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Abstract

News U.S. taxpayers are, in effect, subsidizing the Gulf of Mexico's dead zone, an area of coastal waters where dissolvedoxygen concentrations fall to less than 2 parts per million every summer, according to a new paper published in ES&T (pp 5410-5418). These findings don't bode well for the Gulf, as more and more acres of land are planted with corn to meet the growing U.S. demand for alternative fuels.Scientists studying nutrient inputs that feed the Gulf's hypoxic zone have known that certain intensively farmed areas in the upper Midwest leak more nitrogen derived from fertilizers than others. Now, there's a new twist. Farmers in areas with the highest rates of fertilizer runoff tend to receive the biggest payouts in federal crop subsidies, says Mary Booth, lead author of the paper and a former senior scientist with the Environmental Working Group. What's more, they have fewer acres enrolled in conservation programs compared with other parts of the Mississippi River basin (MRB).Modeling the major sources of nitrate in the MRB, Booth and her colleagues found that fertilizer runoff is responsible for 59% of springtime nitrate loading to the Gulf, atmospheric deposition for 17%, animal waste for 13%, and municipal wastewater for 11%.These findings are consistent with earlier analyses but go a step further by homing in on the seasonal aspects of nitrogen flux rather than annual loading, says Richard Alexander, with the U.S. Geological Survey. "Spring flux is what matters most in predicting the formation of the [Gulf's] hypoxia zone," he adds.Booth's team added data from NaNcy R abal ais, louisiaNa uNiveRsities MaRiNe coNsoRtiuM