Managing nitrogen to keep food production within environmental limits
Nitrogen is an essential nutrient for crop production, but excess nitrogen lost from crop and animal production has detrimental effects on the environment and human health. Sustainable nitrogen management thus require finding the right balance between nitrogen’s benefits for crop yields and its environmental externalities. This thesis describes the further development and application of spatially explicit models to assess trade-offs in nitrogen management in Europe and globally. It presents spatially explicit boundaries for agricultural nitrogen inputs and losses in view of several environmental impacts: biodiversity loss resulting from nitrogen emissions and re-deposition onto terrestrial ecosystems, eutrophication of aquatic ecosystems caused by nitrogen runoff, and groundwater contamination through nitrate leaching. Furthermore, the climatic impact of anthropogenic nitrogen use is quantified by estimating how much additional carbon is stored in forests due to nitrogen deposition. Results show that nitrogen losses in Europe and globally need to be reduced substantially to respect environmental thresholds, unless nitrogen management is improved. However, in some regions nitrogen inputs can still increase before thresholds are exceeded. Spatially explicit information on various nitrogen indicators provided in this thesis can be used to support policy making for sustainable nitrogen management in Europe and globally.