Urban Land Use and Food Supply: the Example of Vienna

Since 2008 more than half of the world's population live in cities and in 2050 it will be more than two thirds. Urbanization increases not only the cities themselves, but also their responsibility to provide a `Good Life for All´ within planetary boundaries. Global agreements such as the Paris Climate Agreement, the UN Sustainable Development Goals or the Biodiversity Charter underpin and secure these aspirations. While 55% of the global population live in urban areas, it is estimated that 1-3% of world´s land is urbanized. Hence, cities are characterised by land scarcity and urban land use conflicts crystallize around issues such as food production, housing, recreational areas or transport infrastructure. Nevertheless, soil and its biological productivity through photosynthesis is the prerequisite of every life on this planet and urban land use does not end at the city gates: food is just one example of how the city is connected to its hinterland, nation, and to the rest of the world. Their supply with agricultural products is feeding the city, but also connects it with both social and ecological impacts on people (e.g. farmers) and the environment at the place of production resp. processing. From this point of view, the responsibility of urban areas as consumption `hotspots´ does not end at their city borders. Recently, a broader awareness of environmental impacts by consumed goods could be observed. An important contributor here is the communication and visualization of footprints, which are sustainability indicators that quantify resource use or ecological consequences of certain products. Some well-known examples are probably the ecological footprint, which measures the biologically productive area required, resource footprints for water and land or the carbon footprint, which illustrates the greenhouse gas emissions associated with the consumption of a product or lifestyle. Especially in the context of cities, contrasting consumption and production-based accountings has been proved to provide important insights for options to reduce ecological impacts of cities. In the course of the IN-SOURCE project, we quantify urban land use intensities both inside and outside of city borders applying the concept of HANPP (Human Appropriation of Net Primary Production) as a further environmental footprint indicator. HANPP measures the depth of human interventions into the biological productivity of ecosystems. Net primary production (NPP) is the amount of biomass produced by the process of photosynthesis minus the plants' own energetic requirements in an ecosystem. Human appropriation of NPP occurs through two distinct processes: first, land cover/use change (e.g., from forest to cropland, HANPPluc) alters ecological patterns and processes, including NPP, and second, via agricultural and forestry harvest, biomass is removed from ecosystems (HANPPharv). HANPP can be calculated for territorial units, e.g. cities or nations, and it also allows to relate the land use intensity of cities within their borders with impacts beyond. In this contribution, we focus on impacts associated with urban food supply in order to contextualize and explore these impacts within the urban food-water-energy nexus (FWE nexus). In IN-SOURCE, we developed the HANPP Explorer as an interactive web application, which enables stakeholders and other practitioners to access insights from this research and interactively explore the topic. The HANPP Explorer intends to provide knowledge of the manifold dimensions of urban food, thereby gaining new perspectives on urban land use and opening up possible future developments for discussion.