Projecting the future of nitrogen pollution

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http://pubs.acs.org/doi/full/10.1021/es9002179?cookieSet=1

Projecting the future of nitrogen pollution

Rhitu Chatterjee
Environ. Sci. Technol., Article ASAP
DOI: 10.1021/es9002179
Publication Date (Web): February 4, 2009
Copyright © 2009 American Chemical Society

Heavier rainfall due to climate change will exacerbate the effects of increased fertilizer use for corn-based ethanol production, causing a significant increase in nitrogen levels in rivers, according to a new study in ES&T (DOI 10.1021/es801985x). The good news is that if farmers choose organic practices and reduce fertilizer use, the impact of heavy rains will lessen and nitrogen pollution levels might drop to below present-day levels, the study concludes.

The study by research fellow Haejin Han of the University of Michigan and colleagues is the first to simultaneously model the changes in nitrogen runoff across space—18 watersheds in the Lake Michigan basin—and over time, the past 20 years. Using a model they developed, the researchers then project future variations in nitrogen loading under different land-use and climate scenarios.

The study reinforces an old message for lawmakers: current decisions on land use and agriculture will have a strong impact on the future availability of freshwater and the health of our aquatic and coastal ecosystems, says David Allan, one of the authors on the study. It also reinforces the notion that two factors drive the future of nitrogen pollution, he notes: climate change and how much nitrogen humans use on land.

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The researchers projected future nitrogen fluxes under different land-use and climate scenarios—business as usual, increased dependence on organic farming, increased fertilizer use from corn-based ethanol production, a 5% increase in rainfall, and a 10% increase in rainfall. The analysis revealed that the combined effect of 10% more rainfall and more ethanol production would increase nitrogen levels in rivers by 24%. But more use of organic farming practices could slash nitrogen levels in rivers by 7%, even if rainfall increased by 10%.

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