The decline of a hidden and expansive microhabitat: the subnivium

Abstract

The subnivium is the seasonal microhabitat at the snow–ground interface and serves as a refuge for a diversity of species. Increasingly warmer winters are disrupting the continuity of snow cover, and likely the stability of the subnivium. To examine how the extent and duration of this sensitive and widespread below‐snow habitat will shift under warming winters, we deployed fully automated winter greenhouses across latitudinal and land‐cover gradients to monitor subnivium conditions under different climate‐change scenarios and predicted subnivium occurrence across the Great Lakes region. In a +3°C warming scenario, we found little change in subnivium extent or duration, whereas a +5°C scenario produced widespread and marked reductions in both extent (loss of 200,000 km2, a 45% decline) and duration (>1 month decline). Although the subnivium appears resilient to moderate future warming, we predict abrupt and extensive changes in response to increased winter warming, which will have sweeping ecological and environmental consequences in high‐latitude ecosystems.