PhD Student: Maria Susana Orta Ortiz
Supervisor: prof. Davide Geneletti
Nowadays, cities face several challenges that threaten urban resilience and citizens' quality of life and well-being. For example, they have to deal with the effects of climate change, the rapid and increasing urbanization, the degradation of urban and peri-urban ecosystems, environmental pollution, social inequity, and environmental injustices, human health issues, flood risks, and food insecurity (European Commission, 2015). Nature-based solutions (NbS) have been proposed as a sustainable way to address such challenges by aligning social and economic development goals with nature and biodiversity conservation (E. Cohen-Shacham et al., 2016). These solutions leverage the benefits that people gain from ecosystems (i.e., ecosystem services, (ES)) and include all those actions aimed to create, restore, or preserve ecosystems. Some examples include river and wetland restoration to manage urban stormwater, the conversion of brownfield into urban parks for microclimate regulation and the enhancement of recreational activities, and the creation of street trees and conservation of forest patches to improve urban air quality. Considering the growing support of NbS from policy agendas, my doctorate aims to enhance the current knowledge about the advantages and disadvantages of the NbS approach for city planning in economic, social, and environmental terms.
In the initial months, I investigated through a literature review approach, the design variables of NbS that impact on the hydrological and pollutant control performance. These variables relate to vegetation, soil, physical and location features that support the NbS design at different levels of detail. The review provides designers with qualitative and quantitative data on how design choices will affect the functioning and provision of runoff mitigation and water purification. It also highlights the trade-offs among NbS functions associated with specific design variables and further discusses the strategies that can be adopted to address them and properly target specific stormwater management goals. Moreover, to avoid underestimating benefits for stormwater management, the results indicate suitable indicators to quantify water-related services according to NbS types.
Currently, I am assessing the cumulative benefits that people can obtain if NbS are replicated, spread, and scaled up from local scale (e.g., punctual greening interventions in few urban blocks), to neighborhood scale (e.g., planting trees in a great part of neighborhood streets and converting all suitable rooftops into vegetated one) and, ultimately, the whole city. Specifically, I am examining the effects that scale and NbS location have on the supply of ES compared to their demand. We conduct this assessment using the case study of Las Palmas de Gran Canarias, Spain, focusing on several services that have already been identified as relevant in the urban development plans and documents by the local authorities. Expected results will show the curve of benefits across scales and possible breaking points of the trend; for example, when supplied services are not proportional to the reduced demand, any social and environmental benefits will not compensate for the additional investment to upscale NbS. Based on this information, we will discuss the key elements that enhance the effectiveness of upscaling NbS to address multiple urban challenges.
 E. Cohen-Shacham, Walters, G., Janzen, C., Maginnis, S., 2016. Nature-based Solutions to address global societal challenges.
 European Commission, 2015. Towards an EU Research and Innovation policy agenda for Nature-Based Solutions & Re-Naturing Cities.