What is the Subnivean Layer?
The space between the ground and the snow pack is known as the subnivean layer. The subnivean snow layer holds in heat from the ground, providing a warm, safe place for many animals and plants in the winter.
As our temperatures warm and snowfalls drop, the plants and wildlife that depend on the snow cover to survive our winters are at risk.
Losing the Subnivean Layer
In Minnesota, we have seen a decrease in total snow cover in the winter over the last 50 years. Less snow means a shallower subnivean layer that does not last as long and is less predictable. Without the protection of the subnivean layer, it will become much more difficult for many plants and wildlife to survive our winters.
Plant leaves and roots can be damaged by extreme temperatures and frequent freezing and thawing. They may grow slower and flower later. Learn more about how less snow cover is impacting our sugar maple trees.
Reptiles and Amphibians
Reptiles and amphibians may come out of hibernation too soon if the ground thaws early. If they do, late spring snow storms can kill them.
Migrating birds in the spring may not be able to find enough to eat along the way if overwintering insects don’t survive.
Mammals like mice and moles may be left exposed to harm without the warmth and safety of the snow.
More wooly bear caterpillars that are dormant all winter are killed by repeated freezing and thawing than just one winter freeze.
Protecting Our Native Species
At Three Rivers, protecting and preserving plants and wildlife has always been a priority.
- We successfully reintroduced several species into our parks, including bullsnakes, trumpeter swans, regal fritillary butterflies and ospreys.
- We monitored and studied the habits of turtles in the winter.
- We actively manage our deer populations to protect our forests and the wildlife that depend on them.
- We use camera trapping to keep an eye on what's active in or missing from our parks.
- We restore high-quality habitat to attract and sustain native wildlife.
While climate change is threatening some species, we are taking steps to help ensure their survival. Learn more about what our Natural Resources Management team is doing to improve and protect our environment.