HIGH RESOLUTION NATURAL ARCHIVES OF HUMAN ACTIVITY AND CLIMATE VARIABILITY IN EASTERN AUSTRALIA OVER THE LAST 200 YEARS

The Australian Nuclear Science and Technology Organisation (ANSTO), in collaboration with several Australian universities and government organisations, has been leading a project investigating the impacts over the last 200 years of climate variability and human activity on ecosystems in eastern Australia. The research focuses on high-resolution analysis of sediment cores from lakes using a range of techniques, including radio-isotopic, microfossil, trace element and sediment analyses. Pivotal to this research has been the determination of chronologies and sedimentation rates through the measurement of naturally occurring radio-isotopes in the sediment. Microfossil analysis has been invaluable in reconstructing changes in vegetation, as well as the impacts of anthropogenic activity and climate variability on aquatic systems. Trace metal concentrations and stable isotope analyses have provided evidence of pollution, including inputs from industrial, rural and urban activities. Three case studies are presented as examples of this research.

Pollen, charcoal, trace metal and 210Pb analyses of sediment cores obtained from several sites in western Tasmania have provided evidence of the impacts of mining and forestry in the region. The records of trace metal concentrations, in particular, demonstrated significant temporal and spatial trends, providing clear, previously unidentified evidence for the aerial transport of trace metal pollutants across the region.

High resolution radio-isotope and microfossil analyses of sediment cores from the Myall Lakes in eastern Australia have provided evidence of cyclical fluctuations in the populations of aquatic plants and algae throughout recent history. This is thought to be linked to ENSO related climatic variability as well as, in more recent years, anthropogenic impacts on the system.

Similar work carried out in the Lake Burragorang catchment in NSW identified the impact of damming on sediment accumulation as well as the influx of trace metal pollutants in association with high rainfall events.