Research Doctorate - Doctor of Philosophy (PhD) / The records of environmental change in Australia’s arid zone can be greatly enriched by employing a multi-proxy approach and landscape-scale analysis. This research uses these tools to construct a palaeoenvironmental history of the Paroo/Warrego Region. While the Region’s flow regimes and water balances are characterised by medium-term (decadal) variability (Young, 1999), its hydrological records are inadequately brief. Subsequently, land and water management decisions are based on short term data, risking irreversible damage, desertification or loss of diversity. A better understanding of this highly dynamic landscape can thus improve the land and resource management outcomes. While dating was constrained by a lack of funds, the Paroo/Warrego history reconstructed from fluvial and aeolian deposits correlated well with events recorded from other inland regions of the Australian continent. In summary, this new research provided evidence of high lake water levels prior to the Last Glacial. The extreme aridity at the onset of Last Glacial caused long term drying of the lakes and mobilisation of the red sand dunes. In latter stages of the glacial phase the aridity gave way to periodic fluctuations between flood and drought events that probably lasted until 16 000 - 14 000 BP. The new climatic regime resulted in formation of gypsum lunettes and later, following reduction in gypsum supply, clay lunettes. The orientation of red sand dunes and lunettes indicates a more northerly extent of the westerlies than in modern times. Around the late Pleistocene-early Holocene boundary the climate became more stable and wetter, but still somewhat drier than during the pre-Last Glacial lacustrine phase. As a result, the region’s lakes reverted to a permanent and semi-permanent status. A strong aridity signal, comparable to the semi-regular droughts of the Last Glacial, was recorded in the Paroo/Warrego lakes during the late 1890s-1940s period of below average rainfall. It was followed by 50 years of wetter conditions with two extremely wet phases in the 1950s and the 1970s. Finally, the most recent records suggest a new drying trend. The semi-arid vegetation appears to have adapted to climate variability, with herbs and grasses expanding with the onset of wet conditions before being replaced by Chenopodiaceae as the landscape started to dry. The fresher lake basins and water courses were likely to provide refuge during prolonged arid phases and dispersal foci during intervening wetter periods, thus enabling greater flexibility in response to changes and enhancing resilience. The European land use interfered with the natural cycles and balances, leading to decrease in ground cover, suppression of fire, increase in runoff and catchment erosion, acceleration of sediment accumulation rates in wetlands, resulting in decline of their water holding capacity, and expansion of woody vegetation. The research improved the processing protocols, reference databases, and transfer of methods to enable greater sample processing efficiency and improve results. The use of multiple proxies (including biotic and abiotic components) and sites, as well as different depositional features, provided access to a broader picture of environmental change than was previously possible. It also facilitated multi-scale resolution, allowing discrimination between localised responses of individual lakes and regional trends. The full value of this research will come from informing natural resource managers, whose actions will shape the future landscapes of the Paroo and Warrego Region.

Research Doctorate - Doctor of Philosophy (PhD) / The records of environmental change in Australia’s arid zone can be greatly enriched by employing a multi-proxy approach and landscape-scale analysis. This research uses these tools to construct a palaeoenvironmental history of the Paroo/Warrego Region. While the Region’s flow regimes and water balances are characterised by medium-term (decadal) variability (Young, 1999), its hydrological records are inadequately brief. Subsequently, land and water management decisions are based on short term data, risking irreversible damage, desertification or loss of diversity. A better understanding of this highly dynamic landscape can thus improve the land and resource management outcomes. While dating was constrained by a lack of funds, the Paroo/Warrego history reconstructed from fluvial and aeolian deposits correlated well with events recorded from other inland regions of the Australian continent. In summary, this new research provided evidence of high lake water levels prior to the Last Glacial. The extreme aridity at the onset of Last Glacial caused long term drying of the lakes and mobilisation of the red sand dunes. In latter stages of the glacial phase the aridity gave way to periodic fluctuations between flood and drought events that probably lasted until 16 000 - 14 000 BP. The new climatic regime resulted in formation of gypsum lunettes and later, following reduction in gypsum supply, clay lunettes. The orientation of red sand dunes and lunettes indicates a more northerly extent of the westerlies than in modern times. Around the late Pleistocene-early Holocene boundary the climate became more stable and wetter, but still somewhat drier than during the pre-Last Glacial lacustrine phase. As a result, the region’s lakes reverted to a permanent and semi-permanent status. A strong aridity signal, comparable to the semi-regular droughts of the Last Glacial, was recorded in the Paroo/Warrego lakes during the late 1890s-1940s period of below average rainfall. It was followed by 50 years of wetter conditions with two extremely wet phases in the 1950s and the 1970s. Finally, the most recent records suggest a new drying trend. The semi-arid vegetation appears to have adapted to climate variability, with herbs and grasses expanding with the onset of wet conditions before being replaced by Chenopodiaceae as the landscape started to dry. The fresher lake basins and water courses were likely to provide refuge during prolonged arid phases and dispersal foci during intervening wetter periods, thus enabling greater flexibility in response to changes and enhancing resilience. The European land use interfered with the natural cycles and balances, leading to decrease in ground cover, suppression of fire, increase in runoff and catchment erosion, acceleration of sediment accumulation rates in wetlands, resulting in decline of their water holding capacity, and expansion of woody vegetation. The research improved the processing protocols, reference databases, and transfer of methods to enable greater sample processing efficiency and improve results. The use of multiple proxies (including biotic and abiotic components) and sites, as well as different depositional features, provided access to a broader picture of environmental change than was previously possible. It also facilitated multi-scale resolution, allowing discrimination between localised responses of individual lakes and regional trends. The full value of this research will come from informing natural resource managers, whose actions will shape the future landscapes of the Paroo and Warrego Region.