It can be tempting to think that the recent wildfire disasters in communities across the West were unlucky, one-off events, but evidence is accumulating that points to a trend.

In a new study, we found a 246% increase in the number of homes and structures destroyed by wildfires in the contiguous Western U.S. between the past two decades, 1999-2009 and 2010-2020.

This trend is strongly influenced by major fires in 2017, 2018 and 2020, including destructive fires in Paradise and Santa Rosa, California, and in Colorado, Oregon and Washington. In fact, in nearly every Western state, more homes and buildings were destroyed by wildfire over the past decade than the decade before, revealing increasing vulnerability to wildfire disasters.

What explains the increasing home and structure loss?

Surprisingly, it’s not just the trend of burning more area, or simply more homes being built where fires historically burned. While those trends play a role, increasing home and structure loss is outpacing both.

As fire scientists, we have spent decades studying the causes and impacts of wildfires, in both the recent and more distant past. It’s clear that the current wildfire crisis in the Western U.S. has human fingerprints all over it. In our view, now more than ever, humanity needs to understand its role.

From 1999 to 2009, an average of 1.3 structures were destroyed for every 4 square miles burned (1,000 hectares, or 10 square kilometers). This average more than doubled to 3.4 during the following decade, 2010-2020.

Nearly every Western state lost more structures for every square mile burned, with the exception of New Mexico and Arizona.

Given the damage from the wildfires you hear about on the news, you may be surprised to learn that 88% of wildfires in the West over the past two decades destroyed zero structures. This is, in part, because the majority of area burned (65%) is still due to lightning-ignited wildfires, often in remote areas.

But among wildfires that do burn homes or other structures, humans play a disproportionate role – 76% over the past two decades were started by unplanned human-related ignitions, including backyard burning, downed power lines and campfires. The area burned from human-related ignitions rose 51% between 1999-2009 and 2010-2020.

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