Fig. 1.

Wildfire activity in western North America has been steadily increasing over recent decades, highlighted by the 2015 Valley Fire in northern California (A) and the 2015 Cougar Creek Fire in Washington (B), which both occurred during the hottest year on record globally. In May of 2016, the Horse River Fire burned through Ft. McMurray, AB, Canada, requiring regional evacuations as fire spread rapidly through intermixed forested and developed areas (C); eventually, more than 2,000 homes and other structures were destroyed (D). Human-caused climate change is now a key driver of forest fire activity, causing over half of the recent increases in fire weather and area burned by wildfire in the western United States (6). Photographs courtesy of CalFire (A), US Forest Service (B), and jasonwoodhead23 (C and D); acquired via https://creativecommons.org.