Climate change pushes pika from traditional sites in the Sierra

This image provided by Stanford University biologist Scott Loarie, shows an American Pika in August 2008 in Desolation Wilderness in El Dorado County, near Lake Tahoe.
This image provided by Stanford University biologist Scott Loarie, shows an American Pika in August 2008 in Desolation Wilderness in El Dorado County, near Lake Tahoe. Associated Press file

The American pika is a tiny animal – about 6 inches long – but scientists say it’s sending a big message about climate change.

This small-eared member of the rabbit family is disappearing from its northern Sierra Nevada range, researchers say. They point to the pika as a harbinger species – an example of how mammals in the Sierras are responding to climate change by retreating to higher, colder elevations and changing their behavior.

In 2013, the state Department of Fish and Wildlife declined a petition to list the pika as endangered, saying it wasn’t at risk of extinction.

More recently, in 2014, researchers at UC Santa Cruz and Fish and Wildlife found that the pika is now scarce in areas where it was once plentiful. The study, which appeared in the Journal of Biogeography, said that if temperatures continue to rise, the pika will disappear from most of the northern Sierra.

The study identified 67 sites in the Sierra where pikas have been known to live – from the slopes of Mount Shasta in the north to the John Muir Wilderness in the south. Researchers found pikas had vanished from 10 of these spots, said Joseph Stewart, a scientist at UC Santa Cruz and the study’s lead author.

While all mammals respond to temperature changes, the pika is particularly sensitive. It dies when its body temperature rises just a bit above normal. Temperatures above 75 degrees can kill a pika in one hour.

“This suggests that the pika is very susceptible to climate change,” Stewart said.

Since 1895, annual average temperatures throughout California have increased by nearly 1.5 degrees, according to the state Office of Environmental Health Hazard Assessment. NASA recently reported that 2014 was the warmest year on record, both for California and the world.

Scientists expect temperatures to keep rising. In order to predict where they’re headed, Stewart used 17 general temperature models from the most recent Intergovernmental Panel on Climate Change report. The IPCC coordinates the efforts of more than 2,000 scientists from 154 countries to form a consensus on climate change and greenhouse gas issues.

“Climate change models predict that summer temperatures in California will increase by somewhere between 4 and 12 degrees depending on how much greenhouse gas pollution we add to the atmosphere,” said Stewart. “That translates from between 39 percent to 88 percent local extinction of pikas by 2070.”

The pika forages during the day in summer. And in the Sierra, summer temperatures are increasing more than winter temperatures, said David Wright, a scientist with state Fish and Wildlife and co-author of the recent pika study.

Wright said that the warmer temperatures would mimic a sea level rise effect on the pika’s habitat, where the mammal would retreat into smaller and more isolated colonies where temperatures remained livable.

“Low places would be inundated by heat,” said Wright. “Eventually, only the peaks will be cold enough.” Wright said he believes this will be the fate of the pika in Plumas and Sierra counties as well as the Lake Tahoe area.

Other mammals living in the region will also be affected, he said, including hibernators such as the marmot and the Belding’s ground squirrel. Higher temperatures could cause these animals to wake early, when the environment might not be right for them to roam or feed.

Of the two species, the squirrel is most at risk. A 2012 study found that populations of the Belding’s ground squirrel had plummeted almost 50 percent because of climate change and development, said Wright.

Decreased levels of snowfall have been implicated in the squirrel’s plight since it relies on a thick blanket of snow for insulation during long period of hibernation. Without that insulation, the species can freeze.

Further study is needed to know how much the squirrel and the American pika will be affected by climate change, Stewart said. To date, only historical sites where the pika has lived have been inventoried in the study. As a result, it is hard to establish how many pikas currently live in the Sierra. Stewart said this lack of information could mean the species is doing better – or much worse – than has been documented.

To glean more information on the plight of the species, Stewart recently conducted additional research on his own at Yosemite National Park. He randomly visited spots in the park where pikas had lived at some point. He found the same population pattern as the larger study did.

“Summer temperatures were the best climate predictor of which sites did not have pikas,” Stewart said.

James Thorne, a landscape ecologist at UC Davis, said the pika study provides important information about how warmer temperatures are changing the Sierra. These changes won’t be limited to mammals, he predicted.

Thorne participated in a recent study that found changes in temperature, combined with the ongoing multi-year drought, have changed the composition of the forest. The study found that the density of large trees in the Sierra has declined due to tree deaths, and the density of smaller trees has risen at higher elevations.

Call The Bee’s Edward Ortiz, (916) 321-1071. Follow him on Twitter @edwardortiz.