One month after Hurricane Katrina tore through the Gulf Coast of Louisiana in 2005, Colette Pichon Battle stood in front of her childhood home near Slidell, surveying the storm’s damage.

The 1930s shotgun-style house remained on its foundation, but barely. It sat eerily amid an acre and a half of downed trees. Its wood siding was warped and covered in mud and its tin roof was peeling off. The air inside smelled damp and foul, and a giant X on the front door meant that the military had searched the premises for survivors.

“I was raised in this house, the same house my mother was born in,” said Pichon Battle. “There it was, gutted by the storm.”

Pichon Battle had been working in Washington, D.C. as a corporate lawyer when the eye of the category 3 hurricane directly hit her hometown on August 29, 2005, pushing a 30-foot wall of water through the city. Most of her family evacuated, but two uncles and an aunt stayed behind as they had for every other storm in their lifetimes. The entire city was devastated, house after house ripped apart by the tidal surge.

Seeing the devastation left in Katrina’s wake, Pichon Battle decided to return to Slidell and help rebuild her hometown. She lived in a tent on the front lawn for the first three months, then spent another two years in a 240-square-foot trailer provided by the Federal Emergency Management Agency. She is now the executive director of the Gulf Coast Center for Law & Policy, a non-profit law firm and grassroots advocacy organization for social and economic equity.

But some of Pichon Battle’s neighbors have yet to return, even 10 years later. Two-thirds of her French Creole community Bayou Vincent have come back. The rest, however, have not—including her mother.

Similar stories litter the hundreds of towns in Katrina’s path. Much of the physical damage the hurricane inflicted has been repaired, but the storm’s emotional cost continues to run deep. Families and communities rooted for generations in the Gulf Coast remain scattered across the country, and some never will return. Their reasons are varied: better jobs, better schools, better housing, better health care, less flood risk.

New Orleans’s population has dropped to 384,000 today from the 484,000 before Katrina—and that includes 30,000 new residents. The Lower Ninth Ward, a historically black and low-income neighborhood, had 14,000 residents before Katrina. Now it has 3,000.

Hurricane Katrina is often considered the first modern climate-related disaster in the United States. Warmer ocean temperatures from the buildup of greenhouse gases in the atmosphere are believed to have fueled the storm’s intensity, and rising sea level contributed to its record-breaking storm surge—making the 1,833 people who lost their lives and the 400,000 people who lost their homes true victims of climate change.

They are, however, by no means the last.

Estimates for the number of people who will be displaced by global warming range from 50 million by 2030 to 1 billion by 2100, said Elizabeth Ferris, director of the Brookings-LSE Project on Internal Displacement and an expert on humanitarian crises. As many as 5 million people and 2.6 million properties in the U.S. could be underwater with four feet of sea level rise, a scenario that scientists say is looking more and more likely by 2100.

Even today, most of the discussion around global warming is focused on its technical, political and scientific aspects, not the complex, emotional decisions that come with a changing climate, said Ferris.

“People sometimes talk about climate refugees, but in very general terms,” Ferris said. “They haven’t really thought through what that means, why people would leave, where they would go and under what conditions. Climate change is going to leave millions of people on the move, and when you start unpacking what that means it is quite complicated.”

Low-lying populations in Alaska, the Pacific Islands, the MeKong Delta and Bangladesh are already starting to relocate as vanishing coastlines threaten homes, food supplies, commerce and drinking water sources. Towns in the Chesapeake Bay and southern Florida are struggling with so-called sunny day flooding, which happens even when there are no storms in sight. Approximately 1,200 flood-prone homeowners have sold their properties to New York State since Superstorm Sandy devastated the East coast in October 2012. Five hundred of these buyouts will help create open space to act as buffers against future storm surges.

But for all the people who have left, there are thousands more in Louisiana, Mississippi and other low-lying areas who refuse to go. Many New Orleanians simply couldn’t afford to leave after Katrina. Most, however, stayed out of loyalty and love for their ancestral and cultural roots.

Since Hurricane Katrina, Louisiana native Monique Harden said she worries every day about being hit by another hurricane. Floodwaters reached her home in 2005, but didn’t make it past the foundation. Many of her neighbors and family members were not so lucky.

“As a New Orleanian, when June 1st would come around, I wouldn’t think, ‘Oh it is hurricane season.’ Now, I do,” said Harden, founder and co-director of Advocates for Environmental Human Rights, a non-profit organization that provides legal support and community advocacy in New Orleans. “You evaluate your risk and plan very differently because of the experience we went through, not just with the storm, but also the displacement.”

But Harden said she’d never permanently leave New Orleans, despite knowing that southern Louisiana is one of the world’s most vulnerable places to the impacts of climate change. The state has lost 1,880 square miles of land in the last 80 years due to rising seas, land subsidence and oil and gas activity, and with it Louisiana’s natural buffer against coastal storms. The Gulf of Mexico could rise another 4.3 feet by 2100 as seas continue to rise and land continues to sink, according to the National Oceanic and Atmospheric Administration. Much of southern Louisiana lies just three feet above sea level.

“New Orleans is my home,” Harden said. “If you are not a person who is defined by where you’re from or where you live, it is easier to get up and go. But when who you are is tied to where you are, it is harder to leave. It is like cutting off part of your body. You want to stay and fight and figure out how to protect it.”

Jonathan Skvarka, executive director of Rebuilding Together New Orleans, a nonprofit that has helped rebuild nearly 500 houses since Katrina, said most of the people he’s worked with did not consider leaving their home an option.

