Identifying functional climate refugia of marine megafauna through analysis of functional diversity

Increasing our understanding of how climate change will influence ecosystems is essential for effective adaptation and mitigation. Ocean management efforts increasingly aim to protect climate refugia, identified as areas where species persist over time or where climate conditions remain stable. However, these approaches have focused on taxonomic persistence, overlooking shifts in functional diversity driven by climate-induced species turnover. Here, we assessed functional climate refugia for marine megafauna in the Northeast Pacific Ocean by computing functional diversity metrics across multiple future emission scenarios. We found that the majority of functionally stable areas are located in the open ocean, while the Southern California Bight is the only coastal ecoregion consistently predicted to act as a functional climate refugia across scenarios. Species turnover best explains changes in functional richness by 2100 under extreme climate emissions scenarios, compared to the moderate and intermediate emissions scenarios. Functional diversity is more stable at temperate and tropical latitudes than at poleward latitudes. Additionally, our analyses show that projected changes in functional diversity under climate change scenarios are driven primarily by a small number of rare observed species. These results highlight opportunities to focus conservation on key species in areas where they support more stable ecosystem function even if species richness declines, thus enhancing ecosystem resilience and the capacity to provide benefits across future climate change scenarios.