Sea level rise in the US may lead to large scale migration by the end of the century, disproportionately impacting certain areas as displaced residents flock inland, according to new research from the University of California.

Climate change already affects millions around the globe, and human migration is a natural response to climate change pressures. The consequences of sea-level rise are “pervasive” and expand beyond coastal areas to disproportionately affect regions of the US. In particular, sea-level rise is affected by two contributing factors: first, volume from melting ice sheets and glaciers and secondly the expansion of seawater as it warms. Predictions find that within just a few decades, hundreds of thousands of homes in the US will be flooded. An estimated 1.8 meters (6 feet) of ocean-level rise may even redraw the coastlines of southern Florida, parts of North Carolina, Virginia, and most of Boston and New Orleans.

“We talk about rising sea levels, but the effects go much further than those directly affected on the coasts,” said Caleb Robinson, USC visiting doctoral researcher from Georgia Tech and the study’s first author, in a statement. “We wanted to look not only at who would be displaced, but also where they would go.”

To address the broader impacts of climate change on populations, researchers designed a machine-learning program using existing projections of sea-level rise after natural disasters like Hurricane Katrina and coupled that data with population projections in order to predict where people will go. They found the impact of rising oceans will be felt across the country – not just coastal areas at risk of flooding – forcing people to move inward. In the US alone, at least 13 million people may be forced to relocate by 2100, with the greatest effects being felt by areas immediately adjacent to the coast.

The number of additional incoming migrants in the 1.8-meter sea-level rise scenario when compared to "business-as-usual". The map shows migrants as a percentage of each county's population. Dilkina and Robinson/PLOS One

The most popular relocation spots will be land-locked cities like Atlanta, Houston, Dallas, Denver, and Las Vegas. Suburban and rural Midwest will also see large influxes of people relative to their smaller local populations.

Notably, population movement will not follow previously established patterns and may create competition for jobs, increased housing prices, and pressure on services and infrastructure. This may require that cities throughout the country handle new populations by rethinking future plans for infrastructure and services.

“When migration occurs naturally, it is a great engine for economic activity and growth,” said co-author Juan Moreno Cruz, an economist and professor at the University of Waterloo.

“But when migration is forced upon people, productivity falls and human and social capital are lost as communities are broken apart. Understanding these migration decisions helps economies and policy makers prepare for what is to come and do as much as possible to make the influx of migration a positive experience that generates positive outcomes.”

The authors note that their projections are based largely on assumptions that may be impacted by knowledge gaps and data limitations. Even so, the results could help city planners and policymakers plan for the expansion of infrastructure and services.

“We hope this research will empower urban planners and local decision-makers to prepare to accept populations displaced by sea-level rise. Our findings indicate that everybody should care about sea-level rise, whether they live on the coast or not. This is a global impact issue,” said study author and computer scientist Bistra Dilkina.

The study is published in PLOS One.