"There might be a scientific reason that the old-growth trees in Yosemite National Park don't seem quite as big or as plentiful as those in your grandfather's early snapshots of the park.

The number of large-diameter trees -- those at least 3 feet across -- has dropped 24 percent over the past seven decades due to 'moisture stress,'according to scientists at the U.S. Geological Survey and the University of Washington.

That is, they're parched -- and global warming is a likely culprit, experts said.

The die-off of these forest behemoths affects the appearance of a park that draws more than 3.5 million visitors a year. Scientists also worry it could affect wildlife, exacerbate climate change and stunt regrowth after wildfires."

Kelly Zito Reports For The San Francisco Chronicle August 9, 2009. [2]