Featured Research

from universities, journals, and other organizations

Changes In Australian Ecosystems Tied To Arrival Of Exotic Animals

Date:
December 21, 2000
Source:
University Of Colorado At Boulder
Summary:
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.

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.

Related Articles


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-Boulder’s 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 region.

The emu eggshells were biochemically analyzed for two different carbon isotopes that reflect the birds’ diet, said Miller, also a professor in CU-Boulder’s geological sciences department. High proportions of the "heavy carbon," or carbon 13, in the eggshells indicate the emus were eating primarily grasses, while lower proportions of carbon 13 indicate their primary diet was bushes and trees.

To evaluate changes in vegetation in south-central Australia since European colonization, the team derived proportions of grasses compared to bushes and trees in the diet of emus that laid their eggs between 300 and 14,000 years ago. The team then compared eggshells collected in the past 25 years with those going back to the last glacial maximum 15,000 years to 30,000 years ago and even as far back as 65,000 years ago, he said.

"Not even at the last glacial maximum has the proportion of emu diet of grasses been so small," he said. "We suggest unprecedented changes in ecosystems occurred in south-central Australia within the past 300 years, resulting in a dramatic reduction in the proportion of grasses in the emu diet."

Eggs laid by emus during the last glacial maximum reflect a lack of grasses in their diet, he said. A 1997 study by Miller and colleagues indicated systematic burning by the earliest human colonizers altered the vegetation patterns enough to diminish the effectiveness of summer monsoons that periodically drenched northern Australia, triggering increased aridity over much of the continent’s interior and decreasing grasses.

In January 1999, Miller and colleagues published a paper in Science magazine indicating the earliest humans who peopled Australia some 55,000 years ago inadvertently disrupted the continent’s food chain by burning vast areas of native vegetation, resulting in the extinction of most large animal species. The study showed an ostrich-sized bird known as Genyornis -- as well as 85 percent of the Australian "megafauna" weighing more than 100 pounds -- disappeared about 50,000 years ago.

"Australia has a fragile ecosystem where the soils are significantly depleted in nutrients," said Miller. "I would speculate that even if all the exotic animals were removed, it would take the ecosystems a long time to recover because the soils lack resiliency."


Story Source:

The above story is based on materials provided by University Of Colorado At Boulder. Note: Materials may be edited for content and length.


Cite This Page:

University Of Colorado At Boulder. "Changes In Australian Ecosystems Tied To Arrival Of Exotic Animals." ScienceDaily. ScienceDaily, 21 December 2000. <www.sciencedaily.com/releases/2000/12/001220080729.htm>.
University Of Colorado At Boulder. (2000, December 21). Changes In Australian Ecosystems Tied To Arrival Of Exotic Animals. ScienceDaily. Retrieved November 1, 2014 from www.sciencedaily.com/releases/2000/12/001220080729.htm
University Of Colorado At Boulder. "Changes In Australian Ecosystems Tied To Arrival Of Exotic Animals." ScienceDaily. www.sciencedaily.com/releases/2000/12/001220080729.htm (accessed November 1, 2014).

Share This



More Plants & Animals News

Saturday, November 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Watch Baby Goose Survive A 400-Foot Cliff Dive

Watch Baby Goose Survive A 400-Foot Cliff Dive

Buzz60 (Oct. 31, 2014) For its nature series Life Story, the BBC profiled the barnacle goose, whose chicks must make a daredevil 400-foot cliff dive from their nests to find food. Jen Markham has the astonishing video. Video provided by Buzz60
Powered by NewsLook.com
World's Salamanders At Risk From Flesh-Eating Fungus

World's Salamanders At Risk From Flesh-Eating Fungus

Newsy (Oct. 31, 2014) The import of salamanders around the globe is thought to be contributing to the spread of a deadly fungus. Video provided by Newsy
Powered by NewsLook.com
Alcoholic Drinks In The E.U. Could Get Calorie Labels

Alcoholic Drinks In The E.U. Could Get Calorie Labels

Newsy (Oct. 31, 2014) A health group in the United Kingdom has called for mandatory calorie labels on alcoholic beverages in the European Union. Video provided by Newsy
Powered by NewsLook.com
Malaria Threat in Liberia as Fight Against Ebola Rages

Malaria Threat in Liberia as Fight Against Ebola Rages

AFP (Oct. 31, 2014) Focus on treating the Ebola epidemic in Liberia means that treatment for malaria, itself a killer, is hard to come by. MSF are now undertaking the mass distribution of antimalarials in Monrovia. Duration: 00:38 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins