An ecosystem hidden under the snow
Under the snow there is a hidden ecosystem. Called the subnivean space, or subvinium, it survives in winter, at the border of the frozen ground and the lower layer of snow. And those who have been studying it for ten years are wondering about its future, in the era of global warming.
Until recently, where one would have thought that everything was in hibernation, this space instead allows insects such as beetles, spiders and frogs to spend part of the winter, protected from the cold by the layer of snow (Nivean: from the Latin nivis, which means snow, and sub, which means below). When the sunlight filters down there, even plants start to bloom there before spring. Experts estimate 20 centimeters of snow cover, preferably light snow, which allows this small ecosystem to survive: warm air from the ground rises, turning the lower layer of snow into vapor. A space barely a few centimeters high is then formed, surmounted by a frozen ceiling.
On occasion, one finds even small mammals there: Scientistrecalls in a recent articlethat in 2015 a Norwegian team managed to install cameras in such a space, thanks to which moles and shrews could be observed entering and exiting.
< p>But what will happen with global warming? The experts who speak of it as a unique ecosystem, also characterized it in 2015 as a threatened ecosystem. Milder winters reduce the depth of snow cover, and therefore the insulation these critters enjoy. Winter rain can expose some to the open air, and kill them when the temperature drops below freezing. Ecologists Jonathan Pauli and Ben Zuckerberg of the University of Wisconsin at Madison estimate that North America has lost 800,000 square kilometers of snow cover per decade since the 1980s, in addition to shorter winters .
Wood frogs are particularly at risk, as they survive the cold by letting their bodies freeze: a substance in their blood protects their cells from damage that ice crystals could cause. But a day that is too hot “wakes up” the frog, which then “freezes” again, a cycle that can be fatal to it.
This phenomenon affects even the trees themselves. The researchers studied the case of the cypress, a tree which, on the Pacific coast, has seen its population decline, despite the fact that the most resistant can live for centuries. It seems that these trees die in greater numbers in regions where the snow cover has decreased: deprived of this “insulation”, the shallowest roots are more exposed to freeze-thaw, and they die.