Study: Farming Cause of River Chemistry Changes
a study published in "Nature" by researchers at Louisiana State
University and Yale University, farming has significantly changed the
hydrology and chemistry of the Mississippi River, injecting more carbon
dioxide into the river and raising river discharge during the past 50
LSU Professor R. Eugene Turner and graduate student Whitney
Broussard, along with their colleagues at Yale, tracked changes in the
discharge of water and the concentration of bicarbonate, which forms
when carbon dioxide in soil water dissolves rock minerals. Bicarbonate
in rivers plays an important, long-term role in absorbing atmospheric
carbon dioxide, a greenhouse gas. Oceans then absorb this carbon
dioxide but become more acidic in the process, making it more difficult
for organisms to form hard shells -- a necessary function in coral
reefs, for example.
Researchers concluded that liming and farming practices, such as
changes in tile drainage, tillage practices and crop type, are most
likely responsible for the majority of the increase in water and carbon
in the Mississippi River, North America's largest river.
"It's like the discovery of a new large river being piped out of
the corn belt," said Pete Raymond, lead author of the study and
associate professor of ecosystem ecology at the Yale School of Forestry
& Environmental Studies.
The research team analyzed 100-year-old data on the Mississippi
River warehoused at two New Orleans water treatment plants and combined
it with data on precipitation and water export.
"The water quality information we used has been sitting idle for
over 50 years in an attic in New Orleans, waiting to be discovered,"
said Broussard, who is pursuing a doctoral degree in coastal ecology at
LSU. "I felt like a treasure-hunter when we opened those boxes in that
100-plus degree attic to find those data logs. You never know where
your research will take you if you're open to suggestion and
serendipity." Turner, distinguished professor of coastal ecology,
added, "and [where it will take you] if you have the benefits of
long-term collaborations of trusting and high-quality academic research
The research team used the data to demonstrate the effects of this
excess water on the carbon content of the river and argue that the
additional water in the river is altering the chemistry of the Gulf of
Mexico by increasing the amount of nutrients and pollution the river
transports to the Gulf.
"We're learning more and more about the far-reaching effects of
American agriculture on rivers and lakes. This also means that the
agricultural community has an incredible opportunity to influence the
natural environment in a positive way, more than any other contemporary
enterprise," said Broussard. "If we want to clean the water, we have to
steward the land with right agriculture."