Wind, drought worsen fires, not bad forest management, scientists say

WASHINGTON — Both nature and humans share blame for California’s devastating wildfires, but forest management did not play a major role, despite U.S. President Donald Trump’s claims, fire scientists say.

Nature provides the dangerous winds that have whipped the fires, and human-caused climate change over the long haul is killing and drying the shrubs and trees that provide the fuel, experts say.

“Natural factors and humancaused global warming effects fatally collude” in these fires, said wildfire expert Kristen Thornicke of the Potsdam Institute for Climate Impact Research in Germany.

Multiple reasons explain the fires’ severity, but “forest management wasn’t one of them,” University of Utah fire scientist Philip Dennison said.

Trump tweeted on Saturday: “There is no reason for these massive, deadly and costly forest fires in California except that forest management is so poor. Billions of dollars are given each year, with so many lives lost, all because of gross mismanagement of the forests.”

One reason that scientists know that management isn’t to blame is that some areas now burning had fires in 2005 and 2008, so they aren’t “fuel-choked closed-canopy forests,” Dennison said.

In those earlier fires, Paradise was threatened but escaped major damage, he said. In the current blazes, it was virtually destroyed.

The other major fire, in Southern California, burned through shrub land, not forest, Dennison said.

“It’s not about forest management. These aren’t forests,” he said.

The dean of the University of Michigan’s environmental school, Jonathan Overpeck, said Western fires are getting bigger and more severe. He said it “is much less due to bad management and is instead the result of our baking of our forests, woodlands and grasslands with everworsening climate change.”

As of Monday, more than 34,200 square kilometres have burned. That’s more than a third higher than the 10-year average.

The two fires now burning “aren’t that far out of line with the fires we’ve seen in these areas in recent decades,” Dennison said.

“The biggest factor was wind,” Dennison said in an email. “With wind speeds as high as they were, there was nothing firefighters could do to stop the advance of the fires.”

These winds, called Santa Ana winds, and the unique geography of high mountains and deep valleys act like chimneys, fortifying the fires, Thornicke said.

The wind is so strong that fire breaks — areas where trees and brush have been cleared or intentionally burned to deprive the advancing flames of fuel — won’t work. One of the fires jumped over eight lanes of freeway, about 45 metres, Dennison said.

California also has been in drought for all but a few years of the 21st century and is now experiencing its longest drought, which began on Dec. 27, 2011, and has lasted 358 weeks, according to the U.S. Drought Monitor. Nearly two-thirds of the state is abnormally dry.

The first nine months of the year have been fourth-warmest on record for California, and this past summer was the secondhottest on record in the state.

Because of that, there are millions of dead trees, which provide fuel for fires, Thornicke said.