| Summary: | The colonization of Australia (ca 55,000-45,000 years ago) and subsequent human dispersal across the continent is set against a background of large-scale changes in regional climates and environmental conditions. Specifically, changes in the Australian monsoon resulted in a significant expansion of the extent of monsoon-fed inland lakes and moisture-demanding vegetation in the mid-continent between ca 65,000 and 45,000 years ago, with the subsequent aridification of the continent. Known changes in the external factors affecting regional climates, in particular changes in insolation, atmospheric composition and changes in the extent of polar ice sheets, during the past 70,000 years would have had a significant impact on the Australian monsoon. These changes in climate would in turn have led to changes in the vegetation cover, changes that in turn influence water- and energy-exchange between the land and the atmosphere, and thus produce feedbacks on the climate system. Changes in climate and vegetation influence the fire regime, which in turn influences climate via biophysical and bigeochemical feedbacks. Changes in climate, hydrological conditions, vegetation cover and fire can have profound impacts on both the speed and pathway of human colonization. However, the deliberate or accidental setting of fire by human colonists also affects the vegetation cover and such activities may be implicated in the Late Quaternary aridification of Australia and the development of fire-adapted vegetation there. Earth system models provide the only way of disentangling the different strands of such a complex system in order to determine the relative importance of different factors in explaining observed palaeoenvironmental changes. Here, as part of a major new project (ACACIA) to investigate the interactions between climate, vegetation changes, natural wildfires and human activities, over the past 70,000 years in Australia, we investigate the implications of known changes in external forcing (insolation, ice sheet extent and ...
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