Distributional shifts change the biodiversity-ecosystem stability relationship under climate change

Distributional shifts under climate change are increasingly recognized as a biotic change worldwide. However, the effects of distributional shifts on ecosystem variability through changes in biodiversity remain to be clari[fi]ed. In this study, to elucidate the impact of population-level distributional shifts under climate change on community structure and ecosystem function through ecological hierarchy, we investigated the temporal changes in alpha and beta diversity, the contribution of individual species to the observed changes in biodiversity, and the changes in the relationship between biodiversity and ecosystem variability, using over 25 years of data on about 700 species. We found that ecosystem variability was largely stabilized by beta diversity, especially in the present period (2012 to 2021), because beta diversity increased due to the invasion of species that were distributed mainly in tropic and subtropic areas. Despite the effect of beta diversity, ecosystem variability increased in the present period. This increase in ecosystem variability was caused by the spatially synchronized temporal variation in sea-bottom temperature, which resulted in synchronized temporal variation in species abundance among local communities, as well as the increased impact of alpha variability on ecosystem variability. These results indicate that the impact of alpha diversity on ecosystem variability is more changeable than the impact of beta diversity on ecosystem variability under climate change, suggesting the importance of focusing on changes in alpha diversity resulting from local colonization from other habitats and local extinction in existing habitats.