The Value of Temporary Wetlands

March 30, 2009 by  

By Doug Leier

The Prairie Pothole Region of North Dakota

The Prairie Pothole Region of North Dakota

A recent rainy spell has rekindled somewhat the time-worn debate over the value of wetlands, small ones in particular.

North Dakota has hunreds of thousands of these small, shallow wetlands. They’re often called temporary wetlands because they typically only hold water for a few weeks after spring snow melt, or after heavy summer rains like we had a couple of weeks ago. Most of the year, because of evaporation and water absorption into the ground, they are dry.

North Dakota also has a lot of larger, deeper wetlands that usually hold water year-round. While the state once had an estimated 5 million acres of wetlands, and today only about 2 million acres remain, North Dakota’s combination of wetlands is still part of the best waterfowl production habitat in North America.

It’s widely known that wetlands and waterfowl are closely tied, but wetlands have other benefits, and one of them is the capacity to hold water and keep it from running into river systems. That benefit is on my mind as I write this, as the same rain that is pounding my roof and cycling my sump pump is also creating localized flood conditions.

Other Wetland Benefits

Waterfowl rely heavily on a temporary wetland such as this one

Waterfowl rely heavily on a temporary wetland such as this one

It’s not that the restoration of North Dakota’s 3 million acres of altered wetlands would prevent flooding, especially in my urban neighborhood, where concrete, asphalt and rooftops all serve to shuttle water to the lowest point much more quickly than if the area was still a grass prairie.

In fact, look at all the square miles of concrete in any of the state’s larger cities, and you can easily understand how quickly water from a heavy rain moves from parking lots and driveways to city streets to storm sewers to the local river. Before the growth of our cities, that water would either have soaked into the ground, or run off naturally in much reduced volume.

Now, I’m not advocating turning back the clock to an earlier, more pristine time. We live here, and to do that, we’ve changed a lot of things. And because we’ve changed things, we sometimes have to tolerate the consequences.

Out in the country, the amount of water a small one-half-acre wetland can hold won’t save a town from a devastating flood. But when thousands of those small wetlands are breached, and the water runs out via ditches and channels and eventually winds up in a large lake or river system, it can add significantly to a flood that is occurring naturally.

When it comes to high water over large areas, even a few inches of extra water can mean a dike breached or homes flooded that would not otherwise have occurred.

Providing Cleaner Water and Habitat

Water can accumulate quickly in a wetland, but it takes awhile for it to recede. As the water slowly percolates down through the wetland bed, it is naturally filtered and becomes part of the regions aquifer. Vegetation growing in wetlands also helps filter chemicals and fertilizers out of water, rather than that water running off and into our river and lake systems.

Value to Waterfowl

Blue Wing Teal brood

Blue Wing Teal brood

I’ve had many people – some of them avid duck hunters – ask me about the real value of those small wetlands for ducks. Honestly, you can see a lot of big wetlands out in the country and it’s probably understandable to wonder if that isn’t enough.

It’s not, and the truth is those small wetlands are more important for breeding ducks than big lakes. The small shallow wetlands are breeding territories for ducks, and they are also the first water to warm up in spring and provide nutrient-rich aquatic insects that fuel the duck production process. If you’re a duck hunter and are indifferent about small wetlands, that seems a bit of a double standard.

As this column is printed, biologists across the nation are assessing and tabulating duck breeding conditions in North Dakota and elsewhere on the duck production grounds of North America. Heading into last winter, many of North Dakota’s remaining small wetlands were dry. Spring runoff did little to fill them.

Seasonal Wetland

Seasonal Wetland

Abundant rain in late May helped start the recharging process, but how much that will help the initial duck nesting process remains to be seen.

But again, the relationship with ducks and other wildlife is only part of the value of those small wetlands. In some parts of the state, every drop of water stored in a wetland is one less drop running into a flooding river or lake.

Fact is, they benefit each of us, and it’s at this time of year those benefits might be most evident.


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