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Louisiana’s coast is disappearing, and its population has already started to retreat. The shoreline, the most exposed in the world, is projected to move more than 30 miles inland of New Orleans and all of coastal Louisiana will become uninhabitable. The state has a narrowing window to plan for managed relocation that could be a model for other areas facing climate challenges, according to a new study coauthored by Yale School of the Environment’s Brianna Castro.

“Louisiana is a canary in the coal mine. It is one of the rare places where we’re already clearly seeing climate-motivated depopulation combined with other social and economic factors,” said Castro, assistant professor of urban sustainability at YSE.

Castro worked with an interdisciplinary team of scientists from Tulane University, Florida State University, and Coastal Carolina University on the study, which was published in Nature Sustainability. The team noted that the current population retreat in Louisiana offers a “first mover advantage,” which provides opportunities to learn what policies and plans are effective in advancing social welfare and environmental quality during relocation. By acknowledging the inevitability of the shoreline’s retreat now, the state can begin managed relocation — an orderly, multigenerational transition of people and infrastructure to higher ground — and set an example of how areas around the world can plan for climate adaptation, they noted.

“Transition planning offers significant first-mover opportunities, including the development of innovations in infrastructure and housing that is affordable for people on the move,” said study coauthor Jesse Keenan, the Favrot II Associate Professor in Tulane’s School of Architecture and Built Environment.

What kind of retreat do you want? Do you want to incentivize it and then people go naturally for jobs, housing, and lifestyle amenities — or do you want people to wait and then have to leave abruptly in crisis.”

Population losses in the state’s coastal communities have been significant following Hurricane Katrina, which devastated the region in 2005. About 25% of the population of Orleans Parish has left the area and more than half relocated from rural Cameron Parish. Castro characterizes this as a “pulse retreat,” in which a major weather event triggers a sharp drop in population that never rebounds to pre-storm levels.

To help them understand where coastal populations may be headed, the researchers also looked to the distant past, identifying previous coastal retreats by combining census data with archaeological records of Indigenous populations and geological data from the Last Interglacial period (roughly 125,000 years ago).

“We had the opportunity to look backwards to look forwards to assess, what do we know, what can we expect?” Castro said.

The records showed that Indigenous communities in the Mississippi Delta were highly mobile, shifting settlements in response to an exceptionally dynamic landscape at that time. The influx of Europeans with more attachment to place has led to more static communities, but as current landscapes shift from climate change, today’s shoreline communities need to be nimble as well, the researcher noted.

However, current development in coastal states provide different scenarios for relocation. In many areas of the U.S., such as Florida and Alabama, development continues unabated in high-risk zones with few plans for how to adapt to climate impacts and coastal degradation.

“If you keep building, people will come. So, then, what kind of retreat do you want? Do you want to incentivize it and then people go naturally for jobs, housing, and lifestyle amenities — or do you want people to wait and then have to leave abruptly in crisis?” Castro said.