Gulf dead zone may grow due to flood

Washington-As flood waters recede from communities and farmland along the upper Mississippi River, scientists fear a surge of nutrient runoff flowing down the Mississippi to the Gulf of Mexico will dramatically increase the size of the hypoxic zone this summer, similar to circumstances that were observed in the wake of the historic 1993 flood. Some scientists estimate that the dead zone in the Gulf may cover more than 10,000 square miles this summer, compared with 7,900 miles in 2007, and many blame the heavier fertilizer load brought down by the flooding river as the primary cause. Steven DiMarco, a professor of oceanography at Texas A&M University, was quoted as saying that nitrates from fertilizer runoff are not the only culprit, however. DiMarco said the massive amount of floodwater helps trap oxygen-depleted water near the Gulf floor, while less dense water stays near the surface and keeps oxygen from reaching the lower dead zone waters. Kathy Mathers of The Fertilizer Institute noted as well that “fertilizer is not the only source of nutrients, and livestock waste and wastewater treatment plants are just as likely to be sources.” Mathers told Green Markets that increased water flows still represent the strongest correlation to the size of the hypoxic zone, and water quality concerns are likely to follow flooding events that bring lots of sediment and other materials down the river. She noted, however, that a recent paper published by the International Plant Nutrition Institute found good reason to believe that significant declines in nitrogen discharges to the Gulf are proceeding through voluntary measures being taken by farmers. In other flood-related news, the Alliance for Agricultural Growth and Competitiveness (AAGC) urged USDA Secretary Edward T. Schafer to grant penalty-free early releases from the Conservation Reserve Program (CRP) for non-environmentally sensitive cropland. AAGC said the crop losses caused by the flood have “eroded the outlook for grain and oilseed stocks and prices in this crop year and beyond.” AAGC, representing some 130 agricultural organizations, sent a letter to Shafer on June 25 claiming that “an early-out, penalty-free release of non-environmentally sensitive CRP cropland would be a significant positive step to encourage increased supply which would allow producers to more fully benefit from strong market demand.” AAGC applauded Schafer’s decision to allow penalty-free haying and grazing on certain CRP land, but said that alone “will not adequately alleviate the direct pressure on the livestock industry or the increased feed cost pressures on other segments of agriculture and food industries.”