Urban dwellers depend on the generation of ecosystem services for their welfare. The city of Stockholm is growing, and a 25% increase in population is projected by 2030. The effects of urban development were estimated through the quantification of nitrogen (N) leakage to the Baltic Sea under two urban development scenarios. We found that total net N load will increase by 6% or 8%, depending on which growth scenario is applied, and population increase by itself will contribute at least 15% of the point source N leakage. Technical improvements in sewage treatment could, according to our results, decrease total N load to the Baltic Sea by 4%. Based on our results, we conclude that proactive measures such as spatial urban planning can provide a constructive tool for sustainable urban development on regional as well as national and international scales, depending on geographical context as well as the ecosystem services' scale of operation.