Past climate change effects on mammals may mirror global warm...( A thousands-of-years-old peek at the ...)

A thousands-of-years-old peek at the effects of climate change on small mammals in the western United States may provide a snapshot of the future impact of global warming on animal populations. When the climate of the Great Basin of the western U.S. shifted dramatically and became more arid between 8,300 and 5,000 years ago, the number of small-mammal species plummeted, with some becoming locally extinct, according to University of Washington archaeologist Donald Grayson. In a study published in the current issue of the Journal of Biogeography, Grayson also reported that the population balance among small mammals was substantially altered, with arid-loving kangaroo rats becoming the dominant species.

Grayson's data are based on analysis of more than 184,000 mammal bones and teeth recovered in stratified layers from Homestead Cave in north-central Utah, near the eastern edge of the Bonneville Salt Flats. It is the largest sample of small mammal fossils from the western U.S. ever studied. The bones and teeth were deposited over a period of about 11,300 years, extending back to the late Pleistocene epoch, by foraging owls that roosted in the cave. The cave is at an elevation of about 4,000 feet.

"This research is important because it is the first detailed analysis of what is likely to happen to mammals in this region under conditions of global warming," said Grayson. "It has implications of how we deal with global warming and how we set up and manage wildlife preserves. If we don't intervene the impact on mammals will be tremendous. There will be local extinctions across the valleys of the Great Basin and into the mountains."

The climate in the Great Basin, which includes most of Nevada and portions of California, Idaho Oregon and Utah, was different in the late Pleistocene and the early Holocene, the epoch which began about 10,000 years ago. The area was much wetter and cooler, and dotted with marshes and shallow lakes, according to G
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Contact: Joel Schwarz
joels@u.washington.edu
206-543-2580
University of Washington
9-Jan-2000