Abstract
<jats:p>Climate change poses a continuing threat to marine biodiversity and ecosystem stability. As sentinel species, marine mammals can provide early indications of climate-driven changes in marine ecosystem health. Previous studies have advanced our understanding of climate-driven shifts in marine mammal distributions, yet the relationships between species’ current distributional characteristics and projected responses, as well as associated changes in community composition and functional structure, remain poorly understood. In this study, we applied Maxent to predict the current and future potential distributions of 114 marine mammals, and quantified species-level habitat changes in terms of area, latitudinal position, depth distribution, and fragmentation. Then, we further tested whether these projected responses were associated with species’ current distributional characteristics and used multidimensional diversity metrics to assess changes in community composition and functional structure. The results show that habitat contraction was projected for more species than habitat expansion, and most species shifted poleward. Current latitude, but not habitat area, was associated with interspecific variation in projected responses: high-latitude species generally experienced greater habitat contraction and poleward shifts but reduced fragmentation. At the community level, climate change was projected to reorganize taxonomic composition and functional structure globally, with pronounced latitudinal differences. High-latitude communities were projected to experience the immigration of functionally distinct species, whereas low-latitude communities were projected to experience species emigration. Mid-latitude transition zones were projected to undergo pronounced species and functional replacement. Overall, the spatial distributions of taxonomic and functional diversity were projected to shift toward higher latitudes, while their future hotspots were expected to exhibit lower diversity levels and reduced coverage by existing marine protected areas. More concerningly, extensive areas of harmful functional homogenization were projected to emerge in the future, many of which overlap with high human pressures. Our findings highlight the importance of considering multiple biodiversity metrics in climate change impact assessments.</jats:p>