The Future of Urban Climate Vulnerability in Southeast Asia: Linking downscaled shared socioeconomic pathways to the drivers of urbanisation in Mumbai, Manila and Jakarta

Reducing future climate vulnerability at the local level depends on consistent policies and setting clear roles and responsibilities. Unfortunately, these are often missing in developing countries, given that different agencies and actor groups develop local adaptation and urbanisation policies with little streamlining and integration. More fundamentally, research combining local adaptation and urbanisation is rare, especially that which provides future-oriented, long-term pathways. This policy and research gap clouds decision-making, fuels potential maladaptation, and saps policy effectiveness, especially in the highly vulnerable coastal Southeast-Asian cities. To shed light on this problem, this research asks: How do three shared socioeconomic pathways (SSP) shape the future drivers of urbanisation for Mumbai, Manila and Jakarta? We approach this question by combining mixed qualitative narratives and quantitative estimates of urbanisation drivers from the regional SSPs developed by Petzold and colleagues (in press). Petzold et al. downscaled three SSPs (matching SSP 1, 2, and 3) to the metropolitan areas of Mumbai and Jakarta in a participatory scenario approach that yielded narratives on themes like population, labour, health, and migration. We applied this method to Manila and extracted the significant factors driving urbanisation from the three regions, forging integrated urbanisation and adaptation pathways. The results include region-specific qualitative narratives of future development and quantitative estimates of the urbanisation drivers with their associated levels of uncertainty. We present these results across the themes of population growth, urban structure types at the metropolitan cores, inner and outer peripheries, urban planning, infrastructure, informality, and inequality, among others. Stakeholder engagement supported validating the research assumptions and narratives and developing the estimates through a hierarchical analytical process. This mixed methods approach sheds light on the relationship between urban development and risks in highly urbanised and at-risk cities in Southeast Asia, considering the social drivers of vulnerability and the physical drivers of exposure. Its limitations include data and research scarcity, despite which it bridges the gap between urbanisation and adaptation policy and research. It also provides a globally nested approach to future development built on transdisciplinary research and validated with local knowledge. It presents methods suitable to other cities in the region, as well as insights for the future development and risk assessment of Mumbai, Manila, and Jakarta. Future work includes checking the narratives against ongoing processes and future urban growth simulations to provide critical insight for local decision-makers into their adaptation agendas.