An unexpected signal from Greenland's bears
On Dec. 15, 2025, researchers published evidence that polar bears living in southeastern Greenland are showing distinct changes in the activity of portions of their DNA—changes that appear to track local warming. The team analysed blood samples from 17 adult polar bears collected across two contrasting regions of Greenland and found markedly higher activity of so‑called "jumping genes" in bears from the warmer, more variable southeastern coast. Those regions of elevated activity include genetic neighborhoods tied to fat processing, ageing and cellular stress, pointing to a biochemical shift that coincides with a rapidly changing Arctic seascape.
The finding is striking because it links a measurable molecular response in a top predator to a specific climatic gradient. Polar bears depend on sea ice to hunt seals; in areas where ice is thinner or retreats earlier in summer, bears face prolonged food scarcity and energetic stress. The new study, led by researchers at the University of East Anglia and published in the journal Mobile DNA, interprets the heightened activity of transposable elements as one part of the bears' genomic response to those environmental pressures.
But the discovery is not a simple story of successful adaptation. Instead, it opens a window onto how wild genomes respond in real time to human‑driven warming—and it raises urgent questions about the limits and consequences of such responses for conservation.
Jumping genes: a quick primer
"Jumping genes" is the informal name for transposable elements, stretches of DNA that can move around the genome or otherwise change how nearby genes are regulated. They were first discovered nearly a century ago and are now known to make up a significant fraction of many vertebrate genomes. Most are normally dormant, but environmental stressors—heat, infection, starvation, pollutants—can lift epigenetic repression and allow transposable elements to become transcriptionally active.
When active, these elements can do several things: they can insert into new genomic positions and disrupt genes, they can carry regulatory sequences that reshuffle which genes are switched on or off, or they can generate small RNAs that alter gene expression networks. In some cases this activity creates new genetic variation that natural selection can act on; in other cases it increases genetic instability and disease risk. The paper from the University of East Anglia documents increased transcriptional activity of these elements in bears from the warmer sector of Greenland, suggesting the animals' genomes are experiencing a change in regulatory state tied to their environment.
That regulatory shift appears concentrated in genomic regions linked to lipid metabolism—biological systems that are crucial to polar bear survival, since fat stores power long fasting periods and fuel reproduction. Observing transposable element activity in those regions therefore has plausible functional relevance, even if the exact consequences remain to be proven.
Interpreting the evidence: promise and caveats
The study's data give a clear and specific signal, but the sample is small: blood samples from 17 adult animals, 12 from northeastern Greenland and five from the southeastern population. Small numbers are common in studies of large, remote mammals, and the authors used careful molecular assays to infer which parts of the genome were transcriptionally active. Still, the limited sample size and single‑timepoint sampling mean several alternative explanations must be considered.
Demography and population structure can produce regional differences in DNA activity that have nothing to do with contemporary climate. Diet, contaminant exposure, disease burden and age profiles also affect gene expression and might partly explain the patterns. Blood is a practical tissue for nonlethal sampling, but gene activity in blood does not always mirror activity in other organs—such as liver or adipose tissue—that govern metabolism and fat storage.
What this might mean for polar bears
There are two broad, contrasting ways to interpret the new data. One is cautiously optimistic: the genome is not inert, and organisms under stress can show rapid regulatory changes that generate new variation. The hotspots of activity near genes for fat metabolism fit a plausible ecological narrative: as sea ice diminishes and hunting opportunities decline, bears that can alter how they store and mobilise energy may have a short‑term survival advantage.
The other interpretation is sobering. Activation of jumping genes can increase genomic instability, accelerate cellular ageing, or produce deleterious mutations. Localised genomic responses in a small subset of the species do not reverse the larger demographic and ecological threats driven by habitat loss. Even if southeastern Greenland bears are exhibiting a molecular coping strategy today, that does not guarantee long‑term persistence once sea ice declines beyond threshold levels or when prey populations collapse.
Ecologists call the hopeful scenario "evolutionary rescue"—where rapid adaptive change prevents population collapse—but rescue depends on several demanding conditions: sufficient population size, heritable beneficial variation, and time for selection to act. The Arctic's pace of warming and the fragmentation of polar bear populations make evolutionary rescue uncertain at best.
Policy and research implications
For conservationists, the study is a double‑edged message. On one hand, molecular monitoring can reveal previously invisible stress responses and identify populations that are already undergoing strong selective pressures. That information could help target management efforts, such as protecting important foraging habitats, reducing local stressors, or prioritising corridors that allow animals to move to more suitable environments.
On the other hand, molecular signs of stress should not be turned into a rationale for inaction on climate policy. The researchers themselves emphasise that these genomic changes do not remove the need to reduce greenhouse gas emissions; they instead highlight how rapidly organisms are being forced to respond. Relying on natural genomic plasticity to save species is both scientifically risky and ethically fraught.
From a research perspective, the paper points to clear next steps: expanding sample sizes across seasons and age classes, sampling multiple tissues where feasible, integrating whole‑genome sequencing with ecological and physiological measurements, and establishing whether any of the observed regulatory shifts are inherited across generations. Experimental work—where appropriate and ethical—would be needed to connect transposable element activity to changes in fat metabolism, reproductive success or survival.
The story of polar bears in southeastern Greenland is thus best read as an early warning: climate change is not only rearranging ice and food webs, it is also nudging genomes into new states. Those states may sometimes help, sometimes harm, and often remain ambiguous until we gather more data. Scientists and policymakers face the urgent task of interpreting these signals without overclaiming their power to stave off extinction.
Sources
- Mobile DNA (journal; research paper published Dec. 15, 2025)
- University of East Anglia, School of Biological Sciences (lead research institution)
