Drought in California has killed more than 102 million trees in a die-off that increases the risk of catastrophic wildfires and other threats to humans, officials say.
The latest aerial survey by the US Forest Service shows there are 36 million more dead trees since May in the state and there has been a 100 per cent increase since 2015.
"These dead and dying trees continue to elevate the risk of wildfire, complicate our efforts to respond safely and effectively to fires when they do occur and pose a host of threats to life and property," US Agriculture Secretary Tom Vilsack said on Friday.
California has endured five years of drought marked by a record low mountain snowpack and warm temperatures. The drought has left trees thirsty and prone to infestation by bark beetles.
Late last year, Governor Jerry Brown formed a task force charged with finding ways to remove the trees that threaten motorists and communities.
Vilsack called on Congress to act, saying more federal funding goes toward fighting fires than forestry management, such as removing dead trees to improve forests' health.
Officials are pushing to turn more trees into lumber, burn them in energy plants or dispose of them in incinerators to eliminate them as fuel for wildfires.
Some environmentalists argue, however, that a die-off is part of a healthy forest's life-cycle. They favour leaving the trees that need to be cut down on the forest floor to decompose and serve as wildlife habitat.
Most dead trees are in the central and southern Sierra Nevada, officials say. However, they're also beginning to find dead trees in Northern California counties such as Siskiyou, Modoc, Plumas and Lassen.