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- Nutrient runoff into the Mississippi River is causing freshwater problems — including "dead zones" in the Gulf of Mexico.
- The Conservancy is piloting projects that filter agricultural runoff with wetlands or other natural methods.
- The techniques could reduce the gulf's dead zones and be a model for other filtration programs worldwide.
By Julianne Beck
As the iconic Mississippi River winds through America's heartland on its way to the Gulf of Mexico, its tributaries deposit an overflow of nutrients from adjacent farmland and urban areas.
The result? An unnatural balance of nitrogen and phosphorous in the Mississippi that threatens important freshwater habitats and contributes to the gulf's growing dead zones.The imbalance puts aquatic, animal and plant life at risk and undermines water-dependent industries and coastal communities.
So scientists at The Nature Conservancy are working with farmers and other landowners in the Mississippi River basin on pilot projects that aim to sustain crop yields while improving the quality and ecological health of the basin's watersheds.
Two of these pilot projects — at the Mackinaw River in Illinois and the Root River in Minnesota — exemplify how the Conservancy is connecting with local partners across the Mississippi River watershed to develop sustainable agriculture models that could be implemented on a broad scale.
Mackinaw River: Wetlands Provide a Natural Nutrient Filter for Farms
Nutrient run-off from farmland threatens the long-term viability of Illinois' Mackinaw River watershed, home to 25 percent of the state's highest quality stream systems.
But since the Mackinaw is closer to its original condition than many other systems in the Midwest, scientists are hopeful that the river will return to a healthier state when nutrients are removed.
To prevent continued nutrient imbalances, the Conservancy has installed artificial wetlands amidst corn and soybean fields on a family-owned farm adjacent to the river. The wetlands function as a natural filter, reducing runoff of excess nutrients from the farm.
Now that the project is a few years along, data show a dramatic reduction in the amount of nitrogen leaving the wetlands. The short-term results reveal that nearly all nitrogen has been removed before reaching the river.
And the wetlands are benefiting wildlife as well — for instance, habitat for an at-risk slippershell mussel population has declined as nutrient levels have increased.
Also, numbers of birds such as Sora rails and migratory waterfowl such as sandhill cranes are already increasing in the wetlands.
Conservancy scientists will next assess the essential qualities of an agricultural wetland's success: location and size. Area farmers are paying close attention to the progress at the demonstration farm to evaluate potential wetland installations on their own properties.
"Our goal is to help farmers implement practices that are good for the environment and for their bottom line," says Tim Lindenbaum, a Conservancy science technician who also operates the demonstration farm project.
Minnesota: Northern Farmland Equipped with Bioreactors
Along the Root River in southeast Minnesota, the Conservancy is working with corn and soybean farmers to install bioreactors — long trenches filled with woodchips that help filter out excessive nutrients and reduce erosion.
Bioreactors have been used for filtration purposes before — but the Root River bioreactors were installed in combination with infiltration ponds.
When planted with native vegetation, these ponds collect nutrient-enriched runoff before sending it on to the bioreactors — a combination never before attempted. And since the Root nourishes and shelters migratory birds and rare fish, the bioreactors could benefit wildlife as well.
"We're creating habitat for wildlife including frogs and ducks, and reducing excess nutrients before they reach the Root River," says Blufflands Conservation Coordinator Rich Biske. "In addition, we expect this approach will reduce flooding impacts such as erosion."
According to Biske, an additional benefit of the ponds is that they help contain rainfall on farmland, slowing the pace of water eroding the banks of each tributary.
The bioreactors and ponds will be monitored for 10 years along with additional sustainable agriculture practices such as cover crops, which help reduce the erosion that leads to sedimentation in the tributaries, create wildlife habitat and remove nitrogen.
If the approach of combining bioreactors and infiltration ponds meets scientists' expectations, it can be employed anywhere farms are drained by underground pipes, which is common in the Mississippi River Basin.
Working Together Across the Mississippi River Basin and the World
These projects demonstrate how local efforts can have global impact — both directly and as models for other projects:
Gulf Dead Zones:
- The Mississippi River is one of the largest contributors of nitrogen to the Gulf of Mexico, one of the world's largest oceans. In the gulf, nitrogen fuels blooms of oxygen-hungry algae that dominate areas now devoid of other aquatic life — areas known as dead zones.
- As the amount of nitrogen arriving in the gulf has grown in the last century, so has the reach of these dead zones — which have doubled in size in the last 20 years. The effects have been particularly detrimental to wildlife and fisheries in this naturally diverse and valuable region.
- So if these projects prove effective on a large scale, they could help maintain the health of a main source of finfish and shellfish in the United States.
Worldwide Impact:
- In the near future, these programs may be replicated in similar systems along the Paraguay-Parana River in Brazil, the Yangtze River in China, and other regions where a need to increase food production for growing populations puts additional stress on lands and waters.
"Sustainable agriculture is critical to restoring the health of the Mississippi River, and providing a secure economic future for farmers," says Michael Reuter, the Conservancy's director of conservation programs for the central United States. "We are finding that what we learn in one part of the world has application in another part of the world. So we look forward to collaborating with a wide variety of partners to implement solutions on a broad scale."
Julianne Beck is a media relations manager for The Nature Conservancy.
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Photo credits (top to bottom, left to right): © Tim Lindenbaum/TNC (Harvest time at Franklin Demonstration Farm, Mackinaw River watershed, Illinois); © Tim Lindenbaum/TNC (Soft-shelled tortoise at Franklin Demonstration Farm, Mackinaw River watershed, Illinois)
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