Feds warn climate change could harm giant sequoias Warming temperatures could soon cause California's giant sequoia trees to die off more quickly unless forest managers plan with an eye toward climate change and the impacts of a longer, harsher wildfire season, federal researchers warned Thursday. Hot, dry weather over the last two decades already has contributed to the deaths of an unusual number of old-growth pine and fir trees growing in Yosemite and Sequoia National Parks, according to recent research from the U.S. Geological Survey. In the next decade, climate change also could start interfering with the giant sequoias' ability to sprout new seedlings, said Nathan Stephenson, one of several scientists speaking Thursday at a government agency symposium on how global warming could affect the Sierra Nevada....