Global Cold-Water Coral Biodiversity Redistribution Under Projected Climate Change.

Cold-water corals (CWCs) are key ecosystem-structuring species across the world's oceans, yet their global distribution, diversity patterns, and vulnerability to climate change remain poorly understood. Here, we delineated the global biogeography of CWCs and assessed how their biodiversity patterns may shift under future climate change scenarios. Using an ensemble of machine-learning models, we predicted the distributions of 741 CWC species, spanning Octocoralia, Scleractinia, Antipatharia, Zoanthidae, Pennatulacea, and Filifera, under present-day conditions and forecasted changes in species richness, community composition, and climate refugia under two contrasting Shared Socioeconomic Pathways (SSP1-1.9 and SSP3-7.0). Further, we identified biogeographic regions based on species co-occurrence patterns and statistically validated them. Our results showed major biodiversity hotspots in the Gulf of Mexico and the Caribbean Sea, and delineated ten distinct bioregions, each with varying species richness, depth distribution patterns, and generally low levels of endemicity. While the global extent of the CWC biome may persist in the future, we forecasted pronounced poleward and depth shifts in species distributions, particularly under high-emission scenarios, resulting in biodiversity losses in shallow and low-latitude regions and increased community turnover. Our findings highlight the growing threat of climate change to CWC biodiversity and deep-sea ecosystems and the need for urgent climate action, aligned with the Paris Agreement. By identifying biodiversity hotspots, emerging climate refugia, and regions at greatest risk, this study offers a global framework to inform conservation priorities and support efforts to safeguard CWC biodiversity in the long term.