Skip to content
"There's a lot going on — it just isn't visible," wetland scientist Erik Kiviat says of marshes and other seemingly frozen wintry habitats. (Image: Pierce Johnston)

The Secret Lives of Wetlands in Wintertime

The Hudson Valley’s wetlands may seem dead as winter sets in. But under the (frozen) surface, lots of things are happening.

by Robert Lawrence
Share:

A whole range of wetland habitats can be found between the estuaries and the highlands of the Hudson River Valley. There are tidal marshes, vernal pools, and calcareous fens, along with assorted bogs, meadows, and swamps. These wetlands are all hotspots of biodiversity that buzz with life in warm weather. Then, as the creeping winter sends songbirds south, the wetlands that they leave behind seem to become ecological ghost towns. 

But beneath the snow and ice, wetlands continue supporting life in hidden ways throughout the winter.

“There’s a lot going on — it just isn’t visible,” says Erik Kiviat, who is a wetland scientist working with Bard College, and co-founder of Hudsonia, Ltd. Since the 1970s, Kiviat has spent a lot of time observing wetland wildlife throughout the year, especially in the Tivoli North Bay marshes near Bard in Dutchess County.

Wetlands continue supporting life in hidden ways throughout the winter. (Image: Pierce Johnston)

“I can remember going out and spending half a day or a day out in North Bay in the winter, or walking around the edge of the marsh in the winter, and I’ll see a few birds, actually,” he recalls, listing a few of the small birds that occasionally decide to stick out the colder months. As for the larger birds like geese, ducks, and heron, “they will go somewhere that isn’t frozen,” he says. “So that might be the mouth of a stream flowing into the Hudson River, or it might be out in the main river farther to the south where it is a little warmer and it doesn’t freeze as much.”

Wetland mammals, on the other hand, prefer to hunker down rather than migrate. “Beavers and muskrats build lodges or burrows that they spend most of the cold weather in, and they can swim out under the ice and get to food,” Kiviat says, noting that they also rely on caches of food stored in their winter hideaways.

As for the turtles, some might bury themselves for the winter in a muddy burrow known as a hibernaculum. Others may just rest at the bottom of a pond beneath a cover of ice, as Kiviat has seen with Blanding’s turtles in the region. “They just sat on the bottom under the ice, and they get up every couple of weeks and move around a little, and then stay still again,” he says. In this state, a turtle’s patient heart still beats once every few minutes until the thaw arrives. Many frogs, salamanders, and even some tadpoles also pass the winter buried in the mud or waiting in repose. For these wetland reptiles and amphibians, winter just means life in slow motion.

Amphibians have ways of dialing back their metabolisms or otherwise going into resting states to survive the winter. (Image: Alasdair James / iStock)

Small fish in wetland habitats can also dial back their metabolism in colder water that may be lacking oxygen and food sources when covered in ice. Kiviat says that killifish in brackish marshes may even bury themselves in the mud to pass the cold season. “I’ve dug them out of the mud in the intertidal zone a few times in the winter,” he says. “So, there’s a lot of different behaviors, and it depends on the species and the habitat.”

At the bottom of the wetland food chain there are a host of tiny aquatic crustaceans, insect larvae, and other microfauna. These have their own strategies to pass the winters too, says Alyssa Liguori, an Assistant Professor of Biology at SUNY New Paltz who is surveying populations of such critters throughout the year in nearby lakes and ponds. She says water fleas and other little crustaceans can switch to sexual reproduction when it gets cold and produce loads of eggs that remain dormant in the water until spring.

Other microfauna may switch food sources, or go into a resting state, or employ other strategies in the winter, she explains. When the water gets cold, “obviously that’s just going to slow them down. Maybe they won’t be reproducing, maybe they won’t be moving around as much, but they can go in deeper waters and survive.”

Wetland plants like cattails and common reeds serve key winter roles, like offering roosting sites for birds or filtering out debris during storm surges. (Image: Pierce Johnston)

Although plant life mostly comes to a halt in the winter, some wetland plants like cattails and common reeds still have an important role to play throughout the year, says Stuart Findlay, aquatic ecologist emeritus with the Cary Institute of Ecosystem Studies. “When fall comes, they don’t fall over and die right away. They’re what we call ‘standing dead,’” he says, noting how appropriate the term is for the concurrent Halloween season.

Through the winter, these rugged plants continue acting as roosting sites for birds and as barriers that filter out debris during storm surges. “If you had a nasty nor’easter in February that’s carrying lots of debris around, these standing dead plants actually slow the water down a bit,” Findlay explains. “They capture some of that debris rather than having it wash up on shore.” This keeps floating logs and branches from flooding onto streets, railroad tracks, and properties near wetlands.

Although wetland vegetation may seem dead in the winter, most plants still have living roots below. Deep down there in the soil, the temperature is cool, but not frozen, and mostly constant throughout the year. And this means that beneath the mud, “there’s still stuff going on but it’s a lot slower and more evenly spread out across the seasons,” Findlay says. Anaerobic bacteria deep in the sediment, for instance, play a key role in decomposing organic debris and keeping carbon buried deep under water and soil rather than in the atmosphere above. 

Wetlands serve as carbon sinks, absorbing the gas deep underground rather than allowing it into the atmosphere above. (Image: Pierce Johnston)

This slow process of sequestering carbon in the sediment, year after year, over hundreds and thousands of years, makes every wetland an ancient ecosystem that cannot be easily restored once it is lost. That’s why it’s lucky new statewide wetland protections went into effect on Jan. 1. The protections came as amendments to New York’s Freshwater Wetlands Act, first enacted 50 years ago, now requiring higher levels of wetland protection in flood-prone areas, and highlighting the importance of wetlands even in urban areas.

As autumn’s fallen leaves gather on the surface of a pond, sink to the bottom in the winter, and add the layer of another year to the muddy sediment below, wetlands do essential work to stabilize life cycles and carbon cycles in our environment. And that work doesn’t stop during the winter.

Robert Lawrence lives in Montgomery, N.Y., where he works as a science writer and enjoys visiting the many parks of the Hudson Valley with his wife and little boy. He is originally from drier climates and holds a Ph.D. in biochemistry from Arizona State University.

Explore More — Viewfinder +

Climate Solutions
How to Get in on the Refillability Game
Land + Air + Water
Restoring Resilience to Mawignack Preserve
Land + Air + Water
Can Hops Make a Comeback in New York?
A close view of a hop growing on a vine. Behind it is a red barn.
Land + Air + Water
Protecting Forests by Managing the Exploding Deer Population
Climate Solutions
Floatovoltaics Makes Waves Approaching the Valley

Search Viewfinder:

Latest Posts

Subscribe!

Get the latest articles delivered right to your inbox  — for FREE!