Never mind that the NOAA show California temperatures, at least where the trees are, and the Northwest as a whole to be below normal. Global warming blamed for tree death in West
By Tom Knudson
tknudson@sacbee.com
Published: Thursday, Jan. 22, 2009
Tree mortality rates have doubled in old-growth forests across the Sierra Nevada and western United States because of rising temperatures associated with climate change, a new study has found.
The study, which will be published Friday in the journal Science, suggests that if the trend continues, the region's majestic conifer forests may become younger, smaller and far more sickly -- making them vulnerable to massive die-offs from insect attacks and other causes.
"Effectively, everywhere we looked we saw mortality rates increasing," said Nathan Stephenson, co-leader of the study and a research ecologist with the U.S. Geological Survey in Three Rivers near Sequoia and Kings Canyon National Parks. "That to me is a red flag that says there is potentially something pretty big going on."
While the actual increase may not appear large -- mortality rates have risen from about 1 to 2 percent across the region over the past quarter-century -- it is significant, Stephenson said.
"You can imagine if they doubled in the human population," he said. "We'd sure take notice and go, 'Oh my gosh. What's happening that's causing twice as many people to die every year?' "
Read more about this story Friday in The Bee and at sacbee.com, and read coverage of indications of global warming's effect on the Sierra Nevada at sacbee.com/sierra.