Humans caused wipeout of Australian fauna

Humans caused wipeout of Australian fauna - The arrival of human beings in Australia devastated the local fauna so much that huge extinctions soon followed.

Up until now, the extinction of Australia's megafauna had been a mystery.

Australian scientists said they pinpointed hunting by humans as being the primary cause of the disappearance of many species about 40,000 years ago.

They made the discovery by using a new method of tracking the abundance of large herbivores through time by counting spores of dung fungi.

"The spores of these fungi can be preserved in sediments in swamps and lakes," team leader Professor Chris Johnson from the School of Zoology at the University of Tasmania said.

"As those sediments accumulate over time, they create a historical record of the abundance of very large herbivores in the environment."

Pollen and charcoal particles are trapped in the same sediments, so the team found it could match up the history of abundance of large herbivores with changes in vegetation and fire.

This was done by using radiocarbon dating.

The team examined sediment at Lynch's Crater on the Atherton Tableland in north Queensland.

"It showed that the abundance of large mammals was stable until just before 40,000 years ago when it suddenly crashed," Professor Johnson said.

"This rules out climate change as a cause of extinction as there were several periods of climate drying before the extinction and they had no effect on abundance, and when the animals did go extinct the climate was stable.

"But the extinctions followed very soon after the time that people arrived in the region. So it seems that people did it.

While the study did not directly address how people caused extinction, the scientists say circumstantial evidence suggested it was most likely the result of hunting.

"Beforehand, the environment seems to have been quite open, probably with patches of rainforest separated by areas of open grassland and there was very little fire," Professor Johnson said.

Soon afterwards, fire increased and the vegetation turned into widespread eucalypt forest.

"Probably these changes were caused by the decrease in consumption of plant material by large herbivores, which allowed forest to spread and also resulted in a build-up of dry fuel for bushfires."

Professor Johnson believes that the extinction of the megafauna was the catalyst for ecological changes which were profound.

"These results should provoke us to look at `natural' places in a new way, as landscapes that have been fundamentally changed by the indirect effects of early Aboriginal people."

The team included scientists from the Australian National University, the University of Adelaide, the University of New South Wales and Monash University. ( news.com.au )