March 27, 2012

How Australia’s magnificent megafauna disappeared

diprotodon_140_270312.jpgNew study claims that humans, rather than climate change, were responsible for the extinction of giant marsupials

Published in “Science”, the new study is based on exploration of sediment cores to delve deep into Australia’s past.  The evidence suggests that the arrival of humans coincided with the loss of this continent’s big herbivores: from giant kangaroos and scary marsupial lions to monster birds and Komodo dragon-like reptiles. 

diprotodon_450_270312.jpgArguably more surprising and of greater interest, the decline of this megafauna appears to have led to ecological changes that caused Australia’s rainforest to become savannah.

According to the study: “large herbivores have strong effects on ecosystems, by maintaining vegetation openness and patchiness, removing material that would otherwise fuel landscape fire, dispersing seeds, and physically disturbing soil and recycling nutrients. Therefore, megafaunal extinction might have caused major changes to vegetation and the functioning of ecosystems.”

The research was based on analysis of fossilized fungal spores that need big herbivore dung to live.  These samples – taken form sediment cores in Lynch’s Crater, northwest Australia – demonstrated that mega-herbivores like the rhino-sized Diprotodon existed until around 41,000 years ago when it seems their population suddenly dropped, almost to zero.  This date approximates closely to the arrival of the first human populations.

The study also found evidence of two climate change impacts in the sediment cores, but both of these occurred prior to 41,000 years ago.  This indicates that while the megafauna here survived climatic upheavals, they were not able to survive overhunting by humans.

Some scientists are suggesting the implementation of trials to “re-wild” some of Australia with exotic megafauna to see if they could provide the long-lost and much needed ecological services.

Sources: Mongabay and The Aftermath of Megafaunal Extinction: Ecosystem Transformation in Pleistocene Australia. Susan Rule, Barry W. Brook, Simon G. Haberle, Chris S. M. Turney, A. Peter Kershaw, and Christopher N. Johnson. Science. 23 March 2012: 335 (6075), 1483-1486. DOI:10.1126/science.1214261.


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