National and watershed-scale damages from the release of nitrogen beyond the farm, factory, tailpipe and table

Background/Question/Methods

Human demand for food, fuel, and industrial products results in the release of 61% of newly fixed anthropogenic N to the environment in the US each year. This 15.8 Tg N yr^-1 release to air, land and water has important social, economic and environmental consequences, yet little research clearly links this N release to the full suite of effects. Here we connect the biogeochemical fluxes of N with existing data on N-associated damages in order to quantify the externalities of N release related to human health, ecosystems and climate regulation for the US at national and watershed scales. Release of N to the environment was estimated 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).

Results/Conclusions

We use these estimates of N loss from human uses with information on cost of nitrogen in various forms across the N cascade in order to estimate annual damage cost ($USD in 2008 or as reported) of anthropogenic N leaked to the environment by scaling specific N losses with the costs associated with human health, agriculture, ecosystems, and the climate system. Eutrophication of freshwater ecosystems and respiratory effects of atmospheric N pollution were important across HUC8s. Significant data gaps remain in our ability to fully assess N damages, such as damage costs from harmful algal blooms and drinking water contamination. Nationally, potential health and environmental damages of anthropogenic N in the early 2000s totaled $210 billion yr⁻¹ USD (range: $81–$441 billion yr⁻¹).  While a number of gaps and uncertainties remain in these estimates, overall this work represents a starting point to inform decisions and engage stakeholders on the costs of N pollution.