Guest essay by Eric Worrall

Just like the USA, Australian Megafauna disappeared from Australia soon after humans arrived, but scientists claim the evidence suggests climate change was responsible.

Giant kangaroo victim of climate change

Robyn Wuth
MAY 18 2020 – 12:11PM

Giant kangaroos and enormous crocodiles that lived 40,000 years ago in tropical northern Australia died out because of climate change, a study has found.

As the rest of the world was running from giant man-eating carnivores, Australia was home to a kangaroo that stood 2.5 metres tall and weighed a massive 274kg.

It fought for its place in the food chain alongside a marsupial “lion” and the world’s largest wombats.

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“The megafauna at South Walker Creek were uniquely tropical, dominated by huge reptilian carnivores and mega-herbivores that went extinct around 40,000 years ago, well after humans arrived on to mainland Australia,” said palaeontologist Scott Hocknull.

“Their extinction is coincident with major climatic and environmental deterioration both locally and regionally, including increased fire, reduction in grasslands and loss of fresh water.

“Together, these sustained changes were simply too much for the largest of Australia’s animals to cope with.”

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Read more: https://www.canberratimes.com.au/story/6760372/giant-kangaroo-victim-of-climate-change/

The abstract of the study;

Extinction of eastern Sahul megafauna coincides with sustained environmental deterioration

Scott A. Hocknull, Richard Lewis, Lee J. Arnold, Tim Pietsch, Renaud Joannes-Boyau, Gilbert J. Price, Patrick Moss, Rachel Wood, Anthony Dosseto, Julien Louys, Jon Olley & Rochelle A. Lawrence 

Explanations for the Upper Pleistocene extinction of megafauna from Sahul (Australia and New Guinea) remain unresolved. Extinction hypotheses have advanced climate or human-driven scenarios, in spite of over three quarters of Sahul lacking reliable biogeographic or chronologic data. Here we present new megafauna from north-eastern Australia that suffered extinction sometime after 40,100 (±1700) years ago. Megafauna fossils preserved alongside leaves, seeds, pollen and insects, indicate a sclerophyllous forest with heathy understorey that was home to aquatic and terrestrial carnivorous reptiles and megaherbivores, including the world’s largest kangaroo. Megafauna species diversity is greater compared to southern sites of similar age, which is contrary to expectations if extinctions followed proposed migration routes for people across Sahul. Our results do not support rapid or synchronous human-mediated continental-wide extinction, or the proposed timing of peak extinction events. Instead, megafauna extinctions coincide with regionally staggered spatio-temporal deterioration in hydroclimate coupled with sustained environmental change.

Read more: https://www.nature.com/articles/s41467-020-15785-w

The issue of the possible role of Aboriginals in megafauna extinction is as sensitive in Australia as elsewhere. From the study;

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The ODP820 charcoal record illustrates an increased fire frequency starting ~44 ka, intensifies from ~40 ka, and peaking ~28 ka^23,27,43(Fig. 3g). While anthropogenic landscape burning has been attributed to these increases over the last 50,000 years^27,43, this has been challenged and a more likely explanation involves the complex relationship between climate and vegetation with fire frequency⁴⁷. Importantly, the increased and sustained burning from ~44 ka indicates a fundamental shift toward environmental deterioration and instability that would have impacted the survival of megafauna. 

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A role for people in the extinction of Sahul megafauna through their direct extirpation has been previously proposed. However, with no evidence of butchery or kill sites, it has been proposed that extinction occurred rapidly across Sahul shortly after human arrival^{12,13,14,22,52,53,54,55}. In the absence of evidence for direct extirpation, indirect human-mediated factors such as landscape burning have been proposed but are difficult to differentiate from non-human factors^{15,16,21,56,57}.

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Read more: Same link as above

I suspect humans at least contributed to Australian megafauna extinction, despite the delay between human arrival and extinction. Suggesting humans had very little to do with megafauna extinction requires accepting the hypothesis that the abrupt extinction of megafauna which had likely survived for millions of years, and the arrival of humans at roughly the same time, was all just a big coincidence.

It is not necessary to believe that humans ate all the megafauna, for humans to have played a role in their extinction. A 2013 study suggested land clearance in Australia can cut local rainfall in half. Fire wielding humans can clear a lot of land, deliberately or otherwise.