Another great American migration is now underway, this time forced by the warming that is altering how and where people can live. For now, it’s just a trickle. But in the corners of the country’s most vulnerable landscapes — on the shores of its sinking bayous and on the eroding bluffs of its coastal defenses — populations are already in disarray.

A couple of miles west of downtown Slidell, Louisiana, and just upstream from the broad expanse of Lake Pontchartrain — the 40-by-24-mile-wide brackish estuary separating what is now the mainland from New Orleans — a five-room shotgun house sits on a plot of marshy lawn near the edge of Liberty Bayou. Colette Pichon Battle’s mother had been born in that house. Colette, bright-eyed and ambitious, devoutly Catholic, a force on the volleyball court, was raised in the house until the day she left for college. The family’s very identity had grown from the waters of the marsh around it. From a humble rectangle of wood, framed onto brick stanchions that kept it hovering several feet above the ground, shaded by the long beards of Spanish moss hanging from the limbs of towering oaks and a hardy pine, a family was born. Its Creole heritage near the acre of low-lying land goes deeper than the trees, deeper than the United States as a nation, to around 1770. Those roots withstood the tests of centuries: slavery, war and more than their share of storms.

Then, Hurricane Katrina arrived. Colette was in her law office in Washington, D.C., in 2005 when she saw a graphic weather forecast on the television screen: a swirling monster of a Category 5 storm, broader than anything she’d ever seen before, was headed straight for her family home. She rushed into a conference room and called her mother.

On the bayou, people don’t run from storms. They cope with a familiar nuisance the way Minnesotans cope with the snow. For all Colette’s life, the hurricanes that routinely swept Louisiana were more cause for bonding than for fear — families would gather in one place, bringing the food that had to be eaten before the power went down, and they’d barbecue it and talk and share stories while the storm passed overhead. That the water would sometimes come wasn’t a surprise; it was why the home was elevated. But time and warming and the erosion of a protective coastline had already changed the nature of the storms. And Katrina looked different. “I need you to get out of there,” Colette told her mom.

Mary Pichon Battle, a vibrant 60-year-old schoolteacher, had raised her children to travel the world. She was a living tie to Liberty Bayou’s rich history, one of the last remaining people there still fluent in the Creole language. And she’d clung to that home, even with the boot of Louisiana on her back, throughout the Civil Rights era, all while raising Colette, teaching her French and Creole, and then sending her off to Kenyon College in Ohio, and to law school at Southern University in Baton Rouge. Liberty Bayou wasn’t just an asset. It was her history, her identity. She saw no reason to leave. Colette, though, acting on instinct more than habit, was insistent. Mary would drive to her brother’s house in Breaux Bridge, just a few hours away. It would only be for a couple of days. Then she’d be back.

All around, people were taking flight. The displaced from New Orleans and the coastlines headed north toward higher ground, gathering the people of Slidell along with them. When the storm hit, it pushed a surge of waters across the lake onto its north shore. The shotgun house filled steadily, the water pushing Mary’s cherished paintings of Jesus off their hooks and setting them afloat, along with the contents of boxes of family photographs — prints of Colette and her twin brother as babies; photos of her grandmother, a beauty, before she used a wheelchair. All were carried toward the rafters, and lost, as the peak of the house’s tin roof disappeared. Slidell was inundated by tidal surges more than 20 feet deep. The water washed through buildings downtown at head height, transforming the entirety of the flat, low-lying landscape into a sea pocked only by occasional trees and obstacles jutting from the water. By the time those surging waters sloshed back into the lake, flowing south again to overcome the levees around New Orleans, the community of Liberty Bayou, for the most part, had already been destroyed. Mary Pichon Battle, who’d packed just three days’ worth of clothes and left a lifetime’s worth of belongings, had little to come home to. The house was unlivable. “It was in the water, in the ocean,” Colette recounted. “The tidal surge took it.” And much of Slidell had gone with it.

As tens of thousands of people continued to leave the wreckage of Louisiana in the weeks and months following the storm — and Mary remained a refugee — Colette moved back home. Fifteen generations on the bayou, a legacy in jeopardy, exerted a gravitational pull she could not resist. The devastation spoke to her. The rebuilding beckoned. She thought about the survivors.

