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. By 2070, it will lose about 75% of its remaining wetlands. Eventually, all of coastal Louisiana will become uninhabitable, research has showed. 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'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, an assistant professor of urban sustainability at Yale School of the Environment.
For the study, published May 4 in the journal Nature Sustainability, Castro worked with an interdisciplinary team of scientists from Tulane University, Florida State University, and Coastal Carolina University. 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 of its effected population — 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 said.
"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 Jesse Keenan, an associate professor in Tulane's School of Architecture and Built Environment and coauthor of the study.
Population losses in the state's coastal communities have been significant since Hurricane Katrina devastated the region in 2005. About 25% of the population of Orleans Parish, a densely populated city-parish along the Mississippi River, 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 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 what was to an exceptionally dynamic landscape even at that time. During the 18th and 19th centuries an influx of Europeans, who brought more attachment to place and infrastructure, has led to more static communities. But as current landscapes shift as a result of 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, the researchers said.
"If you keep building, people will come," Castro said. "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?"
