In the Great Basin, scientists track global warming
Note: This article is a sidebar to this issue's feature story, "The Ghosts of Yosemite."
Eugene Raymond Hall, one of biologist Joseph Grinnell’s first graduate students, was "a robust, pipe-smoking, extroverted individual," known for his stubbornness and rough edges, writes historian Barbara Stein. In many ways, he was unlike his reserved mentor, but his scientific enthusiasm was very Grinnellian. Hall directed the Museum of Natural History at the University of Kansas, where he established a renowned zoology program and passed Grinnell’s methods on to his own students. His Mammals of Nevada, published in 1946, is considered a classic text.
Today, Hall’s diligent fieldwork, along with that of his influential professor, is helping define the scope of global climate change. Wildlife biologist Erik Beever, along with a handful of collaborators and students, is using Hall’s work to document marked declines in pikas.
Pikas, tiny, short-eared relatives of rabbits, live at high elevations throughout the Western states. Though they’re little bigger than baseballs, they’re hard to miss. Hikers who frequent rocky mountain slopes are familiar with their high-pitched calls, and with the imposing "hay-piles" the animals construct; since pikas do not hibernate, they use the piles as a winter food supply, and perhaps for protection from the cold.
In the early 1990s, when Beever first revisited 25 Great Basin pika populations recorded by Hall and others, it was obvious things had changed. Though the rocky talus slopes looked the same as when Hall had visited about half a century earlier, six of the 25 populations had completely disappeared.
The disappearances followed a definite pattern. "In five of the mountain ranges we studied, the populations at lower elevations are gone, and the populations at higher elevations remain," says Beever. Previous research showed that pikas have a low tolerance for high temperatures, and Beever’s analyses suggested that climate played a strong part in the declines. While some of the animals may have found cooler climes uphill, pikas don’t generally move very far; many of the lower-elevation pikas Hall and others saw may have simply died out.
Beever, until recently a researcher with the U.S. Geological Survey in Oregon, visited the sites a second time between 2003 and 2005, and found that two more pika populations had blinked out during the previous decade.
Since Beever and his coworkers first published their results in 2003, the photogenic pika has become something of a poster child for global warming’s impacts on the Western states. But Beever, now a wildlife biologist with the National Park Service Great Lakes Network in Wisconsin, cautions that pikas are only a small part of a larger tale. "Each species has its own behavior and its own life history," he says, "and each one will respond differently to climate change."
Nonetheless, the pika provides a stark look at what is possible: A warming climate threatens to sweep the species right off the map. Within Beever’s 17 remaining study sites, the lower edge of the population has moved an average of 130 yards uphill since the 1990s. And at four of those sites, there are so few animals that long-term survival of the populations looks unlikely.
"One of the things that managers tend to do when species are lost is to say, ‘Well, we can reintroduce it,’ " says Beever. "But if the climate is unsuitable, then the relocation will be in vain."