Just in time for Christmas:  Changing climate conditions in Siberia are threatening the herds of reindeer that characterize the Russian region.

Man-made global warming caused thinning sea ice and higher humidity in the Arctic Barents and Kara Seas; instead of falling on places like the Yamal Peninsula as cold, fluffy snow, the weather has been rainy.  But then, the temperature plummets and creates a thick ice layer that kills the usual food supply of lichen and other vegetation.

"Reindeer are used to sporadic ice cover, and adult males can normally smash through ice around two centimeters thick," says Bruce Forbes at the University of Lapland in Rovaniemi, Finland.  But events in 2006 and 2013 saw ice layers thicker than 10 centimeters. "If we see such events again this year, it could mean that they're becoming more frequent," says Forbes.  "Now is the risk window, and if it happens again, it will be a major problem for traditional reindeer herders still suffering from losses in 2013."

The indigenous Nenet people migrant around the region all year, herding semi-domestic reindeer along the way and depending on them for meat, hides, and bones for tools.  But thousands of reindeer died in the most recent icing event, leading many to resort to fishing to survive, as well as depending on help from the Russian government.

"This has implications both for the reindeer populations, as well as the last nomadic tribe in the Arctic for whom reindeer herding has been a way of life for countless generations," said Dr. Marc Macias-Fauria, from Oxford University's School of Geography and the Environment.