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Agriculture and future riverine nitrogen export to US coastal regions: Insights from the Nutrient Export from WaterSheds Model
Citation:
McCrackin, M., J. Harrison, AND J. Compton. Agriculture and future riverine nitrogen export to US coastal regions: Insights from the Nutrient Export from WaterSheds Model. Presented at Soil Science Society of America, Kansas City, Mo, August 13 - 15, 2013.
Impact/Purpose:
Nitrogen release to the environment from fossil fuel combustion and agriculture has important environmental impacts, particularly the eutrophication of coastal waters with associated “dead zones” and harmful algal blooms. Post-doctoral scientist Michelle McCrackin from the National Research Council and colleagues at Washington State University and US EPA have examined the predictions of future nitrogen inputs to the coastal zone based on scenarios of land use and population growth developed by the Millennium Ecosystem Assessment and also two additional scenarios that reflect “business as usual” and “ambitious” approaches to nutrient management. Their analysis suggests that reducing coastal N loads will require aggressive management action to control agricultural N. Under “business as usual” approaches, population-driven increases in crop production increase coastal N loads by 20% (to 2.5 Tg N y-1). Without widespread improvement in agricultural N management, N-induced coastal eutrophication will continue to be a problem for many US coastal areas.
Description:
We examine contemporary (2000) and future (2030) estimates of coastal N loads in the continental US by the Nutrient Export from WaterSheds (NEWS) model. Future estimates are based on Millennium Ecosystem Assessment (MEA) scenarios and two additional scenarios that reflect “business as usual” and “ambitious” approaches to nutrient management. Fertilizer recovery efficiencies (as percent of N-inputs recovered in aboveground plant biomass) are 48%, 48%, 57-63%, and 70% for year 2000 conditions, “ambitious”, MEA, and “business as usual” scenarios, respectively. Modeled total dissolved nitrogen (TDN) export is 2.1 Tg N y-1 in 2000 and ranges from 1.4-2.5 Tg N y-1 in 2030, depending on scenario. Agriculture is the largest source of coastal TDN, representing 32-51% of riverine export. Other sources of TDN include atmospheric N deposition (7-10% of total, depending on scenario), human sewage (9-14%), and N-fixation on non-agricultural land (28-50%). Our analysis suggests that reducing coastal N loads will require aggressive management action to control agricultural N. Under “business as usual” approaches, population-driven increases in crop production increase coastal N loads by 20% (to 2.5 Tg N y-1). Under MEA scenarios, moderate improvements in fertilizer recovery efficiency result in coastal N loads that are relatively unchanged from 2000 (2-2.1 Tg N y-1) despite population growth. In the “ambitious” scenario, coastal N loads decrease 33% in 2030 (to 1.4 Tg N y-1). Fertilizer recovery efficiencies reflected in the MEA and “ambitious” scenarios have not yet been achieved on production scales. Without widespread improvement in agricultural N management, N-induced coastal eutrophication will continue to be a problem for many US coastal areas.