Greater Yellowstone in Peril

The particular threats that a changed climate poses to the Greater Yellowstone Ecosystem—Yellowstone and Grand Teton national parks, parts of six national forests, and more—are detailed in a report, Greater Yellowstone in Peril, released in September 2011 by the Rocky Mountain Climate Organization and the Greater Yellowstone Coalition.

Already, Greater Yellowstone is experiencing changes. The region has gotten hotter at a faster rate than the global average. Summers have especially gotten hotter. If emissions of heat-trapping pollutants go up at a medium-high rate, average summer temperatures in Yellowstone National Park could get as hot as recent summers in Culver City in the Los Angeles area by the end of the century.

Higher temperatures, along with other climate changes discussed in the report, threaten Greater Yellowstone’s unaparalleled natural wonders—as well as the local economies built around them. Visitors to Yellowstone and Grand Teton national parks alone spent an estimated $700 million in 2009, and with a rise in visitation numbers in 2010, that figure presumably increased as well.

Already, whitebark pines, the dominant, ecologically important trees of the region’s highest forests, are suffering widespread mortality from tree-killing mountain pine beetles, now able to spread in epidemic numbers into mountaintops that used to be too cold for them. As a result, grizzly bears, which depend on whitebark pine seeds as a key pre-hibernation food, now face a new threat. Wildfires are now more widespread and extreme. Fishing restrictions are more common, to protect trout stressed by hotter river temperatures.

In addition to those observed threats, the report documents additional major impacts:

  • Greater Yellowstone may well get drier in summer. Across the Central Rocky Mountains region, higher temperatures have already led to reduced snowpack, earlier spring snowmelt and peak flows, and, in some cases, lower summer flows for major basins.
  • The threats to whitebark pines are expected to grow, which prompted a July 2011 decision by the U.S. Fish and Wildlife Service that the ecologically significant trees qualify for protection under the Endangered Species Act. Half of the whitebark pines in the continguous United States are in Greater Yellowstone.
  • A hotter and drier future is also projected to render unsuitable for aspens much of the area this iconic tree now inhabits.
  • Wildfires are projected to continue becoming more widespread. A June 2011 study by leading researchers suggests that over the next four decades Greater Yellowstone could experience five summers with as much wildfire as in 1988, when 35% of Yellowstone National Park burned.
  • Grizzly bears are at greater risk because of the decline of whitebark pines. The seeds of the pines are a crucial pre-hibernation food for the bears.
  • Wolverines and lynx, which are snow-dependent species, face new risks as the region’s snowpacks dwindle.
  • Hotter, drier summers pose major threats to the region’s native coldwater trout, which perish in too-warm waters. One study projects that if summers get just 5.4°F hotter then 47% of Yellowstone cutthroat trout populations would be eliminated.

As Stephen Saunders, president of RMCO and the report’s primary author, said, “A hotter climate is not just melting polar ice caps, it is harming the places that are nearest and dearest to American hearts.”

Downloads and links:

  • The full report in web-friendly format is here (1.5 MB in size) or in high-quality, print-ready format is here (11.6 MB).
  • A news release on the report is available here.

Photograph of aspens in fall, Grand Teton National Park copyright emattil/

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