The increase in corn cultivation in the United States is partly due to the increase in the demand for corn-based biofuels (i.e., corn ethanol). One of the effects of increased corn cultivation is the increased level of fertilizer use. Fertilizer application in corn fields in the Midwestern United States is said to be a “primary source of nitrogen that is exported to the Gulf of Mexico by the Mississippi and Atchafalaya Rivers”. The high levels of nitrogen, in the form of nitrates are causing the development of extensive (> 20,000 km²) hypoxic zones (areas of low oxygen concentration leading to stress/death in aquatic organisms) in the Gulf of Mexico. In an effort to reduce the annual spread of hypoxic zones to less than 5,000 km², the Mississippi Basin/Gulf of Mexico Task Force has set a target of reducing nitrogen export by the Mississippi and Atchafalaya Rivers by 30%. However, a recent study by Simon Donner and Christopher Kucharik showed that “the increase in corn cultivation to meet the goal of 15-35 billion gallons of renewable fuels by 2002”, would “increase the flux of dissolved inorganic nitrogen (DIN) export by the Mississippi and Atchafalaya Rivers by 10–34%”. Through the use of simulation models, they showed that meeting the 15-billion-gallon-biofuel target would make “the already difficult challenges of reducing nitrogen export to the Gulf of Mexico practically impossible without large shifts in food production and agricultural management”..