Global coastal human settlement retreat driven by vulnerability to coastal climate hazards

Abstract

Retreating from coastlines is one potential human response to the increasing threats posed by coastal climate hazards. However, the global extent of coastal settlement retreat, its correlation with local vulnerabilities, and the adaptation gaps remain less understood. Here we analyse night-time light changes for 1992 to 2019 and show that settlements retreated from coastlines in 56% of coastal subnational regions, remained stable in 28%, and moved closer to coastlines in 16% of these regions. Retreat was weakly associated with historical experiences of coastal climate hazards but accelerated in regions with greater vulnerability to coastal climate hazards—indicated by lower infrastructure protection and less adaptive capacity. In 46% of low-income regions, particularly in Africa and Asia, settlements were forced to either maintain their current status quo or move closer to coastlines, revealing the large adaptation gap in addressing future climate change risks. Coastal settlement retreat reflects human behavioural adaptation to increasing coastal climate hazards. Using night-time light data over 1992–2019, this study finds that over half of global coastal settlements have retreated, driven by insufficient infrastructure protection and adaptive capacity.