By Stuart L. Pimm
for NatGeo News Watch
If you think small, furry rodent-like mammals are unappealing, then you have never met a pika! They look like very small rabbits, are often quite tame, and they are enormously endearing. They are usually stuffing their faces with vegetation.
It’s also where they live that makes them so fascinating. If you’re watching a pika the odds are you’re in lovely scenery, with snow-covered mountains nearby. Pikas generally live in mountains–about 8,000 feet above sea level in most of the continental U.S.
At my age, stopping to watch pikas gives me a chance to catch my breath without younger companions ragging me about being out of shape.
NGS stock photo by George F. Mobley
Pikas live in places we often think of as pristine. Yet they have become the poster child for how global warming is harming biodiversity.
There’s a lot at stake here–politically, certainly–but there are some important scientific issues too.
Pikas illustrate what we don’t know–and urgently need to know–about the distribution of all species of animals and plants that live in mountains worldwide.
The American pika lives from California to New Mexico and north into Canada. Elevation is really important to them. As one goes north, the low annual temperatures that they need occur at progressively lower elevations.
The controversy is all about what happens in the future, as the climate warms. As average temperatures rise, the pika’s range may shrink as the animals find lower elevations too hot for them.
[Watch this National Geographic video about pikas.]
Video by Public Television’s Wild Chronicles from National Geographic Mission Programs
How much cooler it is as one climbs into the mountains is well-known. It is, after all, why we visit the West’s mountains in summertime. In early August, I’d rather be outdoors in Telluride than in Washington, D.C.
Last year the world’s leaders in Copenhagen couldn’t agree to keep the planet’s average temperature increase to below 2 degrees C above what it is now. For the pikas a two-degree rise in temperature means climbing an extra 400 meters (1,300 feet) higher to keep as cool as they have in the past.
In some areas, there just isn’t land that is high enough. In others, there just isn’t very much land.
It gets worse: As the range for species that prefer cool temperatures shrinks, it becomes even more fragmented than it is now. Small populations go extinct quickly–especially when they are isolated from other populations that might supply occasional colonists to rescue them.
The Fish and Wildlife Service pika decision sparked several controversies.
First, scientists disagree over how serious are these reductions in ranges.
The Fish and Wildlife Service argued that the temperature projections past the middle of this century are uncertain and that other things besides temperature–specific habitats for example–might matter more to the pikas. They continued that temperatures at the surface of the ground may matter less than temperatures just below ground, where the pikas can hide. And they felt that pikas could probably avoid warmer temperatures during the hottest part of the day.
Dr. Shaye Wolf, of the Center for Biological Diversity, contests all this. “The Service dismissed studies showing that pikas are disappearing due to climate change and studies predicting that they will continue to disappear,” she told me. “Instead they argued that pikas will be able to cope with the massive warming to come. If only pikas were so lucky! The Service should have considered climate change impacts to pikas beyond 2050,” she said.
I agree. Climate projections show progressively hotter temperatures as the century proceeds. That a species doesn’t die out next week isn’t room for complacency if they are going to die out next year.
Mad dogs, Englishmen … and pikas
“The final argument seems particularly specious,” Shaye told me, “If pikas could simply avoid the midday sun–I interrupted her with, “they’d join the mad dogs and Englishmen there!”
Pikas are where they are–high up–likely because they can’t handle heat. “Moreover, the climate is already getting warmer–and some populations have already become extinct,” Shaye pointed out.
National Geographic Grantee, Dr. Rob Guralnick, understands this as well as anyone. “Pikas are going missing on mountain tops,” he says. His colleague, Dr. Liesl Peterson, explains: “Unlike other species, they don’t shut down in the winter. They have to have a high metabolism to keep them going. Then, in the summer, if there’s a hot period, then can’t keep themselves cool enough.”
I knew that my next call would be to Dr. Scott Loarie, a former student of mine, now at the Carnegie Institution for Science, in California. Scott is a modeler. And he sent me a map.
“Using museum specimens from over 400 sites, I built a computer model of where the pika should live–all the areas colored in reds to blues on the map,” he told me.
“It’s good, but not perfect,” I told him, as I overlaid his map on one from the Nature Serve site that has range maps of all the species of mammals in the Americas.
“Agreed,” Scott replied, “the pikas are not on high mountain tops in Arizona–though they might have been in the past.”
“The colors are the probability that the pikas will go extinct in this century–red means they will, while blue means they probably won’t.”
The predicted distribution of the American pika in the U.S. and Dr. Scott Loarie’s predictions of the prospect for where the animal might become extinct. (Blue means unlikely, red means very probably.) The approximate present distribution of the species is outlined in yellow. Data from Nature Serve.
“So how did you estimate those probabilities,” I asked.
“Well, 97 of those sites have been visited at least twice–and the pikas have become extinct in eight of them. Extinction is already happening!”
“What’s important,” Scott continued, “is those extinctions in the last decades have happened in exactly the places the model expects–the low, hot sites, mostly in California and Nevada.”
If Scott’s map is correct, pikas will no longer be charming companions to weary, out-of-breath hikers like me in Nevada, Oregon, and most of California.
Photo by Chris Kennedy/USFWS
There is a wider, political controversy.
Had this species been declared “endangered,” it would have become so because of global warming–and our emissions of carbon dioxide that cause warming. Several people have suggested to me that the Fish and Wildlife Service was under pressure not to classify this species as endangered to avoid that issue.
I knew from our work together, that Scott wanted to tell me something else.
“This is a perfect candidate for citizen science. It’s an easy-to-identify mammal familiar to every hiker. We need help from everyone who visits these mountains, to record if, and where they see these mammals,” he said.
I’m sure the Fish and Wildlife Service would agree. They concluded their finding, “we ask the public to submit to us any new information that becomes available concerning the threats to the pika … or its habitat at any time.”
The ultimate arbiter of the controversies would be more data. If the pikas keep disappearing from progressively higher mountains, the accusatory finger of global change would be impossible to deflect.
It wouldn’t be just North America’s pika at risk. There are thirty species worldwide–all living in places that we might have thought untrammelled and far from human impact. (I saw my first pika high in the mountains of Afghanistan.)
And it wouldn’t just be pikas. Scott and I know from our research that some large fraction of species worldwide–perhaps 20 percent–might live too close to the top of their nearest mountains to survive an increase of 2 degrees C.
How many such species are at risk is uncertain–it depends on our incomplete knowledge of the elevations where species live. That’s something than any naturalist with a GPS or even a good, old-fashioned map could tell us.
The scientific community really needs that help.
Professor Stuart L. Pimm is a conservation biologist at Duke University, North Carolina. A former member of the National Geographic Committee for Research and Exploration, Pimm is the author of dozens of books and research papers, including the book “The World According to Pimm: A Scientist Audits the Earth.”