Sea level rise could reshape the US and trigger mass migration

The study, conducted by researchers at the University of Southern California (USC), is the first to use machine learning models to project migration patterns resulting from sea level rise.

Using these models, the team found the impact of rising oceans will ripple across the country beyond coastal areas at risk of flooding, as affected people move inland.

When Hurricane Harvey gushed through the Texas coast back in 2017, displaced residents flocked inland in an attempt to rebuild their lives in the disaster’s aftermath. Within decades, the same thing could happen on a much larger scale due to climate-change-driven rising sea levels, said Professor Bistra Dilkina, an assistant professor of Computer Science at USC.

In the US alone, 13 million people could be forced to relocate due to rising sea levels by 2100. As a result, cities throughout the country will grapple with new populations. Effects could include more competition for jobs, increased housing prices, and more pressure on infrastructure networks.

“Sea level rise will affect every county in the US, including inland areas,” said Dilkina, the study’s corresponding author and associate director of USC’s Center for AI for Society. “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.”

According to the research, most popular relocation choices will include land-locked cities such as Atlanta, Houston, Dallas, Denver and Las Vegas. The model also predicts suburban and rural areas in the Midwest will experience a disproportionately large influx of people relative to their smaller local populations.

Sea level rise is caused primarily by two factors related to global warming: the added water from melting ice sheets and glaciers and the expansion of seawater as it warms.

According to experts, within just a few decades, hundreds of thousands of homes on the US coast will be flooded if this phenomenon continues. By the end of the century, 1.83m (6ft) of ocean level rise would redraw the coastline of southern Florida, parts of North Carolina and Virginia and most of Boston and New Orleans.

To predict the trajectory of sea level rise migration, the USC team took existing projections of rising sea levels and combined this with population projections. Based on migration patterns after Hurricane Katrina and Hurricane Rita, the team trained machine learning models – a subset of artificial intelligence – to predict where people would relocate.

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

The researchers found the greatest effects of sea-level rise migration will be felt by inland areas immediately adjacent to the coast, as well as urban areas in the south-east US. The model also showed more incoming migrants to Houston and Dallas than previous studies, which flagged Austin as the top destination for climate migrants from the south-eastern coast.

Researchers noted that this result shows that population movement under climate change will not necessarily follow previously established patterns.

Sea level rise could also re-route people relocating from unaffected areas, the researcher added. Counties surrounding Los Angeles, in particular, could see tens of thousands of migrants whose preferred coastal destinations are now flooded choosing alternative destinations.

The results of this study could help city planners and policymakers plan to expand critical infrastructure, from roads to medical services, to ensure the influx of people has a positive impact on local economies and social wellbeing.

As well as machine learning tools as of late, satellite altimetry has heavily contributed to the better understanding of rising sea levels.