| Summary: | The Arctic is warming four times faster than the global average, and plant communities are responding through shifts in species abundance, composition and distribution. However, the direction and magnitude of local plant diversity changes have not been explored thus far at a pan-Arctic scale. Using a compilation of 42,234 records of 490 vascular plant species from 2,174 plots at 45 study areas across the Arctic, we quantified how species richness and composition have changed over time during a period of up to four decades (1981 – 2022), and identified the geographic, climatic and biotic drivers behind these changes. Despite plant species richness being greater at lower latitudes and warmer plots, pan-Arctic species richness did not change directionally over time at the plot level. However, 99% of the plots experienced changes in species abundance, with 66% of plots either gaining or losing species. Species richness increased most where temperatures had warmed most over time, and shrub expansion led to greater species losses and decreasing richness. Yet, Arctic plant communities did not become more similar to each other over time, suggesting that no biotic homogenisation has occurred thus far. Overall, we found that Arctic plots changed in richness and composition in all possible directions, yet climate and biotic interactions still emerged as the main drivers of directional change. Our results show a variety of diversity trends, which could be precursors of future changes for Arctic plant biodiversity, ecosystem function, wildlife habitats and livelihoods for Arctic Communities.
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