SEQUOIA NATIONAL FOREST, Calif. — 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. Some models show noncoastal California warming by 2.7 degrees between 2000 and 2050, one of many reasons President Obama pledged last week to use executive powers to cut carbon pollution.
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.