Human-induced land subsidence causes many coastal areas to sink centimetres per year, exacerbating relative sea level rise (RSLR). While cities combat this problem through investment in coastal infrastructure, rural areas are highly dependent on the persistence of protective coastal ecosystems, such as mangroves and marshes. To shed light on the future of low-lying rural areas in the face of RSLR, we here studied a 20-km-long rural coastline neighbouring a sinking city in Indonesia, reportedly sinking with 8–20 cm per year. By measuring water levels in mangroves and quantifying floor raisings of village houses, we show that, while villages experienced rapidly rising water levels, their protective mangroves experience less rapid changes in RSLR. Individual trees were able to cope with RSLR rates of 4.3 (95% confidence interval 2.3–6.3) cm per year through various root adaptations when sediment was available locally. However, lateral retreat of the forest proved inevitable, with RSLR rates up to four times higher than foreshore accretion, forcing people from coastal communities to migrate as the shoreline retreated. Whereas local RSLR may be effectively reduced by better management of groundwater resources, the effects of RSLR described here predict a gloomy prospect for rural communities that are facing globally induced sea level rise beyond the control of local or regional government.

This chapter assesses ACM’s potential as a pathway to address the flooding problem of Greater Jakarta, significantly exacerbated by land subsidence and climate change. It is based on a thought experiment by the authors to envision application of this approach to the problem and is not the result of empirical work. A background of Jakarta’s flooding is first provided and subsequently its framing as a ‘wicked problem’. Results of the thought experiment are then discussed, focusing on three questions: (i) Can ACM be applied, given Jakarta’s flooding governance structure? (ii) Will ACM’s social learning work for the flooding problem? And (iii) if ACM were applicable to Jakarta’s case, what operational indicators would apply? The chapter concludes with recommending a two-step ACM pathway: (1) adjusting the current flooding governance structure, for which leadership is needed with a long-term vision and the application of adaptive governance at the river basin scale; (2) shaping the enabling conditions for learning that stimulate creativity in and discovery of new problem framings and solutions outside the policy system. While the authors recognise the considerable challenges when applying ACM to the flooding of Greater Jakarta, the crisis stage it has reached necessitates adaptation approaches that can break the cycle of narrow, longstanding paradigms, policy beliefs, and maladaptive pathways..