“There are these trees here,” she says, describing the deeply rooted, majestic oaks that dot the landscape of southern Louisiana and the Mississippi coast. The tidal surge snapped the pines like Pixy Stix. The briny ocean water turned grasses brown and dead, killing animals and fish both, along with flowers and shrubs. “Not everything made it,” she said, “but these trees, these oaks, they made it. And they stood.”

Colette knew that her home might never be rebuilt. She knew her mother might never come back. But she tells the story, grasping for an explanation for why she herself returned, trying to find words that could describe the role she felt suddenly compelled to fulfill. “And I feel more like that, right?” she says, comparing herself to the aged oaks. “I feel like that. I’m watching other trees go down, I’m watching changes, but I’ve got the roots that are strong enough to hold.”

And so Colette became the resistance, pushing back against all the forces arrayed against her: the storm after the storm. She thought, at the time, she’d join a great healing, the rebuilding that would bring her mother home and the restoration of all the ties that gave life there meaning. She would bring the whole Bayou home. She began to talk about the risks in terms that the bayou communities around her could not recognize. She warned that if they failed to rebuild, to be resilient, the only option would be to migrate away from Louisiana’s southern coast — that while the recovery from the storm looked bleak, the alternative could be far worse. “People thought we were crazy,” she says, “but that’s how it begins.”

People have always moved as their environment has changed. But today, the climate is warming faster, and the population is larger, than at any point in history.

As the U.S. gets hotter, its coastal waters rise higher, its wildfires burn larger and its droughts last longer, the notion that humankind can triumph over nature is fading, and with it, slowly, goes the belief that self-determination and personal preference can be the driving factors in choosing where to live. Scientific modeling of these pressures suggest a sweeping change is coming in the shape and location of communities across America, a change that promises to transform the country’s politics, culture and economy.

It has already begun. More Americans are displaced by catastrophic climate-change-driven storms and floods and fires every year. The Internal Displacement Monitoring Centre, the global nongovernmental organization researchers rely on to measure the number of people forcibly cast out of their homes by natural disasters, counted very few displaced Americans in 2009, 2010 and 2011, years in which few natural disasters struck the United States. But by 2016 the numbers had begun to surge, with between 1 million and 1.7 million newly displaced people annually. The disasters and heat waves each year have become legion. But the statistics show the human side of what has appeared to be a turning point in both the severity and frequency of wildfires and hurricanes. As the number of displaced people continues to grow, an ever-larger portion of those affected will make their moves permanent, migrating to safer ground or supportive communities. They will do so either because a singular disaster like the 2018 wildfire in Paradise, California — or Hurricane Harvey, which struck the Texas and Louisiana coasts — is so destructive it forces them to, or because the subtler “slow onset” change in their surroundings gradually grows so intolerable, uncomfortable or inconvenient that they make the decision to leave, proactively, by choice. In a 2021 study published in the journal Climatic Change, researchers found that 57% of the Americans they surveyed believed that changes in their climate would push them to consider a move sometime in the next decade.

Also in 2021, the national real estate firm Redfin conducted a similar nationwide survey, finding that nearly half of Americans who planned to move that year said that climate risks were already driving their decisions. Some 52% of people moving from the West said that rising and extreme heat was a factor, and 48% of respondents moving from the Northeast pointed to sea level rise as their predominant threat. Roughly one in four Americans surveyed told Redfin they would no longer consider a move to a region facing extreme heat, no matter how much more affordable that location was. And nearly one-third of people said that “there was no price at which” they would consider buying a home in a coastal region affected by rising seas. When Redfin broadened its survey to include more than a thousand people who had not yet decided to move, a whopping 75% of them said that they would think twice before buying a home in a place facing rising heat or other climate risks.

Global migration experts say that what is happening in Louisiana is a textbook case of how climate-driven migration begins: First, people resist their new reality. Second, they make modest, incremental adjustments to where they live. Slidell, after all, is still within commuting distance of friends and jobs in St. Bernard Parish to the south. Third, they climb the ladder toward a safer place, rest on a rung for a while, and then continue on, only to be replaced by others worse off than they are, climbing up behind them.

