air pollutants that follow a diurnal pattern. Alternative approaches are documented for cases in which FINN fire emissions are adjusted to follow a diurnal profile with minimum emissions at night and peak emissions in the early afternoon (Lassman et al., 2023 ).

The chemical transport model used in this study, CMAQ, does not include feedback effects of wildfire smoke to meteorology. Studies using chemical transport models that account for feedback effects of PM on the radiative balance, planetary boundary layer height, and temperature have documented decreases in temperature of 1–4 K and decreases in PBL height of 50–400 m (Jiang et al. 2012 , Sharma et al., 2022 ). Lower temperatures can slow down the production of ozone whereas shallow PBL height can enhance the concentration of air pollutants. Also, smoke reduces the downward solar radiation, which reduces the isoprene biogenic emissions and lowers the photolysis rates, and in turn can reduce the formation of ozone and secondary aerosol formation. Lassman et al. ( 2023 ) also quantified the effect of wildfires on wind speed and showed that the California wildfires in 2020 reduced wind speed, possibly contributing to slightly less ventilation and higher air pollutant accumulation than the results presented in this study suggest.

This study examines various modeling approaches for assessing the effects of wildfire emissions on ozone and PM2.5 between August 16 and October 28, 2020, a period marked by unprecedented wildfires in California. The research utilizes the FINN database in conjunction with the CMAQ model to estimate the impact of wildfire emissions on air quality. Additionally, the BenMAP-CE model is employed to evaluate the health consequences of air pollution resulting from wildfires.

To address certain limitations in the modeling setup for predicting PM 2.5 concentrations, PurpleAir data was incorporated. The findings indicate that the typically observed negative bias in PM 2.5 displayed by CMAQ is reduced by PurpleAir observations. This reduction in negative bias improves the capability to assess air quality and health impacts related to wildfires. Namely, the study reveals that incorporating PurpleAir data using two distinct methods increases the estimated health impacts of wildfires, resulting in a 9–16% rise in estimated wildfire-induced mortality.

The study observes that California wildfires significantly contributed to elevated levels of ozone and PM 2.5 , with an average increase of 2.5 ppb in daily maximum 8-h ozone and an average increase of 12 μg/m 3 in daily PM2.5 concentrations. These increases are anticipated to lead to a higher incidence of air pollution-related hospitalizations and premature deaths, potentially causing up to 1886 additional hospitalizations and 539 extra premature deaths. Some of the health impacts stemming from the fires are comparable to the benefits gained from long-term air pollution control strategies designed to meet ozone and PM 2.5 air quality standards. Given the escalating frequency of wildfire events driven by climate change, the health benefits derived from reducing anthropogenic emissions are at times offset by wildfire impacts in the state. The incorporation of low-cost sensor data can enhance the predictive capabilities of air quality models during wildfire events, particularly when these models tend to underestimate particle pollution formation on their own.

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Abbreviations

Air quality system

Benefits Mapping and Analysis Program – Community Edition

California Air Resources Board

Community Earth System Model 2

Community Multiscale Air Quality Model

Emissions Factor Model

Emissions Spatial and Temporal Allocator

Fire Inventory from the National Center for Atmospheric Research

False negative rate

False positive rate

Inverse squared distance weighting

Mean normalized bias

Mean normalized error

Moderate Resolution Imaging Spectroradiometer

National ambient air quality standards

National Centers for Environmental Prediction

Nitrogen oxides

Organic matter

Particulate matter with a diameter of 2.5 microns or smaller

Low-cost sensor network by PurpleAir, Inc. (www.purpleair.com)

Reactive organic gases

Surface Fire Model

South Coast Air Basin of California

Sulfur oxides

True negative rate

True positive rate

United States Environmental Protection Agency

Whole Atmosphere Community Climate Model

Weather Research and Forecasting model

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Acknowledgements

Partial support for this research by the University of California Office of the President (UCOP) Laboratory Fees program under award LFR-20-651032 and by the Electric Power Research Institute, Inc. (EPRI) through award DKT200194 is gratefully acknowledged. William Lassman and Jeffrey D. Mirocha contributed under the auspices of the US Department of Energy by the Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Any opinions, findings, recommendations, or conclusions expressed in this publication are those of the writers and do not necessarily reflect the views of the sponsoring agency. Authors thank Brandon Feenstra from South Coast Air Quality Management District for providing insight regarding data collection from the PurpleAir sensor network.

The University of California Office of the President (UCOP) Laboratory Fees program under award LFR-20-651032 provided partial support for this research.

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MCS prepared model inputs, set up modeling and conducted air quality simulations, analyzed results, and prepared the manuscript. SZ and MM prepared the setup of the health Impact model BenMAP. WL contributed to the design of the modeling and the application of kriging in the interpolation of PurpleAir sensor data. JDM contributed to the design of the study and the interpretation of data. MB and DD worked on the acquisition of funding for the project and on project administration and contributed to the conceptualization of the study and to the design of the analyses. DD provided funds and computing infrastructure to conduct the computer simulations. All authors contributed to the writing of the manuscript and the consequent revisions. All authors have read the manuscript and approved the final manuscript.

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Carreras-Sospedra, M., Zhu, S., MacKinnon, M. et al. Air quality and health impacts of the 2020 wildfires in California. fire ecol 20 , 6 (2024). https://doi.org/10.1186/s42408-023-00234-y

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Yale Climate Connections

Climate change is worsening California’s hellish wildfires

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Like a modern-day Ebenezer Scrooge escorted by the Ghost of Summers Yet to Come, California is catching a glimpse of its future summer weather. The view is a hellish one.

Within a two-week span in August, California saw:

– the “ fire tornado ” just north of Lake Tahoe – 130 degrees Fahrenheit heat in Death Valley, which may be the hottest temperature ever reliably recorded on Earth – a largely dry thunderstorm with 11,000 lightning strikes across California over 72 hours, igniting more than 300 wildfires, including two of the three largest ever recorded in the state (and still growing), creating the worst air quality in the world – one million acres burned in California in 2020 with 4 months to go in fire season – tens of thousands of people evacuated from their homes as the fires drew near – rolling power blackouts during a record heat wave – gray, unhealthy air. A blood red sun. Flakes falling from the sky, coating everything below in a layer of white… not snow, but ash.

These ghastly scenes all bear links to climate change, and as a result, climate scientists expect them to occur more frequently in the future as global warming continues to raise temperatures and dry the landscape. As California Gov. Gavin Newsom put it in a recording for the Democratic National Convention, “Climate change is real. If you are in denial about climate change, come to California.”

Better yet, don’t. At least not right now.

The heat dome punishing the American Southwest

California’s severe August weather is linked to a ridge of high pressure, also referred to as a “heat dome,” stuck over the American Southwest. The heat dome pulled moisture from a tropical storm in the Pacific, fueling rare summer storms that triggered the thousands of lightning strikes that have ignited wildfires across the state. The hot air inside the dome contributed to the record heat, which evaporated most of the storm’s precipitation before it could reach the ground. The hot and dry conditions on the ground created more fuel for the fires to spread farther and faster.

According to meteorologist Ryan Maue , as reported in the Washington Post, almost all of the high-powered heat domes over the past six decades have occurred since 1983, and the overwhelming majority of those since 1990. Climate scientists will need to investigate the role that climate change played in the evolution of this particular heat dome. However, a growing body of research suggests that human-caused global warming increases the frequency with which such high-pressure ridges get stuck in one place for long periods of time as a result of wavy patterns forming in a slowed jet stream .

To Penn State climate scientist Michael Mann, lead author of a 2018 study on this subject, the heat dome in the American Southwest looks familiar.

“The extreme heat out West right now is associated with a very strong, stable ridge that resembles, in both its persistence and intensity, the ridge that gave us unprecedented heat, drought and wildfire out west in mid-summer 2018 ,” Mann said in an email exchange. “Knowing that, I would venture a guess that the same atmospheric phenomenon (planetary wave resonance) that was responsible for that setup and the unusually persistent weather extremes in Europe and elsewhere at that time might be playing a role here too. But that assessment will need to be performed by actually doing the diagnostics.”

Climate change is a ‘wildfire threat multiplier’

Climate change has played a key role in worsening western wildfires. In a new study in Environmental Research Letters, a number of foremost experts on California wildfires concluded that the combination of rising temperatures and declining autumn rain – both of which are linked to climate change – over just the past four decades has more than doubled the number of fall days with extreme fire weather conditions. Those findings are consistent with a 2016 study concluding that human-caused climate change doubled the area burned in western U.S. forests since the 1980s.

President Trump, as he has done previously, again blamed the California wildfires on a failure to “ clean your floors … clean your forests .” However, as the new Environmental Research Letters study concluded, “demographic and forest management factors alone are insufficient to explain the magnitude of the observed increase in wildfire extent over the past half-century.” Climate change is playing the largest role in worsening California wildfires, and the study authors described it as “a wildfire ‘threat multiplier’ amplifying natural and human risk factors that are already prevalent throughout California.”

As UCLA climate scientist Daniel Swain and colleagues found in a 2018 study , climate change is shifting precipitation patterns in California, leading to more rain in the winter but less in the autumn and spring seasons, bookending the state’s already dry summer months and lengthening the annual wildfire season. Wildfire threats associated with normal weather variations, like California’s already low 2020 precipitation at just 62% of average, are amplified by the rising temperatures and decreasing autumn rainfall caused by climate change.

