Organisms Dependent On Sub-Snow Ecosystem Threatened By Melting Snow Cover

Diminishing snow cover in the Northern Hemisphere is a threat to numerous species of plants and animals that depend on the snow blanket for survival, according to a recent report from a team at University of Wisconsin, Madison.

The researchers say plenty of plants and animals rely on the "subnivium," a seasonal micro-environment beneath blankets of snow, for survival because it offers warmer temperatures, consistent humidity and the absence of chilling wind.

Organisms as small as bacteria or as big as bears depend on the subnivean habitat to survive through the winter.

"Underneath that homogeneous blanket of snow is an incredibly stable refuge where the vast majority of organisms persist through the winter," said Jonathan Pauli, a UW-Madison professor of forest and wildlife ecology and a co-author of the new report, according to a news release. "The snow holds in heat radiating from the ground, plants photosynthesize, and it's a haven for insects, reptiles, amphibians and many other organisms."

According to Pauli and his colleagues, snow cover in the Northern Hemisphere has diminished by as much as 3.2 million square kilometers during March and April since the 1970s.  Moreover, the period of maximum snowfall has shifted from February to January and spring melt has accelerated by nearly two weeks.

"There are thresholds beyond which some organisms just won't be able to make a living," said Pauli. "The subnivium provides a stable environment, but it is also extremely delicate. Once that snow melts, things can change radically."

Diminishing snow habitats have prompted the U.S. Fish and Wildlife Department to call for placing the wolverine, which lives in the snowy highlands of the American Rocky Mountains, on the endangered species list, the Associated Press reported Tuesday.

Plant life will also be affected by reduced snow cover, the researchers state. For example higher plant mortality and reduced biomass due to tissue damage may be a result of plants being directly exposed to cold temperatures and more frequent freeze-thaw cycles.

According to Benjamin Zuckerberg, also of UW-Madison,  the greatest effects on the subnivium will occur on the margins of the Earth's terrestrial cryosphere, the parts of the world that get cold enough to support snow and ice, whether seasonally or year-round.

"The effects will be especially profound along the trailing edge of the cryosphere in regions that experience significant, but seasonal snow cover," he said. "Decay of the subnivium will affect species differently, but be especially consequential for those that lack the plasticity to cope with the loss of the subnivium or that possess insufficient dispersal power to track the retreating range boundary of the subnivium."

The research was published May 2 in the journal Frontiers in Ecology and the Environment.