Seagrass Biodiversity Under the Latest‐Generation Scenarios of Projected Climate Change

ABSTRACT Aim The potentially cascading consequences of climate changes on redistribution of habitat‐forming species, like seagrasses, remain a major research gap. Empirical demonstrations of local population changes are increasingly reported without a globally integrated predictive framework as a leading testable hypothesis. Therefore, here, we aimed to estimate changes in species richness, community composition, and areas of climatic refugia under future climate scenarios. Location Global scale. Time Period Present‐day conditions (from 2010 to 2020) and for three Shared Socioeconomic Pathway (SSP) scenarios of future climate change (from 2090 to 2100). Major Taxa Studies Seagrasses (plantae). Methods We coupled seagrass occurrences with environmental predictors (temperature, salinity, nitrate, wave energy, and ice) in stacked species distribution modelling. Results Models estimated a present global extent of 917,169 km 2 with high species richness in Temperate Australasia, Indo‐Pacific, and Temperate North Pacific. Future projections predicted widespread spatial redistribution, with Arctic expansions, losses in lower latitudes, and deeper vertical ranges, while globally maintaining the area extent occupied worldwide by seagrass species (only 5% of change). Species richness increased poleward under more drastic scenarios (SSP3‐7.0 and SSP5‐8.5), with losses in tropical zones (30 o N to 30 o S). Local climatic refugia are retained in all scenarios but decrease under higher emissions. Additionally, even where seagrass species remain, widespread community composition changes were predicted. Main Conclusions Our findings serve as baselines to inform, anticipate, and mitigate cascading consequences of shifts in seagrass ecosystems that provide essential services for humanity.