Declining snow cover in a warming world spells trouble for plants and animals that survive harsh winters in a beneath-the-snow habitat, U.S. researchers say. Scientists at the University of Wisconsin-Madison say winter and spring snow cover in the Northern Hemisphere is in decline, threatening many plants and animals that depend on the space beneath the snow to survive the blustery chill of winter. In the "subnivium," a term used to describe the seasonal microenvironment beneath the snow, life from microbes to bears take full advantage of warmer temperatures, near constant humidity and the absence of wind, they said. "Underneath that homogeneous blanket of snow is an incredibly stable refuge where the vast majority of organisms persist through the winter," ecology Professor Jonathan Pauli said. "The snow holds in heat radiating from the ground, plants photosynthesize, and it's a haven for insects, reptiles, amphibians and many other organisms." A decaying subnivium would have far-reaching consequences, and many species would be put at risk when temperatures fluctuate, bringing them prematurely out of their winter torpor only to be lashed by late spring storms or big drops in temperature, the researchers said. "Snow cover is becoming shorter, thinner and less predictable," Pauli said in a university release. "We're seeing a trend. The subnivium is in retreat."