evidence: Polar bears could become nearly extinct by the end of the century as a result of shrinking sea ice in the Arctic if global warming continues unabated, scientists said on Monday. Nearly all of the 19 subpopulations of polar bears, from the Beaufort Sea off Alaska to the Siberian Arctic, would face being wiped out because the loss of sea ice would force the animals onto land and away from their food supplies for longer periods, the researchers said. Prolonged fasting, and reduced nursing of cubs by mothers, would lead to rapid declines in reproduction and survival. "There is very little chance that polar bears would persist anywhere in the world, except perhaps in the very high Arctic in one small subpopulation" if greenhouse-gas emissions continue at so-called business-as-usual levels, said Peter K Molnar, a researcher at the University of Toronto Scarborough and lead author of the study, which was published on Monday in the journal Nature Climate Change.