"GIFFORD PINCHOT NATIONAL FOREST -- Gliding across the treetops in the Gifford Pinchot National Forest in Washington State may sound like the latest trend in eco-tourism.
But the gondola on the massive Wind River crane is not used for recreational sport -- it's a research tool being used by scientists at the University of Washington to measure the effects of global warming on trees.
For years researchers have been studying trees' ability to absorb carbon dioxide, one of the major greenhouse gases responsible for global warming, but from the ground they've only been able to get half the picture.
Matt Schrader, a University of Washington researcher, said tree tops have been the hardest for scientists to access, yet are considered the most important to examine the health of trees. ...
A US Geological Survey-led study published in January said tree death rates have more than doubled over the past five decades in the western United States."