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By MARTHA BELLISLE
The Associated Press

The winter grassland fire that blew up along Colorado’s Front Range was rare, experts say, but similar events will be more common in the coming years as climate change sucks moisture out of plants, suburbs grow in fire-prone areas and people continue to spark destructive blazes.

鈥淭hese fires are different from most of the fires we’ve been seeing across the West, in the sense that they’re grass fires and they’re occurring in the winter,鈥� said Jonathan Overpeck, a professor in the School for Environment and Sustainability at the University of Michigan. 鈥淯ltimately, things are going to continue to get worse unless we stop climate change.鈥�

Flames swept over drought-stricken grassy fields and neighborhoods northwest of Denver last week with alarming speed, propelled by gusts up to 105 mph. Tens of thousands of residents were ordered to flee with little notice.

鈥淚 came out of Whole Foods, which is about a half mile from ground zero, and felt like I had to jump in my car and make a dash for my life as the smoke and wind and nearby flames were engulfing the area,鈥� Susie Pringle of Lafayette stated in an email. 鈥淚t was scary!鈥�

Two people were missing as of Sunday and at least seven were injured.聽Officials estimated nearly 1,000 homes and other buildings were destroyed.

The blaze burned at least 9.4 square miles. The cause is still under investigation, though experts say it’s clear what allowed the fire to spread so fast.

鈥淲ith any snow on the ground, this absolutely would not have happened in the way that it did,鈥� said Keith Musselman, a snow hydrologist in Boulder. 鈥淚t was really the grass and the dry landscape that allowed this fire to jump long distances in a short period of time.鈥�

Three ingredients were needed to start this fire 鈥� fuels, a warm climate and an ignition source, said Jennifer Balch, a fire scientist with the University of Colorado, Boulder. 鈥淎nd then you add a fourth ingredient, wind, and that’s when it became a disaster.鈥�

Temperatures in Colorado between June and December were the warmest on record, Balch said. The grasses grew thick because they had a wet spring, but saw no moisture until snow flurries arrived Friday night.

Colorado Gov. Jared Polis on Sunday called the blaze a 鈥渁 horrific convergence鈥� of destructive wind gusts that hit the area following the unseasonably dry and warm winter.

鈥淲e know that with the climate we face higher risks,鈥� Polis said. 鈥淩ight here in city and suburbs.鈥�

Colorado is a dry landscape filled with flammable material for much of the year, Balch said, 鈥渁nd those chunks of time are getting longer with climate change.鈥�

The lesson learned throughout this event is that the 鈥渨ildland-urban interface is way bigger than we thought it was,鈥� Balch said. That means a wider area is under threat of wildfire.

That border area 鈥� where structures built by people meet undeveloped land prone to fire 鈥� has always been the foothills, she said. Firefighters in Boulder consider the interface west of Broadway 鈥� a busy road that passes through the center of town. But Thursday’s fire sparked east of that line, next to thousands of houses that have sprouted up on the east side of the Rockies since the 1990s, Balch said.

鈥淭here were stretches between Denver and Fort Collins that had no development, but now it’s just like one long continuous development track,鈥� Balch said. 鈥淎nd those homes are built with materials that are very flammable 鈥� wood siding, asphalt roofing.

鈥淲e need to completely rethink how we’re building homes.鈥�

The other important change is understanding how these fires start in the first place, she said.

鈥淭here’s no natural source of ignition at this time of year; there’s no lightning,鈥� she said. 鈥淚t’s either going to be infrastructure-related or it’s going to be human-caused.鈥�

鈥淭he way we live in the landscape and our daily activities make us vulnerable,鈥� she said.

Over the past two decades, 97 percent of wildfires were started by people, according to a recent聽study聽by the Cooperative Institute for Research in Environmental Sciences at the University of Colorado, Boulder. Causes have ranged from accidents at construction sites, to a car with a hot tailpipe, to tossed cigarettes.

鈥淚 like to say we need Smokey Bear in the suburbs,鈥� she said. 鈥淲e need to be thinking about how our daily activities can contribute ignitions or sparks that start wildfires.鈥�

Unless people stop climate change by reducing use of fossil fuels, wildfires will threaten communities, Overpeck said.

鈥淭here’s little doubt in my mind that the conditions conducive to really bad wildfire, whether it’s grass or forest, are only going to get worse,鈥� he said.

As more people move to areas where wildfires occur, the threat increases.

鈥淲e’re building towns and cities and infrastructure and so it’s just a matter of time before we have whole towns burning down like we had in California and events like this in Colorado.鈥�

Editor’s note: Associated Press reporter Brittany Peterson contributed to this report.