A record of monsoon rainforest variability from the Kimberley region in northwestern Australia

Abstract

Northern Australia experiences extreme seasonality via the Indo-Australian summer monsoon, with high inter-annual variability in hydroclimate. Understanding the influence of hydrological variability on the landscape through the period of human occupation provides important environmental context to support the interpretation of the rich archaeological and rock art records of the region. The development of terrestrial records of environmental change has remained challenging due to the limited traditional palaeoenvironmental archives in the region. This study reports on the potential of sediments from ecologically significant monsoon rainforest patches to further elucidate the palaeoenvironmental history of the Kimberley. An ~19 000-year record of monsoon rainforest variability is presented, inferred from pollen, charcoal and major element geochemical analysis. Monsoon rainforest-associated taxa vary in abundance through the deglacial and the Holocene, which is compared to broad-scale hydroclimate variability inferred from previous studies in the region. The persistence of arboreal, riparian and monsoon rainforest-associated taxa suggest a positive moisture balance at the site throughout the period archived. Fire activity inferred from micro- and macrocharcoal is greatest over the last ~6000 years, and broadly corresponds to periods when monsoon rainforest-associated taxa are less abundant. Challenges remain in using this type of site as an archive of environmental change, but they also present an opportunity to extend previous records both spatially and temporally with thousands of monsoon rainforest patches present across the Kimberley, and similar ecosystems found across northern Australia.