From ABC, November 24, 2006
Earth hit by 'mass extinction' 250m yrs ago
About 95 per cent of the Earth's marine species and 70 per cent of its land species were wiped out during a "mass extinction" about 250 million years ago, according to Australian and US researchers.
The phenomenon fundamentally changed which species survived in the world's oceans.
Experts at James Cook University in Townsville and The Field Museum in Chicago warned modern human-induced changes to the ecosystem could have a similar impact.
The experts told the latest edition of the journal Science how they came across the culling of species while examining figures on the numbers of marine life forms in communities over the past 540 million years.
Simple species that did not move or search for food were largely wiped out, they concluded, while more complex life forms such as crabs and snails that went looking for food took over.
The biological devastation occurred at the end of the Permian age about 250 million years ago, when the Earth was believed to have had only one continent, surrounded by a single ocean.
The researchers did not go into the cause of what they called a "mass extinction" but, using a new palaeobiology database, they gave what they say are the most exhaustive details ever assembled of the impact.
Peter Wagner, associate curator of fossil invertebrates at The Field Museum, was the lead author of the study, and worked with Matthew Kosnik of James Cook University.
"We think these are the first analyses of this type at this large scale," Mr Wagner said.
"They show that the end-Permian mass extinction permanently altered not just taxonomic diversity but also the prevailing marine ecosystem structure."
The experts say the results of the study could provide a warning on how we treat the ecosystem now.
"Studies by modern marine ecologists suggest that humans are reducing certain marine ecosystems to something reminiscent of 550 million years ago, prior to the explosion of animal diversity," Mr Wagner said.
"The asteroid that wiped out the dinosaurs couldn't manage that."
- AFP