In the last ten years, the federal government and rural landowners have spent increasing sums of money thinning spindly trees and removing underbrush. The aim is to reduce risk from wildfire.
A new study by the Forest Service finds that tree stands need to be "intensively" thinned for that strategy to be effective.
Study co-author David Peterson of the Pacific Northwest Research Station in Seattle says a dense tinderbox forest before thinning could have more than a 1,000 trees per acre.