New Report Shows Rocky Mountain Forests Facing Unprecedented Assault From Insects, Fires, And Heat And Drought Stress

Recent Die-Offs Could Mark Beginning of Range’s Climate-Driven Transformation

Published Sep 10, 2014

WASHINGTON (September 10, 2014) — Forests in the Rocky Mountains are under an unprecedented assault from wildfires, tree-killing insects, and heat- and drought-related stress, according to “Rocky Mountain Forests at Risk,” a report released today by the Union of Concerned Scientists (UCS) and the Rocky Mountain Climate Organization (RMCO). If left unchecked, the climate change that is driving this triple assault could fundamentally alter these forests as we know them, the report says. The forests at risk are defining features of some of America’s most cherished landscapes, including Glacier, Rocky Mountain, and Yellowstone national parks. 

“Heat and drought stress, beetle bark infestations and wildfires are killing trees across widespread areas in the Rocky Mountains,” said Jason Funk, report co-author and senior climate scientist at UCS. “The wildfires, infestations and heat and drought stress are the symptoms; climate change is the underlying disease.”

According to the report:

  • Bark beetle outbreaks have killed trees on a larger scale than ever recorded. In the past 15 years, the beetles have killed trees on western forest lands nearly equal to the size of Colorado. They are killing at a faster rate and on a larger scale than seen in 100 to 150 years of record-keeping.
  • Wildfires in the West are burning more land. Between 1984 and 2011, there has been a 73 percent increase in the average annual frequency of large wildfires (more than 1,000 acres) in the Rocky Mountains.
  • More western trees are dying for no apparent cause. The rate at which western trees have died from no obvious cause—such as insect infestations or wildfire—has doubled in recent decades, with a sharp increase in recent years. Scientists suggest that hotter and drier conditions across the West are driving the increase in mortality.

In the West, temperatures have risen on average about 2 degrees Fahrenheit since 1895 and drought has become more widespread. If climate change continues unchecked, scientists expect the region to become even hotter and drier—and the impacts on its forests even more severe. While all such projections have inherent uncertainty, they suggest that continued climate change could make the Rocky Mountains less suitable for the conifer species that primarily make up the region’s forests.

Projections by the U.S. Forest Service, quantified for the first time in the report, are that if emissions of heat-trapping gases continue increasing at recent rates, by 2060 the area climatically suitable in the Rocky Mountains for lodgepole pine could decline by about 90 percent, for ponderosa pine by about 80 percent, for Engelmann spruce by about 66 percent, and for Douglas fir by about 58 percent.   

“So far, we have had relatively modest climate changes, but they have already jolted our forests,” said Stephen Saunders, report co-author and president of RMCO. “If we continue changing the climate, we may bring about much more fundamental disruption of these treasured national landscapes.” 

The report also documents dramatic changes in three iconic tree species of the Rocky Mountains: 

  • Whitebark pines, a keystone species in high-elevation forests in the Northern Rockies, are already in catastrophic region-wide decline, in large part from climate-change-driven impacts. The U.S. Fish and Wildlife Service has found that the species qualifies for protection under the Endangered Species Act.
  • Aspens abruptly died across large areas of their range in the early 2000s, triggered by an exceptionally hot and dry stretch that peaked in 2002. U.S. Forest Service projections, again quantified for the first time in this report, suggest that by 2060 the areas in the Rocky Mountains climatically suitable for aspens could decline by about 61 percent. The areas where aspens declined early this century are the same areas modeled to become less suitable for the species, suggesting the recent decline might be the beginning of a climate-induced change in aspen populations, with aspens disappearing from some parts of the Rocky Mountains.
  • Piñon pines, widespread in the southernmost Rocky Mountains and across the Southwest—and the state tree of New Mexico—suffered a mass die-off in 2002-2003, again triggered by severe drought and exceptional heat. Scientists have called this “a sudden ecosystem crash in response to climate change.” 

“Conditions in the Rocky Mountains are changing quickly and may outpace the forests’ abilities to adapt,” said Funk. “Land managers need to respond with strategies that can make the forests more resilient. If we’re going to preserve Rocky Mountain forests, we also need to reduce carbon emissions to slow the pace of these changes.”