Wetland who’s who: Do you know your bogs from your fens?

Published: July 25, 2019

Wetland in Yukon, Canada Pi-Lens/shutterstock

So what is a wetland, you ask? A marsh is one of five officially defined wetland types in Canada—along with swamp, bog, fen, and shallow open water (see below). Defined as ecosystems saturated with water or sub­merged for all or part of the year, wet­lands are hotbeds of biodiversity. For hundreds of species of plants, animals, and insects in Canada—from a host of water-loving plants to single-celled protozoa to fairy shrimp to muskrats to moose, from shy songbirds to stickle­backs to raptors—wetlands offer pantry, sanctuary, harvest, home. They serve as the primary habitat for species such as snapping turtles and swamp sparrows, and as essential “truck stops” for migratory birds. Many at-risk species need wetlands to survive.

Wetlands weren’t always prized. Long considered bug-infested, pestilential wastelands, they were once routinely drained for farming, filled in for construction, or treated as drainage ditches for industrial waste. Between 70 and 80 per cent of the wetlands in Canada’s urban south have been repurposed this way. Those that remain are threatened by pollution, development, and climate change. A 2018 report by Ontario’s Environmental Commissioner lambasted the provincial government for allowing wetland loss to persist. Proposed changes to the Species At Risk Act may further erode wetland protection.

There’s hope, though. Fifty years ago, it would have been unheard of for a government to be chastised for eliminating swamps. Though wetlands were once reviled because it was tricky to erect a house on one or to run a road over one, we now see that for ecosystems to function well, they’re key, even making urban areas more resilient. From New Brunswick’s famed Tantramar Marshes to Ottawa’s internationally significant Mer Bleue Bog and the Prairie Pothole Region, 14 per cent of Canada’s land mass, or 127 million hectares, is wetland. That’s a quarter of the wetlands on Earth.

Wetlands who’s who

Could you tell a swamp from a marsh, or a bog from a fen? Wetland environments are often found side by side, and their borders blur. A marsh may ring a pond. A fen may nestle between a swamp and a bog. In Canada’s north, vast expanses of fens and bogs are known as muskeg, and any given fen might be in the midst of a hundred-years-long transformation into a bog. Here are the basics.

Marsh: Characterized by still or slow water supporting stands of tall grasses, cat­tails, bulrushes, water lilies, pickerelweed, and blue flag iris, the marsh is the wetland we most recognize. Usually on the edge of a lake or a pond, a marsh may dry up season­ally, and it boasts rich mineral soil. Marshes serve as habitat for a host of species, including muskrats, bitterns, ducks, marsh wrens, soras, and turtles. They’re also important spawning grounds for many fish, including largemouth bass and sunfish. 

Bog: Poorly drained peatlands 10,000 years in the making, these granddaddies of wetland ecosystems, found chiefly in the north, are cut off from groundwater: a bog’s water comes only from collected snow­melt and rain. Peat (acidic, oxygen-poor, decomposed vegetation) is heaven for the sphagnum mosses that form thick red­dish or green­ish cushions. Look for tufted cottongrass, Labrador tea, cranberries, blueberries, songbirds, foxes, weasels, fishers, and hawks.

Fen: Fens are like bogs-in-the-making: with peat less than 40 cm deep, they’re less acidic and draw on groundwater. Vegeta­tion can be “perched” or floating. Sedges dominate, but marsh grasses and trees such as cedar or dwarf birch mix in. Rare flora, such as the aptly nick­named fen orchid, thrive in fens country­wide. Also common are voles, deer, and buckbean, a flowering herb.

Swamp: If you see trees, you’re likely in swamp territory. Swampland—land which either lies beneath nutrient-rich water or is water­logged (when a dug hole will immediately pool)—is populated by woody plants: thickets of willows and alders, or stands of black spruce, tamarack, or poplar. Rabbits and moose love these moody, misty habitats, as do skunk cabbage, swamp sparrows, moles, mice, and many waterfowl species. 

Shallow Open Water: Call it a pothole, a pond, or a slough (pro­nounced “slew”): a small, shallow, stand­ing body of water up to two metres deep. It may be ringed with marsh or serve as the transition between lake and marsh­land. Duckweed, milfoils, water lilies, and water hyacinths flourish here. Hibernat­ing frogs burrow in the mucky bottom. Gut­weed, a notable pond plant, fills with air, floats, and attracts hungry insects with its slimy coating of bacteria. Look for water boat­men and back­swimmers.

Find out what wetlands do for you and how to be a wetland guardian.

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