Scientists can’t yet say whether climate change played a role in the rare lightning storms that ignited the August 2020 fires, but it certainly exacerbated the hot and dry conditions that allowed the wildfires to spread farther and faster.

Wildfires and COVID attack the same organs

The wildfire smoke has spread across much of the state, often deteriorating air quality to levels deemed “unhealthy” or “hazardous.” Climate scientist Drew Shindell has incorporated air pollution data into climate models and recently presented his findings in testimony to Congress . He concluded that the adverse impacts of air pollution and heat are much worse than previously thought, “roughly double those that would have been obtained using older evidence,” while air pollution “damages lungs, hearts, brains, skin and other organs … affecting virtually all systems in the human body.”

Also see: How to protect yourself from wildfire smoke

The 2020 wildfires of course overlap the ongoing COVID-19 pandemic, which likewise damages lungs and also hearts, brains, and other organs . The virus has spread particularly rapidly through several prisons, many of whose inmates California uses to fight wildfires for $2 to $5 per day plus $1 per hour when out fighting fires. As a result, only 90 of the state prisons’ 192 inmate fire teams are available to assist with the wildfires this summer. Prison inmates normally account for 23% of California’s wildfire fighters. Thus the pandemic is putting a strain on the state’s fire-fighting resources, which are already thinly spread in light of the sheer number and size of the August 2020 wildfires across the state.

California’s perfect storm

California in August 2020s is experiencing its version of a “perfect storm”: A heat wave caused by a high-pressure dome, which also triggered rare lightning storms, igniting hundreds of wildfires across the state during a relatively dry year with an ongoing pandemic. High electricity demand during the record heatwave also combined with poor planning by electric grid operators , resulting in isolated rolling blackouts over two days.

Some parties have exploited this unfortunate situation to blame renewable energy for the blackouts, but in reality, a number of factors played a role, including reduced production from fossil fuel gas plants that struggled to operate in the heat.

In the end, experts agree that the only way to lessen the threat-multiplying effects of climate change is to slow global warming by transitioning away from fossil fuels as quickly as possible, while building a smarter and greener power grid that can handle the added stresses brought on by the kinds of extreme climate change-amplified weather California is suffering through.

Like Ebenezer Scrooge in the Dickens story, we still have the ability to change our future outlook for the better.

Dana Nuccitelli

Dana Nuccitelli, research coordinator for the nonprofit Citizens' Climate Lobby, is an environmental scientist, writer, and author of 'Climatology versus Pseudoscience,' published in 2015. He has published... More by Dana Nuccitelli

August 24, 2020

Fast-Moving California Wildfires Boosted by Climate Change

Nearly two dozen large blazes have burnt more than 1 million acres of the state

By Anne C. Mulkern & E&E News

Embers blow off a burned tree after the LNU Lightning Complex Fire burned through the area on August 18, 2020 in Napa, California.

Justin Sullivan Getty Images

Firefighters battled nearly two dozen wildfires in California yesterday after a week of raging blazes blackened more than 1 million acres across the state.

The fast-moving fires, which are seen by many scientists as a sign of climate change, have killed five people, destroyed more than 1,000 structures and forced thousands to flee. More than 238,000 people either evacuated or were ready to go as more thunderstorms threatened to light new fires yesterday afternoon, according to officials.

Still-active fires are affecting at least 23 counties in Northern California, stretching from Butte to Fresno. Two of the blazes rank among the largest in state history.

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The LNU Lightning Complex Fire, a group of fires centered in Napa and Sonoma counties, has grown into the second-largest blaze ever seen in California. The SCU Lightning Complex Fire, a cluster of blazes in Santa Clara, Alameda and nearby counties, is the third-largest.

Altogether, the fires have burned an area the size of Rhode Island.

"The scope [of the damage] is absolutely astonishing," said Daniel Swain, a climate scientist at UCLA. It's "hard to impress on people just how vast the acreage burned is, especially considering there were no strong offshore winds" to drive the spread.

President Trump on Saturday issued a major disaster declaration to fulfill a request by Gov. Gavin Newsom (D) to bolster the state's emergency resources. Meanwhile, the National Weather Service issued a red flag warning for more thunderstorms and lightning through today.

The racing flames show how climate change is affecting the nation's most populous state, experts said. Hotter temperatures, less dependable precipitation and snowpack that melts sooner lead to drier soil and parched vegetation. Climate change also affects how much moisture is in the air, Swain said.

"It's actually drying out the air during these extreme heat events," which zaps plants of additional moisture, Swain said. That left much of the state a tinderbox when hundreds of lightning strikes scorched the countryside last week.

"This is really a testament to how dry the vegetation is, in terms of how quickly these fires spread when they were ignited by lightning," he said.

The amount of land burned last week is more than the total burned in all of 2018, and more than double the amount burned in 2017, according to data released by the California Department of Forestry and Fire Protection (Cal Fire).

The fires on Saturday burned part of the oldest state park in California, Big Basin Redwoods State Park in Santa Cruz County. Flames damaged historic buildings, the campground and "all of the infrastructure," said Christine McMorrow, a spokeswoman with Cal Fire. It wasn't known whether redwood trees were engulfed.

The blazes threaten to outpace the state's ability to respond. Nearly all of Cal Fire's crews are in the field, with some working 72-hour shifts. Oregon, Washington, Nevada, New Mexico, Texas and other states sent firefighters, equipment or both. Officials said more than 13,000 fire personnel were on the scene.

"We have more people, but it's not enough," Newsom said at a Friday news conference. "We have more air support, but it's not enough."

Repeat fire trauma

Fires erupted beginning Aug. 15 when more than 1,200 lightning strikes hit the baking landscape within 72 hours.

Those came "the exact week that we were experiencing some of the hottest temperatures ever recorded in human history, 130-degree temperatures in the southern part of the state," Newsom said. It was "maybe the hottest modern recorded temperature in the history of the world," he said.

He was referring to the temperature of 130 degrees Fahrenheit on Aug. 16 in Death Valley, a high not reached on Earth in 89 years. The highest temperature ever recorded on the planet is 134 Fahrenheit. It was reached in 1913 in Death Valley. Its accuracy is disputed by some observers because there was a lack of modern technology ( Climatewire , Aug. 18).

Altogether, more than 12,000 lightning strikes hit California last week, igniting over 600 fires. Firefighters knocked down smaller ones, but others merged into major "complex" fires.

The week was filled with horror stories and heroic efforts. Volunteers helped evacuate senior citizens from a Vacaville retirement home in the middle of the night as a fire raced toward the facility. Others helped rescue "dozens and dozens of individuals with intellectual disabilities" in Santa Clara, Newsom said.

Hundreds saw their homes destroyed.

"Tuesday night when I went to bed, I had a beautiful home on a beautiful ranch," Hank Hanson, 81, of Vacaville, told the Associated Press. "By Wednesday night, I have nothing but a bunch of ashes."

State Assemblywoman Cecilia Aguiar-Curry, who represents the Napa wine region, said at a news conference Friday that she has "half a dozen really good friends who don't have a home right now."

The American Red Cross, wary of the coronavirus pandemic, put some survivors in hotel rooms so they could be separated from other evacuees, said Jim Burns, a Red Cross spokesman. Others went to evacuation shelters where protocols were in place to keep people spaced out. The Red Cross was also talking to colleges to see whether dorm rooms were available.

The fires swept across heavily populated cities that have endured major fires in recent years. Susan Gorin, a Sonoma County supervisor, lost her home in the 2017 Tubbs Fire, a blaze that killed 22 people. She built a new house in the same location; on Friday, she found ashes on her patio from a nearby firestorm.

"It just seems so terrifyingly familiar," Gorin said as she traveled to Lake Tahoe to escape the smoke and mayhem. "This is now the third major fire in four years. We are battle-weary."

Climate connection scrutinized

Swain with UCLA and other scientists earlier this year published a study that said climate change has doubled the number of extreme-risk days for California wildfires.

It said temperatures statewide rose 1.8 degrees Fahrenheit since 1980, while precipitation dropped 30%. That doubled the number of autumn days that offer extreme conditions for the ignition of wildfires ( Climatewire , April 3).

The heat is expected to get worse with time. Climate models estimate that average state temperatures will climb 3 degrees Fahrenheit by 2050 unless the world makes sharp cuts in greenhouse gas emissions, said Michael Wehner, a senior scientist at Lawrence Berkeley National Laboratory.

Even with emissions cuts, average temperatures would rise 2 degrees by midcentury, he said.

Jon Keeley, a senior scientist at the U.S. Geological Survey Western Ecological Research Center, argued that the study from Swain and others failed to show that hotter temperatures are driving wildfires.

"Show us data that shows that level of temperature increase is actually associated with increased fire activity," Keeley said. "They don't show that."

Keeley added, "We ought to be much more concerned with ignition sources than a 1- to 2-degree change in temperature."

A big contributor to large California fires is that the state has focused on extinguishing blazes for about a century rather than allowing for controlled burns, he said. That has caused dead vegetation to accumulate.

Trump has accused California of failing to "sweep" its forests, which he has linked to fires in the state.

