Calif.'s Sierra a 'living lab' for climate change

In parts of California's Sierra Nevada, marshy meadows are going dry, wildflowers are blooming earlier and glaciers are melting into ice fields. Scientists also are predicting the optimal temperature zone for giant sequoias will rise hundreds and hundreds of feet, leaving trees at risk of dying over the next 100 years. As indicators point toward a warming climate, scientists across 4 million acres of federally protected land are noting changes affecting everything from the massive trees that can grow to more than two-dozen feet across to the tiny, hamsterlike pika. But what the changes mean and whether humans should do anything to intervene are sources of disagreement among land managers. "That's the tricky part of the debate: If humans are causing warming, does that obligate us under the laws of the National Park Service to try to counteract those effects?" said Nate Stephenson, a research ecologist with the U.S. Geological Survey. "How do you adapt to a changing climate if you're a national park?" added Stephenson, who is 30 years into a study of trees in the largest wilderness in the continental U.S., Sequoia-Kings Canyon National Park. Since 1895, the average temperature across California has increased by 1.7 degrees, and experts say the most visible effects of that warming occur within the Sierra Nevada, where low temperatures are rising and precipitation increasingly falls as rain rather than snow. The state's two largest rivers — the Sacramento and San Joaquin — originate in the Sierra. The range also is home to Lake Tahoe, the largest alpine lake in North America; Mount Whitney, the highest peak in the Lower 48; and the nation's only groves of giant sequoias, the largest living things on earth. There are mounting concerns about the beloved sequoias, whose sprawling, 10-foot-deep root systems make them especially vulnerable to drought and heat. Because the trees exist only in such a small region, scientists are debating whether to irrigate the 65 groves in the southern Sierra to help them endure warmer temperatures. Otherwise they fear the trees could die. During the last warm, dry period 4,000 to 10,000 years ago, their numbers were greatly diminished, according to pollen evidence collected by researchers at Northern Arizona University. "I don't want to say that because we're seeing one thing, that's how it will play out," said Rob Klinger who is studying alpine mammals for the USGS's Western Ecological Research Center. "The endgame of our study is determining whether there will be uniform change or will it be patchwork. If you look at evolutionary time scales, species have gone through these changes before, and they handle it."...more