Climate

Trees Are Dying From ‘No Obvious Cause’ In Rocky Mountains, Report Says

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The Rocky Mountain forests that traverse the West are under unprecedented danger from climate-related impacts according to a new report from the Union of Concerned Scientists (UCS) and the Rocky Mountain Climate Organization. The Rockies include national parks like Yellowstone, Grand Teton, and Glacier National Park, and are facing a “triple assault — tree-killing insects, wildfires, and heat and drought — that could fundamentally alter these forests as we know them.”

According to the report, titled “Rocky Mountain Forests at Risk,” many western trees are dying from “no obvious cause” like the bark beetle epidemic or increasing threat of wildfire, with scientists suggesting that these deaths are due simply to the hotter and drier conditions associated with climate change. The mortality rate for old-growth trees in undisturbed forests has doubled recently, with a sharp increase in recent years, and there’s been no compensating increase in the number of seedlings.

According to National Climate Assessment figures in the report, given very low future carbon emissions, average temperatures in the six Rocky Mountain states could rise to about 3°F above 1971–2000 levels by mid-century. However if emissions remain unchecked, this number could double or triple. In all scenarios, bark beetle infestations are likely to increase, larger wildfires are expected, and early snowmelt and reduced snow cover would lead to water stress.

This would make the climate less suitable for characteristic Rockies’ species, including lodgepole pine, Engelmann spruce, ponderosa pine, and Douglas fir, as well as iconic species including whitebark pine, aspen, and piñon pine.

“These species could be eliminated from much of their current ranges, potentially changing the fundamental makeup and extent of Rocky Mountain forests,” write the authors.

In a statement Stephen Saunders, report co-author and president of RMCO, said that while climate changes have been modest so far “they have already jolted our forests,” and “if we continue changing the climate, we may bring about much more fundamental disruption of these treasured national landscapes.”

In the early 2000s, aspen trees abruptly died across large areas of their range due to hot and dry conditions. U.S. Forest Service projections 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.

Tens of millions of trees have died in the Rocky Mountains over the past 15 years as average annual temperatures have risen more in the Rocky Mountain region than in the U.S. as a whole, increasing 2.1º F since 1895.

“Conditions in the Rocky Mountains are changing quickly and may outpace the forests’ abilities to adapt,” said Jason Funk, report co-author and senior climate scientist at UCS, in a statement. “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.”