Giant Australian animals were not wiped out by climate change

Jul 01, 2013
Giant Australian animals were not wiped out by climate change

(Phys.org) —Researchers have ruled out climate change as the cause of extinction of most of Australia's giant animals, including giant kangaroos, three metre-tall flightless birds and the Tasmanian tiger, around 50,000 years ago.

There has been much debate over the cause of the extinction of Australian's or '', says Professor Patrick De Deckker from the ANU Research School of Earth Sciences.

"The extinction happened around the same time as humans moved into the area, which also coincided with a change in the type of plant food available to megafauna," Professor De Deckker said.

"These events have led to several theories of the cause of extinction, including climate change. But the timing of these events was uncertain. We didn't know which one happened first, so we couldn't begin to understand what could have caused the extinction."

Professor De Deckker and his ANU colleagues, in collaboration with a team in the Netherlands, analysed a sediment core taken from the sea bed, off the coast of Kangaroo Island in the offshore canyons of the Murray River.

"Sediment cores provide a record of the past," said Professor De Deckker. "From the core we were able to reconstruct sea-surface temperature over the past 135,000 years, as well as variations in the type of vegetation in the Murray Basin, allowing us to piece together the order of these events."

The team found that sea-surface temperature varied by only 3°C at the time of the extinction – a minor variation compared to other times in the record – indicating that the extinction did not occur in a period of major climate change.

The core also revealed a shift in vegetation type immediately after the megafaunal extinction.

"Before and during the extinction period, 70 per cent of the vegetation was typical of northern Australia today. Immediately after the extinction, this value dropped to 35 per cent," said Professor De Deckker.

"Some people have suggested that this dramatic change in food sources might have been the cause of the megafaunal extinction, but we've shown that this was in fact a result of the extinction. Our idea is that with fewer herbivores around to eat them, substantial fuel remained in the landscape, which eventually led to massive fires.

"Our work unveiled the presence of a compound in the core that is produced as a result of plant material burning. This compound appeared after the megafaunal extinction and lasted some 3,000 years."

Professor Tim Flannery predicted this finding two decades ago.

"The nature and relative timing of these events turns out to be exactly as first hypothesised by Professor Tim Flannery in 1990," said Professor De Deckker.

"Professor Flannery suggested that the abrupt extinction of the herbivorous megafauna meant shrubs grew unchecked, increasing the amount of flammable material. This explanation has caused considerable and ongoing controversy, but is now supported by our evidence.

"While clearly demonstrating significant ecosystem after-effects of megafaunal extinction, the evidence from the core does not provide an explanation for the cause of the extinction, it does not support as a cause.

The research is published in the journal Nature Geoscience.

Explore further: Geologist seeks clues about the most rapid and dramatic climate change in Earth's history

More information: dx.doi.org/10.1038/ngeo1856

Related Stories

Giant moa had climate change figured out

Aug 06, 2012

(Phys.org) -- An international team of scientists involving researchers from the University of Adelaide has used ancient DNA from bones of giant extinct New Zealand birds to show that significant climate and ...

Coral survival's past is key to its future

Feb 14, 2012

Florida Institute of Technology researchers are taking an historical approach to predict the extinction risk of reef-building corals. Led by Robert van Woesik, professor of biological sciences, the researchers are examining ...

3Qs: The ethics of species 'de-extinction'

Mar 25, 2013

Scientists are closing in on the capacity to clone extinct species using biotechnology and DNA samples from the ancient past, a process that is called "de-extinction." The prospect of bringing back extinct ...

Recommended for you

Software models ocean currents for oil and gas search

1 hour ago

A study involving the use of streamline visualisation has found the technology can help guide electromagnetic transmitter and receiver placements, thereby aiding the search for oil and gas on the seafloor.

User comments : 6

Adjust slider to filter visible comments by rank

Display comments: newest first

mememine69
1.3 / 5 (16) Jul 01, 2013

Find me one single IPCC warning that says anything more than "could".
For 28 years science has agreed a "crisis" "COULD" happen and have NEVER agreed it "WOULD" happen. Now who's the fear mongering neocon?
All science has to do to "save the planet" and end this "costly debate" is just say their crisis is as real they love to say comet hits are............eventual!
So, just what has to happen NOW for science to say their crisis WILL happen not just might and could and possibly happen...............complete and "irreversible heating of the planet"? How close to the edge will the lab coats take us before they say their crisis is "inevitable" not just "possible" for another 28 years?
Anda
4.5 / 5 (8) Jul 01, 2013
Mememine... Dumb idiot :)
You haven't read the article or
You haven't understood the article and
Your writing doesn't have any relation to the article and
You even don't know what you are talking about.

Fuck! "Irreversible heating of the planet"??? What you talking about? (you don't know) Never heard about that before.

You are so so so so STUPID!
FainAvis
4.1 / 5 (9) Jul 01, 2013
mememine69
Consider this scenario: I see a truck running helter skelter down the hill toward you in the act of stepping off the kerb. Do I call out, "mememine69 look out! There is a truck barrelling down the highway that COULD hit you if you step out now!" Or do I wait, and when the emergency services come to clean up the mess, your guts and bones, should I tell them, "I saw the truck coming, but I knew he wouldn't listen to me, so I just kept my trap shut"?
Chromodynamix
1 / 5 (3) Jul 02, 2013
It could be a massive 'truck'!

http://ngm.nation...86/view/
deepsand
2.8 / 5 (13) Jul 02, 2013

Find me one single IPCC warning that says anything more than "could".
For 28 years science has agreed a "crisis" "COULD" happen and have NEVER agreed it "WOULD" happen. Now who's the fear mongering neocon?
All science has to do to "save the planet" and end this "costly debate" is just say their crisis is as real they love to say comet hits are............eventual!
So, just what has to happen NOW for science to say their crisis WILL happen not just might and could and possibly happen...............complete and "irreversible heating of the planet"? How close to the edge will the lab coats take us before they say their crisis is "inevitable" not just "possible" for another 28 years?

One wearies of your constant pecking at one aspect of a subject like an insane woodpecker looking for a grub in a block of concrete.
Sinister1811
2.2 / 5 (6) Jul 02, 2013
It makes me wonder if some of these animals (like the megalania and thylacoleo) were still around, would they be able to solve our invasive species crisis? Even wild dogs/dingoes have little impact on large invasive herbivore populations like camels, water buffalo, horses, donkeys and wild pigs. The government spends billions of dollars every year trying to eradicate invasive species.