Using chainsaws, heavy machinery and controlled burns, the forest workers are trying to turn the tide on worsening wildfires in the U.S. West.It’s a multi-billion dollar cleanup of forests choked with dead trees and undergrowth.By logging and burning trees and low-lying vegetation, officials hope to lessen forest fuels and keep fires that originate on federal lands from exploding through nearby cities and towns.The enormity of the task is evident in an aerial view of California's Tahoe National Forest, where mountainsides are colored brown and gray with the vast number of trees killed by insects and drought.After work on the Tahoe was delayed last year, Forest Service crews and contractors recently started taking down trees across thousands of acres.The efforts have drawn criticism from some environmentalists and local residents for cutting too many trees."We're asking the Forest Service to make their treatments lighter, to focus on smaller trees and shrubs, leave the larger trees and ensure that the scenery that and recreation opportunities that people enjoy along the north Yuba River are protected," said Steve Evans, CalWild director.In the Tahoe National Forest's North Yuba region, small towns tucked into the forest’s canyons escaped disaster two years ago when the Dixie fire raged just to the north, destroying several communities and burning about 1,500 square mile (3,900 square kilometers) in the Sierra Nevada range.Those communities also escaped another fire to the south that burned more than 1,000 homes and structures.The previous year, yet another fire killed 15 people and torched more than 2,000 homes and structures in the region.The same conditions that whipped those fires into infernos exist on the Tahoe forest — densely-packed trees and underbrush primed to burn following years of drought.And government computer modeling suggests it’s among the U.S. communities most exposed to wildfires on federal lands.Administration officials say the thinning work is making a difference and will lessen wildfire dangers by the end of the year in more than 200 communities across 10 states.Matt Millar, of the National Forest Foundation, says that forests can bounce back from thinning."I once heard someone describe forest thinning and logging operations as open heart surgery. You know, afterwards, it's not a pretty sight. It can look a little bit rough. But forests recover, and they're very resilient."