Paleovegetational history on Mangaia, south Cook Islands, eastern Polynesia

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  • 東ポリネシア・南クック諸島マンガイア島における古植生変遷史
  • ヒガシポリネシア ・ ミナミクック ショトウ マンガイアトウ ニ オケル コショクセイ ヘンセンシ

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Pollen analysis was conducted on a 750 cm long sediment core from a wetland (21°57'01" S, 157°55'41" W) on the shore of Lake Tiriara, Mangaia Island, Cook Islands. The results showed that fern spores were more abundant from the lowest layer, and secondary vegetation elements such as Trema pollen, and weed elements such as Chenopodiacea pollen, also occurred, confirming that deforestation had already occurred. Conversely, native forest elements such as Ficus and Elaeocarpus pollen grains are present, suggesting that some native forests were still intact. Human settlements on the island of Mangaia were initially limited to the coast, but by the 16th century (1500 AD) they had expanded inland. Approximately 16th centuries of inland migration corresponds to a depth of 300 cm. During this time, tree pollen grains such as Ficus almost disappeared, and instead Arecaceae and Poaceae pollen grains, and fern spores rapidly increased. This is thought to be the result of the migration of humans from coastal areas to inland areas and further deforestation. Coconut (Cocos nucifera) and whistling pine (Casuarina equisetifolia), which were probably introduced by Polynesians, are estimated to have been brought to Mangaia Island in 1000 cal AD and 1400 cal AD, respectively. In addition, Caribbean pine (Pinus caribaea) increases from around 1980 cal AD, and this species was planted by the Cook Islands government from 1984 AD to prevent soil erosion, with concordant results.


  • 名古屋大学年代測定研究

    名古屋大学年代測定研究 5 30-37, 2021-03

    Division for Chronological Research, Institute for Space‒Earth Environmental Research, Nagoya University


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