Yellowstone must prepare for climate change, scientists say

CODY — The impacts from climate change on the Greater Yellowstone Ecosystem – some positive but mostly negative – are occurring now, but changes in public policy could lessen the harmful consequences. There’s still time to minimize the damage, two scientists said.

“Our landscape has been shaped by climate change,” paleoecologist Cathy Whitlock explained. “Relatively small changes in temperature can have a big impacts. The ecosystem is very delicate.”

A swing of nine degrees can trigger glacial or interglacial cycles, she said, citing a past “mega-drought” when the lack of water caused Old Faithful to stop spewing and trees to start sprouting around its cone from 1233 to 1362. Today, the GYE is warmer than it’s been since the last Ice Age and the CO2 levels are probably the highest they’ve been in 3.3 million years, but the droughts haven’t hit the mega-status.

Whitlock spoke during a panel discussion at the University of Wyoming’s Yellowstone National Park 150th Anniversary Symposium on May 27 at the Buffalo Bill Center of the West. The other speakers were paleoecologist Bryan Shuman, hydrologist Steve Hostetler of USGS and ecologist Monica Turner of the University of Wisconsin. Whitlock, Shuman and Hostetler are three of six authors of the “Greater Yellowstone Climate Assessment” of June 2021.

The report addressed the impacts of climate change on water, agriculture, recreation, forests and wildfire. As to energy, it concluded an overall decline in demand with warmer winters.

With the average temperature up more than 2.3 degrees since the 1950s, snowfall has declined 24 inches and will likely continue to decline, Shuman said. Based on the prior average of 100 inches per year, the reduction represents a loss of a quarter of regular snowfall.

“We’ve lost the cold years,” he added.

Although the overall amount of precipitation has remained about the same, spring rain has replaced the loss of snowfall, Shuman said. The consequences include earlier spring snowmelt, about a week now, and less water at summer’s end, which means less water available for recreation and agriculture. The irrigation supply will shrink, while the growing season has lengthened by about two weeks. By 2080, there could be little snowpack.

“Reservoirs have been our buffer,” he said, in a water system that’s heavily managed. Yet higher temperatures increase evaporation, so “we’re facing a significant transition in the water supply.”

Warmer temperatures are also affecting trees. The 1988 fires in Yellowstone occurred in the hottest, driest year since the Park’s founding in 1872, Turner said, yet most of the affected forests have rebounded, showing their resilience. However, future fires will probably be more frequent and more severe.

With shorter intervals between fires, “there will be changes in the forest landscape,” she said. Hotter fires could eliminate seed trees along with the old, dead trees that provide shade for seedlings. If forests don’t have time to recover, the wooded landscape could become open areas. Still, she noted, the impacts will vary as trees in rugged terrain are more resilient.

“Yellowstone will still be a national treasure … and a scientific treasure” in the lessons of how nature responds, Turner added. “I think we’ll still get some positive surprises.”

Both Turner and Shuman noted that policy changes would alter the predictions.

“There’s no deadline to solving the problems, but any delays could lead to more extremes,” Shuman said. “We still have choices and the time to make them. Next summer will be warmer, but the big unknown is what we will do.”

If greenhouse gases can be curbed by mid-century, changes in Yellowstone will be less drastic, Turner said – “It really is in our hands as a society.”

However, if no policy changes are made and temperatures rise 5 degrees by 2100, Shuman described the resulting landscape of the GYE as a “fundamentally different world.”