Recently, the Forest Service redrew its decades-old maps for where to place fire breaks along the Sierra Nevada, moving suppression efforts down from the ridge lines to lower regions where scientists now believe habitats are at risk from wildfires, Millar said.

One local species troubled by rising temperatures is the mountain-dwelling American pika, or rock-rabbit. The 6-inch-long rodent thrives in cool, mountaintop climates, but at higher temperatures they can overheat and die within hours.

The population has been dwindling and drifting to ever higher elevations, but biologists fear it eventually could run out of mountain.

Still, because it could take years to understand how different animals and plants are influenced by not only rising temperatures, but fires, pollutants, forest management practices and other change agents, park officials said need to proceed cautiously.

"Right now, we're going to focus our efforts on the big icon for the parks, the giant sequoias," said Craig Axtell, superintendent of Sequoia and Kings Canyon National Parks. "But we may find that other problems come up down the road that we don't even know about."