Environment

Tiny hotspots of biodiversity, prairie potholes can ease the effects of climate heating — if we stop draining them

A landscape shot depicting Saskatchewan potholes filled with water. (Photo: Allan Kirk/Can Geo Photo Club)

By long tradition, the farmer has been the sworn enemy of the prairie pothole. Not only do the so-called “bathtubs” of the plains hold enough water to make them inhospitable to crops, but they also interfere with the straight lines that make field work go smoothly. Worse, they attract waterfowl, noted eaters of grain.

The zeal of farmers across the North American prairies to eradicate the pothole is legendary. What began in the early years of European settlement as hand-dug ditches to drain potholes led, by the early 20th century, to massive, steam-powered ditching machines working around the clock to dredge the land, burying drainage tiles to siphon the water into the larger watershed. The result was annihilation across wide swathes of the prairie pothole region, which stretches in an arc from Iowa to southwestern Manitoba across Saskatchewan and into central Alberta.

American avocets wade around a prairie pothole. (Photo: Douglas Chisholm/Can Geo Photo Club)

In Manitoba’s Red River watershed, for example, some 97 per cent of the tiny wetlands have been destroyed, notes Pascal Badiou, a research scientist at Ducks Unlimited Canada’s Institute for Wetland and Waterfowl Research in Manitoba. They are under even more threat as the climate heats.

Today, potholes are in the throes of an image makeover, even among some farmers. Emerging research by Badiou and other wetland ecologists shows that potholes, which formed in depressions when glaciers retreated about 10,000 years ago, influence almost every aspect of the inner workings of the Prairies. “Science is trying to catch up,” Badiou says.

For one thing, the shallow ponds are miniscule hotspots of biodiversity. Perched on the land, isolated from each other, they exist in the biologically precious transition zone from the terrestrial landscape to the aquatic one. That means shorebirds, ducks, bulrushes, grasses, salamanders, toads and insects — including pollinators — gather around their edges. They are among the planet’s best breeding grounds for waterfowl.

Intact, they function as a complex system of different sizes of ponds, each of which supports slightly different species. Most are shallow and range from the size of your bedroom to the area of a few football fields. They store water, replenish underground aquifers and stave off floods.

They soak up carbon dioxide from the atmosphere, fixing it in root systems, soil and plants, a buffer against climate heating. They capture phosphorus from crop fertilizers, keeping it away from streams and lakes. Perhaps most surprising of all, they act like mini air conditioners, cooling the air and keeping it moister even as the destabilized climate makes temperatures hotter and drier. That, plus the presence of pollinators and natural crop-pest-eaters, is a boon to farmers.

Governments, Ducks Unlimited and other organizations are restoring and conserving wetlands, part of the trend toward using nature to heal itself. Even so, Badiou says, more potholes are vanishing every year than are being brought back to life.

Are you passionate about Canadian geography?

You can support Canadian Geographic in 3 ways:

Home

Bathtubs of the plains