Reducing Nutrient Losses From Cropland in the Mississippi/Atchafalaya River Basin: Cost Efficiency and Regional Distribution

Every summer, a “hypoxic zone” in the Gulf of Mexico (dissolved oxygen too low for many aquatic species to survive) is fueled by nutrient (nitrogen and phosphorus) runoff from the Mississippi/Atchafalaya River Basin (MARB), most of which comes from agriculture. This report assesses the most cost-effective way of achieving a 45-percent reduction in cropland nutrient loads to the Gulf. While the largest baseline contributors to nitrogen deliveries to the Gulf are the Ohio and Upper Mississippi Basins, with more than 60 percent of baseline nitrogen loadings, the Lower Mississippi accounts for more than 43 percent of N and P load reductions to the Gulf under a cost-effective strategy for hypoxia control. Costs per unit of nutrient reduction are lower here than in other regions, in part because of proximity to the Gulf and less opportunity for instream removals of N and P as nutrients flow to the Gulf.