Chico California

By Bill Walker

This summer, the Park Fire burned more than 425,000 acres near Chico, Calif. – the fourth-largest wildfire in the state’s history. It started when an arsonist pushed a flaming car into a grassy, brush-strewn gully, sparking California’s largest-ever deliberately set wildfire. But what set the Park Fire apart from the 7,194 wildfires that have burned more than 1 million acres in California this year was how fast it grew.

After first igniting on July 24, it spread an estimated 5,000 acres an hour – about one football field a second. In 24 hours it burned 150,000 acres, and in 72 hours incinerated an area larger than San Francisco. Fire experts said it was among the fastest-growing wildfires in history.

As it burned, Zeke Lunder, director of Deer Creek Resources, a wildfire management consulting firm in Chico, told The Washington Post that in 25 years of mapping large fires throughout the Western US, he couldn’t recall another blaze that spread so far so fast. He said the Park Fire “was moving in ways we aren’t used to seeing.”

It’s settled science that the climate crisis is increasing the number and frequency of wildfires. A 2016 study estimated that from 1984 to 2015, human-caused climate change contributed to the burning of almost twice the acreage in 11 Western states than might have burned in its absence.

Now, new research confirms that Western wildfires are also spreading faster.

In a study published Oct. 24 in the journal Science, a team of researchers analyzed images from NASA satellites to track the day-by-day spread of more than 60,000 fires in the continental US from 2001 to 2020.

They found that in that period, the average peak daily growth rate of wildfires in the West more than doubled. In California, wildfires spread almost four times as fast in 2020 as in 2001. They cited other research predicting that if global warming continues at its current pace, the frequency of the fastest-spreading fires in the West could double in 30 years.

“The modern era of megafires is often defined based on wildfire size, but it should be defined based on how fast fires grow,” the researchers wrote. “Speed fundamentally dictates the deadly and destructive impact of megafires… [F]ire speed matters more for infrastructure risk and evacuation planning.”