Sea-Level Rise Will Send Millions of U.S. Climate Refugees to Inland Cities

When rising waters from superstorms like Katrina or Sandy inundate heavily populated coastal communities, vast numbers of people will abandon their destroyed homes and flee for safety and shelter elsewhere.

Where will they go — and how will their destination cities cope with them?

That’s the focus of a new study that projects as many as 13.1 million Americans could become climate refugees by the end of this century, an influx of people that could stress inland cities, particularly those already grappling with population growth, urban development, traffic congestion and water management.

“We typically think about sea-level rise as a coastal issue, but if people are forced to move because their houses become inundated, the migration could affect many landlocked communities as well,” said Mathew Hauer, a demographer at the University of Georgia and author of the study, published in the journal Nature Climate Change. “For many inland areas, incorporating climate change scenarios into their strategic long-range planning would be an appropriate strategy.”

While other research has assessed sea-level rise with the goal of planning critical infrastructure to protect fragile populated coastlines, this study is believed to be the first to model the destinations of millions of displaced coastal migrants.

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Net changes in population by state due to migration from sea-level rise. Source: Nature Climate Change

“[This is] fascinating,” said Richard Alley, professor of geosciences at Pennsylvania State University, who was not involved in the study. “The global equivalent of this paper may be even more important. Climate refugees may become common if we continue to drive rapid climate change. Looking at where those refugees might go, as well as where they will come from, will provide better information for planners and voters considering adaptation and mitigation.”

The study predicts that Atlanta, Houston and Phoenix will be among the most likely destinations for climate refugees, whether for the short or long term.

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Net changes in population by metropolitan area due to migration from sea-level rise. Source: Nature Climate Change

“We know that people tend to migrate short distances or to areas with embedded social networks and family ties,” Hauer said. “Atlanta, Phoenix, Dallas, Orlando, and Austin are all major cities located near coastal areas. Naturally, they would be the top destinations.”

The study estimates both the number and destinations of potential sea-level rise migrations in the United States during the coming century.

“I used IRS county-to-county migration data to project future migration patterns using a time series model,” Hauer explained. “The projected migration patterns are sort of like pipes in a plumbing system. They tell you where water could go, but not how much water.” The “water” in this analogy comes is the estimated number of Americans at risk from sea-level rise.

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Projected migration linked to sea-level rise by state. Florida is expected to produce the largest number of migrants. Source: Nature Climate Change

After Katrina struck New Orleans in 2005, as many as 400,000 residents evacuated, some temporarily, some permanently, many to live with friends and family, others to places unknown. No comprehensive records exist of their destinations. Many people did come back to the city, although not necessarily to their former homes. African-Americans in particular returned at a much slower pace than their white counterparts, because their homes had been in neighborhoods more severely damaged by flooding.

Income levels also play a role. The new study estimates that coastal residents with an annual incomes of more than $100,000 might be better able to invest in protective measures against sea-level rise and, as a result, less likely to migrate.

Kevin Trenberth, a noted climate scientist at the National Center for Atmospheric Research, who was not involved in the study, said that numerous factors influence and complicate migration trends following a flood.

“Sea-level rise from climate change occurs slowly and gradually, but its effects are profound and manifested when three things or more come together — a storm surge on top of a high tide on top of sea-level rise — so it affects people not as a gradual process, but rather as an episodic, catastrophic one,” he said. “Hurricane Katrina or Superstorm Sandy are likely poster children for this.”


Source: National Center of Atmospheric Research

“The questions that arise are whether an area is abandoned and rebuilt elsewhere, or maybe just abandoned, or whether it is rebuilt where it was,” he added. “Often there are other things in play, [such as] insurance or if the state decides to condemn certain areas for building.”

Michael Mann, a climate scientist at Pennsylvania State University, who was not involved in the study, said the research “begins to connect the dots” when it comes to the impact of climate change on migration.

“Where are these people likely to go?” he asked. “And what does it mean when they compete with native inhabitants for the same water, food and land? This is really where the rubber hits the road when it comes to climate change and water, food and land security.”


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