The report lists three main factors behind the decline in forest health: insects, drought and wildfires.
Hot, dry conditions have led to a lengthening of the wildfire season, as illustrated by a comparison between wildfire records in the 1970-1986 period and wildfires in the 1986-2003 period. Between 1986 and 2003, the wildfire season lasted nearly three months longer, experienced nearly four times as many fires and burned nearly seven times as many acres.
Wally Covington, director of the Ecological Restoration Institute at Northern Arizona University, says climate change is now unquestionably the cause.
“Until the ’80s or so, it was easy to explain fires as consequence of fuel accumulation,” said Covington. “Now, piled on that are the effects of climate change. We are seeing larger fires and more of them.”
Drought and higher spring temperatures have also made trees more vulnerable to insect infestations. The mountain pine beetle will burrow under trees’ bark and breed, eventually killing the host tree. According to the report, the beetles have killed enough trees to nearly cover the state of Colorado.
The Rockies’ whitebark pine now qualifies as endangered, with the Fish and Wildlife Service predicting that it will go extinct in the next century. Climate conditions have also led to the deaths of 1.3 million acres of quaking aspens between 2000 and 2010. Ninety percent of the region’s piñon pines are now gone, devastated by drought and heat.
If current climate trends hold, the UCS and RMCO write, bark beetle infestations will spread, wildfires will increase in intensity and frequency (even with minimal temperature rise), snow will melt sooner and conifer species like the lodgepole pine, Engelmann spruce, ponderosa pine and Douglas fir will likely go extinct.