Keeley said that "we don't sweep forests here in the U.S., but what we do is prescription burning. ... It's potentially the same thing. It's modifying the fuels prior to a fire."

Swain, the UCLA climate scientist, said global warming is affecting how big fires get and how fast they move.

"What happens when they start burning, what is the character of those fires, and is it changing?" Swain asked. "The answer is yes."

Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net .

You may opt out or contact us anytime.

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The Fires California Grieves—And Needs

In her scorched klamath mountains community, a fire advisor contemplates mortality and renewal.

The author’s favorite hometown swimming hole, on the South Fork Trinity River in Forest Glen, California, after last year’s devastating August Complex fire.  Courtesy of Lenya Quinn-Davidson.

by Lenya Quinn-Davidson | July 19, 2021

On a recent Sunday, I lay alone by my favorite hometown swimming hole, taking in the familiar sensations of the South Fork Trinity River. The hot sun, the light up-canyon wind—sending mist over me each time it swirled past the falls—the buzz and clicking of grasshoppers, the distant sound of trucks passing by on the rural highway above. I looked down at my body and thought how remarkable it was that I’m still me, all these decades later, and the rocks and the trail and the river are still here, moving through time with steady grace. I hadn’t returned to this remote spot in years, but it still felt like home.

Beyond the river corridor, though, things were stark and unfamiliar.

In one hot, windy day last August, fire had dramatically changed this place. Flames ripped across this piece of the river canyon, killing almost every tree in their path and exposing the bare, naked soil beneath. Called the August Complex, it was the largest fire in recorded history, burning more than a million acres of forestland and woodland.

This town, Forest Glen, marked the northern edge of the blaze. It may be one of the smallest towns in California—with only 10 permanent residents—but it has always had a palpable personality, a spirit. When I drove through it that day, taking in the transformation, my eyes welled with tears over the loss. My own hometown, Hayfork, is slightly bigger and 21 miles away, but the grief has rippled out like a stone dropped in water. Mortality is heavy in hand here.

I am on the cusp of 40 years old—only 6 more months until I turn that corner. One thing they don’t tell you about turning 40 is that everyone around you starts dying around then, especially if you are lucky enough to come from a community of loving adults—your parents, their friends, the “aunties” and “uncles” who have known you since birth. One day you’re a kid and they’re looking after you, and the next day you’re 39 and a half, and they’re disappearing, one by one.

After sitting by the river that day, I wound over the mountains and dropped into the valley of my hometown—one of the two largest valleys in the Klamath Mountains, framed on all sides by signs of past fire: snag patches and dead trees, clusters of thick wildflowers, open oak woodlands and meadows, barren ridgetops. This place, my home, has so many fire stories to tell. And my stories are layered there, too, simultaneously dead and alive, just like the fire footprints that surround them.

As in many recent years, the 2020 fire season was record breaking. More than 4.2 million acres burned in California, and smoke blackened the sky, even here by the ocean. Fires burned through coastal redwood forests and scorched giant sequoias in the Sierra Nevada, testing the evolutionary adaptations that have carried some of those trees through thousands of years of fire. Recent reports from Sequoia and Kings Canyon National Parks tell us that 10 percent of the world’s mature giant sequoia trees died in last year’s Castle Fire, and that species was not the only one to suffer losses. With each severe fire season, we lose old pumpkin pines, ancient oaks, and beloved stands of mixed conifer and hardwood, in addition to the structures and other built features that also define home for us.

The loss of familiar landscapes, of specific trees or viewsheds, is the deepest kind of loss—not unlike losing a home or a family member. People are a product of place, and when we lose our sense of place, we lose our identity.

Dave Daley, a Butte County rancher, put words to this deep grief last year , after the Bear Fire burned through his mountain cattle range on the Plumas National Forest:

The fire destroyed our cattle range, our cattle, and even worse our family legacy. Someone asked my daughter if I had lost our family home. She told them “No, that would be replaceable. This is not!” I would gladly sleep in my truck for the rest of my life to have our mountains back. I am enveloped by overwhelming sadness and grief, and then anger. I’m angry at everyone, and no one. Grieving for things lost that will never be the same. I wake myself weeping almost soundlessly…it is hard to stop.

Such losses have manifested over more than a century of mismanagement and bad politics—and maybe most importantly, an increasing disconnect between people and place.

Before European settlement in California, scientists estimate that at least 4.5 million acres burned every year across the state . That’s right—California used to see more fire every year than what we saw in last year’s “historic” fire season.

Though it’s difficult to parse out historical ignition patterns, we know that Native Californians contributed in significant ways to California’s fire regimes, actively shaping landscapes with fire to sustain their cultures and livelihoods. Some fire scientists estimate that Native Americans may have intentionally burned up to 2 million acres a year. Research from the Sierra Nevada tells us that during periods where people were most actively managing their landscapes, and using fire as a tool, climate fluctuations like drought and extreme temperatures were less likely to influence how fires burned.

However, in the early 1900s, this practice of cultural burning was criminalized when federal and state officials initiated an era of fire suppression. The stated goal was to save trees—to protect forests from the very process that had shaped and maintained them through time. Yet we know now those losses weren’t avoided; rather, by removing fire, the losses were stalled, accentuated. It’s clear that the fires that burn now are making up for generations of missed fire. The more we’ve rejected fire as the natural—and human—process that it is, the more volatile it has become.

During last year’s devastating Slater Fire, Bill Tripp, the deputy director of eco-cultural revitalization for the Karuk Tribe, wrote a powerful op-ed reflecting on his people’s connection with fire, and the federal and state policies and practices that continue to this day to threaten their ecology and culture. Just as the land was taken from the Karuk people, so too was their relationship with fire. Bill explained that Karuk people were shot for burning, even as recently as the 1930s, and he lamented the way that fire continues to be misunderstood and mismanaged:

Fire itself is sacred. It renews life. It shades rivers and cools the water’s temperature. It clears brush and makes for sufficient food for large animals. It changes the molecular structure of traditional food and fiber resources making them nutrient dense and more pliable. Fire does so much more than western science currently understands.

Dominant society has missed the mark this last century or so, trying to make static what is so naturally dynamic. We suppressed fire in the name of the trees, but we forgot about the people and the plants and the landscapes that needed fire, as vital as rain or sunshine or snow. Fire can be deadly, but at its core it’s a force of life—refreshing and renewing.

Now it’s early summer, and those of us who work in fire are bracing for yet another record-breaking season. With a backdrop of extreme heat, drought, and unusually dry vegetation, it’s hard to imagine a different outcome. Fire season feels a lot like turning 40: You’re not sure what—or who—the next loss will be, but you know it’s coming. And knowing doesn’t mean you’re ready.

In my work, I focus on bringing fire back. As a fire advisor, I work with individual landowners, tribes and cultural practitioners, community groups, and agencies to build capacity for prescribed fire—to set intentional fires that provide ecological and social benefits, reducing fire hazard but also restoring wildlife habitat and biodiversity, eradicating invasive species, and restoring landscape and community resilience. The idea is to rebuild the relationship between people and fire, and to empower the kinds of change that might bring us back into balance.

Red catchfly flowering among burnt logs in Forest Glen. Native cultures in California understood that fire renews life. This knowledge influences innovative policies that hope to harness fire to promote healthy ecosystems. Courtesy of Lenya Quinn-Davidson.

One of my biggest priorities is to foster innovation and inclusivity in fire management—to bring new, and often oppressed, perspectives and ideas to these increasingly wicked problems. Diversity begets creativity. To this end, I work with partners to create opportunities for under-represented groups in fire, with a focus on women. Much of my work in this arena is through the Women-in-Fire Training Exchange (WTREX), which is international in scope. Here in California, I also work with local communities to bring fire back as a land management tool, and to promote policies that support and elevate those efforts. I have found that people are desperate for positive connections, both with each other and with fire, and this work is the perfect venue to fill some of those gaps.

Recent years have seen an uprising around prescribed fire—a movement—as we Californians explore and reclaim our role in this fire-adapted state. Community-based burn cooperatives have sprung up across the state, providing training, resources, and inspiration for landowners, volunteer fire departments, and community members. Legislators, too, are working to tackle some of the major barriers to prescribed fire, like liability . We are seeing more commitment, both institutional and financial, by our federal and state agencies, as they try to grow and improve their prescribed fire programs. After more than a decade of working on these issues, I am more heartened than ever by the interest and momentum around prescribed fire. We’re finally seeing that we can choose to fight fire, or we can carry it with us.

When I was a kid, my dad talked about a death dream he’d had. He was falling from a cliff, but unlike most dreams where you awaken before you hit bottom, in this dream my dad actually hit the ground and died. He said it was an explosion of color, bright and warm and welcoming. It wasn’t an end, but the beginning of something different. When he died some years later, I was comforted by that story. I still think of it now, as time brings mortality increasingly into focus.

As I hiked out of Forest Glen that day, I looked across the river and saw a pool of orange in a draw behind a boulder: a thicket of wild tiger lilies. Up the trail, nestled in the blackened logs, were bright red catchflies and clusters of fresh, oily poison oak leaves. In that moment, I knew this place wasn’t dead; it was different than I knew, but it was still alive—growing, changing.

