California’s Caldor Fire ripped its way across the Tahoe Basin this week, forcing thousands to evacuate, burning homes and communities in its path, and staining Lake Tahoe’s iconic blue waters with falling ash.

The fire, like many others burning across the U.S. West this year, spread rapidly in part because it’s burning intensely, propelled by hot, dry, windy weather conditions and forests overpacked with trees—food for hungry fire.

But it has also run up against some areas that have been “treated” to reduce their fire risk, patches of forest—some big, some not so big—that have been trimmed in the past, either by hand with chainsaws and masticators or with carefully managed prescribed fire. These treatments are intended to make forests