title: Cost-effective targeting of conservation investments to reduce the northern Gulf of Mexico hypoxic zone.
abstract: A seasonally occurring summer hypoxic (low oxygen) zone in the northern Gulf of Mexico is the second largest in the world. Reductions in nutrients from agricultural cropland in its watershed are needed to reduce the hypoxic zone size to the national policy goal of 5,000 km(2) (as a 5-y running average) set by the national Gulf of Mexico Task Force's Action Plan. We develop an integrated assessment model linking the water quality effects of cropland conservation investment decisions on the more than 550 agricultural subwatersheds that deliver nutrients into the Gulf with a hypoxic zone model. We use this integrated assessment model to identify the most cost-effective subwatersheds to target for cropland conservation investments. We consider targeting of the location (which subwatersheds to treat) and the extent of conservation investment to undertake (how much cropland within a subwatershed to treat). We use process models to simulate the dynamics of the effects of cropland conservation investments on nutrient delivery to the Gulf and use an evolutionary algorithm to solve the optimization problem. Model results suggest that by targeting cropland conservation investments to the most cost-effective location and extent of coverage, the Action Plan goal of 5,000 km(2) can be achieved at a cost of $2.7 billion annually. A large set of cost-hypoxia tradeoffs is developed, ranging from the baseline to the nontargeted adoption of the most aggressive cropland conservation investments in all subwatersheds (estimated to reduce the hypoxic zone to less than 3,000 km(2) at a cost of $5.6 billion annually).
authors.affiliation: School of Environmental and Forest Sciences, University of Washington, Seattle, WA 98195-2100; rabotyag@uw.edu.
authors.forename: Sergey S
authors.initials: SS
authors.lastname: Rabotyagov
authors.affiliation: Center for Agricultural and Rural Development, Department of Economics, Iowa State University, Ames, IA 50011;
authors.forename: Todd D
authors.initials: TD
authors.lastname: Campbell
authors.affiliation: Grassland, Soil and Water Research Laboratory, US Department of Agriculture-Agricultural Research Service, Temple, TX 76502;
authors.forename: Michael
authors.initials: M
authors.lastname: White
authors.affiliation: Grassland, Soil and Water Research Laboratory, US Department of Agriculture-Agricultural Research Service, Temple, TX 76502;
authors.forename: Jeffrey G
authors.initials: JG
authors.lastname: Arnold
authors.affiliation: Soil Science and Resource Assessment Division, US Department of Agriculture-Natural Resources Conservation Service, Temple, TX 76502;
authors.forename: Jay
authors.initials: J
authors.lastname: Atwood
authors.affiliation: Soil Science and Resource Assessment Division, US Department of Agriculture-Natural Resources Conservation Service, Temple, TX 76502;
authors.forename: M Lee
authors.initials: ML
authors.lastname: Norfleet
authors.affiliation: Center for Agricultural and Rural Development, Department of Economics, Iowa State University, Ames, IA 50011;
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Kling
authors.affiliation: Center for Agricultural and Rural Development, Department of Economics, Iowa State University, Ames, IA 50011;
authors.forename: Philip W
authors.initials: PW
authors.lastname: Gassman
authors.affiliation: Center for Agricultural and Rural Development, Department of Economics, Iowa State University, Ames, IA 50011;
authors.forename: Adriana
authors.initials: A
authors.lastname: Valcu
authors.affiliation: School of Environmental and Forest Sciences, University of Washington, Seattle, WA 98195-2100;
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Richardson
authors.affiliation: Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA 70803; and.
authors.forename: R Eugene
authors.initials: RE
authors.lastname: Turner
authors.affiliation: Louisiana Universities Marine Consortium, Chauvin, LA 70344.
authors.forename: Nancy N
authors.initials: NN
authors.lastname: Rabalais
keywords: Gulf of Mexico; agricultural conservation practices; eutrophication; evolutionary computation; hypoxic zone