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California鈥檚 2020 Wildfire Season

Report Summarizes Record-Breaking Fire Year and Calls for Shift in Strategy

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Orange smokey sky with marine layer and line of wildfire in California coastal hills
A wildfire burns in Sonoma County in 2020 under an orange smokey sky. (Bill Oxford/Getty Images)

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鈥檚 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.

, 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.

鈥淎lthough burned area in 2020 was very high, it is not unprecedented if you take the longer view,鈥 said lead author Hugh Safford, a forest and fire ecologist with the 嘿嘿视频 Department of Environmental Science and Policy and chief scientist at Vibrant Planet, an environmental public benefits corporation. 鈥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.鈥

silhouette of fire fighter as forest blazes with wildfire
A Lassen Hotshot firefighter pauses during the August Complex Fire, which was ignited by lightning strikes on August 17, 2020. (Mike McMillan, Pacific Southwest Forest Service-USDA, CC by 2.0)

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.鈥 - Hugh Safford, 嘿嘿视频

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 鈥渇ire problem.鈥 This is even though climate warming has been more extreme in southern California.

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.

鈥淚n these ecosystems, reducing burned area is a cause of the current catastrophic trends, not a solution to them,鈥 the authors said.

Key 2020 wildfire statistics

The authors summarized 2020鈥檚 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 鈥 mostly homes 鈥 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鈥檚 worst five days of air pollution in history all occurred in 2020, according to CalFire.

orange sky from wildfire smoke over Oakland California street with cyclist and buildings in background
Smoke from the CZU Lightning Complex Fire in Santa Cruz and Napa turns the sky orange over Oakland, California on Sept. 9, 2020. (Getty)

Wildfire-driven air quality in August and September likely also caused 1,200 to 3,000 鈥渆xcess鈥 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鈥檚 120 times more fine particulate matter than California鈥檚 vehicles produced in the same year.

鈥榃e can do something about this鈥

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 鈥 including its effects on tree mortality before 2020 鈥 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.

鈥淓xtreme weather conditions are certainly playing a role, but climate change isn鈥檛 driving all the change we鈥檙e seeing,鈥 said Safford. 鈥淔uel 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.鈥

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, 鈥渢here is no time to lose.鈥

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

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