Climate adaptation: Polar bears adapt genetically to warming Arctic
Using publicly available genetic data from the University of Washington, our team compared polar bears from north-east and south-east Greenland
Polar bear
The Arctic Ocean is at its warmest in 125,000 years, and temperatures continue to rise. More than two-thirds of polar bears are expected to be extinct by 2050, with total extinction predicted by the end of the century.
But our new study suggests that polar bears are showing genetic adaptations that could help them survive warmer habitats. Provided they can find sufficient food and mates, these adaptations may allow some populations to persist despite climate change.
We discovered a strong link between rising temperatures in south-east Greenland and changes in polar bear DNA. DNA acts as the instruction book for growth and development. Through transcription and translation, DNA is copied to produce RNA and proteins, while transposons (TEs) — “jumping genes” — can move around the genome, influencing how other genes function.
Using publicly available genetic data from the University of Washington, our team compared polar bears from north-east and south-east Greenland. The south-east population, which migrated from the north about 200 years ago, has been genetically distinct and isolated since then. RNA sequencing of blood samples allowed us to examine gene activity, including TE behaviour, in relation to climate data provided by the Danish Meteorological Institute.
Temperatures in the north-east are colder and more stable, while south-east Greenland is warmer and more variable. The south-east ice-sheet margin is receding rapidly, reducing hunting platforms and leading to habitat loss, isolation, and food scarcity. North-east Greenland is flat Arctic tundra, while south-east regions feature forest tundra, steep coastal mountains, rain, and strong winds.
Environmental stress can accelerate genetic change. TEs, which make up about 38% of the polar bear genome, are mobile fragments that can reinsert randomly and sometimes help animals adapt. In humans, TEs comprise 45% of the genome, and in plants over 70%. Small molecules called piwi-interacting RNAs usually keep TEs in check, but when stress is high, they can no longer suppress TE activity.
We found that warmer south-east climates triggered mass TE mobilisation across the genome. These TEs appeared younger and more abundant in south-east bears, with over 1,500 “upregulated,” suggesting recent genetic changes that may aid adaptation to higher temperatures. Some TEs overlap genes linked to stress responses and metabolism, hinting at mechanisms for coping with climate change.
Genes associated with heat stress, ageing, and metabolism behaved differently in south-east polar bears, suggesting adjustment to warmer conditions. Active TEs also appeared in genome regions tied to fat processing — key for surviving food scarcity. South-east bears may be slowly adapting to rougher, plant-based diets, while northern populations rely mainly on fatty seals.
Overall, climate change is reshaping polar bear habitats and driving genetic changes, with south-eastern populations showing potential evolutionary responses to warmer temperatures and altered diets. Understanding these adaptations can help researchers predict which populations are most at risk and guide conservation strategies in a warming world.
The Conversation