Remember those David Attenborough documentaries that showed you underneath the snow cover into the world below, home to all manner of creatures and plant life trying to survive through the harsh white winter? Well that same ecosystem — the subnivium — is set to suffer at the hands of a warming climate, according to scientists from the University of Wisconsin-Madison.
Winter and spring snow cover in the Northern Hemisphere is declining year by year, by as much as 3.2 million square kilometres since 1970 through the most important months of Spring, March and April. The maximum level of snow cover as shifted from February to January, and spring melt has accelerated by almost two weeks.
These findings according to Jonathan Pauli, a UW-Madison professor of forest and wildlife ecology, Benjamin Zuckerberg and Warren Porter, also of UW-Madison, and John P. Whiteman of the University of Wyoming in Laramie, authors of the report which was published in the journal Frontiers in Ecology and the Environment which describes the gradual but continual decay of the subnivium.
“Snow cover is becoming shorter, thinner and less predictable,” says Pauli. “We’re seeing a trend. The subnivium is in retreat.”
“Underneath that homogenous blanket of snow is an incredibly stable refuge where the vast majority of organisms persist through the winter,” explains Pauli. “The snow holds in heat radiating from the ground, plants photosynthesize, and it’s a haven for insects, reptiles, amphibians and many other organisms.”
“The winter ecology of Wisconsin and the Upper Midwest is changing,” says Zuckerberg, a UW-Madison professor of forest and wildlife ecology. “There is concern these winter ecosystems could change dramatically over the next several years.”
The consequences of a decaying subnivium will extend far beyond just those creatures who take shelter under the snow. Insects, plants, and other animals that feed migrating birds may simply not survive, leaving nothing for the birds to eat as they fly past. Reptiles and amphibians — which can survive being frozen solid — will suffer when winter ends early but are then hit again by a drop in temperatures. Plants will suffer tissue damage, while voles and shrews will encounter greater metabolic demands as they are more frequently and severely exposed to the elements without their insulating layer of snow.
The greatest threat to the subnivium, however, will take place on the margins of the Earth’s terrestrial cryosphere, according to Zuckerberg, those parts of the world cold enough to support snow and ice 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,” the Wisconsin scientists assert in their report. “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.”
