A study of old and new emu eggshells collected from central Australia indicates a dramatic loss of grasslands beginning roughly 300 years ago was due to the arrival of Europeans and the introduction of exotic grazing animals, according to a new study.

The eggshells of the large, flightless bird are unique in that they can be dated by traditional radiocarbon methods and by a process known as amino acid racemization, said University of Colorado at Boulder Professor Gifford Miller. Racemization involves studying mirror-like changes in amino acids in the eggshells over time, which has proven to be an accurate time clock for dating events going back thousands of years.

"Because these eggshells can be dated by both radiocarbon methods and amino acids, they offer a unique opportunity to look back at ecosystem changes over the last 70,000 years," said Miller, a fellow of CU-Boulders Institute of Arctic and Alpine Research.

The study indicates that grazing mammals introduced in the last few centuries by Europeans have contributed to "a major change in ecosystems" in central Australia, said Miller. "We see a major reduction of plant biomass beginning in the 1800s, which looks like a result of overgrazing by pastoral animals and the introduction of rabbits."

The results of the study were presented at the fall 2000 meeting of the American Geophysical Union held in San Francisco Dec. 15 to Dec. 20. Other authors on the paper include Beverly Johnson, a former CU graduate student of Miller's now at the University of Washington, John Magee and Michael Gagan of Australian National University and Marilyn Fogel of the Carnegie Institution in Washington, D. C.

The eggshells were collected by Miller and Johnson, who conducted lengthy north-south and east-west transects in south-central Australia over the past two years. Miller believes the introduction of rabbits about 150 years ago was a major contributor to the demise of grasslands in the regio
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Contact: Gifford Miller
Gmiler@colorado.edu
303-492-6962
University of Colorado at Boulder
17-Dec-2000