evidence: Polar bears will be wiped out by the end of the century unless more is done to tackle climate change, a study predicts. [...] Polar bears are listed as vulnerable to extinction by the International Union for Conservation of Nature (IUCN), with climate change a key factor in their decline. [...] Under a high greenhouse gas emissions scenario, it's likely that all but a few polar bear populations will collapse by 2100, the study found. And even if moderate emissions reduction targets are achieved, several populations will disappear.