It occurred to me that our landscapes are likely closest to death when we freeze them in time—when our need for the familiar interrupts their need for process, when we inadvertently choose big losses by avoiding all the small ones. The changes in Forest Glen didn’t happen in one day last summer; rather, they’d been brewing over more than a century of fire suppression and forest management. Maybe our job now is to gain a bigger perspective—to learn to love process rather than just place. And maybe 40 is my next small fire, an opportunity to refresh and renew, to unleash new parts of myself as I let go of others. I think I’m ready.

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Land of Smoke and Fire: Documenting California’s Endless Season of Heat

Jeff frost and lauren markham, for the longest year: 2020+ project, the longest year: 2020 + is a collection of visual and written essays on 2020, a pivotal year that shifted our way of experiencing the world. in most publications, images work in service to words—here they work in tandem.  //  california residents jeff frost—an artist—and lauren markham—a writer—reckon here with that state’s ever-lengthening fire season, documenting the dire impacts of increasing drought and rising temperatures on life in the golden state..

Have you ever been driving along, headed wherever you’re going, when the landscape suddenly opens up to post-fire char? A scene where blackened trees now spear the skyline, destroyed buildings lean like upright cadavers, and your spirit is brought to its knees? Since May, I have, for a smattering of reasons (reporting trips, a volunteer assignment, a vacation, an outdoor wedding) been on the road, driving through California’s cities and its backwoods, its deserts and its mountain meadows, its twisting river valleys and agricultural flats. And everywhere I’ve gone, I’ve encountered these excruciating scars.

Fire, that trickster’s loot, that gift from the gods, burned more than 4,000,000 acres of my home state last year—a number so vast it is mere abstraction. Most of the impacts of climate change are abstractions until they’re at your own door. How about this: the amount of California that’s gone missing is almost equivalent to the state of Massachusetts in size.

“We’re burning here,” I texted the Massachusetts side of family last September. For two weeks, I’d been living in a hellscape of toxic smoke, but back east they were all just carrying on with their lives. A few days later, the sky was so thick with soot that it was dark all day as if the sun, so weary with us, had opted not to rise. I might have stayed in bed, mourning and cowering, but had to go to work. Instead of driving I rode my bike with the logic that, if my home state was being cremated, I should at least be present for it, prostrate under its remains. I pedaled through that ceaseless twilight as the particulate wreckage of California blotted the sky.

Fire, now a normative fixture of our landscapes, our fears and our dreams, is easy to anthropomorphize. In the newspapers and in our diaries, fires rage like angry men. The fingers of the flames lick like a human tongue. Fires jump roads and climb hillsides; they outrun us, like thieves, or chase us, like assassins. To consider fire in our own image is an attempt to rend it from abstraction. But a fire, after all, is just fire—merely heat, oxygen and fuel.

This year promises even more fire. The flames have become backdrop to our lives. Perhaps because of this proximity, I’m beginning to feel compassion for fire—so maligned. Perhaps we anthropomorphize fire not just to understand it in human terms, but as a coded mechanism of blame. For the real threat is our overheated planet, our mismanaged forests, our foolish festivities and faulty wiring and interminable greed, human civilization’s wretched sprawl. The threat isn’t fire, it’s us.

Last weekend, I visited the Bristlecone pines national forest, home to what are perhaps the oldest trees in the entire world. We wound uphill from the sweltering flats of the Owens Valley, where thousand-year-old groundwater is pumped into aqueducts to keep Los Angeles’s pools filled and lawns green, to 14,000 feet where the ancient trees had set root over 4,000 years ago. Because their high desert landscape is so harsh, the Bristlecones develop a thick, impervious bark, which keeps them safe from pets and blight and which makes it highly unlikely that they’ll catch fire. The harshness of their landscape, in other words, is what permits them their eternity.

Looking out from their sparse forest, these trees have been witness to genocide, to men mining deep into the earth for profit, to the railway, the advent of power, the invention of the car, the airplane, fossil fuel. And in recent years, these trees have seen so much smoke rise. Today’s massive fires, it occurred to me there in the shadows of these endangered forbearers, are just the grand externalization of longstanding wounds. Like the trees, we humans find ways to survive our environments. I wish for thicker bark, though, for a home not on fire.

–Lauren Markham

_______________________________

Photography and video by Jeff Frost

The Longest Year: 2020 + is a collection of visual and written essays on 2020, a pivotal year that shifted our way of experiencing the world. Edited by Rachel Cobb, Alice Gabriner, and Elizabeth Krist.

Rachel Cobb   is a photographer who lives in New York City. She has worked for numerous publications including The New York Times , TIME  and Rolling Stone magazine. Her award-winning book Mistral: The Legendary Wind of Provence was published by Damiani in 2018. More of her work can be found here .

Alice Gabriner is a visual editor, instructor and mentor with 30 years of experience at publications, including The New Yorker, The New York Times, National Geographic , and TIME .  For the first two years of the Obama administration, she served as Deputy Director of Photography.

A National Geographic photo editor for over 20 years, Elizabeth Krist is on the boards of Women Photograph and of the W. Eugene Smith Fund, helps program National Geographic ’s Storytellers Summit, and advises the Eddie Adams Workshop. She curated A Mother’s Eye for Photoville and CatchLight, and the Women of Vision exhibition and book.

Jeff Frost and Lauren Markham

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2020 Incident Archive

• 494,489 Total Emergency Responses
• 8,648 Wildfires
• 4,304,379 Acres Burned
• 33 Confirmed Loss of Life
• 11,116 Structures Destroyed

Incident Map

2020 fire year.

The 2020 California wildfire year was characterized by record-setting wildfires that burned across the state of California as measured during the modern era of wildfire management and record keeping. As of the end of the year, nearly 10,000 fires had burned over 4.2 million acres, more than 4% of the state's roughly 100 million acres of land, making 2020 the largest wildfire season recorded in California's modern history. California's August Complex fire has been described as the first "gigafire" as the area burned exceeded 1 million acres. The fire crossed seven counties and has been described as being larger than the state of Rhode Island. On August 19, 2020, California Governor Gavin Newsom reported that the state was battling 367 known fires, many sparked by intense thunderstorms on August 16–17. In early September 2020, a combination of a record-breaking heat wave, and Diablo and Santa Ana winds sparked more fires and explosively grew the active fires, with the August Complex more than doubling the Mendocino Complex's size to become California's largest recorded wildfire. Pictured: The LNU Lightning Complex which burned across wine country in August 2020.

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The Californians with nowhere to go as wildfires rage – photo essay

Tens of thousands have been forced to leave their homes to escape the flames. Photographer Rachel Bujalski meets evacuees

A t the Sonoma County Fairgrounds in Santa Rosa, California, Michelle and Carlos Jacinto sat in their car at the fairgrounds to eat lunch and take a break from their designated temporary evacuation center. They left their home in Forestville two nights ago, as wildfires tore through the state .

They packed up the car with their dogs, pictures and important papers. Michelle and Carlos had come to this evacuation center last year during the fires, but they said this time was different: they were required to wear masks and keep distant from other people in a gymnasium.

Barbara Pagett sat in the back of her friend Kevin Denny ’s car with her cat in a carrier after arriving at a temporary evacuation center at the same fairgrounds. They had just found out the site was open after having spent two days as evacuees. After they evacuated the first night and found the Petaluma evacuation center was closed, they were forced to spend $300 for two nights at a hotel.

Dennis O’Leary and his wife, Patricia , set up their sleeping bags in a park in Forestville, where they would spend their second night after evacuating from Guerneville.

“We didn’t want to end up in a crowded place and didn’t want to go too far from where we live and thought we could stay in this park. Everyone in Forestville has been really understanding, and they opened the park bathrooms for us and all the restaurants are close for resources if we need.”

Katherine Champion and her friend Chris Dawson sat at the parking lot in Forestville after evacuating from their home in Rio Nido and contemplated where to go next. Katherine said her dad had called her and said she needed to evacuate since she had been waiting the fire out for two days. Tonight she said they would sleep at a friend’s house and hopefully not get moved.

Whitney Millstone sat with her partner, Wes Colunga , and her dad, Jason Millstone , at the Forestville parking lot after fleeing their home in Guerneville. A helicopter had flown over their house and announced over the intercom that they needed to leave immediately.

Whitney said: “It’s one of those moments where you’re sitting here and you’re like, ‘What else can happen in the midst of this pandemic?’ I could lose my job, I could lose everything.”

Jim Laughlin and his friend and neighbor Jean-Pierre sat outside in a community park listening to wildfire updates on the radio in Forestville, where they had slept the night before in their truck after evacuating from Guerneville.

Emely Jeanpierre folded and organized her clothes and belongings at a designated temporary evacuation zone after evacuating from the campsite where she lived on the Russian River for 12 years. Emely evacuated on Wednesday evening as mandatory orders were called in her area. In a rush, she had to bring her boats out of the water, get food for her cat and dog, pack up all her things and get out of Guerneville as quickly as possible.

Pat Spiva sat in her car in Forestville deciding where to go next after she evacuated on Tuesday from her home in the area. Her dog is sick and she needs to stay in her car to take care of him.

