Yale Environment 360: The day may soon come when some of the 19 polar bear populations in Canada, Alaska, Greenland, Norway, and Russia will have to be fed by humans in order to keep them alive during an extended ice-free season or prevent them from roaming into northern communities. Some bears may have to be placed in temporary holding compounds until it is cold enough for them to go back onto the sea ice. In worst-case scenarios, polar bears from southern regions may have to be relocated to more northerly climes that...