Assessing the spatial and temporal distribution of nature-based solutions benefits. Combining economic valuation, participatory GIS and stakeholder perspectives

This thesis investigates how the spatial and temporal dynamics of nature-based solutions (NBS)—in particular the distribution of their benefits across space and time—shape their economic valuation, stakeholder perceptions, and public acceptability. While NBS are known to deliver benefits that vary across locations and over time, these dimensions have so far received limited attention in both assessment frameworks and planning processes. Addressing this gap, the thesis pursues three objectives through complementary empirical approaches. First, a systematic review examines how spatial and temporal dimensions are included i cost-benefit analyses (CBA) studies of urban NBS, revealing that spatial and temporal distribution of NBS benefits are largely overlooked. Second, semi-structured interviews with local stakeholders in Trento explore preferences and motivations regarding the spatial scale and temporal distribution of NBS benefits. Results highlight a preference for small, spatially distributed interventions and long-term solutions, driven by considerations of equity, feasibility, and integration into the urban fabric. Third, a participatory mapping survey with 286 citizens investigates preferences for the “temporal effectiveness” of NBS—defined as their capacity to deliver benefits in the short, medium, and long term—and the potential for conflicts among groups with differing temporal preferences. Findings show that citizens, like stakeholders, often value long-term interventions, but diverging views can generate spatial conflicts in dense urban areas. Taken together, the three studies demonstrate that temporal lag is not necessarily a barrier to NBS acceptability, as both stakeholders and citizens may support delayed but higher long-term benefits. They also show that equity and accessibility concerns weigh heavily in spatial preferences, sometimes more than overall benefit maximization. The thesis argues that incorporating spatial and temporal benefit trajectories into valuation frameworks and planning practices is crucial to capture the real value of NBS and to enhance their social legitimacy. These insights point to the importance of portfolio strategies that combine quick, distributed measures with long-maturing, high-impact interventions.