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Scientists explain why wildfires are happening, why we can't put out every fire and how to move forward in an ever-changing climate鈥�

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 , 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 , and , 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鈥檚 not just the trend of , or simply . While those trends play a role, increasing home and structure loss is outpacing both.

As fire scientists, we have spent decades studying the and , in both and . It鈥檚 clear that the current in the Western U.S. has human fingerprints all over it. In our view, now more than ever, humanity needs to understand its role.

Wildfires are becoming more destructive

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.

Humans increasingly cause destructive wildfires

Given the damage from the wildfires you hear about on the news, you may be surprised to learn that . 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 鈥� 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.

This is important because wildfires started by human activities or infrastructure have and characteristics that can make them more destructive.

Unplanned human ignitions typically and that dry out easily and burn quickly. And people have built more homes and buildings in areas surrounded by flammable vegetation, with the number of structures , with every state contributing to the trend.

Human-caused wildfires also beyond the summer months when lightning is most common, and they are particularly destructive during late summer and fall when they .

As a result, of all the wildfires that destroy structures in the West, human-caused events typically structures for every square mile burned, compared to lighting-caused events.

The December 2021 Marshall Fire that destroyed more than 1,000 homes and buildings in the suburbs near 色吧亚洲, Colorado, . Powerful winds racing through neighborhoods and vegetation that was unusually dry for late December.

As human-caused leaves vegetation more flammable later into each year, the consequences of accidental ignitions are magnified.

Putting out all fires isn鈥檛 the answer

This might make it easy to think that if we just put out all fires, we would be safer. Yet a focus on is, in part, what . Fire risks just accumulate for the future.

The amount of flammable vegetation has increased in many regions because of an absence of burning due to emphasizing fire suppression, preventing and a fear of fire in any context, well exemplified by . Putting out every fire quickly removes the positive, in Western ecosystems, including clearing away hazardous fuels so future fires burn less intensely.

How to reduce risk of destructive wildfires

The good news is that people have the ability to affect change, now. Preventing wildfire disasters necessarily means minimizing unplanned human-related ignitions. And it requires more than message that 鈥渙nly you can prevent forest fires.鈥� Infrastructure, like downed power lines, some of the deadliest wildfires in recent years.

Reducing wildfire risks across communities, states and regions beyond individual actions. We need and for , provide power and , as well as mechanisms that ensure changes work .

Actions to reduce risk will vary, since how people live and how wildfires burn vary widely across the West.

States with large tracts of land with little development, like Idaho and Nevada, can accommodate widespread burning, largely from lighting ignition, with little structure loss.

California and Colorado, for example, require different approaches and priorities. Growing communities can in flammable landscapes, support , and when wildfires do threaten communities.

remains the elephant in the room. Left unaddressed, warmer, drier conditions will exacerbate challenges of living with wildfires. And yet we can鈥檛 wait. Addressing climate change can be paired with in an increasingly flammable West.

, Professor of Fire Ecology, ; , Associate Professor of Geography and Director, Earth Lab, ; , Ph.D. Student, Dept. of Geography, , and , Director of the Earth Lab Analytics Hub,

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