Article Dans Une Revue Nature Communications Année : 2022

The macroeconomic effects of adapting to high-end sea-level rise via protection and migration

Daniel Lincke
Jochen Hinkel

Résumé

Climate change-induced sea level rise (SLR) is projected to be substantial, triggering human adaptation responses, including increasing protection and out-migration from coastlines. Yet, in macroeconomic assessments of SLR the latter option has been given little attention. We fill this gap by providing a global analysis of the macroeconomic effects of adaptation to SLR, including coastal migration, focusing on the higher end of SLR projections until 2050. We find that when adapting simultaneously via protection and coastal migration, macroeconomic costs can be lower than with protection alone. For some developing regions coastal migration is even less costly (in GDP) than protection. Additionally, we find that future macroeconomic costs are dominated by accumulated macroeconomic effects over time, rather than by future direct damages, implying the need for immediate adaptation. Finally, we demonstrate the importance of including autonomous adaptation in the reference scenario of economic assessment studies to avoid overestimation of adaptation benefits.

Climate change is already visible via bio-physical impacts around the world, which are expected to increase, depending on future greenhouse gas emissions 1,2 . This will trigger a range of socio-economic consequences and risks. To adapt effectively, and as a motivation for climate change mitigation, it is key that policy makers understand these potential consequences as well as the socio-economic effects of adaptation.

The literature has identified sea-level rise (SLR) as one of the major risks from climate change 2,3 . Even when meeting the target of the Paris agreement of staying well below 2 °C of global warming, mean and extreme sea levels are projected to rise substantially during the 21st century 1 . It has also been shown that SLR will continue for further centuries and can only be slowed down but not avoided 4 . The regions facing highest risk from SLR are small island states, delta regions, and often regions of the global south 5-7 , but SLR also poses significant risks for developed regions 8-10 .

There are various adaptation options to combat SLR, which can be categorized into: advance (creating new land seawards), protection (blocking inland propagation of mean and extreme sea levels), retreat (giving up land and out-migration of people), accommodation (reducing vulnerability to flooding through, e.g., floodproofing buildings or early warning systems) and ecosystem-based solutions (supporting advance, protection and/or retreat through restoring and maintaining coastal ecosystems) (cf. Oppenheimer et al. 7 ). It has been shown that adaptation in the form of coastal protection can be very effective at reducing impacts 11-13 , and also that protection and advance is costefficient for densely populated and urbanized areas, but inefficient and very expensive relative to local GDP for rural and less densely populated areas 11,14-16 . Accommodation can be particularly effective for small rises in sea levels, but ceases to be so for higher SLR 7 . As a result, high SLR may trigger coastal retreat and the associated out-migration of people, a possibility that has received increasing attention in the literature. Accelerated SLR and increased coastal flooding has the potential to displace millions of people 17-21 . As an example, even under cost-benefit optimal protection decisions, it is estimated that 17 to 72 million people globally will have to migrate from coastal areas during 21st century 22.

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Dates et versions

hal-04682547 , version 1 (30-08-2024)

Identifiants

Citer

Gabriel Bachner, Daniel Lincke, Jochen Hinkel. The macroeconomic effects of adapting to high-end sea-level rise via protection and migration. Nature Communications, 2022, 13 (1), pp.5705. ⟨10.1038/s41467-022-33043-z⟩. ⟨hal-04682547⟩

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