What Colette hoped to avoid was the situation unfolding to her south, in the small Indigenous community of Isle de Jean Charles. There, Biloxi, Chitimacha and Choctaw people were clinging to an exposed tendril of Louisiana’s subsiding land. The Choctaw people had escaped to the south in the first half of the 19th century, finding refuge in the rural wild marshes of the uninhabited coast as white Americans pursued a brutal campaign of ethnic cleansing that drove the rest of the tribe — and tens of thousands of others — west on the Trail of Tears. Nearly 200 years later, the descendants of those exiles described a land where horses and cattle roamed across solid earth and their grandfathers slung freshwater bass and catfish out of Lake Tambour. The area now referred to as the Isle covered 22,000 acres.

But then the waters began to rise. Levees built along the Mississippi blocked the natural flow of sediment to replenish the marsh soils, while the oil companies dug thousands of miles of canals. The canals allowed salt water to overcome freshwater marshes, choking off plant life that also nourished the delicate ecosystem. It killed the wetlands and led the land to subside and erode. All the while, the climate got hotter, and the water levels of the Gulf of Mexico rose, doubling the effect of the change. Lake Tambour became a map label in an open sea of salt water. Today, 98% of the Isle’s land is gone.

When the U.S. Army Corps of Engineers began to build a 72-mile system of levees, dams and locks to protect the southern Louisiana coast in the early 2000s, it decided it was too expensive to include Isle de Jean Charles, and so it cut the small Indigenous community of around 325 people out of the protection zone. Isle de Jean Charles was forsaken as irredeemable, counted among the first sacrifices of sovereign land that the U.S. government would make to climate change. And ever since the Corps’ decision, the people living there have been forced to consider where they’ll go when they lose their land entirely. By the time of Katrina, they had started to negotiate a way out — a total and complete retreat. It seemed likely that a community that had held together for hundreds of years would be scattered on the wind. Their hope was that if they fled all at once, they could move together. Perhaps the fabric of community and spiritual support, and the legacy of culture and heritage, could be preserved. It just might have to be moved somewhere else, though.

Colette Pichon Battle watched that painful progression to her south and wanted nothing of it. Her heart ached at the injustice she observed there, where an Indigenous tribal community could not rally the same protections from their representatives in the towering capitol buildings in Baton Rouge and Washington as the wealthier, white towns around them, and where they were left to fend for themselves against the consequences of an upheaval they did not cause.

In her town, the rebuilding process unfolded slowly. The displaced, she said, returned on weekends, driving determinedly from Atlanta or Dallas to swing hammers and cart off debris. Mary Pichon Battle, who had moved to join family in Dallas, visited once in a while, too. But when she came, little was familiar. St. Genevieve’s, the Catholic church with its small cupola sitting on an idyllic grassy shoreline on the edge of the bayou, had collapsed into a heap of broken red brick. Never mind that right up until the storm the congregants sat segregated, with Slidell’s white residents on one side and its Creole parishioners on the other. To Mary it represented home and God, so she joined makeshift prayer sessions on the heavily damaged church grounds, gathering in the shade of a majestic oak tree. Colette and her mother both thought only about the day the homecoming could be permanent.

But a tree on uneven ground under the hot Louisiana sun was no match for Mary’s ever-more frail and tired body — even if it did offer a reunion of brothers and neighbors. The discomfort began to overshadow the joy. In town, the visits grew demoralizing and progress less and less visible. Abandonment began to happen quietly. “At first, after the storm, it’s volunteers pulling out trash,” says Colette, about all the work the community did in the months after the disaster. “Then, it’s not destruction, but the aftermath of destruction.” Streets and yards get cleaned up, but homes are not yet rebuilt and people still do not live there.

The faces in the grocery store remain unfamiliar, the fence-line conversations with neighbors infrequent, the fence lines themselves overgrown with vines because there is no one there to tend them. This stage, the reconstruction stage, demands that people dig deep into their pockets and savings — often savings they do not have. Each visit back to Slidell becomes a reminder of the burden and the stress. Eventually, the space between the trips got longer, and more painful. The fights with the government and insurers for payment became more desperate, and less successful and more exhausting. The applications for federal and state aid more futile, and less fair.

