New research suggests that ancient polar bear populations shrank as sea ice dwindled, adding weight to concerns about the predator's future as climate change melts the Arctic. "The population size seems to have decreased at a time when temperatures went up and sea ice went down," said Paul Szpak, a professor at Trent University and a co-author of a newly published paper that looks at bear populations and habitats over thousands of years.
Szpak and 19 colleagues from 11 institutions brought together three strands of inquiry to reach their conclusions — genetic analysis of old bear skulls from a Danish archive, habitat modelling based on long-ago climate and study of distinctive elements in those bones that reveal diet. The polar bear genome has been completely mapped, allowing scientists to measure the genetic diversity of any one group of bears. More diversity suggests more bears. "How different the bears are from one another on a genetic level can be a marker of population size," Szpak sai