Foresters say Colorado has about 834 million standing dead trees, threatening to worsen wildfires and degrade vital water supplies that flow from forested mountains.
The Colorado State Forest Service said Wednesday the number of dead trees has risen nearly 30 percent in seven years.
They are most visible in forests infested by the mountain pine beetle and the spruce beetle, which have together attacked more than 7,900 square miles in Colorado.
Dead trees can burn more intensely than living ones. They can also worsen erosion, contaminating runoff from rain and melting snow.
Officials say 80 percent of the state's population relies on runoff from forested watersheds.
Dead trees are also a threat in California, where the U.S. Forest Service says drought has killed more than 102 million trees.