The years passed, and suddenly it was a decade since the storm. Eventually, people gave up. So began another stage of migration, not the stage in which people flee, but the one in which they decide never to come home. In Slidell, the periodic visits were saved for special occasions, crawfish boils, communions and funerals. Then, even those slowed. “You realize they got their voting card in a different city … or it just became easier to go to church at your kids’ home in Atlanta or wherever,” Colette says. “Your community is now dispersed across the U.S., and the thing that kept us together was proximity and seeing each other all the time. And so eventually, you lose the culture.” Her mother, Mary, was never to return home. Slidell’s Creole existence — the language — slipped away with her. She had graduated from “climate displaced” to “climate migrant.”

That is not to say that Slidell, though, shriveled up and died, the way Isle de Jean Charles was dying. Viewed through the lens of climate migration, Slidell, and all of St. Tammany Parish around it, was a confounding place. Because even as those who were displaced found it unlivable, others found it irresistibly inviting. The dramatic change facing southern Louisiana was relative — better for some than where they began, worse for others for the fragility it brought. Though Slidell’s loss was devastating for Colette and the long-standing community she’d been raised in, the small city seemed like refuge to people coming from farther south. And so it became a stopping point for climate evacuees fleeing from other, even more vulnerable places. Even today in Slidell, people can’t decide if they are coming or going. The small city is strangely booming.

There are some 60 miles still between Slidell and the actual coast of the state of Louisiana. In late 2022, I drove east on State Route 90 north of Houma, then south along vanishing branches of land until I reached what felt like the end of the earth. Billboards advertised <a href="http://Hurricaneaid.com" rel="nofollow">Hurricaneaid.com</a>, and in places huge trees lay lodged against the broken walls they’d fallen on during Ida a year earlier. The roofs of many houses still had gaping holes, all signs that people here were unable to recover from one storm before the next one hit.

Soon enough, though, it’s not the dilapidation, but the water that commands my attention. It is suddenly everywhere. Just as when you’re standing on a broad, flat beach while the tide comes in, you almost don’t notice the loss of land until it is already gone. Lawns fade into water, which looks swollen and rises right to the joists of the bridges that connect each driveway to the main road. The farther south I go, the closer the water comes to the pavement, until it is but an inch or two shy and in places spills out over it. More and more homes here, entering the towns of Montegut and then Pointe-aux-Chenes, sit destroyed from earlier storms, and there are fewer signs of rebuilding, more indications of surrender. Boats sit dry and askew on their hulls in driveways. I pass what looks like a small orange spaceship — a flying saucer of metal with sealed portal windows like a submarine. It is an escape pod, likely washed ashore from one of the large oil platforms in the Gulf. And there is a sense that here, too, people will one day need it.

Then the road ends. It had to end. I bumped up over a levee and passed through an enormous steel floodgate, 15 feet high, at least 5 feet thick, built in 2017 as a part of the larger coastal hurricane protection system that is the state’s last defense. On the other side, the expansive, sunny sky drops straight to the water, which, though calm and at low tide, now brims over the top of the road and into a parking lot. On this day, the lot is full of pickup trucks and boat trailers belonging to people who drove here, to the end of the road, for a day of fishing. In the distance, the scraggly skeletons of tall, once-majestic trees reach up out of the cordgrass, a reminder that not long ago this wasn’t marshland at all. To the right, across a canal and outside the protection zone of the levee, I can see Isle de Jean Charles. A sign on the side of the marina building with half its roof torn off reads, “Bayou Living. Kick back and relax.”

In the 18 years since Katrina, Louisiana’s southernmost territories had started to hollow out, steadily accelerating their quiet migration northward as Louisianans fled their coast. It is, indeed, the next great migration already well underway. In St. Bernard Parish, the thin escarpment of delicate soil still extending east from downtown New Orleans and the levees of the Mississippi River, the population has decreased by 39%. The houses that remain tower above the land, having been raised on to stilts 10 feet — even 25 feet — into the sky. They indicate that the people who remain are committed to live on land they know is disappearing, and that they will stay there, for a while longer anyway, content to treat their homes like islands.

