Biofuels threaten sealife in Gulf of Mexico

Environmental Research Web, by Liz Kalaugher: Nitrogen from fertilizer applied to corn (maize) fields in the US midwest enters the Mississippi and Atchafalaya rivers and flows into the Gulf of Mexico. It’s been implicated in causing the "dead zone" that appears in the gulf each summer – an area of low oxygen that kills organisms living on the seafloor. Now, scientists in North America say that the increase in corn cultivation needed to meet targets for renewable fuels in the US Energy Bill could increase the annual flux of dissolved inorganic nitrogen to the gulf by as much as one-third.

"We found that meeting the ethanol production targets set for the year 2022 in the Energy Policy will increase nitrogen levels in the Mississippi by 10-34%," Simon Donner of the University of British Columbia told environmentalresearchweb. "This will make the already difficult challenge of reducing the 'dead zone' practically impossible."

…When nitrogen from agricultural fertilizers enters the ocean via this river system it boosts the growth of phytoplankton. As these organisms die, they accumulate at the bottom of the ocean, where their decomposition can lower the oxygen concentration to dangerous levels. This hypoxia creates a "dead zone", killing marine organisms such as crabs, fish, anemones and sea stars. The result has serious implications not only for ecosystems but also for the fishing industry. In recent years the dead zone in the Gulf of Mexico has been more than 20,000 km2 in size. The Mississippi Basin/Gulf of Mexico Task Force hopes to reduce the zone to less than 5000 km2 but recent research indicates this could need a reduction in nitrogen export of up to 55%.

"However, the new US Energy Policy calls for a huge increase in the production of ethanol from corn," said Donner. "If the US pursues this biofuels strategy, there is little hope for reducing the dead zone. The only way to meet the corn ethanol goals and shrink the dead zone to an acceptable size will be to dramatically reduce the non-ethanol uses of corn. That means less animal feed: the US will face a choice between using corn to fuel animals, and using corn to fuel cars."

…"Even with reductions in other uses of corn, the construction of efficient riparian [river-side] wetlands adjacent to fertilized croplands and the implementation of on-farm nitrogen management practices will be necessary to achieve the large reduction in nitrogen loading required," write the researchers in a paper in PNAS. "A massive national wetland restoration project, on the order of 22,000 km2 of wetlands and/or widespread adoptions of efficient nitrogen management practices, like a change in diet and meat production, would not be trivial to implement."…

The dead zone from the Mississippi River basin, Environmental Protection Agency, Wikimedia Commons