Longer, Fiercer Fire Seasons the New Normal with Climate Change

By Georgina Gustin
July 11, 2017

Firefighters in the West are starting to see it every year: an earlier start to the fire season and millions of acres of forest and range burned or ablaze as the summer just begins to heat up.

At least 60 large blazes are currently devouring parts of the West, threatening to make 2017 a record-breaking wildfire year and adding to the 3.4 million acres already burned this year. As early as April, wildfires had scorched more than 2 million acres in the United States—nearly the average consumed in entire fire seasons during the 1980s. At least 20 new, large fires have ignited in the West in the last few days, forcing thousands of people from their homes.

"All the wildfires out West at the moment—it's exploding," said Kevin Trenberth, a climate scientist in the climate analysis section of the National Center for Atmospheric Research. "It was the same last July, with fires all the way up to Alaska."

Forest ecologists and climate scientists say this is the new normal—what the fire historian Stephen Pyne has called the "pyrocene"—and recent research has solidly linked it to human activity. A study last year found that human-caused climate change had nearly doubled the amount of forest burned in the West since 1984.

"Dry periods are getting drier, and the risk of wildfire is greater as a consequence of climate change," Trenberth said. "There's a tremendous amount of fuel out there waiting for the right conditions. Whatever conditions exists, they're always exacerbated by climate change. There's always that heat variable, the increased risk."

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This year, relief appeared to come with heavy snows over the winter, which built up snowpack in the Rocky Mountains and Sierra Nevada, followed by rains this spring. But as temperatures heated up again this spring and summer, that relief may have actually made things worse.

"There are wet times and dry times, but here's the thing: the wet times promote fuel growth, and the dry times increase your vulnerability to fire," said Tim Brown, director of the Western Regional Climate Center in Reno, Nevada. "This year is a great example of that. In the Great Basin [which covers much of the West], that very wet winter caused a tremendous amount of cheatgrass, sagebrush and rabbitbrush. That's all available to burn now."

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In the West, they used to talk about a fire season," Trenberth said. "The fire season used to be 60 days, then 90 days, and now they think it's year-round. There's no pause."

The mountainous West isn't the only area that's becoming increasingly vulnerable. Earlier this year, nearly 1.6 million acres of forest and grassland burned in the Plains and the Southeast, across Texas, Oklahoma, Kansas, Florida and the Carolinas.

Those blazes came on the heels of an already bad 2016 in the Southeast, where hundreds of thousand of acres burned across Appalachia after an especially dry summer turned forests into kindling. Climate scientists say conditions in the Southeast will likely get worse, largely because forests in that region need more water than those in the West and they're not getting it. Making matters worse, communities in the Southeast usually aren't well equipped to battle blazes and are more densely populated.

The warming atmosphere is only partly to blame. Decades of battling fires has meant that fires have been unable to burn naturally, a process that clears out undergrowth. Left to grow, that undergrowth has become fuel.

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At the same time, populations in the "wildland-urban interface" have grown as development has mushroomed across the country. With millions of dollars of construction and human lives at risk, fire departments are increasingly called on to protect investments in naturally fire-prone areas.

The pressure on the Forest Service to cope with bigger, more dangerous fires, meanwhile, has meant more funding going toward fighting blazes and not enough toward preventing them in the first place.

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