The unexpectedly large nitrogen footprint of Australians

Xia Liang1, Allison M. Leach2, James N. Galloway3, Baojing Gu4,5, Shu Kee Lam1, Deli Chen1

1 Crop and Soil Science Section, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria 3010, Australia. E-mail: [email protected]

2 Department of Natural Resources & Earth Systems Science and The Sustainability Institute, University of New Hampshire, 107 Nesmith Hall, 131 Main Street, Durham, NH, 03824, USA.

3 Department of Environmental Sciences, University of Virginia, Clark Hall, 291 McCormick Road, P.O. Box 400123, Charlottesville, VA 22904-4123, USA

4 Department of Land Management, Zhejiang University, Hangzhou 310058, PR China

5 Policy Simulation Laboratory, Zhejiang University, Hangzhou 310058, PR China

Abstract

Anthropogenic release of reactive nitrogen (Nr; all species of N except N2) to the global nitrogen (N) cycle is substantial and it negatively affects human and ecosystem health. A novel metric, the N footprint, provides a consumer-based perspective for N use efficiency and connects lifestyle choices with N losses. Here we report the first full-scale assessment of the anthropogenic Nr loss by Australians. Despite its ‘clean and green’ image, Australia has the largest N footprint (47 kg N cap-1 yr-1) both in food and energy sectors among all countries that have used the N-Calculator model. About 69% of the Australia’s N footprint is attributed to food production and consumption, with the rest from energy consumption. Beef consumption and production is the major contributor of the high food N footprint, while the heavy dependence on coal for electricity explains the large energy N footprint. Our study demonstrates opportunities for managing N loss and lifestyle choices to reduce the N footprint.