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How We Escaped the Worst of the California Wildfires

By Ian Morris

Maybe no one is ever ready for an emergency. August 18th was our thirty-first wedding anniversary. Kathy and I were still debating what we would do to celebrate when the sky behind our house turned Technicolor red and orange. My first thought was how much it looked like the burning of Atlanta in “Gone with the Wind.” A movie. Not real. Yet tiny white flakes—ash, not snow—had been fluttering down for hours, and now the odd charred black leaf was coming too, batting against my face. It was real, but it couldn’t be happening to me.

We had learned from earlier scares that the first few hours of a fire are a chaos of conflicting instructions. Evacuation orders had been issued and cancelled, then issued again. Kathy and I scuttled around doing what last-minute fire prevention we could in the dark. We dragged bits of brush away from the house, so that stray embers wouldn’t ignite them. But what to do with the cans of gas for the generator? We shut all the windows and inside doors. But do we lock the outside doors, or leave them open for firefighters? And what to take? Laptops, cell phones, and power cords; passports; our little stash of cash; a tent (we forgot the blankets and pillows); and some senseless things, grabbed in a panic, like a bag of coffee beans. Otherwise, not much more than the clothes we stood up in and food, medications, leashes, and carriers for the animals.

No two evacuations are the same. For us, animals were the great complication. It would have been hard enough to deal with our four cats and two dogs. But Kathy volunteers in wildlife rehabilitation, taking in orphaned and injured animals until they are ready to be released. We boxed up five baby raccoons—after something of a fight—to take back to Native Animal Rescue’s headquarters, in Santa Cruz, but all we could do in the moment for the two fawns we still had was open the doors to their pen and hope for the best. (Kathy would come back two days later, to catch and transfer them to another rehabber, in San Jose.) The two feral cats who lived under the shed, however, evaded all efforts to trap them. They would have to take their chances.

And then there were the horses. Like most horses in the Santa Cruz Mountains, our two were rescues. The joke you always hear is that rescue horses are free because the costs come later. It certainly felt that way. Smarty, a quarter horse, had no intention of being loaded into a trailer in the middle of the night. It took a lot of shoving, begging, and frayed tempers to get him in. With Ray, the mustang, we didn’t even try. He’d been badly beaten by owners and trainers in the past, and, even in the calmest conditions, would not go near our small trailer. So we walked Ray out, a mile or so through the woods and then along the road, to a ranch where, hopefully, someone could come with a bigger trailer and get us.

We sat in a dark field, the cats yowling, the horses eating, the dogs thinking it was all a great adventure. Behind the ridge to the west, the sky flared red whenever the wind blew, then died back down to a dark gray-blue. By 2 A.M. , the road had gone quiet. All was strangely calm. Maybe it would turn out to be a false alarm after all. Maybe we would dodge the bullet again. But maybe not. Around three, we called Emily Clark, who volunteers with one of the emergency-response teams. We barely knew her, but she’d already called us more than once, offering to drive an hour or so up to Boulder Creek with a big trailer for Ray and lead our little convoy to safety. It now felt like time to accept her offer.

I’m no horseman myself, so they gave me the easy job of holding onto Ray’s lead rope (passed through the trailer’s window) until he was on board. Surprisingly, he did as he was told. Thinking we were done, I stopped paying attention, whereupon Ray decided to back out again, pulling the lead rope and my hand back through the steel bars on the window. When a twelve-hundred-pound horse decides to go somewhere, there’s not a lot you can do to stop him. But they’d told me to hold onto the rope, so I did, until someone, I’m still not sure who, yelled into my face to let go. Fortunately, I’d known enough not to wrap the rope around my hand. There were rope burns and a surprising amount of blood, but nothing broken. A reminder that professors are not always the sort of people you want around in an emergency. My net contribution was to take two of the helpers away from loading the horse so that they could bandage me up. By the time they were done, Ray was in the trailer. At 7 A . M ., we were on the road.

We had always known that something like this could, and probably would, happen. In 1860, when the brand-new California Division of Mines and Geology sent the botanist William Brewer to study the state’s woodlands, he wondered whether Americans should be living here at all. Heat waves, he wrote, melted the fat in uncooked meat until it would “run away in spontaneous gravy.” Forests turned abruptly into “great sheets of flame, extending over acres.”

Before Europeans came, Native Californians had found ways to cope with this reality. Many moved seasonally, partly to avoid forest fires. As much as one-sixth of the state was deliberately burned each year, simultaneously removing fuel for wildfires and creating new environments for grasses, acorns, deer, and quail. Most obviously, perhaps, people generally didn’t live in places like the Santa Cruz Mountains, where food was scarce and fires frequent.

Hardly anyone did, in fact, until the eighteen-seventies, when demand for timber to build new cities made the hillsides profitable; the rebuilding of San Francisco, after the earthquake in 1906, turned Boulder Creek into a boomtown, with an impressive twenty-six saloons, gambling houses, brothels, and hotels. Almost every redwood tree in the seventy-mile stretch between San Francisco and Santa Cruz was sawed down—by hand. Once the trees had gone, so, too, of course, did the fire risk and most of the people. Eventually, the mountains started filling up again. Roads, bridges, dams, and electricity opened up the forests to commuters who couldn’t afford the Bay Area, refugees in search of beautiful views or alternative life styles, or both.

This quiet migration of hundreds of thousands of nature lovers has created one of the most unnatural landscapes on Earth. We have sunk wells everywhere, suppressed fires until the forest floors are thick with fuel, and run high-voltage cables right above them. The 2018 Camp Fire —which burned two hundred and forty square miles of northern California, caused an estimated $16.5 billion in damage, and killed eighty-five people—was sparked by a Pacific Gas and Electric power line. According to Cal Fire, the state’s fire-protection agency, one in ten Californian houses are in high-risk areas.

We knew most of this when we relocated from Chicago, in 1995, but no one ever suggested that wildfires made the move a bad idea. They were just background noise, like winter rains and earthquakes. Since then, though, one big thing has changed: the fire season is now seventy-five days longer. Coastal California has a Mediterranean climate, with hot, dry summers and mild, wet winters. It used to be that forests would not dry out enough to make fires a major risk until July; by October or November, the rains would arrive, largely ending the season. Not anymore. Our first real scare, in 2008, was in May. The house has been threatened by fire each of the past three years, every time—except for the latest—in October or November.

This year’s fire came after three days in which temperatures had topped a hundred degrees. Then, in the early hours of August 16th, a lightning storm blew in from the Pacific. Earlier that night, while enjoying a socially distanced birthday party on a beach with two friends, we watched its approach. Lightning was obviously not good, but there was no hint of what was coming as we drove home through what would, in two days, be the center of the blaze. A couple hours later, we were awakened by great sheets of bright white light, crashing thunder, and gales that bent the hundred-foot pines at impossible-seeming angles. It rained for a few minutes. And then, as suddenly as it had begun, it was over.

Throughout the state, lightning touched the earth nearly eleven thousand times in three days. By the first morning, the fires had begun. The flames had neither a single source, from which they would spread as winds and topography dictated, nor a distinct perimeter, where they could be fought. Instead, hundreds of separate fires burned, merging together and splitting apart, a many-headed hydra defying standard firefighting tactics. Normal fires are named after their starting point, but this one needed to be called “the C.Z.U. Lightning Complex fires,” after Cal Fire’s abbreviation for its entire San Mateo-Santa Cruz unit.

The world is getting hotter because the atmosphere and oceans contain more carbon dioxide than they used to. Air bubbles trapped in polar ice show that, during the coldest spells of the last eight hundred thousand years of ice ages, carbon-dioxide levels typically fell in a range of a hundred and eighty to two hundred parts per million; in the warmest interglacial periods, they might rise toward three hundred p.p.m. But that was before we started burning fossil fuels. Since 1958, when the concentration of carbon dioxide in the atmosphere was first consistently measured, it has been increasing a hundred times faster than when the world warmed up at the end of the last ice age. In 2019, the concentration reached 409.8 p.p.m., a level not seen in three million years.

No one can say categorically that fossil fuels caused the C.Z.U. fire, but too many of us are living in the wrong places, and the weather has gone wild. It used to be that hardly anyone in the mountains had air conditioning, because we rarely needed it, but every year now brings perhaps a dozen days in the nineties. The winters are getting drier, yet they also deliver storms of the sort we’d been told should only happen once a century. Everyone here is used to mudslides, in which saturated soils slither downhill and block roads, but in January, 2017, it rained so hard that we also got slip-outs, in which the dirt under roads liquefied and the roads simply disintegrated. When scientists talk about climate change making parts of the world uninhabitable, this is what it looks like.

Our initial plan was to set up camp with the cats, dogs, and horses at a showground eleven miles from Boulder Creek, but by mid-afternoon orders came to evacuate that, too. We ended up at the BackStretch ranch, in Aromas, in the farm country twenty-five miles farther south. Kathy had once volunteered there, and thought they might take in Ray and Smarty. In fact, its owners—Dennis and Janece Barwick—took in not just us and five of our friends but also a couple dozen other refugees, with their own array of animals. Coops full of dazed-looking chickens were unloaded off pickup trucks. Horse trailers were converted into kennels for multiple cats. Temporary corrals were thrown up for irate donkeys and peculiar-looking ponies. It could be hard to hear over the braying, whinnying, clucking, and barking, but everywhere dogs were sleeping through it all, in the dust. I felt like I had wandered into one of the migrant camps along Route 66 in Steinbeck’s “ The Grapes of Wrath .”

