Options for reducing a city's global biodiversity footprint - The case of food consumption in Vienna

Urban food consumption contributes significantly to global biodiversity loss. To ensure a sustainable food supply for the growing urban population a transformation of food production and consumption patterns is necessary. Here, options for reducing the food -related biodiversity footprint of Vienna (Austria), a high -income city in Europe were assessed regarding measures of product substitution, demand reduction through avoidance of waste and caloric overconsumption and a shift from imports to domestic production. The biodiversity footprints of 24 food consumption patterns were calculated with a life -cycle -assessment approach applying country- and primary biomass -specific factors for vertebrate species loss derived from a high -resolution global countryside speciesarea -relationship model that incorporates land -use intensity and spatially -explicit information on Vienna's source regions. Compared to the baseline food consumption in Vienna of 2010, diets with less animal products could reduce the footprint by 21%-43%, while waste reduction and adhering to the recommended caloric intake could reduce the footprint by 5% and 9%, respectively. Decreasing the demand for primary biomass under alternative diets could also free up domestic cropland and allow for reducing imports and relocating production from abroad to Austria. This could reduce Vienna's biodiversity footprint additionally by 5%-21%, depending on diet and demand level, due to comparatively higher yields and lower native species richness in Austria. Results further indicate that shifting towards a vegetarian diet requires the least product substitution per footprint reduction among the examined alternative diets. Substituting animal products with plant -based alternatives from area -efficient production systems located outside of biodiversity hotspots emerges as a promising strategy for Western cities to reduce their biodiversity footprint.