Midwestern manure gets more blame for the "dead zone" in the Gulf of Mexico

Manure from farms in the Mississippi River watershed is an even bigger reason behind the "dead zone" — an area devoid of life in the summer — in the Gulf of Mexico off the coast of Louisiana, reports Phillip Brasher of the Des Moines Register (which produced the maps).

"The study by the U.S. Geological Survey also says that manure runoff from pasture, rangeland and feedlots is a bigger contributor to the problem than previously thought," Brasher writes. "The dead zone, which lies along the coast of Louisiana and Texas, is created when phosphorus and nitrogen flow out of the Mississippi River and encourage the growth of algae in the Gulf. The algae growth robs the water of oxygen, forcing fish, shrimp, crabs and other sea life from the region."

Fertilizer runoff from corn and soybean farms has long been identified as the source of much of the nitrogen and phosphorus in the Gulf. As farmers increase acreage and their use of fertilizers, scientists say the problem could get worse, Brasher explains.

"The study, released Tuesday, said Illinois, Iowa, Indiana, Missouri, Arkansas, Kentucky, Tennessee, Ohio and Mississippi contribute 75 percent of the nitrogen and phosphorus that reaches the Gulf," Brasher writes. "Those states represent just one-third of the land drained by the Mississippi River or its tributaries." (Read more)