Summers that feel like those in Los Angeles are coming to America's favorite park.
These warming temperatures will imperil everything from native cutthroat trout to aspen forests and the $700 million in annual economic activity that they and other gems in the park generate by attracting tourists, the report said.
The report, the first evaluation of how climate change will affect the greater Yellowstone ecosystem, is a joint project of the Rocky Mountain Climate Organization, a nonprofit that advocates for carbon emission reductions by drawing attention to the likely consequences of climate change, and the Greater Yellowstone Coalition, a conservation organization concerned with the park and the land around it.
The authors used two warming scenarios developed by the Intergovernmental Panel on Climate Change, one based on a medium-to-high-range level of carbon emissions in the future and another one based on a lower set of carbon emissions.
Already Yellowstone, which sits at a relatively high average elevation of 8,000 feet above sea level in Wyoming, Montana and Idaho, is warming faster than the rest of the globe, the report found. It has warmed 1.4 degrees on average over the last decade, compared to the one-degree global average increase.
The results of even this relatively small change have been noticeable in all aspects of the park, the report said, from glacial ice to reductions in the birthrates of at least one migratory elk herd, whose main food source, meadow grasslands, is drying out too quickly in the summer season.
Most notably, warmer temperatures have allowed infestations of tree-killing beetles that previously had been held in check by the frostiest nights of the year.
But that 1.4-degree increase is just a precursor of what is to come, the report found. Taking the average of 16 computer models of climate future that were fed data from five different local weather stations, the report predicted that summer temperatures in Yellowstone could be expected to rise as much as 9.7 degrees by the end of the century. The authors considered summer particularly significant because it is the peak season for visits to the park.
"What we humans are doing to the climate isn't just melting polar ice caps, it's disrupting the places that are nearest and dearest to us," said Stephen Saunders, R.M.C.O.'s president and lead author of the report. "Already, threads are being pulled out of the tapestries of Yellowstone and other special places, and they are losing some of their luster."