Progress and gaps in climate change adaptation in coastal cities across the globe

In the realm of adaptation to climate change, coastal cities deserve special attention as they are faced with an abundance of climate impacts while also being engines of economic development, trade, innovation and culture with, in theory, high adaptation potential. While there is eclectic evidence for urban adaptation, we are lacking a global overview of the extent to which coastal cities are on track to prepare for and adapt to climate risks. Building on and complementing highly relevant findings from the Global Adaptation Mapping Initiative (GAMI), this paper presents findings from a global review of empirical evidence for adaptation in coastal cities. We systematically analysed adaptation actions reported in the scientific literature for 199 coastal cities across the globe with the aim to provide the first stocktake of empirical evidence of adaptation in coastal cities. To do so, the paper addresses four key questions: (1) How is evidence for coastal urban adaptation spread across the globe? (2) Which hazards and trends of exposure and vulnerability are reported? (3) Which responses are reported and which actors are involved in their implementation? And (4) What is the speed, scope, depth and evidence of risk reduction due to adaptation? Using the World Bank’s income groups and city sizes as cross-cutting lines of analysis, our findings show that there is comparatively little published knowledge on coastal urban adaptation in low and middle income economies.  Reported adaptation measures are predominantly designed based on past and current, rather than future, patterns in hazards, exposure, and vulnerability. The results unravel that city governments, particularly in high-income countries, are more likely to be reported as implementers of institutional and infrastructural responses, while coastal cities in lower-middle income countries are often reported to rely on households to implement behavioral adaptation. Finally, the assessed evidence mostly presents coastal urban adaptation that is rather slow, of narrow scope, and not transformative. In sum, the paper provides a nuanced picture of the current state of adaptation in coastal cities. It highlights fields of progress as well as key gaps to be tackled in the future.