Report: Climate Change at Yellowstone Threatens People, Wildlife

“Beautiful.” “Gorgeous.” “Breathtaking.” “Magnificent.” These are just a few of the words that tourists often use to describe the splendor that is the Greater Yellowstone Area, comprising approximately 22 million acres of wilderness in northwestern Wyoming, southcentral Montana, and eastern Idaho, including Yellowstone and Grand Teton National Parks. A new study brings to mind an entirely different lexicon, however: “Dry.” “Hot.” “Threatened.”

Produced by scientists at Montana State University, the U.S. Geological Survey (USGS), and the University of Wyoming, “The Greater Yellowstone Climate Assessment” scrutinizes the effects of human-caused climate change on the region, which encompasses not only two national parks, but also five national forests, three wildlife refuges, 20 counties, one Indian reservation, and a smattering of state and private lands. It includes an analysis of the past, as well as a forecast for the future.

Looking backward, scientists studied climate change in Greater Yellowstone from 1950 to 2018. During that time, they found, the average annual temperature in the region increased by 2.3 degrees, which is as high or higher than any other period in the last 20,000 years and likely the warmest in 800,000 years, according to geologic studies. Also of note is the average annual snowfall, which has decreased by 23 inches since 1950, they observe. The combination of higher temperatures and reduced snowfall means the spring thaw now commences two weeks earlier than it did in 1950, while stream runoff reaches peak flows eight days sooner.

Looking forward, scientists expect warming and drying trends to continue through the end of the century. By 2100, they predict, average annual temperatures in Greater Yellowstone will increase by an additional 5 to 10 degrees, yielding 40 to 60 more days per year with temperatures above 90 degrees. Simultaneously, they forecast a 9% to 15% increase in annual precipitation—drier conditions in the summer due not only to increased temperatures but also to continued shifts in stream runoff, which by the end of the century could reach peak flows a full one to two months earlier than present conditions.

Under the most extreme scenarios, the snowpack in Greater Yellowstone could decrease dramatically. From 1986 to 2005, winter snowfall covered 59% of the region. By the end of the century, that number could be as low as 1%.

“The decrease in snow is due to the increase in temperature over time, which [causes] more precipitation to fall as rain instead of snow,” explains report co-author Bryan Shuman of the University of Wyoming.

The effects of a changing climate on humans, wildlife, and plant life will be real and potentially serious.

“Greater Yellowstone is valued for its forests, rivers, fish, and wildlife,” says USGS scientist Steve Hostetler, co-lead author of the report. “The trend towards a warmer, drier climate described in this study will likely affect ecosystems in the region and the communities that depend on them.”

Perhaps the biggest consequence of climate change in Greater Yellowstone is water scarcity. Currently, cities as far west as Los Angeles depend on snowmelt from Greater Yellowstone for water. Less snowpack means less water—especially in the summer when scientists foresee a seasonal water deficit in Greater Yellowstone of up to 79% by the end of the century.

That deficit could make the region more vulnerable to drought and wildfires, both of which have far-reaching consequences. At risk, for example, are the livelihoods of farmers and agricultural producers, the security and reliability of critical infrastructure, the health of fish and wildlife, and the strength of local economies that depend on recreation and tourism.

Consider one of the region’s most popular tourist attractions: Old Faithful at Yellowstone National Park. Although the famous geyser currently erupts once every 90 to 94 minutes, eruptions—and visitations to see them—could cease altogether during a period of severe, extended drought. Even the park’s pristine forests are endangered; if wildfires destroy them, and there isn’t enough water to support tree growth, some landscapes might convert to grassland.

Although scientists’ predictions are dire, their report nevertheless leaves room for optimism: By measuring and monitoring the impact of climate change now and in the future, they suggest, community stakeholders can devise climate adaptation strategies that will help them weather the storm—both figuratively and literally.

Says Montana State University Regents Professor Emerita of Earth Sciences Cathy Whitlock, co-lead author of the report, “The assessment is intended to provide the best available science on past, present, and future conditions in the [Greater Yellowstone Area] so that stakeholders have needed information to plan ahead.”