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Vanishing Pools Lose Their Allure

By Valerie Rose Redmond
External Affairs and

Rex Johnson
Migratory Birds

Vanishing pools earn bragging rights for exotic vacation hotels and resorts.  While they are sought-after amenities, coveted in exclusive estates and other luxurious places, vanishing pools take on a different connotation in the conservation arena.

Shallow, temporary and seasonal wetlands that hold water for short periods in the spring and summer in the Midwest literally are vanishing pools, but sadly their disappearance may all too soon become permanent.

How does it affect you and why should you care?  The answer is in the silence.

Fifty years after the publication of her iconic book that captivated the nation, Rachel Carson’s voice echoes in the foreshadow of what could someday become the silent spring that she so eloquently fictionalized in its first chapter.

Carson’s immortal words trickle down through the cattails, amid the glistening snow melt, and run off into the seasonal wetlands that are now under a constant and pervasive threat: the conversion of native prairie for agricultural, industrial and commercial uses.  Drainage, residual soil depletion, and the temporal nature of these wetlands also put them at high risk.

Temporary wetlands include both seasonal wetlands, which result from winter snow melt and spring rains and shallow wetlands, such as swamps and marshes. These wetlands, while fleeting, are critical to both the resident waterfowl and the transient water birds that utilize them as stopovers during the spring migration.

Because they are shallow, seasonal wetlands are the first to warm up and provide open water and food for wildlife.  These wetlands, teemed with snails, aquatic insect larva and adults and even smaller crustaceans called zoo plankton, are an abundant and valuable food source for wildlife.  Migrating birds are most often associated with cropped wetlands.

Ducks feed heavily on waste grain, full of energy-rich carbohydrates and fats.  Shorebirds and ducks that are preparing to breed feed on snails, insects, worms and other invertebrates, rich in the protein and calcium that is essential for egg production. Migrating shorebirds that fly short distances between migration stops may actually double their body weight in a few days feeding on these invertebrates, and if they fail to put on the required weight they may not survive migration, literally falling dead out of the sky.

There were once about 1.9 million of these temporary and seasonal wetlands in the prairies of Minnesota and Iowa. Today there are only about 230,000 left.  Many of these cropped wetlands were once completely or incompletely drained and the drainage system has become decrepit.  They are at high risk of drainage because they eventually dry up and landowners want to utilize the acreage. The problem is that these partially drained wetlands in cropland provide much of the wetland wildlife value that Minnesota and Iowa still have.

“Shallow wetlands may be the most essential elements of the prairie pothole region landscapes,” said wildlife biologist Rex Johnson. “Their loss has imperiled many species that are unable to move long distances between wetlands. They are primary sites of ground water recharge that feed our wells and irrigation systems.  In aggregate they hold back millions of acre-feet of flood water in the spring and after heavy rains.”

The loss of these wetlands, exacerbated by high crop prices that make drainage system repair more appealing, increases fragmentation of the landscape for species that have limited mobility.

While there are many determining factors, including residential and commercial development, cropped wetlands are at the highest possible risk of being drained despite state and federal legislation that were passed to constrain drainage.  The primary protection for cropped wetlands is “Swampbuster”, a Farm Bill provision that delivers sanctions to landowners who drain or fill prohibited wetlands. Since participation in the Farm Bill program is voluntary, high commodity prices have recently made the program less attractive and more and more landowners are opting out and draining or enhancing drainage of cropped wetlands.

These wetlands are relatively easily restored by breaking tile lines, plugging ditches and scrapping out accumulated sediments.  Costs vary from a few hundred to a few thousand per wetland.

But esoterics aside, the drainage of these critically important ecosystems have broader human implications, as well.  Climate related extreme weather has increased dramatically over the past few decades. Colossal storms, rising temperatures, unrelenting drought, and devastating floods proliferate in the news. Sustaining and restoring seasonal wetlands are effective strategies for flood risk reduction and climate change adaptation. Wetlands reduce peak flooding by acting like natural sponges on the landscape. They are a clean water supply.  They produce fertile soils, improve water quality, and ultimately increase food production.

These pools of life are valuable assets, yet they are in danger of vanishing from the landscape forever. The loss of seasonal wetlands affects wildlife and people.  Breathtaking in its sheer perfection and resonating with the melodious harmonies of life, the natural world is one we have chosen to preserve both for us and our children. To leave them a world like the one that we were born into or one that is better is more than a desired legacy, it’s a responsibility.   Climate change and changing landscapes are jeopardizing that future. Carson warns us of the dire prospects of a silent spring. Vanishing pools lose their allure when juxtaposed with future generations surrounded by resonating silence, deprived of the peace and enjoyment of the natural world.

Click here to download a technical article by Rex Johnson on the Importance of Shallow Wetlands.




Last updated: April 12, 2013