Human-caused wildfires destroying more homes, buildings in the West

Wildfires started by humans accounted for more than three-quarters of the homes and buildings lost to fire in the West during the past two decades, and structure losses increased by nearly 250% from 2010 to 2020 over the prior decade, according to new research led by a University of Montana fire ecologist.

The report from Philip Higuera, a UM fire ecologist and professor, and his co-researchers at the University of Colorado Boulder, provides public officials, developers and citizens more information on how to potentially curb the costliest damage from wildfire as the climate changes, fire seasons expand and people increasingly move into wildfire-prone areas of the western U.S., Higuera said in an interview.

It also presents an opportunity for Montana to learn from denser states that have seen wildfires destroy entire communities and cause costly losses, he said.

“The answer is not to stop all fires, right? We know that we’ve failed at that for over a century and it’s part of why we are where we are, so we know we can’t do that,” Higuera said. “So, what we want to do is to help focus in on what are the most relevant fires to immediate human wellbeing?”

The new research was published Feb. 1 in the Proceedings of the National Academy of Sciences-Nexus. The team analyzed 15,001 wildfires that occurred in the West from 1999 and 2020. Those fires destroyed around 85,000 structures and cost an estimated $29.7 billion in estimated suppression costs, according to the paper – accounting for the vast majority of acres burned, suppression costs and structure loss across the country.

The research found that while the amount of land burned in the West increased by 30% in the 2010-2020 period compared to the decade before, the number of structures that burned – primarily buildings and homes – increased by 246%.

The research also found that unplanned human ignitions – including backyard burns, abandoned campfires and power lines hitting vegetation – accounted for fires that led to 76% of the structures lost from 1999 to 2020.

As more buildings take foot in the wildland urban interface where there are more grasses, trees and other fuels, people not only expose themselves more to wildfire but increase the likelihood they or their neighbors start one that threatens their own homes, Higuera said.

“It’s not just that we have structures in flammable vegetation, and then lightning-ignited fires roar in and destroy homes. That’s not what’s happening,” Higuera said. “There’s also a very strong relationship between how much area burns from human-related ignitions and how many structures we have in flammable vegetation.”

The research notes that the area in the West burned by wildfires has doubled during the past four decades, partially exacerbated by climate change causing drier conditions, but also in part due to policies that focused primarily on fire suppression rather than stewardship.

While the more arid climate has expanded the typical Western fire seasons, according to the research, the human-caused fires have been even more consequential to that expansion and more costly.

“While the West-wide fire season for human-related ignitions was 42 days longer than for lightning-ignited fires and peaked in late July, the peak in structure loss from human-related wildfires occurred in late October,” the paper notes.

“So, it’s a good example of how climate change is interacting with human behavior,” Higuera said. “And we can change both, but one of them, we can change much more quickly.”

More than 60% of the structures destroyed from 1999 to 2020 occurred during some of the worst fire seasons on record, in 2017, 2018 and 2020, the researchers found. During the past five years, wildfires have destroyed homes in West Kootenai, Glacier National Park and near Flathead Lake.

Higuera said Montana was fortunate to have wilderness areas that see wildfire often, like the Bob Marshall Wilderness, which also have little development. But as more building occurs within and closer to areas with flammable vegetation, he said officials should keep the research “front and center” when deciding how to manage fire risks.

“We’re not saying what you should do, but if we ignore it, we’re going to end up where other states are across the West that have developed without this top of mind,” he said. “We can look to the other states that have greater density of structures in flammable vegetation – whether it’s Washington, Colorado or California – and that is where we’ll end up if we don’t do something different.”

While 77% of the structures in the West lost from 1999 to 2020 were in California, every Western state aside from New Mexico saw more buildings lost to fire, according to their report.

“An expected outcome of the increased structure abundance across the West in recent decades is an increase in both area burned from human-related ignitions and wildfire-caused structure loss, predominantly from those very ignitions,” the researchers wrote.

The paper breaks states into different types of environments – “high burn-high loss,” “low-burn-low loss” and “high burn-low loss” – in order to compare how much land typically burns to how often structures are lost in wildfires.

The researchers noted that only 12% of the fires they analyzed involved structure loss, while only 6% of lightning-started fires involved any loss of buildings.

But in states like California and Colorado, where humans more often live in flammable vegetation, people’s homes and other buildings were more likely to burn. But the researchers noted that extreme years – like 2017, 2018 and 2020 – can move states to different categories.

Montana, for instance, moved from a “low-burn, low loss” categorization toward a “low burn-high loss” one as it saw more structures lost in 2010 to 2020 compared to the decade prior despite small decreases in the land area that burned.

In January, Republican Gov. Greg Gianforte announced $3 million in funding for 11 projects aimed at reducing fuels in the wildland urban interface, forest restoration and public education about wildfire risks. He also proposed tripling the state’s wildfire suppression fund, to up to 12% of the general fund in the second year of the biennium.

The paper offers a few suggestions to reduce losses even as expansion occurs, including considering building with more fire-resistant materials, doing more fuel removal work on vegetation near buildings and homes, and finding ways to keep that equitable across various socioeconomic areas.

Higuera said he feels the paper’s findings on human-caused fire and its conjunction with climate change should inform policymakers regardless of why the climate is changing.

He said officials should triple down on communicating the risks of how people can easily start fires both during and outside the typical fire season. In Montana, he said, that would mean that in June, communicating that fuels could be dry enough to lead to fires if the state saw a warm and dry spring. The same would go for December if there hadn’t been significant snow through the fall and start of winter.

Higuera said officials should consider the report and think about modifying and amplifying Smokey Bear’s message that “only you can prevent wildfires.”

“That’s the other part, in addition to amplifying the message, is to really, really share that message … where it’s particularly important for preventing structure loss in times of the year that we’re not necessarily used to thinking about it if we just think about our past experiences or our parents’ experiences,” he said.