Over half of global coastal settlements are retreating inland due to intensifying climate risks
University of Copenhagen
A new study using satellite nightlight data reveals that more than half of the world’s coastal settlements have retreated inland over the past 30 years in response to intensifying climate hazards. The study coauthored by University of Copenhagen researchers also identified regions moving towards the coast despite the risks.
For centuries, coastlines have attracted dense human settlement and economic activity. Today, more than 40 percent of the global population lives within 100 kilometers of the coast, where facing accelerating sea-level rise, coastal erosion, flooding, and tropical cyclones.
Although moving away from the coast - known as “retreat” - is often viewed as an adaptive strategy, its global extent and drivers have remained unclear. A new study published in Nature Climate Change fills this gap by providing the first global evidence that coastal retreat is driven more by social and infrastructural vulnerability than by historical exposure to hazards.
The study was conducted by an international team led by researchers from Sichuan University and included remote sensing experts from the University of Copenhagen (Alexander Prishchepov and Shengping Ding, IGN). It maps settlement movements across 1,071 coastal regions in 155 countries. By integrating nighttime light observations with global socioeconomic datasets, the researchers found that 56% of coastal regions have retreated from the coast from 1992 to 2019, and 16% of regions, including the Copenhagen area in Denmark, have moved closer to the coast, while 28% have remained stable.
A Growing but Uneven Global Shift
“More than half of the world’s coastal regions are moving away from the shoreline, with Africa (67%) and Oceania (59%) leading the retreat. However, in parts of Asia and South America, many communities continue to expand toward the coast” explains co-author Dr. Shengping Ding, who just defended his PhD thesis on a topic relevant to the article at the Department of Geosciences and Natural Resource Management at the University of Copenhagen.
The study highlights 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 improvement, reliance on coastal land and lack of alternative resources. This leaves millions more exposed to coastal flooding and erosion.
Interestingly, retreat is most common in middle-income countries. Researchers say these nations sit at a tipping point: they possess enough institutional capacity and financial resources to support relocation, yet have not reached the level of wealth where they can rely solely on protective infrastructure.
Meanwhile, both low- and high-income regions tend to stay near or move even closer to the coast - though for very different reasons. Poorer regions often expand shoreline settlements in search of livelihoods, infrastructure access, and economic opportunity. In contrast, wealthier regions may feel confident in their ability to manage climate risks, relying on advanced infrastructure, early warning systems and coastal defenses.
Vulnerability, not past experience, mainly drive coastal retreat
Recently, the increased risk of floods and resulting damages to coastal settlements has sparked debate in Denmark, with critics accusing politicians of delaying promised policies that would protect property owners from damages.
Despite this, Denmark , exemplified by the capital region of Copenhagen, is amongst the minority of regions moving closer to the coast these past decades, the research shows.
“Compared to poorer regions, Denmark has strong infrastructure and greater capacity to adapt to rising coastal risk. Danes also tend to trust that policymakers will do what is necessary to protect vulnerable coastlines. Places like Copenhagen and Aarhus historically served as major trade and industrial coastal cities. However, trust alone may not be enough, with documented erosion in parts of Denmark, proactive inland planning and resilience measures are becoming increasingly important” says Co-author Associate Professor Alexander V. Prishchepov, Department of Geosciences and Natural Resource Management, University of Copenhagen.
Interestingly, it is not the frequency of past disasters in a region that mainly drives coastal retreat, the study shows. Instead, it is the current vulnerability to coastal hazards which accelerates it - particularly where infrastructure protection is limited and adaptive capacity (social, economic and political means) is low.
“Our analysis shows that coastal retreat mostly happens a response to low protection and weak adaptive capacity in places where communities don’t have the means to protect themselves. Such regions tend to experience faster retreat, not necessarily because of more hazards, but because they lack the capacity to stay,” adds Shengping Ding.
The study used the method “mixed-effects modelling” - a statistical tool that enhances the analysis of complex data structures by incorporating both fixed and random effects. This approach demonstrated that a 1% improvement in a region's adaptive capacity resulted in a 4.2% reduction in retreat speed, and a 1% increase in structural protection led to a 6.4% reduction.
Lessons for global coastal adaptation
Alexander V. Prishchepov highlights that the study provides valuable lessons for climate adaptation worldwide, including in Denmark, where land reclamation and coastal development are extensive.
“Our research shows that vulnerability, not just hazard exposure, determines whether communities adapt proactively or are forced to retreat reactively. For countries like Denmark, where coastal expansion continues, understanding these global dynamics is crucial for policymakers to avoid future maladaptation”, says Prishchepov. “Globally, we must shift from reactive retreat to proactive planning, integrating social vulnerability into long-term coastal management.”
He also points out the importance of further research.
“Though this research offers valuable insight into global migration patterns, more study is needed to fully understand them. Particularly in socially-fragile regions such as African countries, night-time light data may not tell the whole story, as economic activity and settlements extent are not necessarily linked to luminous activity in regions with limited electrification,” says Prishchepov.
Read the study, “Global coastal human settlement retreat driven by vulnerability to coastal climate hazards”.
Journal
Nature Climate Change
Article Title
Global coastal human settlement retreat driven by vulnerability to coastal climate hazards
