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Nichola Strandberg

University of Southampton, UK

March 28, 2023

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Biotic homogenisation of South Pacific Island vegetation through the Holocene

The increasing similarity of plant species composition between distinct areas is leading to the biotic homogenisation of global ecosystems. Human actions such as ecosystem modification, the introduction of non-native plant species, and the extinction or extirpation of endemic and native plant species drive this trend.  However, little is known about when this process of homogenisation began or pre-human patterns of biotic similarity. Here we investigate vegetation trends across the South Pacific islands during the Holocene using fossil pollen records from 20 sites on 15 islands. The site comparisons show increasing similarity between pollen records throughout the Holocene which began to accelerate between 3400–2900 cal. years BP, synchronous with the timing of human colonisation of the Southwestern Pacific islands. More recent pollen records appear to be more biotically homogenised as people were present on the islands for the majority of the periods studied. While biotic homogenisation is often referred to as a contemporary issue, we have identified earlier homogenisation patterns across the Pacific islands.