Sierra Summit

Conversations and observations about California's mountains

October 9, 2008
Yosemite climate change - new article in Science magazine
Two months ago, I spent a few days in the high country of Yosemite with U.C. Berkeley emeritus professor of zoology Jim Patton, trapping and studying one of the first-known living casualties of climate change in California, the alpine chipmunk (left).
At the time, Patton talked excitedly about an article he and others were preparing that linked the upward shift of small mammals in Yosemite to global warming. Now that paper has been published in the Oct. 10 issue of the prestigious journal Science, representing the first peer-reviewed documentation that climate change is stirring ecosystem disruption in one of the world's most iconic national parks. 
"Recent trends do not bode well for several mid- to high-elevation species" in Yosemite, the article says.
To document their findings, Patton and others relied upon an unusual source: 90-year old field notes kept by pioneering California mammalogist Joesph Grinnell and his colleagues who tromped through Yosemite in the early 20th century trapping animals and jotting down almost everything they observed in small field notebooks. To learn more, check out my recent piece in the Bee  at:

I've also blogged on the topic at:

When Patton returned to Grinnell's old trap lines in 2003 - and simultaneously consulted Grinnell's field notes -  he quickly noticed things had changed. Animals common in Grinnell's camps were no longer there. They had moved up the mountain. One was the alpine chipmunk,  which was so widespread in Tuolumne Meadows in 1915 that Grinnell's men tossed sandwich scraps to them. "They're not there now," Patton told me.  "We looked for them extensively." Indeed, the animal can today be found no lower than 9,800 feet and is running out of real estate and at risk of extinction. In the field, Patton - shown below - is a bit like the creatures he studies; he is full of energy and - at 67 - he  scampers from rock to rock and up the mountain ahead of much younger colleagues. 
What makes the Science study doubling fascinating is that researchers did not set up to explore climate change. That came later. "The most dramatic finding ... was the upward elevational shift of species. When we asked ourselves, `What changed?' it hit us between the eyes: the climate," Craig Moritz, director of the Museum of Vertebrate Zoology at U.C. Berkeley and lead author of the study said in a press release. 
Overall, the study noted, night-time low temperatures in the central Sierra Nevada region have climbed three degrees Celsius over the past century (7.4 degrees Fahrenheit) over the past century. Of 28 species monitored, half expanded their ranges upslope. The average uphill shift was just over 1,500 feet.
"These kinds of changes in community composition have been going on forever," Patton said in the U.C. Berkeley press release. "The only thing that makes this different is that it has probably happened in our lifetime. It is the speed with which these changes are taking place that gives one pause."
Patton is one of America's most accomplished mammalogists and not surprisingly a disciple of Joseph Grinnell and his Yosemite camp mates. "The impressive thing about these guys is ... what incredibly observant natural historians they were," Patton said. "In pouring over these notebooks, I keep pulling out tidbits that are amazingly perceptive. These guys where out there thinking about what they were seeing and what it meant in a larger context long before most other people."
 Science does not publish its articles online, for free. To track down the Yosemite piece, you'll have to visit your library or subscribe. Alternatively, you can read the U.C. Berkeley press release/article about the paper and research at this link:

Bee potos by Tom Knudson

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About Sierra Summit

The Author
Tom Knudson lives in the Sierra Nevada and travels widely throughout the range. His hobbies include fly-fishing, backpacking and cross-country skiing. He is the recipient of numerous journalistic awards, including two Pulitzer Prizes, one for a 1992 Sacramento Bee series "Sierra in Peril," a watershed work about environmental threats to the mountain range. E-mail Tom at

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