Plio-Pleistocene Climate and Faunal Change in Central Eastern Australia

Understanding the responses of Plio-Pleistocene terrestrial vertebrates to long-term trends in climate change in central eastern Australia has advanced considerably in recent years following the recovery and documentation of a series of remarkable fossil assemblages. The middle Pliocene Chinchilla Local Fauna of SE Queensland preserves a diverse suite of vertebrate taxa suggestive of a paleoenvironment consisting of wetlands, closed wet forest, open woodlands, and grasslands. Local extinctions of numerous arboreal and terrestrial woodland species suggest that significant faunal and habitat reorganization occurred between the Pliocene and Pleistocene, in part, reflecting the expansion of open woodlands and grasslands. Middle Pleistocene deposits in the Mt Etna region of central eastern Queensland contain extensive fossil assemblages of rainforest-adapted vertebrates dated >500-280 ka. Such faunal assemblages show remarkable long-term stability despite being subjected to numerous glacial-interglacial climatic shifts. However sometime between 280-205 ka, a major faunal turnover/extinction event occurred, where the previously dominant rainforest-adapted faunas gave way to xeric-adapted forms. Independent paleoclimatic records suggest that this shift was a result of increased climatic variability and weakened northern monsoons. Late Pleistocene deposits of the Darling Downs, SE Queensland, provide an important temporal extension to the Mt Etna region. Recent studies have demonstrated minimally, a three stage extinction of local megafauna (giant land mammals, birds and lizards). Associated radiometric and optical dating indicates that the progressive loss of megafauna from the region was initiated at least 75 kyr before the continental colonisation of humans. The progressive changes in megafaunal community dynamics were most likely driven by intense climatic changes (i.e., increased aridity) associated with the last glacial cycle. The potential role of humans in the final extinctions (post-human colonisation) is unclear However if humans did have a detrimental impact on the last surviving megafauna, it is likely that they simply compounded upon longer-term climate-driven processes. Independent paleoclimate information suggests that Plio-Pleistocene climates were complex beyond glacial-interglacial cyclicity, and hence, faunal responses were similarly complex.