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Fanning the Flames: Climate Change and Wildfires in California

Large-scale forest fires can happen anywhere in the United States. In 2019 the National Interagency Fire Center, based in Boise, Idaho, coordinated emergency logistical responses to major wildfires in 30 states. During 2011-2020 an average of 7,520,000 acres have burned annually across the country, taking thousands of homes and causing dozens of deaths each year.

In this past decade accidental fires in the American West and Southwest have become increasingly destructive of private property, especially in California. This increase is only partially due to the number and extensiveness of the fires; it is also due to a growing population of humans willing to build and buy valuable homes in highly risky areas. As summarized by Jason Metz, a former insurance investigator now on the editorial staff at Forbes Advisor, of the ten American metropolitan areas most at risk of catastrophic damage from wildfires seven are in California, two are in Colorado, and one is in Texas.

According to Metz, 15% of forest fires are sparked by lightning. The other 85% are caused by people being careless with cigarettes, campfires, brushfires, and gasoline-powered tools as well as electrical equipment. In addition to these common causes, every year there are a few unusual cases of deliberate arson by criminals and neglected maintenance by power utilities.

All firefighters learn that three factors essential for fire are air, fuel, and heat—specifically enough heat energy to ignite a flash point and sustain an oxidation chemical reaction. Efforts to explain the apparent spike in forest fires have led researchers to consider all three factors as possibilities to be investigated. In other words, although the proximate cause of most wildfires may be human carelessness, the larger context creates changing conditions regarding air, fuel, and heat that gradually make wildfires more severely threatening.

Regarding air, the concentration of oxygen in the earth’s atmosphere is constant at 21% but wind patterns blowing counterclockwise from high-pressure systems over the interior Great Basin east of the Sierra Nevada Mountains have been peaking in recent years—driving downhill Santa Ana winds in southern California and Diablo winds in northern California. Regarding fuel, increasing damage by insects, particularly the mountain pine beetle, is adding to the standing deadwood and forest-floor litter. Entomologists agree that the recent lack of hard winter freezes has allowed the beetle population to explode, resulting in the killing of millions of trees. Regarding heat, environmental scientists conclude that global warming is the most significant contributing factor.

It is important to realize that some species of plants depend on fire to fulfill the life cycle. For example, certain conifer trees do not release their pinecone seeds until scorched by fast-moving flames. In this sense it is accurate to say that they have co-evolved with fire. In prehistoric times when Native Americans noticed that lightning started fires they learned to start their own, carefully planning the scope and scale of the burn to alter forest habitat to their own advantage. These intentional burns continued for over 5,000 years until they were outlawed by the California government in the nineteenth century.

In the February 2020 issue of Nature Sustainability (www.nature.com/natsustain) Rebecca Miller of Stanford University, Katherine Mach of University of Miami, and Chris Field of Stanford University published a rigorous technical study proposing a return to controlled burns as a way to reduce the deadwood problem. The authors acknowledged, however, that existing California laws as well as lack of funding and trained personnel rendered such a solution unlikely. To their dismay, politically conservative columnists used the article as an opportunity to fix blame for wildfires on California Democrats, due to poor land management policies.

In response, Miller, Mach and Field replied to the Republican pundits and at the same time a more general readership in Scientific American: “The science is clear. Climate change plays an undeniable role in the unprecedented wildfires of recent years. More than half of the acres burned each year in the western United States can be attributed to climate change. The number of dry, warm, and windy autumn days—perfect wildfire weather—in California has more than doubled since the 1980s.”

Although California meteorologists used to speak of a fire season in late fall, the number of dry, warm, and windy days has risen around the calendar to establish the threat of wildfires as a constant phenomenon. These year-round fires are mostly small outbreaks, however, that are quickly extinguished.

Wikipedia contains an informative entry entitled “List of California wildfires,” which explains that the size of California is approximately 100,000,000 acres, and that since 2000 the area that burns annually has ordinarily ranged between 0.1% and 1.6%. The entry is actually three lists: largest wildfires, deadliest wildfires, and most destructive wildfires. The lists document that wildfires are nothing new in California. As three examples, the Santiago Canyon Fire of 1889 burned 300,000 acres, the Berkeley Fire of 1923 destroyed 640 businesses and homes, and the Griffith Park Fire in Los Angeles County in 1933 killed up to 58 firefighters.

Nevertheless the damage done in recent years is alarming. The Atlas Fire in October 2017 burned 781 structures and killed 6 people. The Tubbs Fire, also in October 2017, burned 5,643 structures and killed 22. The Camp Fire in November 2018 burned 18,804 structures and killed 85, including 51 in the town of Paradise. The fire known as the LNU Lightning Complex in August 2020 burned 1,491 structures and killed 6, while the North Complex Fire, also in August 2020, burned 2,320 structures and killed 15.

