Early in 2019, a year before the world shut its borders completely, Jorge A. knew he had to get out of Guatemala. The land was turning against him. For five years, it almost never rained. Then it did rain, and Jorge rushed his last seeds into the ground.
The corn sprouted into healthy green stalks, and there was hope — until, without warning, the river flooded. Jorge waded chest-deep into his fields searching in vain for cobs he could still eat.
Soon he made a last desperate bet, signing away the tin-roof hut where he lived with his wife and three children against a €1,500 advance in okra seed. But after the flood, the rain stopped again, and everything died. Jorge knew then that if he didn’t get out of Guatemala, his family might die, too.
Even as hundreds of thousands of Guatemalans fled north toward the United States in recent years, in Jorge’s region — a state called Alta Verapaz, where precipitous mountains covered in coffee plantations and dense, dry forest give way to broader gentle valleys — the residents have largely stayed.
Now, though, under a relentless confluence of drought, flood, bankruptcy and starvation, they, too, have begun to leave. Almost everyone here experiences some degree of uncertainty about where their next meal will come from.
Half the children are chronically hungry, and many are short for their age, with weak bones and bloated bellies. Their families are all facing the same excruciating decision that confronted Jorge.
The odd weather phenomenon that many blame for the suffering here — the drought and sudden storm pattern known as El Niño — is expected to become more frequent as the planet warms. Many semiarid parts of Guatemala will soon be more like a desert.
Rainfall is expected to decrease by 60% in some parts of the country, and the amount of water replenishing streams and keeping soil moist will drop by as much as 83%. Researchers project that by 2070, yields of some staple crops in the state where Jorge lives will decline by nearly a third.
Scientists have learned to project such changes around the world with surprising precision, but — until recently — little has been known about the human consequences of those changes. As their land fails them, hundreds of millions of people from Central America to Sudan to the Mekong Delta will be forced to choose between flight or death. The result will almost certainly be the greatest wave of global migration the world has seen.
In March, Jorge and his 7-year-old son each packed a pair of pants, three T-shirts, underwear and a toothbrush into a single thin black nylon sack with a drawstring. Jorge’s father had pawned his last four goats for €2,000 to help pay for their transit, another loan the family would have to repay at 100% interest. The coyote called at 10 pm — they would go that night. They had no idea then where they would wind up, or what they would do when they got there.
From decision to departure, it was three days. And then they were gone.
For most of human history, people have lived within a surprisingly narrow range of temperatures, in the places where the climate supported abundant food production. But as the planet warms, that band is suddenly shifting north.
According to a groundbreaking recent study in the journal, the planet could see a greater temperature increase in the next 50 years than it did in the last 6,000 years combined.
By 2070, the kind of extremely hot zones, like in the Sahara, that now cover less than 1% of the earth’s land surface could cover nearly a fifth of the land, potentially placing one of every three people alive outside the climate niche where humans have thrived for thousands of years.
Many will dig in, suffering through heat, hunger and political chaos, but others will be forced to move on.
A 2017 study infound that by 2100, temperatures could rise to the point that just going outside for a few hours in some places, including parts of India and Eastern China, “will result in death even for the fittest of humans.”
People are already beginning to flee. In Southeast Asia, where increasingly unpredictable monsoon rainfall and drought have made farming more difficult, the World Bank points to more than eight million people who have moved toward the Middle East, Europe and North America.
In the African Sahel, millions of rural people have been streaming toward the coasts and the cities amid drought and widespread crop failures. Should the flight away from hot climates reach the scale that current research suggests is likely, it will amount to a vast remapping of the world’s populations.
Migration can bring great opportunity not just to migrants but also to the places they go. As the United States and other parts of the global North face a demographic decline, for instance, an injection of new people into an ageing work force could be to everyone’s benefit.
But securing these benefits starts with a choice: Northern nations can relieve pressures on the fastest-warming countries by allowing more migrants to move north across their borders, or they can seal themselves off, trapping hundreds of millions of people in places that are increasingly unlivable.
The best outcome requires not only good will and the careful management of turbulent political forces; without preparation and planning, the sweeping scale of change could prove wildly destabilizing. The United Nations and others warn that in the worst case, the governments of the nations most affected by climate change could topple as whole regions devolve into war.
The stark policy choices are already becoming apparent. As refugees stream out of the Middle East and North Africa into Europe and from Central America into the United States, an anti-immigrant backlash has propelled nationalist governments into power around the world.
The alternative, driven by a better understanding of how and when people will move, is governments that are actively preparing, both materially and politically, for the greater changes to come.
