Australia: The Land Where Time Began

A biography of the Australian continent 

Abrupt Change in Vegetation in Southeast Australia Following Megafaunal Extinction in the Late Quaternary

Coinciding with the spread of humans across the Australian Continent there was a substantial mass extinction of the marsupial megafauna (Bowler et al., 2003) across the continent between about 50,000-45,000 years ago (Roberts et al., 2001; Grün et al., 2010). There were also large shifts in the vegetation types across Australia at about this time, though it is uncertain if these changes resulted from the use of fire by the humans (Turney et al., 2008) - which then contributed to the extinction event - or whether the loss of the megafauna grazers (Rule et al., 2012; Flannery, 1990) resulted in the vegetation changes. In this paper the authors¹ reconstruct past vegetation changes that occurred in southeast Australia by the use of the stable carbon isotopic composition of wax n-alkanes produced by higher plants and the used of the accumulation rates of  levoglucosan, a biomarker, to determine the levels of biomass burning from a well-dated sediment core obtained offshore from the Murray-Darling Basin. Their results indicated that the abundance of C₄ plants was 60-70 %, which is generally high from 58-44 ka, and the abundance of these C₄ plants declined to 30 % by 43 ka and there was an increase in the burning of biomass. The transient shift in the vegetation continued for 3,000 years following the period of human colonisation and directly following the extinction of the megafauna that occurred between 48.9-43.6 ka (1). The authors¹ concluded that in this region the extinction of the megafauna was not caused by the vegetation shift. They¹ suggest their data are consistent with the hypothesis that the vegetation change was the consequence of large marsupial browser extinction, and these vegetation changes led to the fire-prone nature of the Australian landscape.

Sources & Further reading

1. Lopes dos Santos, Raquel A., Patrick De Deckker, Ellen C. Hopmans, John W. Magee, Anchelique Mets, Jaap S. Sinninghe Damste, and Stefan Schouten. "Abrupt Vegetation Change after the Late Quaternary Megafaunal Extinction in Southeastern Australia." Nature Geosci 6, no. 8 (08//print 2013): 627-31.