The article states, “During the 2020 wildfire season alone, over 8,100 fires have contributed to the burning of nearly 4.5 million acres of land, making it the largest fire season in California’s modern history.”

The burning of 4,500,000 acres comprises roughly 4.5% of the total land area in the state, or about three times the expected maximum of 1.6% based on the experience of the past twenty years. During the 1950s and 1960s the burn area was about 250,000 acres, or approximately 0.0025% of California land per year. Although it may seem that this increase by a multiplier of 1800 over a span of 50 years represents an unsustainable calamity, it actually is a return to previous levels.

The Wikipedia article goes on to state, “…from a historical perspective, it has been estimated that prior to 1850, about 4.5 million acres burned yearly, in fires that lasted for months, with wildfire activity peaking roughly every 30 years, when up to 11.8 million acres of land burned. The much larger wildfire seasons in the past can be attributed to Native Californians regularly setting controlled burns and allowing natural fires to run their course, which prevented devastating fires from overrunning the state.”

The estimate of 4,500,000 acres burning annually before the Gold Rush in 1849 was reported by Paul Rogers in the San Jose Mercury News of August 23, 2020. His article, “California fires: State, feds agree to thin millions of acres of forests” is a profile of Scott Stephens, professor of fire science in the Department of Environmental Science, Policy & Management at the University of California at Berkeley, and his work at the Fire Sciences Laboratory, also known as the Stephens Lab for Research and Education in Wildland Fire Science.

Case studies conducted by Stephens and his students in the Sierra Nevada Mountains have documented that mechanical thinning and managed fire does not damage populations of other woodland creatures such as mammals and birds. To the contrary, controlled thinning and burning can reinvigorate entire forest habitats. His faculty research description states that he “…is interested in the interactions of wildland fires and ecosystems. This includes how prehistoric fires once interacted with ecosystems, how current wildland fires are effecting ecosystems, and how future fires, changing climates, and management may change this interaction. He is also interested in forest and fire policy and how it can be improved to meet the challenges of the next decades, both in the US and internationally.”

Scott Stephens at UC Berkeley, like his colleagues at Stanford University mentioned above, is finally succeeding at changing public opinion and political will about the beneficial potential of strategic burning on public lands. His interest in improving fire policy internationally is a reminder that the upsurge in large fires is a global phenomenon. Bruce Lieberman, writing for Yale Climate Connections, provided an overview of the problem from an international viewpoint in July 2019.

Currently more than 2,700,000 people in California live within zones of very high fire hazard. Returning to the analysis by Jacob Metz in Forbes Advisor, insurance industry statistics show that in the United States 99% of loss claims originate in California. Some companies are declining to write new policies in the state, or are insuring only highly priced properties. Many states have adopted a FAIR plan (Fair Access to Insurance Requirements), which are pooled risk associations among underwriters. Such coverage is expensive and difficult to acquire; in California a homeowner may apply for insurance from a FAIR plan only after being rejected by three individual companies.

Such disincentives may eventually change consumer behavior. In the meanwhile advice toward mitigation includes installing fire-resistant roofing, trimming overhanging tree limbs, clearing vegetation around the perimeter of dwellings and outbuildings, and having an escape plan. The ultimate futility of such measures suggests that the only reliable firebreak will be the eventual reduction of greenhouse gases in the atmosphere.

Marshall Shepherd. “The science of ‘diablo winds’ fanning California wine country fires.” Forbes October 11, 2017.


Rebecca Miller, Katherine Mach, and Chris Field. “Barriers and enablers for prescribed burns for wildlife management in California.” Nature Sustainability February 2020.


Rebecca Miller, Katherine Mach, and Chris Field. “Climate change is central to California’s wildfires.” Scientific American October 29, 2020.


Alejandra Borunda, “The science connecting wildfires to climate change.” National Geographic September 17, 2020.


Jason Metz, “What to know about wildfire insurance.” Forbes Advisor May 11, 2021.


“Wildfires and climate change.” Center for Climate and Energy Solutions

Henry Fountain, “Wildfires threaten urban water supplies, long after the flames are out.” New York Times June 24, 2021.

Bruce Lieberman, “Wildfires and climate change: what’s the connection?” Yale Climate Connections. July 2, 2019

Kathryn Prociv, “Wildfires erupt after hottest week in history across parts of the West ignited them. “NBC News June 21, 2021.


 “The ecological benefits of fire.” National Geographical Society Resource Library.   January 15, 2020.


Scott L. Stephens, “Let It Burn” and other research reports. University of California at Berkeley Fire Sciences Laboratory. June 12, 2012.

https://nature.berkeley.edu/stephenslab also https://vcresearch.berkeley.edu/faculty/scott-l-stephens

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