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Future riverine nitrogen export to US coastal regions: Prospects for improving water quality considering population growth
Citation:
McCrackin, M., J. Compton, AND J. Harrison. Future riverine nitrogen export to US coastal regions: Prospects for improving water quality considering population growth. JOURNAL OF ENVIRONMENTAL QUALITY. American Society of Agronomy, MADISON, WI, 44(2):345-355, (2015).
Impact/Purpose:
Growing human needs for food and energy have dramatically increased the rate at which nitrogen is released to the environment during the last century. Nitrogen release from fossil fuel combustion and agriculture has important environmental impacts, particularly the eutrophication of coastal waters with associated “dead zones” and harmful algal blooms. 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 achieving reductions in coastal N loading will require aggressive management actions. Depending on year and scenario, agriculture supplies 25-43% of coastal TN, atmospheric N deposition 6-8%, human sewage 6-12%, and natural and particulate N sources account for the remainder. Export of nitrogen to US coastal areas could be reduced 22% between 2000 and 2030 if currently available best management practices and technologies are fully implemented to control N from agriculture, fossil fuel emissions, and wastewater release. If N management does not improve by 2030, coastal N loads could increase by 20% during this time period, due primarily to increases in N from agriculture and sewage. Without these improvements, eutrophication will likely continue to be an issue for US coastal areas, and may worsen in some areas.
Description:
Excess nitrogen (N) in the environment degrades ecosystems and adversely affects human health. Here we examine predictions of contemporary (2000) and future (2030) coastal N loading in the continental US by the Nutrient Export from WaterSheds (NEWS) model. Future output is from storylines of the Millennium Ecosystem Assessment (MEA) and two additional scenarios that reflect “business as usual” and “ambitious” approaches to nutrient management. Modeled total nitrogen (TN) export by rivers to US coastal areas ranged between 2.5 Tg N y-1 in 2000 and 1.9 - 3.0 Tg N y-1 in 2030, depending on scenario. Differences among scenarios reflect the interactions of increased food and energy demands associated with population growth and efforts to reduce losses of N to the environment. Depending on year and scenario, agriculture supplies 25-43% of coastal TN, atmospheric N deposition 6-8%, human sewage 6-12%, and natural and particulate N sources account for the remainder. Our analysis suggests that achieving reductions in coastal N loading will require aggressive management actions. Coastal TN export could be reduced 22% between 2000 and 2030 to 1.9 Tg N y-1 if currently available best management practices and technologies are fully implemented to control N from agriculture, fossil fuel emissions, and wastewater effluent. If N management capabilities do not improve by 2030, coastal N loads could increase 20% to 3.0 Tg N y-1, due primarily to increases in N from agriculture and sewage. As a result, eutrophication will likely continue to be an issue for US coastal areas, and could even worsen in some regions.
URLs/Downloads:
Future riverine nitrogen export to US coastal regions: Prospects for improving water quality considering population growth