In Yosemite, Scientists Find Species Movin' On Up

Scientists have retraced the century-old steps of legendary naturalist Joseph Grinnell through Yosemite National Park. They found that most species have moved to higher, cooler elevations. Their study is published in this week's issue of the journal Science.

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Scientists in California are reporting that over the past century, many animals and birds in Yosemite National Park have migrated up the mountain sides. The reason, they're looking for cooler temperatures. And as the planet gets warmer, more and more species may struggle with the same choice - to migrate or die. NPR's Dan Charles reports.

DAN CHARLES: The oldest detailed records of wild life in Yosemite National Park are at the Museum of Vertebrate Zoology at the University of California, Berkeley. Craig Morris is the director.

Dr. CRAIG MORITZ (Director, Museum of Vertebrate Zoology, University of California, Berkeley): The Museum of Vertebrate Zoology is really unusual for an academic institution in that it has a soul and the sense of purpose.

CHARLES: The old notebooks bound into blue volumes and shelved in glass-fronted book cases are filled with notes from field expeditions. Some of the oldest and most detailed were collected by the museum's first director, Joseph Grinnell, in Yosemite. Grinnell wrote in 1910 that these notes would be most valuable a hundred years later, when other scientist might want to know what's changed.

Mr. MORITZ: So, in 1910, Grinnell set the table, basically told us what to do, and that is to come back in a century.

CHARLES: Craig Moritz and his colleagues did go back recently. They found the same kinds of mice, squirrels, and lizards that Grinnell had seen, but they found many of them in different places. Most had moved to higher elevations.

Mr. MORITZ: We've got one species that's moved a kilometer upwards from the east side over the Sierra Crest to colonize high elevations on the west side. That's a very dramatic change. This is not a subtle stuff we're talking about.

CHARLES: The reason Moritz says is that Yosemite doesn't get as cold anymore. According to weather records, the average monthly low temperature has increased by about six degrees Fahrenheit over the past century. That's a local change, but it's an example of what's likely to happen as global temperatures increase.

Mr. MORITZ: We didn't set out to look for an effect of climate change. It has hit us right between the eyes when we started looking at the data.

CHARLES: Their study appears in this week's issue of the journal Science. And right next to it in the magazine, there's a paper about the potential effects of global warming on wildlife in the tropics. Robert Colwel in the University of Connecticut studied plants and insects in the valleys and mountains of Costa Rica and found that half of them stay within a fairly narrow range of temperatures. If the earth warms up as predicted, they'll probably have to move. But species in the tropics, he says, have a particular problem.

Dr. ROBERT COLWEL (Department of Ecology and Evolutionary Biology, University of Connecticut): It's a very long way to somewhere that's cooler.

CHARLES: Temperatures in the tropics are the same across thousands of miles, from Mexico City to Sao Paulo, Brazil.

Dr. COLWEL: The point is that the only escape route - if they have to move - the only route is basically uphill.

CHARLES: Just as they did in Yosemite. Many probably will have to climb more than 2,000 feet, Colwel says, into entirely new areas. Some may not be able to make the leap. He also says it's not clear how many species will remain behind in the hottest areas, the tropical lowlands. Some biologists are optimistic. They say creatures in the tropical lowlands won't mind if it gets hotter. They'll stay put. But Colwel isn't so sure.

Dr. COLWEL: There is no evidence whatsoever that they're able to tolerate any amount of more heat, and I asked, why should they be an exception. Why should they not be adapted to their current climate?

CHARLES: So as thousands of tropical species move uphill, the rich diversity of life in the lowlands could start to disappear. Dan Charles, NPR News, Washington.

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