It was just after sunrise on New Year’s Eve when climate scientist Daniel Swain paused outside his home in Boulder county, Colorado. Snow was beginning to fall and a strong acrid smell – “like burned plastic”, Swain said – hung on the newly chilled breeze.
A fast-moving wildfire had torn through the area the day before, leaving devastation in its wake. Driven by winds of more than 100mph, what started as a small brush fire swiftly consumed nearly 1,000 homes within 24 hours.
While relatively small in size – just 6,000 acres – the wildfire was the most destructive in Colorado’s history, a feat that speaks to the growing danger of what Swain calls the “urban fire storm”. Areas where suburban sprawl meets landscapes primed by drought and other climate conditions to burn – known as the wildland urban interface (WUI) – are growing, posing new threats in places once considered safe from wildfire.
The Colorado fire engulfed neighborhoods and commercial districts alike, forcing 35,000 people to flee their homes. It torched a Target, a Tesla dealership, and a Costco, not long after unsuspecting Sunday shoppers were evacuated. Two people are still missing.
“The wildland urban interface extends over a far broader area than many folks realize – and it is also dynamic,” Swain said. “Most of the time it is true that these areas are safe from wildfire but given conditionally extreme wind conditions and extreme drought, they became part of that interface.”
That the fire also happened in December, a time once considered well outside of fire season, has also raised alarm. “It was strange to have the snow start falling,” Swain said, “and to have that smell of the remnants of almost 1,000 homes wafting through the air.”
The area had had one of its warmest winters. This year, the 30in of snowfall Boulder typically gets by December failed to appear. The region saw just 1.6in of precipitation since the beginning of August. “That’s natural variability,” Atmospheric scientist Matthew Cappucci noted on Twitter, “But in warmer world, it’s easy to evaporate more of what little water falls.” When the fire ignited, drought levels in the area were classified as “extreme” by the US Drought Monitor.
It’s long been clear that what’s considered “fire season” is stretching longer, covering more months of the year. And, while that increases the number of days when a fire could start it also brings conditions in line with winter weather patterns – like dry wind – that vastly increase the danger. Strong gusts aren’t unusual in Colorado, especially in the Boulder area, but without snow and rain to dampen the risks, disaster was able to strike.
“A lot of these events – from fires to mudslides – are just a consequence of extreme events many months in the making,” said Andrew Hoell, a meteorologist for the National Oceanic and Atmospheric Administration’s physical sciences laboratory, noting the compounding effect drought and heat has had on fires. Record-low precipitation was intensified by record-high temperatures. It’s a recipe for disaster, and one that Hoell is familiar with.
“I am used to talking about extreme events,” he said. But, based in Boulder, this one hit close to home. His house was spared, but many in his community, both colleagues and friends, lost their homes. “It always gets you down. But when it’s your friends, your neighborhood, your community – it is a whole different ball game.”
Thousands without homes are searching through the rubble and trying to put back the pieces. Recovery is expected to take years. The cause of this blaze is still under investigation. The Boulder county sheriff, Joe Pelle, told reporters that downed power lines, which were initially suspected as the ignition source, have been ruled out.
Most fires are still started by people, intentionally or not, and with more people living in high-risk areas, the dangers only continue to mount. “What the science said is that growth is occurring faster in the wildland urban interface than anywhere else” said Carrie Berger, fire program manager of the forestry & natural resources extension fire program at Oregon State University. “That’s where people are moving most rapidly.”
A third of US homes currently stand in the WUI and that number is only going to grow as the construction march into the wildland continues, and as higher temperatures increase the boundaries of burnable land. That’s why scientists and disaster experts are pushing for a shift in focus from suppression to preparation.
“We live in a fire landscape,” Berger said. “I don’t think there’s any place that is safe from wildfire.” She emphasized the need for a community approach to fire safety, complete with home hardening techniques like reducing vegetation that brushes up to buildings, crafting and coordinating plans, and using fire-resistant building materials.
Climate scientist Daniel Swain echoed her calls. While this disaster hit close to home, he emphasized that the next one could occur anywhere. “This is not a unique problem to Boulder county. This is not a unique problem to Colorado. This is not even a unique problem to the American west – and I think this comes at a surprise to most people,” he said.
As temperatures rise and aridification spreads into other landscapes, big blazes could erupt out of the forested areas in the upper midwest. They could spread through Florida, burn in Georgia, or blacken suburban New Jersey the way they do now in California and Colorado.
“All of a sudden you have conditions that really aren’t all that different from what they would be like in the west,” Swain says. “That might make things possible that were simply impossible before.”