Wetlands are the key to reducing nitrate runoff in waterways

In July 2017, the Gulf of Mexico’s dead zone, an area with low oxygen levels, reached its largest size ever, measuring roughly the area of New Jersey. The dead zone is a major cause for concern, as it poses a threat to life in marine ecosystems.

One of the biggest contributors to the dead zone is fertilizer runoff from agricultural operations in the Midwest. Nitrate concentrations from fertilizer make their way into waterways and can get into drinking water and eventually end up in the Gulf of Mexico, further adding to the dead zone.

Tackling the dead zone and agriculture runoff has been a priority for many researchers, but now, a new study has found a promising solution to the problem.

The research has found that multiple wetlands, or “wetland complexes” in a watershed, are five times more effective at reducing nitrate levels in waterways than other land management strategies.

The study, conducted by researchers funded by the National Science Foundation and published in the journal Nature Geoscience, emphasizes the importance of wetland restoration and conservation.

“This study demonstrates that retaining or restoring wetlands in intensively managed agricultural watersheds would reduce nitrate in rivers and improve local water quality, while also reducing nitrate exports to the Gulf of Mexico hypoxic [dead] zone,” said Tom Torgerson, director of the National Science Foundation Water, Sustainability, and Climate program.

For the study, the researchers collected water samples from over 200 waterways in the Minnesota River Basin over a period of four years.

The samples were analyzed and compared to geospatial information on land use in the river basin which showed how the wetlands specifically reduced concentrations.

The researchers discovered that wetlands in a watershed reduce fertilizer runoff, but the arrangement of the wetlands dictates their effectiveness.

Wetlands are extremely important in flood management and are a vital part of the ecosystem, but wetlands are shrinking in place of agriculture and economic development.

The study shows that wetlands could be the solution to reducing nitrate concentrations in waterways and need to be preserved, restored and protected.

“Our work shows that wetland restoration could be one of the most effective methods for improving water quality in the face of climate change and the increasing global demand for food,” said Jacques Finlay, an ecologist at the University of Minnesota and a co-author of the study.

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By Kay Vandette, Earth.com Staff Writer