Understanding the interrelations between food consumption and the preservation of natural resources in urban food systems

We evaluated the environmental sustainability of local agricultural production within two urban food systems comprising two medium-sized cities in Southern Germany by considering the susceptibility of the local ecosystem and compared supply from local agriculture under different production intensities with demand in the two cities. We took the nitrogen (N) surplus target per hectare of agricultural land from the German Sustainable Development Strategy, which builds on the UN Sustainable Development Goals, as a measure for ecosystem carrying capacity to derive a scenario for a site-adapted local agricultural production intensity. Using life cycle assessment, we calculated environmental impacts for the prevalent commodities produced within agriculture surrounding the cities of the studied urban food systems. Impacts were related to kg of protein from the overall agricultural output. Further we related protein supply from local agriculture within the urban food systems under the different production intensities to protein demand in the cities based on available consumption data. Adopting local agricultural production intensity towards the N surplus target within the defined regions around the cities substantially reduced environmental impacts per kg of protein from local agriculture for all impact categories compared to the present production intensity. Under a siteadapted production intensity local agriculture would still be able to supply protein demand in the cities of the urban food systems. However, a shift from an animal protein-based to a more plant protein-based diet would be required to make the urban food systems overall more sustainable