Borealization: a biodiversity refugium and evolutionary cradle during the Permian–Triassic climate crisis

Understanding how organisms track suitable environments during rapid climate change is constrained by the brevity of modern observations. Using the fossil record, we identify the mid- to high-latitude Boreal Ocean as a regional biodiversity refugium during the Permian–Triassic climate crisis. Additional Boreal successions indicate sustained diversity and comparatively hospitable conditions. Biogeographic reconstructions reveal that 30% of Sassendalen taxa survived the extinction event, with two-thirds expanding or shifting their latitudinal ranges into the Boreal Ocean. More than 90% of newly evolved species originated there, and their lineages subsequently dispersed at differing rates into other regions throughout the Early Triassic. These findings identify poleward migration and high-latitude refugia as key drivers of biodiversity persistence and evolutionary recovery during climate crises.