Rising temperatures are having a profound effect on the level of snow cover throughout much of Northern Hemisphere, in particular winter and spring snow cover is in sharp decline. Many animals and plants rely on this snow cover for insulation during the winter, with diminishing levels many species face possible extinction.
The “subnivium”, as its known by researchers, is the seasonal microenvironment beneath the snow. It’s a refuge of sorts from the harsh winter environment — warmer temperatures, almost constant humidity levels, and no wind. Many species are dependent upon it for their lives.
But as temperatures have been rising over the past century, snow cover has been diminishing.
In a new study published recently in the journal Frontiers in Ecology and the Environment, researchers from the University of Wisconsin-Madison have described in detail the gradual decay of the Northern Hemisphere’s ‘subnivium’.
“Underneath that homogenous blanket of snow is an incredibly stable refuge where the vast majority of organisms persist through the winter,” says Jonathan Pauli, a UW-Madison professor of forest and wildlife ecology and a co-author of the new report. “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 press release continues:
Since 1970, snow cover in the Northern Hemisphere — the part of the world that contains the largest land masses affected by snow — has diminished by as much as 3.2 million square kilometers during the critical spring months of March and April. Maximum snow cover has shifted from February to January and spring melt has accelerated by almost two weeks.
“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 decline of this ecosystem, as with any other, will have far reaching consequences, affecting many species. A decaying subnivium will put large pressures on “reptiles and amphibians, which can survive being frozen solid, are 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. Insects also undergo phases of freeze tolerance and the migrating birds that depend on invertebrates as a food staple may find the cupboard bare when the protective snow cover goes missing.”
“There are thresholds beyond which some organisms just won’t be able to make a living,” says Pauli. “The subnivium provides a stable environment, but it is also extremely delicate. Once that snow melts, things can change radically.”
Plants will be profoundly affected as well. Being directly exposed “to cold temperatures and more frequent freeze-thaw cycles can cause tissue damage both below and above ground, resulting in higher plant mortality, delayed flowering and reduced biomass. Voles and shrews, two animals that thrive in networks of tunnels in the subnivium, would experience not only a loss of their snowy refuge, but also greater metabolic demands to cope with more frequent and severe exposure to the elements.”
The most significant effects on the subnivium will be seen along the edges of the planet’s terrestrial cryosphere, meaning along the edges of the portions of the world that experience cold enough temperatures to support snow and ice.
“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.”
“As an ecological niche, the subnivium has been little studied. However, as snow cover retreats in a warming world, land managers, the Wisconsin researchers argue, need to begin to pay attention to the changes and the resulting loss of habitat for a big range of plants and animals.”
“Snow cover is becoming shorter, thinner and less predictable,” says Pauli. “We’re seeing a trend. The subnivium is in retreat.”
Twitch the loss of this ecosystem the possibility is there for a significant number of extinctions, and loss of genetic diversity. Just another nail into the coffin of the 6th great mass extinction event that we are currently in the midst of.