Environmental change and the arrival of people in the Australian region

Abstract

Continuous pollen and charcoal records, predominantly from well dated marine sediments, provide a good spatial coverage of patterns of change in vegetation, climate and biomass burning within the northern Australian - southern Indonesian region through the late Quaternary period. Northern hemisphere ice volume and monsoon forcing is conspicuous on orbital timescales with general expansion of wetter communities under higher precipitation during interglacials and their contraction under drier glacials. However, this picture is regionally complicated by both southern hemisphere monsoon and long term El Niño - Southern Oscillation influences. The charcoal records suggest a complex pattern of burning with generally more frequent or intense fires during climate transitions and also during drier periods except when and where fuel availability became a limitation. Superimposed on this largely cyclical pattern is a trend, within the last 300,000 to 200,000 years, towards more open canopied vegetation and increased burning. It is considered that regional reorganisation of oceanic and atmospheric circulation were the major causes of the early part of this trend although a human contribution cannot be totally discounted. Marked and sustained changes in vegetation and burning patterns within isotope stage 3 (IS3), corresponding with dated archaeological evidence for the presence of people and for megafaunal extinction, suggest that this was the time of the major, if not the first, invasion of Australasia by people within the Pleistocene period.