Wildfires among ponderosa pines and Douglas firs of the U.S. West have long been part of nature's cycle of renewal, as much as the changing of the seasons.

But as climate change makes the region more arid, wildfires have grown more frequent and ferocious. Scientists worry the hottest blazes could end up obliterating swathes of some forests forever.

"When you get these large areas burned there are no surviving trees to reseed these areas," said Jon Keeley, a research scientist with the U.S. Geological Survey. "It is causing a shift from forest to other vegetation types, mostly shrublands and grasslands."