The long-run impact of climate change will leave New Orleans uninhabitable, a recent academic article says. More than one million Louisianans who live near the Gulf coast are threatened over the rest of the century.
In the Nature Sustainability
The article's authors said public officials should begin planning for the climate-driven migration of residents of New Orleans and hundreds of thousands of others in southern Louisiana because rising sea levels will ultimately flood the land.
"Louisiana can develop managed relocation frameworks while still having choices, rather than implementing them under crisis conditions," the paper said.
That migration is already underway since the turn of the century, reflected in sizable population losses for New Orleans and coastal parishes, which have been regularly battered by hurricanes.
The authors stated that during the Last Interglacial period, about 125,000 years ago, temperatures were 0.5-1.5 degrees Celsius above pre-Industrial Revolution temperatures. By way of comparison, scientists generally believe the world is now 1.3 to 1.5 C above the pre-industrial temperatures because of human-generated global warming, which continues to raise temperatures.
The authors say in the Last Interglacial period in the south Louisiana area sea levels were at least 3 meters and probably 7 meters higher.
"With a threshold rate of rising sea level rise for marsh survival that has already been crossed and an (imminent) loss of 75% of remaining wetlands that may be a reality by 2070, the embanked New Orleans area may well be surrounded by the Gulf of Mexico before the end of this century," they wrote.
If sea levels rise 3 meters, "at best" the New Orleans metropolitan area would become highly exposed, they said. "No coastal-defense system is expected to be effective when rising sea level rises to more than 7 meters."
Absent major actions to curb emissions contributing to global warming, the authors say current warming is on track to be 2.6 C above pre-industrial levels by 2100 and this would be expected to push sea levels beyond an additional 7 meters, though the timing is unclear. The elevations of New Orleans vary from about three meters below sea level to about six meters above.
The area is threatened not just by sea level rise but by reduced levels of sediments flowing in the area's rivers into the Gulf of Mexico, which historically served to add to the coastline. Additionally, extraction of water and oil from under the land has caused and is causing land subsidence.
Other academics over the last few decades have also said rising sea levels endanger New Orleans.
John Hallacy, president of John Hallacy Consulting, said, "The science is verifiable but the politics need to heed the news. It is not clear if this is the case. Evidence is needed before rash decisions are made."
"There is a need to question the [municipal bond] issuers on what kind of action plan, if any, is being implemented," Hallacy said. "The market then may make its own assessment armed with that information."
John Mousseau, executive vice president and chief investment officer at Cumberland Advisors, said, "We always think that climate risk in hurricane prone areas should be reflected by extra spread in the bond market but, in our opinion, it rarely is."
David Victor, distinguished professor of innovation and public policy at the University of California, San Diego, said, "The idea that the window of opportunity to save New Orleans has closed seems hyperbolic, not least because it does not look closely at the pace at which defenses can be mounted and it treats 'New Orleans' as a single unit. There are very high value parts of New Orleans that probably will be protected – and thus 'saved' in the authors' parlance – even with a lot of sea level rise, just as Venice and Amsterdam and other places of high value but high vulnerability get protected."
In Louisiana, "The impetus is on policy makers to look closely at forecasts of sea level and other perils – looking at the extremes, not just the much gentler median scenarios – and plan accordingly," Victor said. "Bondholders should do the same – asking questions of those planners and issuers."
Victor said, "I would not use the comparisons with the last interglacial as a forecast of sea level rise for the time periods relevant for human planning – let alone the 10 to 30 years relevant for muni debt. I'd use the climate models because they deal much better with rates of change – and those rates (to years and decades) are really what matter for planning." The Nature Sustainability article gets its most dramatic sea level rise figures from the last interglacial, Victor said.
Some scientists have been more modest than the Nature Sustainability article authors in their predictions for sea level rise. The Climate Portal of the Massachusetts Institute of Technology in June 2024 said by 2100 sea levels could rise somewhere between 8 inches to more than six feet.
The rate of sea level rise has accelerated in recent years, said Tim Dixon, distinguished university professor at University of South Florida.
"New Orleans faces very severe challenges; investors need to look at those challenges with eyes open, as must policy makers," Victor said. "That those challenges are massive does not mean that parts of the region won't face them and must, necessarily retreat."
A sediment diversion project that
"The governor cut funding for projects to protect the coast over ideology," said Joseph Krist, publisher of Muni Credit News. "That comes as the issue of paying for maintaining the [Mississippi] levee system has moved front and center. This paper serves as a response to ideology. Whether it's enough to influence behavior is unclear."
Partly as a result of flooding from Hurricane Katrina in 2005, New Orleans' population has declined. Its 2025 estimated population was down 25.3% from 2000, according to the U.S. Census. Most of the nearby coastal parishes have also lost population since 2000.
"Although population loss reflects Louisiana's statewide trends, coastal areas exhibit greater losses and a distinct pulse–retreat pattern of net migration," the paper said.
Mousseau said along with Katrina,
"Population loss is frequently a negative but the underlying reasons driving the trend are most important," Hallacy said.
While U.S. median housing prices have gone up 4.6% since about July 2022, New Orleans median housing prices have gone down 19% in the same period, according to Zillow.com.
"Declining property values are a concern for the entities that collect taxes," Hallacy said. "Soaring insurance rates are problematic in many jurisdictions around the nation… In the long term, it is possible that valuations may turn around but there is no certainty on the matter."
"The absolute and relative negative performance of New Orleans median house prices is the 'Bermuda Triangle' effect of population loss, less robust job market, and the higher carrying costs of home – both property taxes and insurance cost," Mousseau said. Bond investors seek higher yields from issuers with declining property values.
The Nature Sustainability article comes out as
Neither spokespersons for New Orleans Mayor Helena Moreno nor for Gov. Jeff Landry responded to requests for comment for this story.
