Rocky Mountain Forests at Risk: Confronting Climate-driven Impacts from Insects, Wildfires, Heat and Drought

This report by the Union of Concerned Scientists (UCS) and the Rocky Mountain Climate Organization documents the latest evidence on how climate change is already disrupting the forests of the Rocky Mountain region and what scientists project for the decades ahead - and suggests how to best address these challenges.

Tens of millions of trees have died in the Rocky Mountains over the past 15 years, from the triple assault of tree-killing insects, wildfires, and stress from heat and drought. Colorado alone could lose 45% of its aspen stands over the next 45 years. Pine bark beetles have already killed 46 million acres of trees across the west, an area nearly the size of Colorado.

According to UCS, climate change is the driving force behind these impacts, bringing hotter and drier conditions that amplify existing stresses, as well as cause their own effects. Projections by the U.S. Forest Service that were included in the report, predict that if GHG emissions continue increasing at recent rates, by 2060 the area climatically suitable in the Rocky Mountains for lodgepole pine could decline by about 90%, for ponderosa pine by about 80%, for Engelmann spruce by about 66% and for Douglas fir by about 58%.

Tree-Killing Insects:
Native bark beetles have always been agents of change in western forests. In the early 2000s, however, bark beetle outbreaks across western North America, including the Rocky Mountain region, killed more trees, at a faster pace, for longer periods, and over more acreage than any other known infestations.

More Wildfires:
Wildfires have always been an important feature of the forest cycle. But in today’s Rocky Mountain forests, the number of large wildfires has risen dramatically. One study documented a 73 percent increase in the annual number of large wildfires in the region from 1984 to 2011. Scientific research has linked these increases in wildfires to a changing climate. One important change is higher spring temperatures, which produce earlier spring snowmelt and peak streamflows, leaving forests drier and more flammable in summer.

More Heat and Dryness:
Tree mortality has been highest in recent years. Scientists suggest that hotter and drier conditions across the West are driving these changes.

The report includes a call to action:  

  • The future of Rocky Mountain forests depends on how much and how quickly we can curb heat-trapping emissions.
  • The dramatic impacts these forests already face - and our scientific understanding of what's driving them - mean that unchecked heat-trapping emissions will bring more abrupt, damaging, and potentially irreversible effects.
  • As individuals, we can help by taking action to reduce our personal emissions. But to fully address the threat of global warming, we must demand action from our elected leaders to support and implement a comprehensive set of climate solutions.
  • The choice is stark: We can act now to preserve the cherished landscape of the Rocky Mountains - or we can sit by and watch this treasured resource degrade irrevocably. The ultimate fate of these majestic forests is up to us.

Publication Date: September 2014

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Resource Types:

  • Assessment


  • Air temperature
  • Drought
  • Precipitation changes
  • Wildfires

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