Global warming causing dramatic changes in Yosemite. [View All]

Global warming stalks Yosemite
Retracing the steps of a meticulous early 20th century biologist, researchers find that some of the park’s tiniest residents have moved a startling distance uphill

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On the east side of the Sierra, Grinnell and his assistants only saw piñon mice below 7,000 feet, a finding confirmed by other researchers throughout the central part of the range. Patton's group found numerous mice frolicking in the talus slopes of Lyell Canyon, 10,200 feet above sea level and about eight miles from the nearest Grinnell sighting. The distance was too great to be the work of just a few wandering individuals; it was clear to Patton that the range of the piñon mouse, and its habitat, were far different now than in 1915.

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There is little question...that the entire park is warmer than it was during Grinnell's time. Snow is melting earlier in the spring, and Lyell Glacier, like other glaciers throughout the Sierra, is disappearing. Researchers at Portland State University in Oregon found, using another series of historical photographs, that the surface area of the western lobe of Lyell has shrunk 30 percent since 1883, and the eastern lobe has contracted 70 percent.

Weather records from Yosemite Valley show a 9 degree Fahrenheit increase in mean minimum temperatures over the past century. Though weather data from higher elevations are spotty, Museum of Vertebrate Zoology researcher Robert Hijmans estimates that mean minimum temperatures throughout the central Sierra rose 5 degrees Fahrenheit over the last 100 years.

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The Intergovernmental Panel on Climate Change, considered the global scientific authority on the subject, foresees that between 1990 and 2100, Earth's average surface temperature will increase by between 2.5 and 10.4 degrees Fahrenheit. "The projected rate of warming," the panel concluded in its most recent report, "is much larger than the observed changes during the 20th century, and is very likely to be without precedent during at least the last 10,000 years."

Yosemite National Park, like all national parks, is supposed to muffle these and other "vastly more conspicuous" transformations wrought by humans, to use Joseph Grinnell's expression. "It would seem to me that national parks should comprise pieces of the country in which natural conditions are left altogether undisturbed by man," Grinnell wrote to Yosemite Superintendent W.B. Lewis in 1920. Yet the Grinnell resurvey team has found that when it comes to global warming, Yosemite is no refuge.

"Places like Yosemite mean so much to so many people," Patton reflects. "People think we've preserved this piece of the environment, but we haven't. The high-elevation species, those that seem to be retracting upwards, have no place to go -- so when they go, they're gone, and they're never coming back."

http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2005/11/27/ING66FMV901.DTL