Subnivium: The secret ecosystem hidden beneath the snow

An ephemeral ecosystem of tunnels in the snow is home to insects, frogs, rodents and even flowering plants. But as the climate changes, is it about to collapse?

By Ute Eberle

ECOLOGIST Jonathan Pauli used to spend a lot of time keeping track of animals over winter – often across cold, harsh landscapes that seemed inhospitable to life. It always surprised him that as soon as the weather got warmer in early spring, insects would pop up. “Snow fleas would emerge from underneath the snow,” Pauli recalls. Where, he wondered, had they been hiding?

Eventually, he discovered some old scientific papers from the 1940s and 1960s. They revealed a secret world that Pauli, a researcher at the University of Wisconsin-Madison, has been studying ever since: a hidden ecosystem under the snow. It is found in a clandestine space between the snowpack and the soil beneath, which is sheltered from the bitter cold and is where some insects, spiders, frogs and even small mammals spend at least part of the winter. Concealed from the world above, flies buzz, plants thrive and animals forage, hunt and give birth in this so-called subnivium (from the Latin sub, meaning under, and nivis, meaning snow). But what will happen to this winter wonderland and all the creatures it shelters as the climate warms up? That’s the topic of Pauli’s most recent research.

Every winter, as the white stuff covers up to 40 million square kilometres of the northern hemisphere, the subnivium forms wherever and whenever the conditions are right. “There needs to be around 20 centimetres of snow that is not too dense,” says Ben Zuckerberg, also at the University of Wisconsin-Madison. …