We pitched our tent in a shady spot between some picnic tables, a standpipe, and a portable toilet (a better location than it sounds—no one enjoys hunting for the bathroom in the darkness of a ranch at night). Meanwhile, Dennis and Janece worked the phones, ordering extra hay for horses, rustling up R.V.s to put humans in, and organizing neighbors to bring over meals, clothes, and bedding.

There is something awe-inspiring about kindness on this scale, and it infected everyone. In those first few days, most of the volunteers who usually worked at the BackStretch were off doing animal rescue in the fire zone (one of our Boulder Creek friends, a good man around a horse, ended up in a hospital with blood poisoning, after being bitten by a cat he was saving); and, without being asked, everyone just pitched in and took over. Every day, a thousand gallons of water had to be delivered into horse troughs, a ton of hay into feed bins, and two tons of droppings carried away. Droppings were my job—even if I could not be trusted with a lead rope, I knew a thing or two about shovelling up. I will never again grumble about the meagre amount that Ray and Smarty generate.

On the face of it, evolution favors selfishness. Animals that focus on staying alive, well fed, and sexually active—that is, ones that act selfishly—have more chances to pass their genes on to the next generation. Other things being equal, selfish genes should, therefore, outbreed altruistic ones. Yet they clearly do not. Humans have somehow become animals who shovel up others’ dung, rescue their cats, and keep flames from their homes. To explain this, evolutionists who call themselves “group-selection theorists” say we need to think about culture as much as genes. Biology, they point out, has given us brains so powerful that we can work together to put men on the moon and build quantum computers. Much more than any other animal, humans depend on group coöperation to flourish, which means that, for us, natural selection operates at the social as well as the genetic level. The more a group’s members help one another, the better the group as a whole can do—and so, at the group level if not at the genetic, natural selection rewards humans who show humanity.

Not that this makes us all saints. For every Dennis or Janece who stepped up in the crisis, some old friend fell strangely silent. And then there are the outright sinners, such as the illegal pot-grower charged with setting a fire near Big Sur, the man arrested for stealing the wallet of a firefighter who was battling the C.Z.U. blaze, or the bright sparks who set San Bernardino County alight with a smoke bomb intended to reveal their unborn child’s gender. Ask any refugee from the flames: ain’t no dungeon deep enough, no hellfires hot enough, for free riders, villains, or fools. But group-level selection turns enough humans, enough of the time, into righteous enforcers of morality that altruism is, on a very deep level, part of who we are.

And not just us: anthropologists studying a fifty-thousand-year-old Neanderthal skeleton, from Iraq, found that, despite being deaf, possibly blind in one eye, and barely able to walk, this man had lived long enough to allow multiple injuries to heal, reaching the ripe old age (for a Neanderthal) of forty-plus. Even the soberest scientists conclude that he must have received constant support from able-bodied friends and family. Neanderthals, like us, were humane, yet even chimpanzees and bonobos, our closest genetic kin among surviving species, show only the slightest traces of altruism. Animals like Dennis and Janece are very recent sprouts on the tree of life.

We camped out at the ranch for two more nights. It gets cold before dawn in coastal California, even in August, and the ground where we pitched our tent was anything but even. We repeatedly rolled off the blow-up mattress that Dennis and Janece had lent us, waking up on sharp sticks and lumpy stones. On the fourth day, Emily, who had come to our rescue with her big trailer, called up and insisted that we, the cats, and the dogs join her and her husband, Bruce—and their own cats, dogs, and horses—in their house. Because we had no idea when, or even whether, we would get back to our home, we felt that we couldn’t impose on them for long. A friend and her husband offered us the use of a little cottage in their back yard whenever we needed it, and other Samaritans stepped up, too, but Emily and Bruce wouldn’t hear of us going through yet another relocation.

And so we stayed on, with our own bedroom and bathroom, in Emily and Bruce’s beautiful house, with its ocean view. Ours was a five-star, white-privilege evacuation. Even the cats calmed down in the comfort that Emily and Bruce provided. We had wonderful company, long conversations, fine food and martinis, faster Internet access than at home, and a big-screen TV—on which we watched, night after night, California burning, a plague slaying thousands, the Gulf Coast flooding, rioting in the streets, and a President , seemingly bent on banishing our better angels, sowing discord from the White House.

It is hard not to feel like these are the end times. Yet, if a career in archaeology and history has taught me anything, it is not to underestimate the human capacity to adapt, to innovate, and to find solutions. On average, we live thirty years longer today than our great-grandparents did, grow four inches taller, and earn six times as much. (These are global averages: in much of Africa and Asia, changes have been even faster.) In 1900, few men and almost no women had a say in choosing their own leaders. As recently as 1960, the year I was born, nearly half of the people on Earth still could not read or write their own names. The human condition has improved more in the past hundred years than it did in the previous hundred thousand, and, for all we know, the next hundred will go better still. 2020 does not have to be the new normal.

Although only one person was killed in the C.Z.U. fires, and the flames were stopped some yards from downtown Boulder Creek, nine hundred and twenty-five houses did burn, leaving perhaps three thousand people homeless. Six of those houses belonged to good friends. You can no longer tell yourself that this isn’t really happening when you’re holding a friend who’s lost everything. I can find words for an essay like this, but not for a moment like that.

In the old days, the only way to know if your home had burned was to wait until the roadblocks were removed and then drive up to see for yourself. It’s hard to imagine what it was like rounding the last bend. I suspect there are no atheists in a forest fire. Now, though, you can follow the fire online, on maps updated multiple times a day. If your house turns yellow on the map, up to twenty per cent of it has burned; if red, it has gone. No news really is good news. Gradually, as we compulsively checked the maps, our confidence grew that we were going to make it. By the end of the first week, the firefighters had secured a line along the Route 9 corridor, a mile or so from us.

We got back almost exactly two weeks after we left. Our place looked pretty much as we had left it. Someone had been inside, opening doors and knocking things over, but nothing had been stolen or vandalized. The garden was dry and shrivelled, but mostly still alive. Despite fourteen days without water, the tomatoes and basil were, in fact, going gangbusters. The feral cats had not only stuck around but brought a friend to stay with them. Even our disasters were vaguely comical: three wild pigs had taken up residence in the yard, cooling off in a trough and uprooting everything else. So we set to work, cleaning out our stinky fridge, fixing the damage the pigs had caused, and preparing for next time. The fire season is barely half done and it is a hundred and eleven degrees outside.

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By Robert P. Baird

By Amy Davidson Sorkin

By Adam Iscoe

California wants to harness more than half its land to combat climate change by 2045. Here's how

C alifornia has unveiled an ambitious plan to help combat the worsening climate crisis with one of its invaluable assets: its land.

Over the next 20 years, the state will work to transform more than half of its 100 million acres into multi-benefit landscapes that can absorb more carbon than they release, officials announced Monday. The so-called nature-based solutions will span natural and working lands such as forests, farms, grasslands, chaparral, deserts and other types of ecosystems and urban environments.

The first-of-its-kind plan — part of Gov. Gavin Newsom's California Climate Commitment geared toward helping the state reach carbon neutrality by 2045 — includes 81 targets that will help harness the power of millions of acres across the Golden State.

"We're setting aggressive and ambitious new targets to use California's lands to fight the climate crisis," Newsom said in a statement. "This scale of action is unprecedented, and yet another example of California punching above its weight. From restoring and conserving lands to greening our urban spaces and treating more acres to prevent wildfires, we're protecting nature and allowing it to work for our communities."

Among the 2045 targets announced Monday are 33.5 million acres that will be managed to reduce wildfire risk, mostly through fuel-reduction activities and beneficial fire practices . Those practices include cultural and prescribed burns, which are intentional fires designed to sear through overgrown vegetation and other material that can act as fuel for flames.

To get there, the state seeks to conduct 1.5 million acres of wildfire risk reduction activity per year by 2030; 2 million acres per year by 2038, and 2.5 million acres per year by 2045, most of which will be applied to forests, shrublands, chaparral and grasslands, which together comprise about 67% of the state.

(By comparison, the California Department of Forestry and Fire Protection completed about 105,000 acres of fuel treatment, including 36,000 acres of prescribed burns during the 2023 fiscal year, according to agency data. The U.S. Forest Service completed about 312,000 acres of combined treatment and burns).

The plan also calls for 11.9 million acres of forestland to be managed for biodiversity protection, carbon storage and water supply protection by 2045, and 2.7 million acres of shrublands and chaparral to be managed for carbon storage, resilience and habitat connectivity, among other efforts.

"We've had a really strong environmental conservation movement in California, and we're clearly strong on climate action, but we haven't integrated nature into our climate agenda," said Wade Crowfoot, California's natural resources secretary. "And so this is really the next tangible step to do that."

State officials on Monday also announced California's first new state park in nearly a decade. Dos Rios will span 1,600 acres near the confluence of the Tuolumne and San Joaquin rivers in Stanislaus County. Dos Rios — California's 281st state park — will open June 12, and will provide preservation benefits as well as floodplain protection, officials said.

Crowfoot noted that nature-based solutions are gaining attention not only in the state, but also on the international stage, with the Intergovernmental Panel on Climate Change validating their critical importance in ongoing efforts to stabilize the climate.

