Assessing the Geographical Variability and Reduction Potential of the Nitrogen Footprint of a Community: A Case Study in Charlottesville, Virginia

Nitrogen (N) is imperative for life on earth, but excess reactive nitrogen can have harmful effects on marine and terrestrial environments, the atmosphere, and human health. Anthropogenic creation of reactive N (Nr; all N species but N2) and subsequent inputs to the environment are largely associated with agricultural production and fossil fuel combustion. While many efforts have been made to decrease N losses to the environment at the production end in both the food and energy sectors, fewer efforts focus on the impacts of consumer choices. This study focuses on how a consumer can impact their community’s contributions to N pollution, and provides a tool to manage that pollution. The community nitrogen footprint tool (NFT) is a metric created to track the impact of a community on excess Nr released to the environment. Applying the community NFT to Charlottesville City for 2017, the total N footprint, local N footprint, and per capita N footprint, were estimated to be 1,400 metric tons (MT) N, 114 MT N, and 30.0 kg N, lower than the US average, respectively. Great geographical variability in the per capita N footprint within Charlottesville City was found, which correlated positively with median household income (p = 0.01) and the proportion of the population that is white (p = 0.01). This result adds evidence from a local context to support the theory that socioeconomically advantaged populations contribute more to local and global environmental change. Census block groups within Charlottesville City which have a higher N footprint have greater opportunities for reduction, and potential changes in consumer choices, influenced by government planning decisions, were examined. It was found that reductions in beef and overall protein consumption could lead to the greatest reduction in total N footprint, and changes in personal transportation could lead to the greatest reduction in the local N footprint.