Scientists: Snowmass site shows ancient forests in climatic flux

Bryan Small works on a mastodon skull that was unearthed near Snowmass in this file photo from May 2011. Many varieties of ancient animal life have been found at the dig. At 9,000 feet, the Snowmass site also is providing a look at high-elevation plant life for the millennia represented that’s unique in North America, scientist Dane Miller said.

The Snowmass fossil site that has yielded mammoth and mastodon tusks and other treasures also is revealing a history of fast-fluctuating forests reflecting changes in climate tens of thousands of years ago.

That history helps point to rapid variations in plant life that can be expected in the future, a scientist involved in studying the site says.

“Plant species respond quickly to climate change,” Dane Miller said last week during a presentation in Carbondale.

Miller is involved in paleobotany and recently earned a master’s degree from the University of Wyoming based in part on his role in research at the Snowmass site. Fossils at the site were discovered in late 2010 during enlargement of Ziegler Reservoir to enhance the Snowmass resort water supply.

Miller is the brother of Ian Miller, who is curator of paleontology at the Denver Museum of Nature & Science and co-author of “Digging Snowmastodon,” the story of the site and the museum’s role in overseeing the excavation and recovery of items there. A grinning Dane Miller is pictured on the book’s cover, shouldering a big, fossilized bone as he was helping dig at the site.

The site drew enormous attention after yielding thousands of bones of mammoths, mastodons, bison, camels and other Ice Age megafauna as well as many smaller animals. But it also provided a plethora of pollen samples and plant fossils such as seeds, logs and conifer cones that give a glimpse of the ecosystems that helped make it possible for various animal life to survive over the millennia.

What that evidence showed was continuing shifts in vegetation as everything from sagebrush to spruce to stunted alpine krummholz prevailed at the site at various times from roughly 135,000 to 75,000 years ago, the timeframe represented at the site. These changes correspond with known periods of warming and cooling and glacier retreat and advancement in North America. The existence of certain vegetation during certain periods was ascertained with the help of a dating process that involves measuring when quartz grains were last exposed to light before being buried by sediment.

Miller said the research indicates things such as a drop in treeline elevation nearly 100,000 years ago of anywhere from 2,000 to 3,500 feet.

“It was much colder up in the Rocky Mountains at high elevation than anyone even knew about,” said Miller, who described that discovery as “a big find.”

The Snowmass site, at 9,000 feet, is providing a look at high-elevation plant life for the millennia represented that’s unique in North America, Miller said. He said scientists would love to have another hundred sites like it “to really sort of synthesize what’s happening with the vegetation long-term at high-elevation.”

But at least for this site, “There was a lot of change. That change could be the same for going into the future,” he said.

High-elevation areas respond in some ways more quickly to climate change than lower down, Miller said. He said the Snowmass site will undoubtedly look different in 100,000 years, but also could show a response to global warming in as little as a century from now.

“If it continues to warm over the next hundred years it’s likely that the treeline is going to move up higher in the mountain elevations, and that’s a response to the climate,” he said in an interview.

Because plants are the foundation of the ecosystem, such a change impacts animals, as is already being seen happening now in the case of pika, Miller said. The small animal, related to rabbits, is found in alpine environments in Colorado.

“They’re responding to the climate change that’s affecting the plants, the plant communities, and the pikas are having to move up farther in elevation,” he said.

Given the uniqueness of the Snowmass site and the lack of understanding up to now about how high-elevation plants respond to climate change, the site is resulting in “a lot of new science,” Miller said.

“It’s all brand new, so we’re still trying to figure out what it all means.”


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