Declining snow levels could leave some creatures near extinction.
During long, bitterly cold winters, a thick blanket of snow helps protect creatures and plants that live in these harsh climates. That is why recently published findings showing a steady decline in snow cover across the Northern Hemisphere are so alarming.
Since 1970, snow in this part of the globe has decreased by as much as 3.2 million square kilometers (1.2 million square miles) during the spring months of March and April, according to a study published May 2 by a team of researchers from the University of Wisconsin-Madison.
In their report, scientists describe the gradual degradation of the “subnivium,” the zone in and underneath the snow pack that creates a seasonal microenvironment for habitats of creatures from microorganisms to hibernating bears. In the subnivium, animals can find refuge against dry, biting winds and cold temperatures.
“Underneath that homogenous blanket of snow is an incredibly stable refuge where the vast majority of organisms persist through the winter,” explained co-author Jonathan Pauli, a UW-Madison professor of forest and wildlife ecology. “The snow holds in heat radiating from the ground, plants photosynthesize, and it’s a haven for insects, reptiles, amphibians, and many other organisms.”
In addition to a decline in the overall area covered by snow over the past four decades, spring melt has accelerated by nearly two weeks and that maximun snow cover has shifted from February to January, according to Pauli and his colleagues, Benjamin Zuckerberg and Warren Porter, also of UW-Madison, and John P. Whiteman of the University of Wyoming in Laramie.
Changes in the subnivium can have drastic consequences for northern ecosystems. Mammals, reptiles, and amphibians are all threatened by fluctuating temperatures, which can force premature emergence from hibernation, exposing them to sudden freezes, spring deluges, or unfamiliar predators. Plants can be damaged or die when their roots are subjected to alternating periods of freezing and thawing.
According to Pauli, there are thresholds beyond which some organisms just won’t be able to make it. While the subnivium provides a stable environment, it is also extremely delicate. “Once that snow melts,” he said, “things can change radically.”
The report warns that the effects on the subnivium will be particularly profound along the trailing edge of the cryosphere, or those parts of the planet that get cold enough to support snow and ice, whether seasonally or year-round. Plants and animals lacking the ability to cope with the loss of the subnivium will be hardest hit.