As California is living through the most dangerous time of the year for wildfires due to dry and windy conditions, experts say a trio of factors make America’s most populous state more at-risk than ever.
Despite several recent wildfires outside of San Francisco and Los Angeles, there have been no significantly deadly and destructive blazes so far in 2019. Nonetheless, the long-term trend in the Golden State is toward bigger, faster-moving and more destructive wildfires, due to a combination of overgrown forests creating more fuel, climate change that causes higher temperatures and less snow, and housing construction in fire-prone areas.
“There’s no simple problem and no one simple answer,” said
statewide fire specialist based at the University of California, Santa Barbara. “It’s all of these things mixed together.”
The Anatomy of a Fire
Whether a fire spreads, and how quickly, depends on a host of factors
A fire starts, creating embers, which the heat and energy pull up into the plume.
Winds grab the embers and can whip them miles away, pushing them past
the fire’s perimeter and sparking additional spot fires.
Embers can travel up to several miles, depending on the conditions. Its size affects burnout time
Homes are vulnerable to embers where they can lodge themselves in eaves and other crevices
Fires can produce embers
from all kinds of vegetation like leaves, pine needles, small twigs
and pieces of bark.
In Northern California, where some of the biggest, most destructive fires have happened, native California hardwood trees cast dangerous embers moderate distances
California’s Mediterranean climate has long been conducive to fire. Its forests dry out every summer and become fuel for when seasonal high winds roar this time of year, creating firestorms when ignited. But in just the last decade, the state has recorded 10 of its most destructive fires, seven of its largest and five of its deadliest.
California’s fire season in the Sierra Nevada mountains is now nearly 75 days longer than it was four decades ago, according to the California Department of Forestry and Fire Protection.
A study published earlier this year by professors from schools including the University of California, Los Angeles found the annual area burned in the state quintupled between 1972 and 2018. The expansion came at the same time warm weather temperatures rose almost three degrees Fahrenheit, melting mountain snowpacks earlier. That results in soil losing moisture faster, which causes trees and brush to dry up, making them more susceptible to burning, experts say.
“Changing climates makes these things more frequent, expands the timing you can get these events,” said
research forester for the U.S. Forest Service’s Rocky Mountain Research Station in Missoula, Mont.
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Fires are only dangerous, however, when they come close to communities where people live and work.
About 11 million Californians, roughly a fourth of the state’s population, live in what foresters call the “wildland-urban interface,” close to highly vegetated areas that easily burn, according to a report last year by researchers at the Massachusetts Institute of Technology.
People who live in densely built urban areas further from wilderness face a far lower risk of wildfires.
Recent wildfires have in many cases followed the same paths as those of historic blazes, but with one big difference: more homes in the way. In Napa County, a 1981 wildfire scorched 23,000 acres, destroying 65 homes and other buildings. Another fire raced through Napa in 2017, blackening 51,624 acres and destroying 781 structures in an area that had since been significantly more developed.
“It almost seems like now that, unless you are up in a wilderness area, you can’t have a fire start that doesn’t soon become a threat to one house or several houses,” said
deputy assistant director of operations for the U.S. Forest Service.