By Jennifer McRae

BOULDER, Colo. (CBS4)– Extreme heat and dry summers are the main cause of tree deaths in Colorado’s subalpine forests. That’s according to research from the University of Colorado Boulder.

(credit: Robert Andrus)

The research looked at tree deaths in subalpine forests that cover more than 10,000 square miles in Colorado.

(credit: Robert Andrus)

Tree deaths have more than tripled since the 1980s due to hot and dry conditions, even in the absence of bark beetle outbreaks and fires.

(credit: Robert Andrus)

The lead author of the study at Washington State University says that it is an early warning sign of climate change.

Jennifer McRae