evidence: Nevertheless, a new study highlights that this trend has deep historical roots, with polar bear numbers in Greenland diminishing over a period of 20,000 years. [...] "It's the rising sea temperatures that drive the decline in the polar bear population. When the sea temperature rises, there is less sea ice, and consequently, fewer seals, which polar bears feed on," explains Michael Westbury. [...] "We see a disturbing connection between population decline and environmental changes. A relatively small increase in water temperature and a small reduction in the amount of sea ice result in a quite dramatic decline in the polar bear population. The relationship is not linear," Michael Westbury continues.