"This is all about improving the health and the resilience of our lands, whether that's forests and deserts and farms and coastal areas," Crowfoot said. "Healthy, resilient lands ... do a better job absorbing and storing carbon, and avoid emissions."

But the move was also prompted by the results of California's 2022 Scoping Plan for Achieving Carbon Neutrality , which analyzed for the first time the amount of greenhouse gas emissions produced and absorbed by the state's lands. The analysis found that California's lands currently emit more than they absorb — principally in the form of wildfires, which spew carbon dioxide and other harmful emissions .

In fact, a recent study found that California wildfires in 2020 — the state's worst fire season on record — released about 127 million metric tons of carbon dioxide equivalent, or almost twice the tonnage of greenhouse gases as the total amount of CO2 reductions made since 2003.

"This shift from carbon sink to carbon emitter is largely due to historic land use decisions, including disconnection from beneficial land management practices utilized by California Native American tribes, and the accelerating impacts of climate change," the governor's office said. "Modeling suggests that aggressive near-term efforts to increase climate action on California's lands will put this sector on the path to course correction."

The plan also comes on the heels of Earth's hottest year on record , which has seen scientists and public officials alike sounding alarms about rapid global changes made worse by fossil fuel emissions.

What's more, the planet is teetering on the brink of 1.5 degrees Celsius (2.7 degrees Fahrenheit) of warming over preindustrial levels — an international benchmark for avoiding the worst effects of climate change — and is already beginning to see worsening wildfires, stronger storms, more severe droughts and accelerating species loss, among other effects.

Reducing carbon emissions is key to preventing such outcomes from getting worse, experts say. The current level of carbon dioxide in the atmosphere is hovering around 425 parts per million — well beyond safe limits .

"The science is very clear: Shifting our lands from a source to a sink requires aggressive near-term action, and the longer we wait, the harder it will become," said Lauren Sanchez, Newsom's climate advisor.

Other items outlined in the plan include managing 3.4 million acres of croplands for healthy soils, drought resilience and below-ground biodiversity, as well as conservation. This includes about 152,000 acres per year by 2030; 206,000 acres per year by 2038, and 209,500 acres per year by 2045.

Much of this work will include practices that sequester carbon and provide multiple benefits on working lands, such as increased water holding capacity and improved nutrient cycling, said Karen Ross, secretary of the California Department of Food and Agriculture.

Indeed, agricultural emissions in the United States account for about 10% of the country's emissions, according to the latest greenhouse gas emission inventory from the U.S. Environmental Protection Agency. The California Air Resources Board estimates that in California, agriculture is the source of 8% of total inventoried greenhouse gas emissions.

"I know that with the continued investment, cooperation and partnerships that we're building, we can continue to be a leader in the nation of putting these practices on the soil, and being [a] carbon sink," Ross said.

But it's not just agricultural land that will play a part in the state's land-use transformation. The program also calls for 4.2 million trees to be planted across California, which will help remove carbon, combat heat and increase access to nature. Studies have shown that areas without trees can simmer several degrees hotter than their leafier counterparts, with poor neighborhoods often bearing the brunt of extreme temperatures .

Trees and vegetation also contribute to more permeable soil that creates more opportunities for water to seep into the ground and replenish groundwater aquifers that have been sapped by agriculture, drought and overuse.

In fact, many of the projects — which will span more than 40 state agencies, tribal partners and stakeholder groups — will have multiple benefits, said Liane Randolph, chair of the California Air Resources Board. For example, healthier forests can mean healthier soils and water tables, as well as reduced wildfire risks and improved air quality.

The solutions were developed "not just to support carbon storage and help achieve carbon neutrality by 2045, but also for the much larger public health and environmental benefits that come with restored and sustained ecosystem health," Randolph said. She added that the phased rollout of the targets means that many Californians will begin to see benefits long before the 2045 deadline.

The governor's plan also includes 1.6 million acres of grasslands managed to restore native grasslands and protect biodiversity; and 1.5 million acres of sparsely vegetated lands — such as deserts and beaches — managed to protect fragile ecosystems. More than 230,000 acres of wetlands and seagrasses will be managed to protect water supply, deliver carbon benefits and buffer communities from flooding.

The cumulative targets amount to nearly 60 million acres across California by 2045, although it's possible some projects will overlap, officials said.

There is currently no specific price tag attached to the work. The state only recently saw several of its key climate programs placed on the chopping block as Newsom seeks to close a massive budget gap.

The work will "require significant investment and levels of action collectively," acknowledged Amanda Hansen, deputy secretary for climate change with the Natural Resources Agency. However, she noted that according to the Scoping Plan, the cost for delivering on the targets is significantly less than the estimated costs for addressing emissions in fossil fuel sectors.

The targets are intended to help guide state policy and investment, Hansen said, and will work in conjunction with the Scoping Plan and with Assembly Bill 1757 , a 2022 bill that required the state agencies to collaborate on setting targets for carbon sequestration and nature-based solutions. The Newsom administration has invested $9.6 billion in nature-based solutions since 2020.

Officials described the plan as "among the most comprehensive in the world" and said they believe it can act as a model for other states and regions.

"These climate targets are a big deal for California, for the nation, and for the world," Sanchez said.

This story originally appeared in Los Angeles Times .

Housing | Should wildfire victims get a break from…

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• Environment

Housing | Should wildfire victims get a break from California’s home solar mandate?

A bill would exempt low and middle income wildfire victims from solar panels requirements on rebuilt homes that didn’t have them when they burned down..

By Ryan Sabalow | CalMatters

Hundreds of homes in Joe Patterson’s Northern California Assembly district burned to the ground in the Caldor Fire .

In the three years since that devastating summer, many of those rebuilding homeowners have ended up on the hook for tens of thousands of dollars, thanks to state laws that require solar panels on new homes — even on those that didn’t have them before they burned down.

“Trust me when I say this: $25,000 to build solar onto a house where people do not have solar is 100% an impediment to rebuilding,” Patterson, a Republican from Rocklin , told the Assembly Natural Resources Committee earlier this week.

Patterson’s Assembly Bill 2787 , which passed the committee unanimously, would give some of those poorly-insured, low- and middle-income homeowners rebuilding after a natural disaster a break from the state’s solar-panel building requirement.

The bill would exempt homeowners at or below the median income for their county from the state’s building codes that require new solar on homes if they’re damaged or destroyed in a natural disaster. The legislation, which would expire in 2028, also would limit the benefit to those who don’t have an insurance plan that would cover the costs of the upgrade to new solar.

The bill now moves to the Assembly Appropriations Committee, where it faces an uncertain future. Last year, that committee killed a similar bill by Republican Assemblymember Jim Patterson of Fresno.

Joe Patterson, no relation,  told CalMatters he expects his bill, which is coauthored by the Fresno Republican, to make it through the committee this time since it doesn’t contain funding for a study like last year’s bill.

It’s another matter whether Gov. Gavin Newsom will sign it if the bill is also approved in the Senate and reaches his desk. In 2022, Newsom vetoed a similar bill, citing the need for solar power to reduce greenhouse gases that are a contributing factor for wildfires.

Solar power is a critical part of the state’s ambitious goal to achieve 90% carbon-free electricity by 2035 and 100% by 2045. Large-scale and rooftop solar is projected to prove more than half of the grid’s power by 2045.

“Extending this exemption would nullify these positive outcomes and instead would increase homeowner energy costs at a time when many homeowners are facing rising electric rates and bills,” Newsom wrote in his veto message .

Asked about this latest bill, Newsom’s press office responded that the governor doesn’t typically comment on pending legislation.

Joe Patterson said he hopes Newsom would support this bill, given that it’s more narrow than the one he vetoed in 2022, and because some Caldor Fire victims with poor insurance say they never received federal disaster relief cash to help them rebuild .

Meanwhile, the insurance crisis in California’s wildfire country has only gotten worse since.

After the devastating wildfire seasons of 2017 and 2018, private insurance companies have been dropping policies for hundreds of thousands of Californians, forcing many to join the state’s home insurer of last resort known as FAIR plan or risk going uninsured.

Just last month, State Farm announced it wasn’t renewing 72,000 California home and apartment policies .

In his testimony before the Natural Resources Committee , Patterson said his district has seen skyrocketing numbers of constituents on the FAIR Plan.

“In 2019, we had roughly 8,100 households covered by the FAIR Plan in my district,” Joe Patterson told the committee. “Now, in 2023, we have 41,000 people covered by the FAIR Plan.”

He said the FAIR plan, at most, will only pay 10% of the costs to upgrade a destroyed home to the most current building codes including mandatory solar panels.

“And that 10% coverage really won’t go very far, especially to cover a solar system that costs about $25,000,” Patterson told the committee.

As Patterson testified, sitting beside him was El Dorado County Supervisor George Turnboo. His district includes Grizzly Flats, which was torched in the Caldor Fire.

“The costly burden on the Caldor Fire survivors trying to rebuild their lives is not worth the minimal benefit solar technology provides them in a very high snow and forest region,” Turnboo said.

Their arguments resonated with the 11 members of the Natural Resources Committee, including eight Democrats, who voted to pass the bill over objections from the solar industry.

