ANU - -

Untitled Document

Research Activities 2007

Earth Environment

Click on the links below to read the 2007 Earth Environment research highlights or Click HERE to download the PDF version 43 pages 2.3Mb

Introduction

The Earth Environment group undertakes research on environmental and climate change with particular emphasis on the interactions between humans and the environment. The group specialises in the development of diagnostic environmental proxies within an absolute chronologic framework that spans a few tens to several hundred thousand years of Earth history. These records are used as a basis for understanding past, present and potentially future environmental and climate changes. Emphasis is placed on the reconstruction of high-resolution environmental records of both human impacts and global climate change using geochemical proxies preserved in the growth banding of foraminifer, marine sponges, fossil and modern corals, speleothems (cave deposits), layered sedimentary deposits and materials preserved in anthropologic sites of special significance.

Dr Mike Ellwood, Dr Steve Eggins, Dr Stewart Fallon, Professor Malcolm McCulloch together with Dr Martin Wille a new Post Doctoral Fellow at RSES are undertaking studies of biogenic skeletons from both modern and ancient marine sequences to determine recent as well as longer-term changes in the chemistry of the Southern Oceans. This research is being conducted in close cooperation with Professor Patrick De Deckker and is part of ANU's new marine science initiative. One of the important processes being examined is changes in the oceans 'biologic pump' which acts as a mechanism to draw-down CO₂ and hence provides an important feedback in modulating climate change. Carbonate as well as silicate secreting organisms (e.g. foraminifer, deep-sea corals and sponges) are being used as archives of ocean temperatures, acidity, nutrient fluxes and ventilation rates. The research is being undertaken using state of the art laser ablation ICPMS (including multi-collector) techniques, high precision U-series dating, accelerator mass spectrometer ¹⁴C dating, combined with boron isotopic analyses to determine changes in seawater pH. The latter is a relatively new approach pioneered at RSES with the potential to provide constraints on the extent of acidification of the oceans from uptake of anthropogenic CO₂.

Human impacts on the environment are being examined at several timescales. On modern timescales we are quantifying the extent of direct human impacts on modern coral reefs from degradation of river catchments, mangrove estuarine habitats and near shore coastal zones being conducted under the auspices of the ARC Coral Reef Centre of Excellence. Work undertaken by Dr Stacy Jupiter, Dr Guy Marion (University of Queensland) and Professor McCulloch have shown that the most severe impacts on coral reefs are due to agricultural practices such as cattle grazing, intensive sugar cane plantations and associated practices such as land clearing. Geochemical records (e.g. Ba/Ca, N isotopes) preserved in the long-lived coral skeletons, show that land-use changes in river catchments has increased sediment and nutrient supplies to many inshore reefs by up to an order of magnitude relative to pre-European 'natural' values. Work is also ongoing quantifying the extent of acidification of corals in the Great Barrier Reef due to increasing CO₂.

On Longer timescales Professor Grün's Linkage proposal on the Willandra Lakes World Heritage Area ranks is especially important for documenting Australia's unique cultural and environmental history. This project is being undertaken jointly in a strategic alliance between the custodians and managers of the area and to build a picture of the continent's human and environmental history before this evidence is irretrievably lost. Professor Grün, Dr Maxime Aubert and PhD student Mr Renaud Joannes-Bayau have been developing and applying least destructive methods such as electron spin resonance and together with Dr Eggins using in-situ laser ablation ICPMS methods to directly date human samples of fossil teeth. This work is showing that modern humans colonised Australia well before sites in Europe. High resolution isotopic analyses of human teeth and associated soils is also being employed by PhD student Ms Tegan Kelly to trace diets and hunting ranges as well as patterns of migration. Dr Mike Gagan and Dr Linda Ayliffe are also continuing their major research program in Indonesia examining closely the links between human evolution and climate. This involves the application of both stable isotope proxies as well as precise U-series dating to corals and speleothems and is being undertaken in collaboration via ARC projects at the Universities of Queensland and Wollongong.

Research on landscape evolution is being conducted by Professor Brad Pillans and Dr Kat. Fitzsimmons using dating methods such as paleomagnetism and optically stimulated luminescence together with Dr Tim Barrows (Dept of Nuclear Physics) who is undertaking studies using cosmogenic nuclides. This work is showing that Australia has some of the world's oldest regolith and landforms as well as providing quantitative measurements of the rates of weathering and denudation that are proving to be exceedingly slow reflecting the tectonic stability and extreme aridity of our continent.