Across North America, the phrase “fuel management” is used almost as often as “climate change” when people talk about wildfires. The idea is simple: forests burn because they are full of fuel, including trees, shrubs, branches, and dried leaves. If you remove some of that material, you make it harder for a wildfire to spread. Provincial governments, towns, and even ski resorts such as Whistler in British Columbia, Canada have invested millions of dollars in “fuel thinning,” which involves sending crews into the woods to cut down trees and haul away brush. While fuel thinning feels like common sense, Dr. Rhonda Millikin, a scientist based in Whistler, and her colleagues have found that what seems like common sense in one type of forest can be dangerously misleading in another. Their research, recently published in the journal Fire, revealed that in Whistler’s coastal rainforests, dense, wet, and shaded ecosystems, fuel thinning often has the opposite effect of what is intended. Instead of making these forests safer, thinning makes them drier, windier, and hotter: exactly the conditions that help wildfires spread.