PhD: Reconstructing Holocene fire regimes on Kangaroo Island, Australia, using organic fire biomarkers

Bushfires, in concert with a warming and drying climate, present one of the greatest risks to economic and environmental sustainability in Australia and many other countries worldwide. Catastrophic fires are expected to become more frequent and intense over coming decades, threatening native plant and animal species, water resources, and human health. Conservation strategies require a deep understanding of how fire affects the development and regulation of terrestrial ecosystems on timescales of decades to millennia, including the role of people in the development and maintenance of those ecosystems. Records derived from sediment archives therefore provide essential knowledge to support the management and conservation of Australia's fire-threatened environments.

In this project, we aim to use organic biomarkers to reconstruct fire regime change on Kangaroo Island, South Australia, during the last ~10,000 years. Pyrogenic sugars (e.g. levoglucosan) and polycyclic aromatic hydrocarbons (PAHs) are organic molecules produced by incomplete combustion of wood. In comparison with charcoal, these organic biomarkers are often better preserved, dispersed more widely, and offer insights into fuel type and burn temperature via differences in molecular composition. We aim to better understand the production and preservation of these biomarkers through analysis of samples collected before and after a major bushfire in 2020. We then aim to use these biomarkers, alongside a suite of complimentary palaeo-environmental techniques, to reconstruct past fire regime change from sediment cores collected from multiple wetland environments.

Kangaroo Island is a globally significant case study, with a unique environmental history. The island is a 'biodiversity hotspot', host to a suite of endemic plants and animals. Importantly, knowledge held by several Nations of the adjacent mainland, supported by archaeological evidence, suggests that people ceased permanent occupation on the island by ~4,100 years ago. It is argued that since the island became uninhabited, a lack of cultural burning led to the characteristic dense and biodiverse modern vegetation. Today, this dense vegetation poses substantial fire risks to residents and economic assets, demonstrated by the Black Summer bushfires of 2019-20. These fires consumed >210,000 ha, nearly half of the island's vegetation, with widespread loss of wildlife and property.