[Aqualist] Megafauna and climate change seminar - University of Wollongong

[Timothy Cohen]

Dear AQUA members,

GeoQuEST at the University of Wollongong has great pleasure sponsoring the visit of Professor Gifford Miller from the University of Colorado.  Giff has a long history of working in the arid zone of Australia and has compiled a unique data set to assess potential changes in vegetation and climate over the last glacial cycle. He will present a GeoQuEST lunchtime seminar entitled:

"Can megafaunal extinction and ecosystem restructuring across semi-arid Australia be disentangled from natural climate change?"

Date: Tuesday the 23rd September, 2014
Venue: Building 41 (Science Building), Rm 153
Time: 12.30 - 1.30 pm


ABSTRACT:



For nearly 200 years the explanation for Australian megafaunal extinction has been debated, with climate change and human colonization the primary contenders.  Following colonization, humans became widespread across the continent between 50 and 45 ka, as indicated by archaeological visibility.  The timing of megafaunal extinctions continues to be debated, as many of the extinct taxa are rare in the fossil record, but the most parsimonious explanation is that most of the megafauna became extinct before 45 ka.  The late Quaternary is notorious for its fickle climate, and recent research indicates climate change occurred about the same time as humans colonized the continent and megafauna disappeared, complicating a solution.  Our team's research has shown that an abrupt change in ecosystem function occurred 50±5 ka, using the dietary intake of the Australian emu over the past 150 ka, as preserved in the carbon isotopic composition in the birds' eggshells.  To test whether this permanent shift at the base of the food chain is related to climate, we developed a calibration set demonstrating that the oxygen isotopes in emu eggshell carbonate provide a reliable proxy for aridity.  This allows us to now compare ecosystem structure and climate from the same source; concordance of the two signals supports a climate driver for ecosystem change, and potentially for megafaunal extinction, whereas discordance supports an aclimatic explanation.  We show that in several regions across the continent both ecosystem structure and climate undergo strong changes, but there is little to no correlation between climate change and ecosystem restructuring.  It therefore appears unlikely that the dramatic shift in ecosystems recorded by the emu dietary record can be explained by climate, whereas the close temporal correspondence of ecosystem change with human colonization provides compelling evidence that the two are intertwined.  We provide evidence for human predation on megafauna, but suggest that predation alone is unlikely to explain the permanent ecosystem reorganization.

Please feel free to pass this on to interested individuals,

Regards

Tim


Dr Tim Cohen
Senior Lecturer - School of Earth and Environmental Sciences
University of Wollongong, NSW, Australia, 2522.

Ph: + 61 2 4239 2375
Fax: + 61 2 4221 4250
E-mail: tcohen at uow.edu.au
http://smah.uow.edu.au/sees/UOW101441.html