This panorama, taken about 10 miles west of Flagstaff, Ariz., shows a nearly 360-degree view of forest land. The trees on the left side of the road have been thinned by foresters; the stand on the right has been left untouched.
In a treated forest, workers cut some of the smaller trees and sometimes use prescribed fires to clear away undergrowth. Fires in more open forests are less likely to burn with enough intesity to reach and destroy the tree crowns.
The untreated forest is a result of a century of Forest Service policy of aggressively combating all fires. This has created large, dense stands of trees that are vulnerable to bigger fires.