Feeding the flames: how colonialism led to unprecedented wildfires across SE Australia

The Black Summer bushfires (2019-2020) cost the Australian economy over 100 billion dollars and burnt a total of 18 million hectares. In just one season, around 20% of Australia's Eucalyptus forests burnt down and billions of animals perished. Recent catastrophic fires in Australia and North America have made scientists and policymakers question how the disruption of First Nations' burning practices has impacted fuel loads. For instance, we have learnt from modern Australian Indigenous communities, historical literature, and art works that Indigenous peoples have used cultural burning to rejuvenate patches of land and preserve open vegetation for hunting and cultural purposes. The advent of British invasion brought a change in the type of fire regimes and landscape management across much of the continent, which may have led to an increase in flammable fuels in forest settings. However, the actual degree of land-cover modification by early settlers has only been often debated in the academic literature and within management stakeholders.

The quantification of past land cover is needed to address such debates. Pollen is the key proxy to track past vegetation changes, but pollen spectra suffer from some important biases e.g. taphonomy, pollen productivity, dispersal capability. Estimating past vegetation cover from sedimentary pollen composition requires to correct for productivity and dispersal biases using empirical-based models of the pollen-vegetation relationship. Such models for quantitative vegetation reconstruction (e.g. REVEALS) have yet been mostly applied in the Northern Hemisphere in the last 15 years - here we present recent applications of this methodology from Australia. We show the quantification of land cover changes through pre- and post- British invasion on multiple records (n=51) across the southeastern Australian region. This represents the first regional application of REVEALS within the Australian continent.

We provide the first empirical evidence that the regional landscape before British invasion was a cultural landscape with limited tree cover as it was maintained by Indigenous Australians through cultural burning. Our findings suggest that the removal of Indigenous vegetation management has altered woodland fuel structure and that much of the region was predominantly open before colonial invasion. The post-colonial land modification has resonance in wildfire occurrence and management under the pressing challenges posed by climate change.