Hybrid animals like 'grolar bears' not expected to be common consequence of climate change
EPA/Friso Gentsch/Newscom

Hybrid animals like 'grolar bears' not expected to be common consequence of climate change

When it comes to visually depicting climate change, few symbols are as widespread or emblematic as a polar bear floating on a melting iceberg. Many scientists have predicted that habitat loss will force species into new geographical ranges—areas where they may begin to overlap, compete, and even mate with closely related natives. And indeed, there have been observations of the grizzly/polar hybrid 'grolar' bear confirmed by DNA analysis. But a new study in Nature Climate Change predicts that the overall occurrence of these hybridization events between closely related species will actually be relatively low: On average, only 6.4% of species are expected to come into geographic contact with a hybridization possibility by the end of the century. The authors used computer models to generate a prediction of Earth’s climate from 2071 and 2100 and then analyzed how different species of birds, mammals, and amphibians would need to migrate to stay in suitable habitats. Birds had the highest rate of new overlap (11.6%)—a finding the authors attribute to the animals’ large geographic range. Mammals and amphibians clocked in at 4.4% and 3.6%, respectively. Additionally, because of the sheer number of different species that live there, 85% of all future hybrid meet-ups occurred in the tropics. The scientists point out that even their meager estimates are probably on the high side, because roads and other humanmade barriers are likely to reduce how well animals can track to their new ranges.