Recent human impacts on Australian environmental systems: A paleoenvironmental perspective

Australia is in a relatively unique position to provide baseline data on the impact of agriculture, forestry and urban expansion on a large variety of environmental systems. The major phase of European settlement began just over 200 years ago, and this brought a whole new set of cultural and technological practices that rapidly displaced those used by Aboriginal people. To assess the impact of humans it is necessary to establish proper baseline conditions against which change can be measured. This is not easy to do because we know that environments are naturally dynamic, and they are more so when humans are added to the milieu. This paper reviews a number of investigations recently published for southeastern Australia which take a sediment-based approach to compare the environmental changes of the historic period against those of the last 2,000 years. We have particularly focussed on assessing the relative degree of change in vegetation, fire, erosion and eutrophication either side of the pre- and post-European settlement boundary, from a variety of environments and land-uses. The purpose of this paper is to draw together the findings of these studies to look for commonalties in the types and scales of human impacts across southeastern Australia. We present an 'index of change' for all sites investigated to date, revealing that many environmental systems are characterized by massive changes during these last two centuries in comparison with the previous 2,000 years. This index also allows some quantification of the resilience or fragility of the investigated environments to the imposed land uses. Many of the quantified parameters figure in questions of environmental sustainability (e.g. accelerated erosion, vegetation change, eutrophication). Land management practices have been or are being developed in part because of the recognition of the great and continuing impact of humans on natural systems. Nonetheless, such regulatory control only rarely takes account of the lessons a palaeoecological perspective can bring to understanding process and results of land use.