Coastal Retreat: A Global Trend Driven by Vulnerability

A new study utilizing satellite nightlight data demonstrates that over half of the world’s coastal settlements have retreated inland over the last 30 years as a response too increasingly severe climate hazards.

Researchers from the University of Copenhagen coauthored the study, which also identified regions moving towards the coast despite the risks-including Copenhagen.

For centuries, coastlines have attracted significant human settlement and economic activity. Currently, more than 40% of the global population resides within 100 kilometers of the coast, facing accelerating sea-level rise, coastal erosion, flooding, and tropical cyclones.

while coastal retreat is often considered an adaptive strategy,its global extent and underlying causes have remained unclear.The new study,published in Nature Climate Change, addresses this gap by providing the first global evidence that social and infrastructural vulnerability, rather than historical hazard exposure, primarily drives coastal retreat.

An international team,led by researchers from Sichuan University and including remote sensing experts from the University of Copenhagen (Alexander Prishchepov and Shengping Ding,IGN),conducted the study.They mapped settlement movements across 1,071 coastal regions in 155 countries. Integrating nighttime light observations with global socioeconomic datasets, the researchers found that 56% of coastal regions retreated from the coast between 1992 and 2019. Notably, 16% of regions, including the Copenhagen area in Denmark, moved closer to the coast, while 28% remained stable.

“More than half of the world’s coastal regions are moving away from the shoreline, with africa (67%) and Oceania (59%) leading the retreat. Though, in parts of Asia and South America, many communities continue to expand toward the coast,” explains coauthor Ding, who recently defended his PhD thesis on a related topic at the geosciences and natural resource management department at the University of Copenhagen.

the study reveals a significant adaptation gap: nearly half of low-income regions-especially in Africa and Asia-are unable to retreat, often due to the pursuit of socioeconomic betterment, reliance on coastal land, and a lack of alternative resources. This leaves millions more exposed.