MILWAUKEE - Snow cover in the Northern Hemisphere - and especially along the edge of the Snow Belt, as in Wisconsin - has been shrinking.
That's having implications for a place that most of us don't think about, but where a whole lot is happening during winter's slumber.
Scientists at the University of Wisconsin-Madison have looked into the research of this ecosystem of creeping voles, frozen frogs and growing plant life and concluded this month in an article in Frontiers in Ecology and the Environment that climate change could put much of it at risk.
The problem is vanishing snow.
From 1970 to 2010, maximum snow depth has shifted from January to February over North America. The extent of snow cover in March and April has fallen 7 percent and 11 percent, respectively, over the period.
Spring snowmelt over the four decades had moved up about two weeks.
"It's really important to emphasize that it's a refuge, a seasonal refuge that organisms use to escape inclement seasonal conditions," said Jonathan N. Pauli, an assistant professor of forest and wildlife ecology at UW-Madison.
Indeed, the world beneath the snow can be incredibly stable and hospitable compared with the blowing winds and subzero temperatures above.
The soil slowly gives off heat and warms the air. That produces water vapor and a base layer between the snow and the ground, which is filled with loose granular snow and where temperatures hover just below freezing.
Many invertebrates such as beetles and mites and ticks remain active. So do voles. Lemmings have been known to reproduce during the winter months.
Some fungi proliferate and help to decompose plant life, which helps soil.
Wood frogs, Pauli said, "undergo whole body freezing during the winter."
"If it freezes too much, it outstrips their ability to cryoprotect," essentially by creating a frozen outer layer to shield sensitive organs.
If it's too warm, the frog is forced to go through cycles of warming and cooling.
The loss of snow - or its growing variability - means less protection from the elements, especially in areas such Wisconsin, said Benjamin Zuckerberg, a climate specialist in wildlife ecology.
That's because Wisconsin lies at the southern edge of the Snow Belt, so species here "may become more stressed in the future," he said.