The nation's top Forest Service official says national forests can store more carbon to slow global warming, but he warns that such a goal must be balanced against the risk of catastrophic wildfires.

Forest Service Chief Tom Tidwell told a Senate panel on Wednesday that his agency is trying to manage forests to combat climate change while still easing the risk of wildfires.

The Forest Service is trying to thin out young trees and underbrush to control wildfires that are increasing in frequency and intensity in part because of global warming.

The Forest Service and Interior Department spent about $2.4 billion last year fighting fires, double the average amount spent a decade ago.