5590 Jeff Hecht: Back through the nests of time.
New Scientist 28 August 1993, 10. Changes in the vegetation of four American
national parks over the past century are more extensive than anything that
happened in the previous 5000 years, according to an ecologist at the
University of Minnesota. He blames European settlers for logging, overgrazing
and introducing exotic species. He found the best record of change at the
level of species in the fossilised nests of pack rats at Capitol Reef
National Park in Utah. These desert rodents collect plant fragments and
other objects. In arid climates such as Utah's their nests can survive
unchanged for thousands of years.