Marshall, Burke, Anne Driscoll, Jenny Xue, Sam Heft-Neal, Jennifer Burney, and Michael Wara

Proceedings of the National Academy of Sciences

Published date January 12, 2021

The Changing Risk and Burden of Wildfire in the US

Study key findings

  • The contribution of wildfire smoke to PM2.5 concentrations in the US has grown substantially since the mid 2000s, and in recent years has accounted for up to half of the overall PM2.5 exposure in western regions as compared to <20% from 2005-2010.
  • Increased mortality from climate-change–induced wildfire smoke could approach projected overall increases in temperature-related mortality—itself the largest estimated contributor to economic damages in the United States.

Author quotes

For many people in the western U.S., increases in wildfire risk due to climate change are, along with the direct effect of extreme temperatures, going to be the main climate impact that people experience – much more than sea level rise or hurricanes. This is mainly due to the worsening air quality that most of the U.S. – and particularly the western U.S. – will likely experience as the climate warms and large fires become more frequent. This particular climate impact is one we need to pay a lot more attention to.

Marshall Burke, lead author and associate professor of Earth system science in Stanford’s School of Earth, Energy & Environmental Sciences 

Wildfire smoke is different than rising sea levels or high temperatures because it is an impact caused by an interaction of climate change and human decision making. That means we can do a lot to make the problem better, by changing the decisions we have made about how to manage forests, where we build our homes and how we build them. That leaves me optimistic about the prospects for better outcomes.

Michael Wara, co-author and director of the Climate and Energy Policy Program at the Stanford Woods Institute for the Environment


Recent dramatic and deadly increases in global wildfire activity have increased attention on the causes of wildfires, their consequences, and how risk from wildfire might be mitigated. Here we bring together data on the changing risk and societal burden of wildfire in the United States. We estimate that nearly 50 million homes are currently in the wildland–urban interface in the United States, a number increasing by 1 million houses every 3 y. To illustrate how changes in wildfire activity might affect air pollution and related health outcomes, and how these linkages might guide future science and policy, we develop a statistical model that relates satellite-based fire and smoke data to information from pollution monitoring stations. Using the model, we estimate that wildfires have accounted for up to 25% of PM2.5 (particulate matter with diameter <2.5 μm) in recent years across the United States, and up to half in some Western regions, with spatial patterns in ambient smoke exposure that do not follow traditional socioeconomic pollution exposure gradients. We combine the model with stylized scenarios to show that fuel management interventions could have large health benefits and that future health impacts from climate-change–induced wildfire smoke could approach projected overall increases in temperature-related mortality from climate change—but that both estimates remain uncertain. We use model results to highlight important areas for future research and to draw lessons for policy.

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