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Cost of reactive nitrogen release from human activities to the environment in the United States
Citation:
Sobota, D., J. Compton, M. McCrackin, AND S. Singh. Cost of reactive nitrogen release from human activities to the environment in the United States. Environmental Research Letters. IOP Publishing LIMITED, Bristol, Uk, 10:13 pages, (2015).
Impact/Purpose:
Human needs for food, fuel, and industrial products require the intentional fixation of dinitrogen from the atmosphere, converting nitrogen into forms that can be used by most plants and animals. Unfortunately, nitrogen is not completely used up in producing food, fuel and consumer goods. Approximately 60 percent of the fixed anthropogenic N leaks back into US air, land and waterways where it can cause respiratory problems, drinking water contamination, and eutrophication and contributes to climate change and ozone depletion. Former ORISE post-doc Dan Sobota along with EPA researcher Jana Compton and other colleagues working with EPA tracked this leaked nitrogen into the environment in order to account for the damages to social, economic and environmental systems. For the US, annual damage costs of anthropogenic N leaked to the environment in 2000 totaled $289 billion USD, which is 2% of current Gross Domestic Product and is comparable to annual gross farm profits in the US. Over half of the damages were associated with fossil fuel combustion, because N released from those activities can cause respiratory illness that results in hospital visits and deaths. It is possible, however, to reduce these impacts by making tangible improvements in atmospheric emissions, agricultural N use, food production and wastewater treatment. This analysis provides a starting point to improve N management at watershed, regional, and national scales in the US by allowing stakeholders to illustrate the benefits associated with targeted N reductions by source or sector.
Description:
The leakage of reactive nitrogen (N) from human activities to the environment can cause human health and ecological problems. Often these harmful effects are not reflected in the costs of food, fuel, and fiber that derive from N use. Spatial analyses of economic costs and benefits at management-relevant scales could inform decisions in areas where leakage of anthropogenic N to the environment causes harm. We used recently compiled data describing watershed-level N inputs in the conterminous United States (US) to assess damage costs associated with specific anthropogenic N sources. To do this, we estimated fates of N leaked to the environment (air/deposition, surface freshwater, groundwater, and coastal zones) circa 2000 with models describing N inputs by source, nutrient uptake efficiency, leaching losses, and gaseous emissions at the scale of 8-digit US Geologic Survey Hydrologic Unit Codes (HUC8s). We estimated annual damage cost (US dollars in 2008 or as reported) of anthropogenic N leaked to the environment per HUC8 by scaling specific N inputs and leakages (per kg of N) with mitigation, remediation, direct damage, and substitution costs associated with human health, agriculture, ecosystems, and the climate system. Estimates of environmental N loss by HUC8 ranged from <1 kg N/ha/yr to 125 kg N/ha/yr, with most N leaked to surface freshwater ecosystems. Estimates of currently-available damage costs ranged from $2.52/ha/yr to $3,240/ha/yr among watersheds, with a median of $317/ha/yr, with eutrophication of freshwater ecosystems and respiratory effects of atmospheric N pollution most important across HUC8s. However, significant data gaps remain in our ability to fully assess N damage costs, such as the damages associated with harmful algal blooms or drinking water contamination. Nationally, annual damage costs of anthropogenic N leaked to the environment for 2000 totaled $289 billion, compared against $40 billion in net farm profits. Efforts to improve N use efficiency and reduce the demand for N fixation in a number of agricultural and industrial sectors could reduce these damages.
