How climate change is making fires worse

Federal officials say climate change is intensifying droughts, leading to wildfires far worse than experts or models have predicted.

That is adding to the danger that accompanies one of the U.S. Forest Service’s primary methods of mitigation: the prescribed burn.

“Fires are outpacing our models,” Forest Service Chief Randy Moore said in a statement this week. 

Moore pointed to escalating climate conditions as the reason why an otherwise routine prescribed burn in New Mexico earlier this year escaped to ignite the largest wildfire in state history.

“Climate change is leading to conditions on the ground we have never encountered,” he said.

The Forest Service and most of the scientific community views prescribed burns as a key element in protecting the wildfire-dependent landscapes of the West from the most destructive conflagrations.

The agency said in a report that its personnel followed a prescribed burn plan in New Mexico and the burn conditions appeared to be within approved limits to keep it from escaping.

But persistent drought — which a study in Nature in February called the worst in 1,200 years — has complicated that picture.

“The first year of the drought isn’t that bad, the forests still have some humidity and energy left,” said Marc Castellnou, a fire scientist in Spain’s Catalonia region who consults frequently on fires in the U.S. West.

But Castellnou said after two consecutive years of drought, forests are more vulnerable.

“They’re just weak and stressed and available to burn. They can’t respond,” he said.

In a wetter ecosystem, water evaporating from the landscapes cools it. “But hot weather in a really dry country — there is nothing to do evaporation from,” Castellnou said. “It just keeps getting hotter and hotter, drier and drier. It’s a feedback loop.”

That has been a global problem. In Castellnou’s native Catalonia — a landscape similar in many ways to the American West — it has led to unusually large, fast and aggressive fires. 

“It’s May and fires are already behaving like it’s August or September,” he said. “The models can’t explain what’s happening. We knew climate change would have feedback, faster than expected — but even we didn’t expect this.”

Everything Spain faces, he added, is worse for the U.S. “We’re all having big fires too early,” he said.

In addition to weakening forest ecosystems, the drought also has made forests themselves more likely to burn, fire ecologist Matthew Hurteau of the University of New Mexico told The Hill.

The water in a living tree trunk — or even a dead one — generally keeps it from catching fire, even during a large blaze, he said. “I’m talking like, lying on the ground, kick it and you break a toe,” he said. 

Fire ecologists and forecasters rarely paid attention to such material as dead trees and logs, he said, “because it just wasn’t available to burn.” 

Instead, they focused on the smaller fuels found in branches, shrubs, smaller trees and canopies — trusting that big trees might char on the outside, but their large size and plentiful water content meant they wouldn’t combust.

That view has since changed.

“A lot more energy stored in large logs and dead trees is available to burn now because of sustained drought,” Hurteau said. 

In the aftermath of California’s enormous Creek Fire, “I went up and saw ash lines where big logs had been laying — just completely combusted. Remarkable. I’d seen that before, but never along whole hillsides.”

That fire began on the site of a 2011 to 2017 drought that killed and dried out millions of trees — and when it erupted in wildfire in 2020, stores of energy housed in those trees were able to be released.

That allowed the formation of a colossal pyrocumulonimbus cloud, NASA reported — a fire-created storm system that pulls in air, causing it to grow ever larger in a destructive feedback loop.

The dry conditions mean that fires are behaving in perplexing ways, according to the Forest Service chief.

“This spring in New Mexico, a pile burn of hazardous logs that started in January, smoldered underground for months, persisting through multiple snowstorms and freezing temperatures, before resurfacing as a wildfire,” Moore said in his statement. “That type of event was nearly unheard of until recently.”

In this environment, burn crews are going to have have to be a lot more cautious, Todd Gartner of the World Resources Institute told The Hill.

“We’re going to have to be increasingly conservative in when we use fire, how we use fire, and hew to the less risky side of the paradigm,” he said. “It’s gonna get a bit more spicy in the years ahead, for sure.”

Others emphasized that prescribed burns remain an important tool for forest management and can be key in preventing major fires since they help thin out forests. 

John Bailey, a professor at Oregon State University’s College of Forestry, said that when land isn’t actively managed, plants that fuel wildfires can build up. 

“Particularly out West, fire has been an important part of keeping those fuel levels low,” he told The Hill earlier this month.

“There are a lot of things we can do just generally across our forestlands…to keep those fuel levels down, and part of it is machine work and hand work and part of it is prescribed burning,” he added.

— Rachel Frazin contributed.