John Dodson and colleagues from the School of Geography, University of New South Wales, made, in the 1980s the first substantial attempt to examine environmental change at high resolution using pollen analysis supported by a number of other proxies, for the last few hundred years within southeastern Australia. From the mixture of sites and results a number of useful insights into the nature and degree of human impact, as well as into the benefits and limitations of various sites and proxy methods, were gained. The approach continues to be championed by Scott Mooney, in particular. As concern increases about environmental degradation supported by some belief that environmental problems may be taken seriously, the construction of baseline data on the dynamics of pre-European landscapes and assessment of the impacts of subsequent human activities will provide increasingly important guides to future management.
In response to perceived future demand, and to help encourage this demand, the Centre and collaborators, supported by a Strategic Monash University Research Fund grant, has embarked on a programme entitled ëEnvironmental Change, Prediction and Managementí with the Murray and Yarra basins selected for ëpreliminaryí study. The programme was also designed to support a collaborative project on ëNatural Archives of Human Activity and Climatic Variabilityí set up by the Australian Nuclear Science and Technology Organisation. Central to this programme is river health, detected largely by the study of diatoms in riverine lakes, in association with Cladocera, plant macrofossils, sedimentology, and sediment chemistry. Pollen is used largely to help identify the catchment causes of alterations in stream flow and quality as well as assess or support chronologies developed from radiometric methods.
Cores collected from the lower catchment of the Yarra and middle catchment of the Murray are both considered to cover at least the period of European settlement. The Yarra core illustrates a detailed pattern of changes to vegetation related to initial impact and suggests several subsequent phases of land use. Relationships with diatom assemblages, sediment chemistry and historical data are complex. The Murray core indicates a period of pre-European natural variability prior to initial impact associated with high levels of burning and other types of instability before establishment of agriculture. It shows clear correspondence to changes in water chemistry, in particular pH as determined by diatoms. Both cores show predictably high values for exotics and the Yarra core, in particular, shows an interesting pattern of exotic plant colonisation. These patterns will be important to dating the records. It is considered, from increases in native opportunists in addition to alterations in canopy forest or woodland composition and sediments, that substantial changes to the landscape had taken place before evidence of exotics, and the use of pre-exotic pollen spectra as an indication of pre-European settlement must be adopted cautiously. Environmental variability is lowest within the latter parts of both records and, although a major reason must be river regulation, this feature must be taken into account in any proposed future alterations to landscapes, including rehabilitation.