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Environmental histories that span the last full glacial cycle and are representative of regional change in Australia are scarce, hampering assessment of environmental change preceding and concurrent with human dispersal on the continent ca. 47,000 years ago. Here we present a continuous 150,000-year record offshore south-western Australia and identify the timing of two critical late Pleistocene events: wide-scale ecosystem change and regional megafaunal population collapse. We establish that substantial changes in vegetation and fire regime occurred ∼70,000 years ago under a climate much drier than today. We record high levels of the dung fungus Sporormiella, a proxy for herbivore biomass, from 150,000 to 45,000 years ago, then a marked decline indicating megafaunal population collapse, from 45,000 to 43,100 years ago, placing the extinctions within 4,000 years of human dispersal across Australia. These findings rule out climate change, and implicate humans, as the primary extinction cause.

Records of the past climate and vegetation of Australia are frequently constructed using data generated from the analysis of pollen and pteridophyte spores alone, or in association with sedimentology. We demonstrate that the organic residue prepared for pollen analysis yields other organic-walled microfossils that can be used to provide additional and independent palaeoenvironmental information. These non-pollen palynomorphs (NPP) include microscopic remains of algae, cyanobacteria, fungi, insects, other invertebrates and cormophytes. Our study of the NPP from two Late Quaternary lake records from western Victoria, Australia, provided additional information on water quality, salinity, depth, temperature and nutrient levels to the general environmental interpretation derived from pollen data. From a review of the ecological preferences of taxa, and comparison of the NPP results with pollen and spore curves from the lake records, ecological indicator values were derived. The study confirms the utility of NPP in enhancing environmental reconstructions in Australia, and encourages their routine examination in palynological studies.

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