In Orleans Parish, just a few miles south of Slidell across the Interstate 10 bridge, there are 17% fewer residents today than in 2005. In New Orleans itself, where more than two-thirds of the city’s residents left during Hurricane Katrina, the population still hasn’t recovered. Katrina, it turns out, wasn’t a singular anomalous crisis. It was the beginning of a new era in which the reality of the storms and coastal surges was plain to see and looked nothing like the past. People began to realize that adaptation was less of an option than it used to be. Many simply had to leave. Almost every parish closest to the coast — parishes that have been protected by seawalls and levees, or whose residents have taken advantage of decades of subsidized coastal insurance and federal flood insurance programs incentivizing people to stay and rebuild — has been fast losing population despite those efforts. In those places all the legal mechanisms and incentives that for decades blinded society to the real costs of climate change are beginning to crumble as the true scale of change looms on the horizon.

And yet the population of St. Tammany Parish, where Slidell and Liberty Bayou are, has grown by 40%. People flee. And others arrive. Slidell has become the odd epicenter of America’s new era of climate migration. In 2012, a new seawall was built around the inner core of Slidell, and thousands of new homes were erected across bulldozed spits of marshland infill. Families leaving the parishes farther south stopped here. The price of homes has skyrocketed, driving gentrification that makes it even more difficult for poorer, long-standing residents to rebuild or to find a new home. Traffic is a growing concern; when a single dry causeway is all that connects islands, a car accident can grind life to a standstill. And state and local officials here have adopted language used by migration experts around the world, calling Slidell a “receiver community,” as refugees from the land south of it take new homes.

It all goes to show that there will be no clear-cut boundaries or perfect tipping points for climate and migration. Change, here, means two steps forward and one back, as a mélange of competing and conflicting interests all swirl in cycles of short-term opportunities that may later recede to reveal the persistence of long-term trends. A place can grow even as its core shrivels. A climate migration event, as it begins, comes into focus not as a sharply defined arrow pointing north, but as a hodgepodge of conflicting signals. It suggests that even as the nation’s population shifts north — which on balance it inevitably will — and receiving communities must prepare for mass migration, a part of this evolution will be the story of those who remain in place. And it billboards the fact that new policies and leadership will be demanded by these circumstances, not just to help growing places plan for their future, but to soften the landing of the people left behind.

It’s a strange phenomenon to see residents from Louisiana’s southern coast taking refuge in Slidell, because Slidell isn’t exactly high ground. Much of the city is merely 13 feet above sea level. Parts of it, including the bayou where Colette’s family home is, are significantly lower. So when the people in St. Tammany Parish compete for access to this place and approve building permits for a thousand homes on spits of land with only gabion walls — structures of wire filled with stone — to protect them against the waves of Lake Pontchartrain, what they are really fighting for are the slivers of slightly higher ground, the marginal leftovers, so to speak, between New Orleans to the south and Baton Rouge to the west. Here, the lenders will still lend and the insurers will still engage.

But for how long? Eventually, the lands encircling Slidell are going to be worse off than they are today, and the people moving there may well have no choice but to move on again. In 50 years, according to St. Tammany Parish’s own planning documents, the region encircling Slidell could often be under 6 to 15 feet of water, except for the core protected by a levee. And yet they build anyway.

Several years after Katrina, Colette sat in a community auditorium to hear a team of professors describe the coming sea level changes to the people who lived in the parish. The professors showed a series of time-lapse satellite images of a receding and flooded shoreline. It was something already well-known to researchers, but this was the first time Colette recalls it being shown to the people living in the places that were to be affected. “You see your community is going, and they tell you that this is going to happen no matter what,” Colette said. “So even if we are successful in what we do next, we will lose those places. I couldn’t believe what I saw, that this place I hold so dear and that I have such a long memory of, all of those stories are going to go. Who I am and what I am describing is going to be lost. It’s surreal. That land for me and the right to be there was tied to our freedom. It was the difference between being enslaved and not. And to lose that was to lose everything.”