An algae bloom in Lake St. Clair in July 2015. The lake is bordered by Detroit, Michigan to the west and Canadian farmland to the east. NASA/NOAA
New research shows that increases in rainfall and extreme weather because of climate change will increase the amount of nitrogen polluting rivers and other waterways. The findings underscore the urgency of reforming agriculture to dramatically reduce the use of nitrogen fertilizers.
By Richard Conniff • August 7, 2017
It is a painful lesson of our time that the things we depend on to make our lives more comfortable can also kill us. Our addiction to fossils fuels is the obvious example, as we come to terms with the slow motion catastrophe of climate change. But we are addicted to nitrogen, too, in the fertilizers that feed us, and it now appears that the combination of climate change and nitrogen pollution is multiplying the possibilities for wrecking the world around us.
A new study in Scienceprojects that climate change will increase the amount of nitrogen ending up in U.S. rivers and other waterways by 19 percent on average over the remainder of the century — and much more in hard-hit areas, notably the Mississippi-Atchafalaya River Basin (up 24 percent) and the Northeast (up 28 percent). That’s not counting likely increases in nitrogen inputs from more intensive agriculture, or from increased human population.
Instead, Stanford University researcher Eva Sinha and her co-authors simply took historical records of nitrogen runoff as a result of rainstorms over the past few decades, recorded by the U.S. Geological Survey. Then, assuming for the sake of argument that there will be no change in the amount of nitrogen being added to the environment, they calculated how much additional nitrogen would be leached out of farm fields and washed down rivers solely because of extreme weather events and increased total rainfall predicted in most climate change scenarios. The bottom line: “Anticipated changes in future precipitation patterns alone will lead to large and robust increases in watershed-scale nitrogen fluxes by the end of the century for the business-as-usual scenario.”