Australasian Science: Australia's authority on science since 1938

Final Megafauna Extinctions Not Climate-Related

By Stephen Luntz

A study of Australia’s climate and vegetation over 135,000 years has cast doubt on the possibility that the last megafauna extinctions could have been climate-related, while confirming a 20-year-old prediction about the after-effects of the final wave of extinctions.

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Prof Patrick De Deckker of the Australian National University took samples of sediment cores off the coast of Kangaroo Island. Two were examined for sea-surface temperatures indicated by foraminifera shells deposited, while one was also the subject of a study of the plant vegetation washed down through the Murray River and its tributaries.

De Deckker found a 3°C change in temperature around the last extinctions, far smaller than at other periods and insufficient to explain the disappearance of the megafauna that previously dominated the continent.

“The finger points to humans, but we don’t have the evidence to say it was necessarily us,” says De Decker. “But we are saying it’s definitely not climate change.”

The vegetation deposited on the sea floor near the mouth of the Murray records a 3000-year period of huge fires, which De Deckker says occurred after the megafauna disappeared and would have been a consequence of their demise. “Prof Tim 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,” De Deckker says.

In research published in Nature Geoscience, De Deckker reported signs of a change in the plant types growing in the Murray-Darling Basin...

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