Fire experts reveal ‘major shift in U.S. wildfire norms’ — and people are to blame
New research reveals “a major shift in U.S. wildfire norms,” according to experts — a shift that can be blamed on people.
University of Colorado Boulder scientists have found that human-sparked fires have steadily ticked up in recent years, researchers said in a news release on the study. The findings were published Monday in the journal Global Ecology and Biogeography.
“The leading cause of wildfire ignitions in the United States is shifting away from lightning and towards human activity,” lead author Megan Cattau, a former CIRES and CU Boulder Earth Lab scientist, said in a statement. “And it’s looking like this is going to be our new normal.”
Across the U.S., wildfires are growing larger and striking more frequently as the fire season stretches longer and longer, researchers said.
But even as fires overall grow in size, those sparked by people tend to be smaller and less hot, even though human-triggered blazes are more frequent and take place over a longer time span than blazes sparked by lightning.
The longer season creates a firefighting nightmare, researchers said.
“We can’t even call it a fire season anymore — it’s nearly all year-round,” Cattau, who now works at Boise State University, said in a statement.
There’s been a 17 percent increase in fire seasons, the study found, and “human ignitions have increased 9 percent proportionally.”
Researchers pointed out that lightning-sparked blazes can “only occur during times during the year when weather conditions are conducive to storms,” while human-made fires can happen during usually low-fire times such as spring.
“Areas dominated by lightning ignitions experience fires that are 2.4 times more intense and 9.2 times larger,” the authors write in the study. “Areas dominated by human ignitions experience fires that are twice as frequent and have a fire season that is 2.4 times longer.”
The results showing that fires are increasingly caused by people might not be a surprise.
“As our world sees increased development, we can also expect to see increased human ignitions,” Cattau said. “This shift is also bringing fires into places where there wasn’t fire before, which can damage ecosystems.”
The authors said their findings represent an advance in experts’ understanding of fires: Past studies looked at climate change impacting fire patterns, but “before this study scientists had not yet comprehensively examined the relationship between ignition source and the physical characteristics of fire and their trends over time.”
Cattau and the other researchers filled that gap by bringing together data on ignition trends from 1984 to 2016 across the U.S., analyzing 1.8 million government records and satellite data. Deadly fires that swept through California in recent years — including 2017’s Wine Country fires and the 2018 Camp Fire that killed more than 80 people — happened after the period researchers studied.
Because satellite images don’t reveal the cause of fires (or whether fires were accidental or prescribed burns), Cattau and her team relied on a U.S. Forest Service database to track what ignited each fire.
Combing through that data showed that — in most of the U.S. — human-caused fires are more frequent than those caused by lightning, researchers said, adding that “every single grid east of the Great Plains, and much of the coastal West, was human-dominated over the last 30 years.”
What changing ignition patterns mean for coming fire seasons isn’t clear yet.
“The shift to more human-caused fires results in decreased fire intensity and size, but that may not necessarily be a good thing,” Cattau said. “There’s been a focus on extreme fires, but any deviation from historical fire patterns, from what that land evolved with, can cause problems. Fire is part of the ecosystem. And now its role is changing.”
This story was originally published January 21, 2020 at 7:35 PM with the headline "Fire experts reveal ‘major shift in U.S. wildfire norms’ — and people are to blame."
