Why California’s 2022 wildfire season was unexpectedly quiet

21 December 2022

Published by: https://www.nytimes.com

USA – When a string of wildfires broke out in California this spring, experts saw it as an unsettling preview of another destructive fire season to come — the consequence of forests and grasslands parched by persistent drought and higher temperatures fueled by climate change.

Yet, by the year’s end, California had managed to avoid widespread catastrophe. Wildfires have burned about 362,000 acres this year, compared to 2.5 million acres last year and a historic 4.3 million acres in 2020.

“It’s really just that we got lucky,” said Lenya Quinn-Davidson, a fire advisor for the University of California Cooperative Extension.

This year’s relatively mild wildfire season doesn’t mean that the landscape was much less vulnerable, that the forests were in better condition or that climate change had less of an effect on the intensity and behavior of wildfires than in previous years, Ms. Quinn-Davidson said. Instead, a combination of well-timed precipitation and favorable wind conditions seemed to play the biggest role.

The Mosquito fire, this year’s largest, started on Sept. 6 northeast of Sacramento during a record-breaking late-summer heat wave. But unusually early rains unleashed by a tropical storm in mid-September tempered the blaze and helped fire crews contain it.

California has seen larger, hotter and more intense wildfires in recent years, driven by extended drought and climate change. The five largest wildfires recorded in the state have all occurred since 2018. But California’s wildfire record is punctuated with both “good” and “bad” fire years — a result of short-term, natural weather variability.

Warmer temperatures increase the potential for wildfires, once ignited, to intensify rapidly, spreading faster and scaling higher mountain elevations that might have otherwise been too wet or cool to support fierce fires. Extreme heat and drought, worsened by climate change, kill trees and dry out grass and pine needles, providing abundant fuel for a fire to spread over vast stretches of land.

A warming climate increases the likelihood of fires growing larger and more severe, but it’s not a guarantee that it will happen every year, said Andy Hoell, a climate researcher and meteorologist with the National Oceanic and Atmospheric Administration.

Fires cannot start without a spark. Many are ignited either by lightning strikes or human activity, including untended campfires, unextinguished cigarettes, engine sparks and equipment malfunction. As humans continue to move into the wildland-urban interface, or fire-prone zones on the outskirts of cities, fires started this way will become more likely.

Once a fire is ignited, there are three major ingredients that shape its behavior, experts said: the landscape’s topography, weather (including wind and precipitation) and the availability of fuels. Climate change affects some, but not all, of those elements, said Hugh D. Safford, a fire ecologist at the University of California, Davis and chief scientist at Vibrant Planet, a climate tech company.

Even though the 2022 fire season was quiet by recent standards, major blazes like the McKinney fire triggered evacuations and killed several people. Noah Berger/Associated Press

Usually, California’s fire season extends into October, and seasonal rain arrives later in the fall. But this year featured unusual storms in the summer and early fall that helped suppress dangerously growing wildfires, including the Mosquito and McKinney fires.

In Southern California, fires are often fanned by fast-moving, hot, dry winds known as the Santa Anas (also called Diablos in the northern part of the state). The winds dry out grasses and brush in the Sierra Nevada and pose the greatest fire risk in the fall, when vegetation is usually at its driest.

“We were fortunate this year that the rain started before the winds did,” said Chris Field, director of the Woods Institute for the Environment at Stanford University.

While the state saw fewer acres burn this year than in the last two years, California still recorded comparable numbers of fire incidents. As a result, this year’s fires were much smaller on average.

In previous years, a number of California wildfires had grown to monstrous scales. When fires get large, they draw on more firefighting resources, which can mean fewer firefighters are available to respond to new, smaller fires when they ignite. Those smaller fires then have the opportunity to spread quickly and grow large, particularly in the early days of a fire’s development, said Robert Foxworthy, a firefighter and public information officer for CalFire, the state’s fire agency.

The Mosquito fire grew into the state’s largest of the year, burning through communities in the Sierra Nevada, before it was tempered by unexpected rains. Max Whittaker for The New York Times

Experts warned that looking at acreage burned doesn’t tell the full story of fire danger, and neither does frequency, although those are the statistics that are most readily and comprehensively available.

Those metrics do not describe lives lost, or trees, vegetation and buildings destroyed. And it doesn’t capture damage from flash floods like those that followed the McKinney fire, which triggered massive landslides and ultimately killed scores of fish in the Klamath River.

“A lot of times we get focused on the acreage and the fewer acres burned,” Ms. Quinn-Davidson said, adding that it was important not to lose sight of the several deadly and severe fires that did happen earlier in the year. “We still saw a level of severity that is outside of the historical range of variability,” she said.

To address its growing wildfire crisis, California has begun to ramp up plans for more prescribed burning, the practice of setting controlled, low-intensity burns to rid forests of small trees and brush that can end up fueling larger wildfires. However, forest management and fuel reduction practices had less of an impact on this year’s relatively mild wildfire season than fortunate weather conditions, said Dan McEvoy, a climatology researcher with the Desert Research Institute.

While California’s wildfire season was relatively mild compared to other years in recent memory, it was still destructive and deadly, killing nine people. Wildfires also raged at record levels elsewhere in the United States this year, including in Arizona, Nebraska and New Mexico, and around the world.