Forest fires

Smoke from more than 100 wildfires burning across Canada has been rolling into North American cities far from the flames. New York City, Denver, Chicago, Minneapolis and Detroit each made the list of the most polluted cities in the world at times in May and June 2023 because of the fires. The smoke has triggered air quality alerts in several states. We asked Chris Migliaccio, a toxicologist at the University of Montana who studies the impact of wildfire smoke on human health, about the health risks people can face when smoke blows in from distant wildfires. What’s in wildfire smoke that’s a problem? When we talk about air quality, we often talk about PM2.5. That’s particulate matter 2.5 microns or smaller – small enough that it can travel deep into the lungs. Exposure to PM2.5 from smoke or other air pollution, such as vehicle emissions, can exacerbate health conditions like asthma and reduce lung function in ways that can worsen existing respiratory pr...

As wildfire risk rises in the West, wildland firefighters and officials are keeping a closer eye on the high mountains – regions once considered too wet to burn. The growing fire risk in these areas became startling clear in 2020, when Colorado’s East Troublesome Fire burned up and over the Continental Divide to become the state’s second-largest fire on record. The following year, California’s Dixie Fire became the first on record to burn across the Sierra Nevada’s crest and start down the other side. We study wildfire behavior as climate scientists and engineers. In a new study, we show that fire risk has intensified in every region across the West over the past four decades, but the sharpest upward trends are in the high elevations. In 2020, Colorado’s East Troublesome fire jumped the Continental Divide. AP Photo/David Zalubowski High mountain fires can create...

Wildfires and severe drought are killing trees at an alarming rate across the West, and forests are struggling to recover as the planet warms. However, new research shows there are ways to improve forests’ chances of recovery – by altering how wildfires burn. In a new study, we teamed up with over 50 other fire ecologists to examine how forests have recovered – or haven’t – in over 10,000 locations after 334 wildfires. Together, these sites offer an unprecedented look at how forests respond to wildfires and global warming. Our results are sobering. We found that conifer tree seedlings, such as Douglas-fir and ponderosa pine, are increasingly stressed by high temperatures and dry conditions in sites recovering from wildfires. In some sites, our team didn’t find any seedlings at all. That’s worrying, because whether forests recover after a wildfire depends in large part on whether new seedlings can establish themselves and grow. However,...

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 l...