Toxic algae in North American waterways is on track to get worse, several reports warn, as heavier rainfall is washes a growing volume of nutrients from fields to water bodies, fueling heavier algal growth.
A warmer atmosphere can transport more water, leading scientists to tie the increasing incidence of heavy downpours to global warming. “Climate change will increase the amount of nitrogen [a powerful fertilizer] in U.S. rivers and other waterways by 19% on average over the remainder of the century,” Yale Environment 360 reports, citing a paper published in the journal Science [subs req’d]. The study also projected a increases of up to 24% in the Mississippi-Atchafalaya River Basin and up to 28% in the U.S. Northeast (up 28%).
As Yale 360 recalls, one bloom in western Lake Erie in 2014 forced the city of Toledo, Ohio to cut off water to 500,000 people. “The threat to human health was not hypothetical,” the outlet notes. “Blue-green algae toxins in the drinking water at a dialysis center in Brazil caused 76 deaths from acute liver failure in a 1996 incident.”
The Stanford University research team “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,” Yale states. They found that “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. That’s not counting likely increases in nitrogen inputs from more intensive agriculture, or from increased human population.”
As Inside Climate News explains in its coverage of the research, “nitrogen that washes into rivers and coastal zones comes mostly from fertilizers, feedlots and sewage, but also from car and truck exhaust, power plants, and industrial manufacturing. It’s essential to plant life, but in excessive amounts it becomes a harmful pollutant. In a process called eutrophication, it feeds explosive algae growth; and when bacteria decompose the dead algae, they use up all the oxygen, causing dead zones like those found in the Gulf of Mexico and Chesapeake Bay.”
U.S. National Public Radio reports that the dead zone produced annually in the Gulf of Mexico by fertilizer-fed algal blooms and subsequent eutrophication is the largest ever observed this summer.