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Yale study: agriculture changing chemistry of Mississippi River

Agriculture Changing Chemistry of Mississippi River

Contact: Dave DeFusco, Director of Communications, 203-436-4842

January 24, 2008

New Haven, Conn. –Midwestern farming has injected the equivalent of five Connecticut Rivers and more carbon dioxide annually into the Mississippi River during the past 50 years, according to a study published today in Nature by researchers at Yale and Louisiana State universities.

“It’s like the discovery of a new large river being piped out of the corn belt,” said Pete Raymond [profile], lead author of the study and associate professor of ecosystem ecology at the Yale School of Forestry & Environmental Studies. “Agricultural practices have significantly changed the hydrology and chemistry of the Mississippi River.”

Photo: Jerry Ting

The researchers tracked changes in the levels of water and bicarbonate, which forms when carbon dioxide in soil water dissolves rock minerals. Bicarbonate plays an important, long-term role in absorbing atmospheric carbon dioxide, a greenhouse gas. Oceans then absorb carbon dioxide but become more acidic in the process. “Ocean acidification makes it more difficult, for example, for organisms to form hard shells in coral reefs,” said R. Eugene Turner, a co-author of the study and a professor at the Coastal Ecology Institute at Louisiana State University.

The researchers concluded that liming and farming practices, such as changes in tile drainage and crop type and rotation, are most likely responsible for the majority of the increase in water and carbon in the Mississippi River, which is North America’s largest river.

Raymond said that the research team analyzed 100-year-old data on the Mississippi River that had been warehoused at two New Orleans water treatment plants, and combined it with data on precipitation and water export. “A notable part of this finding is that changes in farming practices are more important than changes in precipitation to the increase in water being discharged into the river,” he said.

The researchers used their data to demonstrate the effects of this excess water on the carbon content of the river, and argue that nutrients and pollution in the water are altering the chemistry of the Gulf of Mexico.

Besides Raymond and Turner, the other co-authors of the study, “Anthropogenically Enhanced Fluxes of Water and Carbon from the Mississippi River,” are Neung-Hwan Oh of the Yale School of Forestry & Environmental Studies, and Whitney Broussard of the Department of Oceanography and Coastal Sciences at Louisiana State University.

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