Identifying future challenges for adaptation to climate change through insights from participatory scenario-downscaling in Mumbai

Populations in many coastal urban areas are increasingly exposed to climate-related hazards, such as rising sea levels, increasing intensities and frequencies of tropical cyclones, and extreme weather events. At the same time, the number of people in coastal cities is growing and, especially in the Global South, these cities are characterised by rapid and often unplanned urbanisation and a high degree of social inequality. Hence, coastal cities are also hotspots of social vulnerability. That coastal cities are climate risk hotspots has been widely acknowledged, and adaptation is happening, especially in terms of planning and reactive responses. However, the current adaptation progress lacks implementation, evidence of effective risk reduction, and long-term pathway perspectives. A global future-oriented approach for a better understanding of the socioeconomic developments shaping challenges to adaptation is the Shared-Socioeconomic Pathway (SSP) framework. Our research uses the case study of Mumbai, one of the world’s most vulnerable cities, to apply a participatory scenario approach, downscaling the SSP narratives to the local level with bottom-up input from diverse local stakeholder groups. Our specific research question is: How do future socioeconomic urban developments affect Mumbai’s social vulnerability and challenges for adaptation? Our results provide three distinct scenario narratives for Mumbai’s socioeconomic development until 2050, including “Wider sustainability transitions”, “Partial exploitation of existing potential and current trends”, and “Increasing barriers through inequality and fragmentation”. The scenario narratives stress the relevance of addressing social inequality in urban change and development processes across different sectors, including labour, housing, transport, and health. A further prominent cross-cutting aspect resulting from the co-development of the scenario narratives with local stakeholders deals with streamlining urban planning across different governance scales (i.e., local and regional) and sectors (e.g., transportation and spatial planning). The SSP downscaling approach also sheds light on several conceptual and methodological challenges. For example, data availability guiding the drafting of plausible scenario assumptions varies significantly across different elements of the scenario narratives. Moreover, the framework is limited in considering local development pathways switching from one scenario track to another and the effects of unforeseen transformations or shocks. In conclusion, our study proves the value of developing globally nested regional scenarios to understand challenges for adaptation, consistent with research on global socioeconomic developments, and the importance of a transdisciplinary approach to guarantee plausibility, consistency and relevance for local contexts. The results of our study are relevant for a holistic understanding of future climate risk and challenges and opportunities for adaptation planning at the local scale.