Connecting climate and human settlement in the tropical South Pacific: Insights from a lake sediment archive from the Southern Cook Islands

The precise timing and sequence of human arrival into the tropical South Pacific islands is contested and there is ongoing debate around the drivers of migration over the past three thousand years. Recent evidence supports the role of changing climate through palaeoclimate evidence that suggests that the South Pacific has experienced shifts between dry and wet periods throughout the human occupation of the region. Here we focus on the importance of relative drought, as islands are space and resource limited with human populations that depend upon agricultural crops that are rainfall dependent. As such, the occurrence of significant drought events likely threatened early Pacific societies, and such an impact proffers a potential driver of migration. Using lake sediment cores from the island of Mangaia in the Southern Cook Islands, this study utilises stable isotopes, geochemistry and diatoms to create a hydroclimate record extending back 2500 years. We show that prior to the arrival of Polynesians into the Southern Cook Islands there was a significant dry period dating to approximately 885-1075 CE and a further dry period from 1320 to 1460 CE coincident with human settlement of the Southern Cook Islands coinciding with agricultural intensification. • A 2500 year hydroclimate and palaeoenvironmental lake record is presented from the Southern Cook Islands in the tropical South Pacific. • New geochemical, stable isotope, and diatom data provide climatic context for human arrival and settlement in eastern Polynesia. • Prior to the arrival of humans into the Eastern Polynesia there was a significant dry period dating to approximately 885-1075 CE. • A second dry period from 1320 to 1460 CE was coincident with permanent human settlement of the island and agricultural intensification.