A Palaeoecological survey of French Island, Victoria's past environment from 9000 years ago

Abstract

Fire has shaped the Australian landscape for millions of years but recent decades have seen intensified fire conditions in southeast Australia due to climate change and land management strategies. Increasing understanding of long-term environmental changes through palaeoecological research has the potential to improve fire and ecosystem management into the future. This study focuses on French Island, Victoria's largest coastal island, where long-term palaeoecological research is lacking. French Island has significant conservation value with one of the largest remaining areas of intact native heathland in Victoria. By analysing Holocene data (from ~9200 years ago to present), we aim to uncover the first long-term record of fire and vegetation on an island landscape that has been under the custodianship of Traditional Owners (Bunurong) for millennia. The project forms part of a larger palaeoecology program across the Bass Strait, aiming to further contribute to southeast Australia's ecological past. Key areas of enquiry include the fire and vegetation history of French Island, the primary drivers of changes in fire regimes, and comparisons with other southeast Australian records. Charcoal and pollen data were analysed from numerous swamp sediment cores on French Island, to interpret these past changes. Results indicate significant changes in fire and vegetation patterns on French Island, driven by climate and influenced by Aboriginal land management prior to the early 1800's. Low levels of burning within a heathland mosaic was maintained between ~9.2-6 ka BP, from high SWW-driven precipitation, less land use and local soil conditions. The onset of low-intensity burning from ~6-2 ka BP, was driven by a drier, more variable, ENSO-dominated climate. The transition from heathland to Eucalyptus woodland followed the onset of this climate-driven burning, due to drier conditions and increasing land use as sea levels stabilised. After ~2 ka BP, major increases in fire frequency and intensity were attributed to land use intensification indicated by archaeological evidence on the mainland of Victoria. Aboriginal cultural burning maintained an open, grassy woodland and heathland mosaic during the late Holocene. The suppression of cultural practices after European colonisation, combined with climate change, led to severe burning and denser vegetation on French Island. Insights into the drivers of past ecological change on French Island can inform fire and ecosystem management strategies and provide answers to questions the Bunurong people have about historical occupation patterns and landscape changes. Implementing a low-intensity fire management approach similar to Aboriginal cultural practices in heathlands and dry sclerophyll woodlands, may help mitigate the risk of severe fires in fire-prone ecosystems across southeast Australia, amid significant ecological change. Show more