This is concluded in a recently published study “Exploring spatial feedbacks between adaptation policies and internal migration patterns due to sea-level rise” in Nature Communications, led by Lena Reimann, a postdoctoral researcher at the Institute for Environmental Studies (IVM) at Vrije Universiteit Amsterdam.
Internal migration will increase in the 21st century due to sea level rise as low-lying coastal land becomes uninhabitable. In collaboration with researchers from the Coastal Risks and Sea-Level Rise (CRSLR) at the German Kiel University and the CUNY institute for Demographic Research (CIDR) at the City University of New York (CUNY), the team developed a model that can account for the effects of sea-level rise on migration patterns within countries.
Focusing on the Mediterranean, they found that countries in that region may face an additional 20 million internal migrants by the year 2100 if no adaptation measures are taken. However, if policymakers opt for ‘hard protection measures’, with dikes placed at large stretches of the coast, the number of internal migrants may be reduced by almost 90 percent.
The second scenario, where dikes are limited to coastal cities and part of the population is relocated, the number of migrants may decrease by about 40 percent. When solely urban hubs around the coast lines are protected by dikes, internal migration might be reduced by 30 percent.
A high number of migrants is not necessarily negative, according to the researchers, provided that the migration is well managed and happens proactively before the impacts of sea-level rise are felt. As most migration is projected to be directed towards inland cities, this may result in fewer people living in coastal stretches that would suffer severe impacts during for instance a flooding. The results of this study can guide adaptation policies that consider their potential effect on migration responses, and can provide insights for spatial and urban planning.