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Lawsuit Puts Fresh Focus on Eric Hovde’s Comments About Older Voters

Pressed on his claims of 2020 election irregularities, the Republican candidate for Senate in Wisconsin has questioned the mental capacity of nursing home residents to vote.

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By Jonathan Weisman

Eric Hovde, the Republican banking executive challenging Senator Tammy Baldwin in Wisconsin, may be developing a problem with older voters.

The bank he leads, Utah-based Sunwest, last month was named as a co-defendant in a California lawsuit that accuses a senior living facility partly owned by the bank of elder abuse, negligence and wrongful death.

Mr. Hovde’s campaign called the suit meritless and said it was farcical to hold the chairman and chief executive of a bank responsible for the actions of a business that it seized in a foreclosure in 2021. Whatever its merits, the suit might have been largely irrelevant to Mr. Hovde’s political campaign had he himself not boasted recently of having gained expertise in the nursing home industry as a lender to such residences.

In comments this month in which he suggested there had been irregularities in the 2020 election, Mr. Hovde drew on that experience to say that residents of nursing homes “have a five-, six-month life expectancy” and that “almost nobody in a nursing home is at a point to vote.” Those remarks were quickly condemned by Democrats in Wisconsin and by the former Milwaukee Bucks star Kareem Abdul-Jabbar.

The recent pileup of problems is an inauspicious start to a campaign that Republicans hope will help wrest control of the Senate from Democrats. Mr. Hovde is one of four affluent Republicans who are running to unseat Democratic incumbents, in Ohio, Montana, Pennsylvania and Wisconsin.

Each of those states either leans heavily Republican in the upcoming presidential contest or is rated a tossup, and the loss of any one of those seats could cost Democrats control of the Senate. The deep pockets of candidates like Mr. Hovde will ease the G.O.P.’s heavy fund-raising burden as the party confronts Democrats’ early financial advantage.

But Mr. Hovde’s stumbles point to a difficulty with that self-funding strategy: With business wealth and business experience come business problems.

The wrongful death lawsuit is a case in point.

In 2021, Sunwest Bank seized the property of a 68-bed assisted living facility in Claremont, Calif., after its owners failed to repay a $6 million loan. The next year, Betty Nottoli, a 94-year-old woman with dementia, moved into the renamed Claremont Hacienda, then owned in part by a newly created subsidiary of Sunwest.

According to a lawsuit filed by her daughter, Patricia Chiuppi, Ms. Nottoli had a series of falls that Ms. Chiuppi says were caused by neglect. Court documents assert that the staff of the facility failed to install pull cords, pendants, bed rails or a bed alarm even after a fall in March. Then, on the night of April 4, 2022, another fall broke Ms. Nottoli’s hip, “which ultimately led to her death on June 19, 2022,” court documents say.

Ben Voelkel, a spokesman for the Hovde campaign, said in a statement that there was “no basis for this claim.” He added: “The lawsuit fails to identify the circumstances surrounding the incident. It admits that they are unknown.”

Lisa Flint, the lawyer representing Ms. Chiuppi, declined to comment at length, saying discovery in the suit was just beginning, with a trial date set for March 25, 2025.

“The documentation from the facility showed bruising, injuries to arms, head, but no real investigation into her falls,” Ms. Flint said.

Initially, only Claremont Hacienda and its parent companies were named in the suit, but on March 25, Ms. Flint amended the complaint to name one of the place-holder defendants: Mr. Hovde’s Sunwest Bank, identified legally as one of the “owners, officers, administrators, managers and/or members” of the elder care facility.

A lawyer for Sunwest, Robert S. McWhorter, said the bank had yet to answer the lawsuit because Ms. Flint had yet to serve it the papers. He said the lawsuit was frivolous, that Sunwest should not have been named, and that the complaint does not allege direct involvement by Sunwest.

Mr. Voelkel said in a statement: “Sunwest Bank was a member of an L.L.C. that came into ownership of the facility through a foreclosure. A third party unrelated to Sunwest and the L.L.C. managed the facility. The lawsuit is meritless, which may be why the filing attorney has not actually served Sunwest and has stopped communicating with the bank.”

He also accused Ms. Flint of being a “Democrat donor,” based on a single $5 donation in 2020 to ActBlue, which consolidates political donations to Democratic candidates.

With a trial set to begin four months after the 2024 election, an elder abuse and wrongful death lawsuit in Southern California might have seemed remote to voters in Wisconsin.

But Mr. Hovde has himself drawn attention to his work in the nursing home world. Pressed by a Milwaukee television newscaster this month on his claims of “issues” in the 2020 election, Mr. Hovde replied , “Look, I do lending into the nursing home community, or used to.” And it is true: Sunwest has claimed millions of dollars in revenue from its assisted living properties, including Claremont Hacienda.

Mr. Hovde went on to cite allegations of voter fraud, appearing to suggest that residents were not in a condition to vote: “The average life expectancy in a nursing home is four to five months. How can you have, you know, the Racine County sheriff finding 100 percent of the people voting, and by the way, kids of parents, elderly parents who are dying, saying, ‘Who voted for my parent? Who did that?’”

Days later, Mr. Hovde pressed a similar point on the Guy Benson political talk show . “If you’re in a nursing home, you only have a five-, six-month life expectancy,” he said. “Almost nobody in a nursing home is at a point to vote, and you had children, adult children, showing up, saying, ‘Who voted for my 85- or 90-year-old father or mother?’”

Mr. Hovde was referring to a real dispute from the 2020 election in Wisconsin. In 2021, the Racine County Sheriff’s Office accused the State Elections Commission of improperly barring people deputized to help with absentee ballots from entering nursing homes to assist older voters. The commission had ruled that such “special voting deputies” posed too much of a health risk during the Covid-19 pandemic, given the toll the disease had already taken on assisted living facilities.

The dispute has lingered. The county sheriff, Christopher Schmaling, a Republican, said nearly a year after the 2020 election that his office received a complaint from a woman whose mother was marked as having cast a ballot even though she died before Election Day. The sheriff’s office said turnout was higher in 2020 than usual, and some nursing home residents who cast ballots had not voted since 2016 or 2012.

But Wisconsin’s overall turnout was sky-high in 2020, at 72.3 percent, and audits of the election found no widespread fraud, in nursing homes or elsewhere.

Mr. Hovde’s suggestion that “almost nobody in a nursing home is at a point to vote” has attracted considerable attention. In Wisconsin, people 65 or older make up 18 percent of the state’s population — and thus a significant voting bloc, especially since they have a high propensity to vote.

In recent days, Mr. Hovde has tried to clarify his comments. This week, he reiterated his belief that “a large percentage” of nursing home residents “are not in the mental capacity to” vote. But he added in an interview on Wisconsin radio, “I think elderly should absolutely vote.”

That might not put the matter to rest — especially since Mr. Abdul-Jabbar, known in much of the country as a Los Angeles Lakers great but remembered by Wisconsin residents of a certain age as a Milwaukee Bucks star, weighed in.

“What’s troubling here is his desire to take away the rights of people who have spent a lifetime contributing to this country based on a physical attribute: age,” Mr. Abdul-Jabbar wrote on his Substack account . He added: “Even if there was some fraud, the goal should be to uncover it, not deny everyone in nursing homes the vote.”

On April 12, the Wisconsin Democratic Party organized a protest against Mr. Hovde in Milwaukee with a small clutch of older voters, elder care workers and nursing home employees. On a windy, cool day, assisted living residents took turns at a Lucite lectern denouncing the Republican and vowing to vote against him.

“It’s clear California bank owner Eric Hovde does not care about seniors or their families,” said Arik Wolk, a spokesman for the Wisconsin Democratic Party.

Jonathan Weisman is a politics writer, covering campaigns with an emphasis on economic and labor policy. He is based in Chicago. More about Jonathan Weisman

Our Coverage of the 2024 Election

Presidential Race

The Trump campaign and the Republican Party plan to dispatch over 100,000 volunteers and lawyers to monitor elections in battleground states  — and work in concert with conservative activists.

The prospect of Robert F. Kennedy Jr. threatening to upend the presidential race  went from an idea to a reality in one of the country’s most consequential battlegrounds, when Kennedy qualified for the ballot in Michigan .

Gov. Kristi Noem of South Dakota, a potential vice-presidential pick for Donald Trump, refused to say whether she would have certified the 2020 election  if she had been in Mike Pence’s position. She also dodged questions about exceptions to abortion bans.

Other Key Races

A high-energy crowd rallied in Pittsburgh to support Representative Summer Lee, a left-leaning congresswoman whose primary is a high-profile test  of whether she can stave off a challenge aimed in part at her stance over the war in Gaza.

After Hamas’s Oct. 7 attack on Israel, pro-Israel political groups put the Democratic Party’s most outspoken critics on notice. The groups have raised millions to challenge candidates they see as not sufficiently pro-Israel, but have spent little  as public opinion shifts.

Pressed on his claims of 2020 election irregularities, the Republican candidate for Senate in Wisconsin has questioned the mental capacity of nursing home residents  to vote.

Nevada’s once-sleepy Republican primary for Senate, which has been dominated by Sam Brown, a U.S. Army veteran, was jolted to life when a deep-pocketed rival  took aim at the front-runner.