Nitrogen, along with phosphorus and potassium, is a primary component of the fertilizers used to improve agricultural yields. After being applied to fields, however, nitrogen can leave the farm as runoff and end up in local waterways. There, excessive levels of nitrogen can cause algae blooms and disruptions to the aquatic ecosystem. Because of this, removing excess nitrogen from waterways is a major field of research. One way to remove nitrogen is to incorporate wetlands into the landscape. Wetlands naturally remove nitrogen by absorbing it for use by growing plants. The amount of area worldwide dedicated to wetlands, however, has decreased over time. Additionally, wetlands are more effective at removing nitrogen if they are located near large nitrogen sources, such as active farmland.
Researchers from the University of Waterloo and the University of Illinois at Chicago recently published a model looking at the impact on nitrogen uptake depending on where wetlands might be placed throughout the country. They developed three scenarios: in the first, new wetlands form randomly throughout the country; in the second, no farmland is converted to wetlands; and in the third, wetlands are put near high-nitrogen-producing areas in the United States Midwest and the California Central valley. The model found that the third scenario almost doubles the amount of nitrogen removal from wetlands as compared to current levels, while the first two scenarios have much smaller effects.
While increasing wetland area by 10% near active farmland would significantly cut the amount of nitrogen run-off in waterways, it would also require converting what is currently highly productive cropland into wetlands. The authors estimate that this would cost about 3.3 billion dollars and use 2% of the United States total cropland area. However, they argue that these costs, while not insignificant, are in line with what we are already spending on our water quality goals. Because of this, they recommend seriously considering incorporating wetlands near major nitrogen-producing agricultural areas.
Frederick Chang is a PhD student at the University of Waterloo in Canada focusing on sustainable development of water resources.
Managing correspondent: Emily Kerr
Original article: Maximizing US nitrate removal through wetland protection and restoration
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