New Orleans is unique among American cities, a colorful cultural and architectural mashup of French and Cajun influences, with a local accent that to outsiders is often  undecipherable. Wander deep into its neighborhoods away from the tourist crowds and it’s easy to forget you’re still in the U.S.

“Our homeowners have said that when they were displaced, the rest of America just didn’t make sense to them,” Skvarka said. “Culturally, it was totally foreign. When you’re talking about someone who has spent 50, 60 years in New Orleans, there is no moving on, there is no wanting to pick up and leave.”

No Easy Answers

Even without the cultural challenge of leaving, climate displacement is an incredibly difficult issue. Humanitarian, climate change and environmental justice leaders argue that you can’t tell someone it is wrong to want to stay in their home, but there are clearly risks involved with that decision.

Climate resiliency projects are getting more innovative and engineers have decades of examples to learn from and improve upon. The Netherlands, much of which lies below sea level, has fought to hold back the ocean for centuries, and the increased threat that climate change will bring has prompted the country to try everything from voluntarily displacing residents to building floating communities. New York City is building a system of flood walls and marshes to safeguard the city from future storm surges, which along with other flood protection measures will cost $20 billion.

Since Katrina, the Army Corps of Engineers has raised, rebuilt and reinforced New Orleans’ levees to be able to withstand a 100-year storm, meaning a storm with a 1 percent chance of happening in any given year, for the next 50 years. The system has been designed so it can be strengthened and made taller as scientists produce more precise sea level rise estimates, said Ed Link, a civil engineer at the University of Maryland who chaired the Army Corps of Engineers-sponsored task force that evaluated how and why New Orleans’ levees and floodwalls failed during Katrina.

This gradual improvement will allow New Orleans to “adapt to what is actually happening as opposed to reacting now to what is currently uncertain,” Link said. “This makes more economic sense in today’s environment of constrained funding. This is the approach that the Netherlands is taking for their flood risk management.”

Even in the Netherlands, though, the lesson was not learned easily. The epic floods of 1953 that killed an estimated 1,835 prompted the building of Delta Works, the system of dams and storm surge barriers. But warnings that those dams were vulnerable did not produce action until 1995, when another huge flood caused more than 200,000 people to be evacuated and hundreds of farm animals died.

Even with massive infrastructure projects, however, there will be places that people will have to abandon eventually because of climate change, said Rob Moore, director of the Natural Resources Defense Council’s water and climate team.

“For areas like NYC and Boston, it is unlikely we are going to move millions of people out of those areas,” he said. “We will have to rely on heavy structural protections. But we can’t do that from the north tip of Maine to Brownsville, Texas. We can’t do it for the whole shoreline.”

Rising flood insurance premiums could force some people out early, Moore said. Others may only leave when water is lapping at their front steps. Governments will need to make sure new people don’t replace those who have left so that the land can be left to act as a natural barrier. That could be a monumental challenge because most homeowners don’t truly understand flood risk, he said.

“Moving, buying a home near the ocean, it is like living the American dream,” said Moore. “If anything, we see that as a reward for a life well lived. But the odds of you getting a 100-year flood in the time you own your home on a 30-year mortgage are worse than if you were playing Russian roulette. It is a better than one-in-six chance, and that’s not even counting a 20- or 50-year flood. Who would want to play Russian roulette with 1.5 bullets in the gun? That’s insane. With climate change, those odds get even worse.”

Staying put also raises serious financial questions. As the risk of extreme weather rises due to climate change, insurance companies are increasingly pulling out of vulnerable areas or raising premiums. Strapped for options, many Americans on fixed incomes have simply started dropping their coverage. Who then should pick up the tab when a disaster rolls in? The cost to rebuild New Orleans and the surrounding region after Hurricane Katrina has been estimated at $150 billion, and the work is not yet done. The Federal Emergency Management Agency, which provides immediate disaster relief and runs the nation’s largest flood insurance program, was $24 billion in debt in 2014.

“There are no easy answers when it comes to climate displacement,” said Moore.

A Mission and a Challenge

Pichon Battle’s childhood home today looks almost exactly like it did before Katrina, and much of the surrounding community has rebounded. New mansions line the shores of Lake Pontchartrain in Slidell, earthen levees have been rebuilt and businesses have reopened. But there are still abandoned homes. She said she is on a mission to get all of her neighbors and family back home.

“When I have conversations with my mom, I hear her pain in the decision to stay in Texas,” she said. “For everything that Texas has offered to many south Louisiana families, it is not Louisiana. My family is not unaware of flooding. We live with a deep respect for how powerful nature can be. Like people who live where there are avalanches or tornadoes, you learn a system of survival and rebuilding. But we saw a massive failure in corporate accountability and government infrastructure, in justice and equity. That’s what people don’t want to go through again.”

The people who have returned to southern Louisiana and Mississippi know they will be flooded again in the decades to come, community leaders said. That’s simply life living on the water’s edge. They see it as a challenge to solve.  

“Our love of this place, our joy in living here, can be the fuel to find the solutions to stay,” Harden said. “If we fail, then it means everything is up for grabs. Where is it safe? Where is there a place where there aren’t wildfires or drought conditions or flooding in America? Where are all 300 million of us going to go to? Some people are looking at us like we’re crazy, but they should be looking at us from a perspective of if they give up their fight, then everyone can give up the fight. There are very few places in this country that are considered climate-proof and there isn’t enough room for all 300 million of us there.”