Global warming and sea-ice loss will contribute to the decline of polar bears (Ursus maritimus), said the study. All photos courtesy iStockThe creatures depend on sea-ice for capturing seals, a source of sustenance for them in the freezing temperatures of the Arctic Circle.The study established the threshold number of days polar bears can fast before cub recruitment and / or adult survival are impacted.Recruitment and survival impact thresholds may have already exceeded for some sub-populations, the study pointed out.Estimating decline of sub-populations was not possible as data linking ice availability to demographic performance was unavailable.High greenhouse gas emissions, rapidly declining reproduction and survival thresholds will endanger the continuance of all but a few high-Arctic sub-populations by 2100.Moderate emissions are unlikely to prevent the local extinction of some sub-populations within this century, the study said.