Energy News  
Did humans Cause Ecosystem Collapse In Ancient Australia?

The PC version of what happened.

Washington, DC (SPX) Jul 11, 2005
Massive extinctions of animals and the arrival of the first humans in ancient Australia may be linked, according to scientists at the Carnegie Institution, University of Colorado, Australian National University, and Bates College. The extinctions occurred 45,000 to 55,000 years ago.

The researchers traced evidence of diet and the environment contained in ancient eggshells and wombat teeth over the last 140,000 years to reconstruct what happened. The remains showed evidence of a rapid change of diet at the time of the extinctions.

The researchers believe that massive fires set by the first humans may have altered the ecosystem of shrubs, trees, and grasses to the fire-adapted desert-scrub of today. The work is published in the July 8, issue of Science.

The scientists plotted diet changes over 140,000 years of two species of large, flightless birds--the now-extinct Genyornis and the surviving emu (Dromaius)--in three Australian locations. They then corroborated their findings by analyzing ancient wombat teeth. "What your mother told you is true: You are what you eat," stated co-author of the study Marilyn Fogel of Carnegie.

"Eggshells and teeth both contain evidence of these animals' diets in different forms of carbon.

All three animals were plant eaters. Different types of plants metabolize different forms of carbon in distinctive ways from the CO2 they take up during photosynthesis. The tell-tale carbon varieties were preserved in the eggshells and teeth and told us what types of plants the animals ate. We saw a sudden shift in plant type coincident with the arrival of humans.

The shifting diet shed light on the extinctions. The animals that relied mostly on the more palatable plant forms died out, such as Genyornis, while the animals that adapted to the less nutritious plants survived, including the emu."

There are three isotopes, or varieties, of carbon found in nature--12C, 13C and 14C. They differ in the number of neutrons in the nucleus. By far the most abundant variety is in the lightest, 12C. About 1% is 13C, a heavier sibling with an additional neutron. There is even less 14C, the unstable, radioactive heavyweight of them all.

"13C is the key," Fogel explained. "There are two main ways plants metabolize 13C . About 85% of plants belong to what is known as C3 photosynthesis group. This group incorporates less 13C than plants belonging to the second most common class, C4.

"Thus, the differences in 13C that we detected in the eggshells and teeth pointed to the type of plants that were consumed. Although, both types of plants were present before the extinctions, we saw a quick shift in dominance from C4 drought-resistant trees, shrubs and grasses, to C3 desert plants."

Why did the scientists point to humans as the instigators of the ecological changes? First, they ruled out the other usual suspect--global climate change.

They looked at their data in 15,000-year intervals back to 140,000 years ago. The period included dramatic climate changes, but no changes in the diet and environment until an abrupt transition was noted that corresponded to the arrival of humans.

"Humans are the major suspect," commented Fogel. "However, we don't think that over-hunting or new diseases are to blame for the extinctions, because our research sees the ecological transition at the base of the food chain.

"Bands of people set large-scale fires for a variety of reasons, including hunting, clearing, and signaling other bands. Based on the evidence, human-induced change in the vegetation is the best fit to explain what happened at that critical juncture."

Community
Email This Article
Comment On This Article

Related Links
Carnegie Institution
SpaceDaily
Search SpaceDaily
Subscribe To SpaceDaily Express
Darwin Today At TerraDaily.com



Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News


'Darwinian Debt' May Explain Lack Of Fish Stock Recovery
Stony Brook NY (SPX) Jan 11, 2006
Why does it take so long for fish stocks to recover from over-fishing? This problem has been worrying both scientists and fishery managers who expect stocks to quickly rebound when fishing stops.







  • China To Go To The Colorado Rockies?
  • New Process Proposed For Drying Lumber
  • Oil Prices Drop As US Rigs Escape Hurricane
  • Producing Ethanol And Biodiesel From Corn Not Worth The Energy: Study

  • Mitsubishi Heavy Seeks US Nuclear Builder Westinghouse For 1.8 Bln Dlrs
  • Nuclear Plant In Japan Reports Vapor Leak But No Danger Of Radiation
  • Analysis: Next G8 Should Focus On Nuclear Proliferation
  • Japanese Nuclear Reactor Shuts Down, No Radioactive Leaks

  • Scientists Seek Sprite Light Source



  • EU Governments Keep National Bans On GMOs
  • Insects Resistant When Single And Double-Gene Altered Plants In Proximity
  • Insects Developing Resistance To Genetically Engineered Crops
  • East African Farming Genetically Transformed

  • Eco-Friendly Motor Rally Sets Off From Kyoto To Celebrate Environment

  • New Low Cost Airlines Take Flight In India
  • Boeing Facing Possible US Charges Over Aircraft Sales
  • EU Urges China To Liberalize Aviation Sector
  • NASA Announces Aerospace Systems Modeling Selection

  • NASA plans to send new robot to Jupiter
  • Los Alamos Hopes To Lead New Era Of Nuclear Space Tranportion With Jovian Mission
  • Boeing Selects Leader for Nuclear Space Systems Program
  • Boeing-Led Team to Study Nuclear-Powered Space Systems

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2006 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA PortalReports are copyright European Space Agency. All NASA sourced material is public domain. Additionalcopyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement