21st Century Sea Ice Loss Will Upend 11,700 Years of Stable Habitat for Bowhead Whales

Bowhead whales (Balaena mysticetus) are strongly associated with Arctic sea ice during their crucial summer feeding period. However, anthropogenic climate change is causing a decline in sea ice concentrations, threatening bowhead whale suitable habitat. To characterise the long-term affinity of bowhead whales to sea ice across the Holocene and project the response of populations to 21st century climate change, we built ecological models of occurrence-environmental relationships using distribution-wide fossil, historical, and contemporary records. We found that throughout the Holocene, bowhead whale habitat suitability was consistently highest in summer average sea ice concentrations of 15%-30%. Projecting these models forward in time to 2100 ce showed that 21st century climate change is set to erode these critical sea ice conditions, resulting in the circumpolar range of bowhead whales contracting by up to 75%. We project that during this century, habitat suitability will decline in all four management populations of bowhead whales by at least 52%, with suitable habitat predicted to vanish completely in the Sea of Okhotsk. It is likely that most viable habitat for bowhead whales will exist outside their current distribution by the end of the century, directly impacting conservation policies. Our results further highlight the vulnerability of Arctic marine endemics in a warming world, showcasing how knowledge of the past can strengthen predictions of species future vulnerability to rapid ocean warming.