Wednesday, July 3, 2013

Climate change frames debate over the extinction of megafauna in Sahul (Pleistocene Australia-New Guinea)



  • by Stephen Wroe, Judith H. Field, Michael Archer, Donald K. Grayson, Gilbert J. Price, Julien Louysd, J. Tyler Faith, Gregory E. Webb, Iain Davidson, and Scott D. Mooney
Around 88 large vertebrate taxa disappeared from Sahul sometime during the Pleistocene, with the majority of losses (54 taxa) clearly taking place within the last 400,000 years. The largest was the 2.8-ton browsingDiprotodon optatumwhereas the ∼100- to 130-kg marsupial lion,Thylacoleo carnifexthe world’s most specialized mammalian carnivore, and Varanus priscusthe largest lizard known, were formidable predators. Explanations for these extinctions have centered on climatic change or human activities. Here, we review the evidence and arguments for both. Human involvement in the disappearance of some species remains possible but unproven. Mounting evidence points to the loss of most species before the peopling of Sahul (circa 50–45 ka) and a significant role for climate change in the disappearance of the continent’s megafauna.
Explaining Pleistocene faunal extinctions remains one of the most challenging problems in the prehistory of Sahul (1–3). The vast majority of extinctions across geological time are wholly attributable to climate-related factors (4), but claims that some, or even all, Pleistocene extinctions of large-gigantic vertebrates (Fig. 1) in Sahul were the consequence of human activity have generated particularly robust debate. Polarized views have emerged to account for the mode and timing of these events (2, 5–11). A paucity of empirical data; shortfalls in radiometric dating; and, until recently, a limited appreciation of the paleoenvironmental record (7, 12) have placed considerable constraints on the ability to resolve “who or what” was responsible for these extinctions. Given these limitations, assertions such as “… the question is no longer if, but rather how, humans induced this prehistoric extinction event” (ref. 13, p. 563) are premature” (read more/not open access).
(Source: PNAS, early addition 2013;  doi:10.1073/pnas.1302698110)



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