A decision approach to evaluate the design and implementation of green infrastructures in urban environments

Abstract: Cities are implementing green infrastructures (GI) to address societal challenges such as climate change mitigation, natural disaster adaptation, and food security. However, we lack the tools and understanding to systematically address the trade-offs and synergies that GIs can create in urban environments (e.g., a GI implemented for improving urban resilience can create or exacerbate inequalities). We propose the Integrated System Analysis of Urban Vegetation and Agriculture (URBAG): an interdisciplinary and participatory decision approach that is geographically explicit to evaluate the design and implementation of green infrastructures in urban environments. It is founded on multi-criteria decision analysis and compares the urban space with and without the GI by employing both exposure and sensitivity analyses. The framework has four phases: 1) Defining the aim, scope, and scale of the assessment (2) Selecting criteria and indicators that line up with the aim of the assessment for the GI, (3) calculating the indicators, and (4) analyzing and determining the impacts according to the weights selected by relevant stakeholders. To illustrate URBAG, we assess various scenarios of peri-urban agriculture in the Metropolitan Area of Barcelona with the overall aim to increase local crop production, restore abandoned lands, and reduce heat wave effects. For the assessment, four criteria were analyzed: (1) Heat Conditions and Exposure, (2) Spaces for cultural and recreational experiences, (3) Food self-sufficiency and (4) Environmental impacts of fertilizer use. The indicators were temporally and geographically determined based on atmospheric model simulations and life cycle assessment. Results showed that an increase in agricultural areas can reduce daytime temperature during heatwaves (up to 1.7ºC), and how these reductions where partially located in areas with large elderly populations, a vulnerable group to heat exposure. The accessibility to green spaces for recreational experiences was also improved by the increase of agricultural areas, but most of these new accessibilities were not located in sensitive areas with high population density. In the case of food self-sufficiency, the scenario with the greatest agricultural area is expected to meet up to 12.8% of the fresh produce demand of the city, while the crop production location does not match the areas with the highest demand of food within the city. Finally, freshwater eutrophication associated to increased fertilizer use due to more agriculture proved insignificant because of the very low value of P equivalent emitted due to short river segments, but the biodiversity indicator points out a significant exposure in already mid-low biodiversity river basins. This case study illustrates the usefulness of URBAG in analyzing the spatial distribution of the impacts of green infrastructure and how it affects the environment and sensitive populations, transferring the scientific knowledge to urban policy and governance for successful GI implementation.

Angelica Mendoza presented a poster entitled “Can circular strategies contribute to sustainable food production in cities? The case of nutrients circulation for urban agriculture in a metropolitan area”. This work focuses on nutrient circulation strategies for urban agriculture using prospective-regionalized Life Cycle Assessment. Angelica evaluates the direct and indirect impacts such as climate change and eutrophication of potential future expansion of urban agriculture.

Can circular strategies contribute to sustainable food production in cities? The case of nutrients circulation for urban agriculture in a metropolitan area

Abstract: Cities will require several transformations to become more resilient, sustainable and multifunctional systems, especially in terms of provision of food. In this study, we attempt to determine to what extent circular strategies can help in the sustainability of future food production of metropolitan areas. In particular we focus on nutrient circulation strategies and further assess theoretical transition scenarios for urban agriculture (UA) using prospective-regionalized LCA integrating knowledge from previous studies on urban land use, nutrients recovery from municipal sources, regionalized LCA of UA and prospective LCA. We apply this approach to the Metropolitan Area of Barcelona (AMB) to evaluate the direct and indirect impacts such as climate change and eutrophication of potential future expansion of urban agriculture as proposed by the urban master plan using the functional unit of yearly total crop production. The various nutrient circularity scenarios proposed include the use of struvite from waste water treatment plants and compost from domestic organic waste. Results show that in light of future resource restrictions, circular nutrient strategies will have an increasingly important role in cities to supply nutrients for urban crop production while reducing impacts associated to UA. However, they need to be considered in terms of their life cycle as alternatives to mineral sources of nutrients and as a reduction in waste management to see the environmental benefits of UA.