USGS Release: Uncertain Future for Joshua Trees Projected with Climate Change (3/24/2011 11:43:48 AM)

FLAGSTAFF, Ariz. — Temperature increases resulting from climate change in the Southwest will likely eliminate Joshua trees from 90 percent of their current range in 60 to 90 years, according to a new study led by U.S. Geological Survey ecologist Ken Cole.
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By using fossil sloth dung found in desert caves and packrat middens — basically, the garbage piles of aptly named packrats — scientists were able to reconstruct how Joshua trees responded to a sudden climate warming around 12,000 years ago that was similar to warming projections for this century.
...The limited ability of rodents to disperse Joshua tree seeds in combination with other factors would likely slow migration to only about 6 feet per year, not enough to keep pace with the warming climate, Cole and his colleagues concluded.