Fertilizer washed from Midwestern fields slowly poisoning Gulf of Mexico; latest story uses Illinois county as example

Excess nitrogen fertilizer washing into the Mississippi River is slowly poisoning the Gulf of Mexico, Ignacio Calderon reports for USA Today and the Midwest Center for Investigative Reporting in the latest take on an old story.

The fertilizer fuels the growth of toxic algae blooms that suck the oxygen from the water and create massive dead zones. "The environmental devastation – increasing blooms and a consistently growing dead zone – has been well documented for decades," Calderon reports. "But changes in the way rain falls, as explained in a yearlong USA Today investigation, have set the stage for things to get much worse, many scientists now believe. The warming planet is bringing more precipitation overall, and more downpours in particular, to the same U.S. regions that grow a majority of America’s fertilizer-dependent crops."

Champaign County, Illinois
(Wikipedia map)

The investigation focused on Champaign County, Illinois, which sheds some of the most surplus nitrogen fertilizer in the nation. After analyzing spring precipitation and nitrogen levels in the nearby Spoon River between 2014 and 2020, "the analysis found that the kinds of extreme rainfall events made more common by a warming planet cause three times as much fertilizer runoff than other rain events and contribute to an outsized share of it in the waterways," Calderon reports.

Most of the nitrogen spikes in the river happened after a rainfall, and the three heaviest storms alone accounted for one-third of all the nitrogen measured in the seven-year period. "The findings mirror a larger study conducted by several researchers that found heavy rain across the Mississippi River Basin also contributed to one-third of the nitrogen flushed to the Gulf of Mexico. This heavy rain happens in just nine days per year.," Calderon reports.

Though the Gulf of Mexico dead zone is the best-known example, runoff-fueled algae blooms are happening in rivers and lakes all over the U.S. The algae not only hurt people and aquatic life, but also emit the greenhouse gas methane. The Environmental Protection Agency "recently found the emissions from blooms could increase 30% to 90% in the next century," Calderon reports. "It’s a devastating feedback loop. Algae blooms contribute to global warming, which increases rainfall [east of the Mississippi River], which then exacerbates fertilizer runoff."