A study of the Arctic says polar bears are one of the most threatened species on earth because of melting sea ice caused by climate change, and without aggressive steps, the animals could be extinct by the end of the century. The University of Toronto study, published Monday in the journal Nature Climate Change, says that polar bears rely on sea ice to reach their prey, usually seals and other water mammals. Researchers who conducted the study say a loss of ice will force the animals onto land, where they must rely on fat reserves due to a lack of food. Co-author of a report on the study Steven Amstrup says the bears currently have less time to feed and a longer time to wait until the ice returns.  He says typically, the ice melts in the early summer and midsummer and returns in fall.  “That period when the ice is absent is getting ever longer and the bears are facing that longer period with less fat on board.” Modelling was used to determine polar bears’ energy requirements while fasting and the thresholds that would limit their survival, alongside a model predicting the future number of days without ice. The researchers used that to estimate when the survival thresholds would be surpassed for 13 Arctic sub-populations that represent 80% of all polar bears. Under a high greenhouse gas emissions scenario, the researchers found the bears’ survival would be “unlikely” in much of the Arctic due to reduced sea ice. But the study maintains that if there was a “moderate emissions scenario” more sub-populations could survive through this century. 
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