When was the South Pacific colonised? A lake sediment approach to understanding climate:human drivers of ecosystem change on remote Pacific Islands

The Pacific islands of Polynesia were among the last places on earth to be colonised by humans. The precise dates of colonisation are debated - a situation which arises from the different sources of evidence (1, 2). New lake sediment records from the Cook Islands (Atiu, Mangaia) and Samoa (Upolu) and Tonga show very clear evidence of disturbance, but what is unclear is to what extent the signal represents the arrival of humans or a change in climate (2). A key question for the analysis of sedimentary records is the ability to distinguish natural variability in the environment of Pacific Islands from that arising from the arrival of humans in a temporal and spatial context. We aim to use a multi-proxy approach based on SedDNA, lipid biomarkers, fossil charcoal, and pollen preserved in lake sediments to identify: a) the presence of humans and/or livestock that were brought with them, and b) the related environmental change. Multiproxy approaches supported by statistical analysis, will be deployed to four sites where we already have good chronological controls and high resolution records of palaeoclimate. We are well placed to apply new methods and higher resolution analyses to address fundamental questions about the response of remote pacific islands to climate and human forcings.