In recent months, the coronavirus pandemic has offered a test run on whether humanity has the capacity to avert a predictable — and predicted — catastrophe. Some countries have fared better. But the United States has failed. The climate crisis will test the developed world again, on a larger scale, with higher stakes. The only way to mitigate the most destabilizing aspects of mass migration is to prepare for it, and preparation demands a sharper imagining of where people are likely to go, and when.
In November 2007, Alan B. Krueger, a labour economist known for his statistical work on inequality, walked into the Princeton University offices of Michael Oppenheimer, a leading climate geoscientist, and asked him whether anyone had ever tried to quantify how and where climate change would cause people to move.
Earlier that year, Oppenheimer helped write the UN Intergovernmental Panel on Climate Change report that, for the first time, explored in-depth how climate disruption might uproot large segments of the global population.
But as groundbreaking as the report was — the UN was recognised for its work with a Nobel Peace Prize — the academic disciplines whose work it synthesized were largely siloed from one another. Demographers, agronomists and economists were all doing their work on climate change in isolation, but understanding the question of migration would have to include all of them.
Together, Oppenheimer and Krueger, who died in 2019, began to chip away at the question, asking whether tools typically used by economists might yield insight into the environment’s effects on people’s decision to migrate.
They began to examine the statistical relationships — say, between census data and crop yields and historical weather patterns — in Mexico to try to understand how farmers there respond to drought. The data helped them create a mathematical measure of farmers’ sensitivity to environmental change — a factor that Krueger could use the same way he might evaluate fiscal policies, but to model future migration.
As they have looked more closely, migration researchers have found climate’s subtle fingerprints almost everywhere. Drought helped push many Syrians into cities before the war, worsening tensions and leading to rising discontent; crop losses led to unemployment that stoked Arab Spring uprisings in Egypt and Libya; Brexit, even, was arguably a ripple effect of the influx of migrants brought to Europe by the wars that followed.
And all those effects were bound up with the movement of just two million people. As the mechanisms of climate migration have come into sharper focus — food scarcity, water scarcity and heat — the latent potential for large-scale movement comes to seem astronomically larger.
North Africa’s Sahel provides an example. In the nine countries stretching across the continent from Mauritania to Sudan, extraordinary population growth and steep environmental decline are on a collision course.
Past droughts, most likely caused by climate change, have already killed more than 100,000 people there. And the region — with more than 150 million people and growing — is threatened by rapid desertification, even more severe water shortages and deforestation. Today researchers at the United Nations estimate that some 65 percent of farmable lands have already been degraded.
“My deep fear,” said Solomon Hsiang, a climate researcher and economist at the University of California, Berkeley, is that Africa’s transition into a post-climate-change civilization “leads to a constant outpouring of people.”
The story is similar in South Asia, where nearly one-fourth of the global population lives. The World Bank projects that the region will soon have the highest prevalence of food insecurity in the world.
While some 8.5 million people have fled already — resettling mostly in the Persian Gulf — 17 million to 36 million more people may soon be uprooted, the World Bank found. If past patterns are a measure, many will settle in India’s Ganges Valley; by the end of the century, heat waves and humidity will become so extreme there that people without air-conditioning will simply die.
If it is not drought and crop failures that force large numbers of people to flee, it will be the rising seas. We are now learning that climate scientists have been underestimating the future displacement from rising tides by a factor of three, with the likely toll being some 150 million globally.
New projections show high tides subsuming much of Vietnam by 2050 — including most of the Mekong Delta, now home to 18 million people — as well as parts of China and Thailand, most of southern Iraq and nearly all of the Nile Delta, Egypt’s breadbasket. Many coastal regions of the United States are also at risk.
Through all the research, rough predictions have emerged about the scale of total global climate migration — they range from 50 million to 300 million people displaced — but the global data is limited, and uncertainty remained about how to apply patterns of behavior to specific people in specific places.
Now, though, new research on both fronts has created an opportunity to improve the models tremendously.
A few years ago, climate geographers from Columbia University and the City University of New York began working with the World Bank to build a next-generation tool to establish plausible migration scenarios for the future. The idea was to build on the Oppenheimer-style measure of response to the environment with other methods of analysis, including a “gravity” model, which assesses the relative attractiveness of destinations with the hope of mathematically anticipating where migrants might end up. The resulting report, published in early 2018, involved six European and American institutions and took nearly two years to complete.
The bank’s work targeted climate hot spots in sub-Saharan Africa, South Asia and Latin America, focusing not on the emergency displacement of people from natural disasters but on their premeditated responses to what researchers call “slow-onset” shifts in the environment.
They determined that as climate change progressed in just these three regions alone, as many as 143 million people would be displaced within their own borders, moving mostly from rural areas to nearby towns and cities. The study, though, wasn’t fine-tuned to specific climatic changes like declining groundwater. And it didn’t even try to address the elephant in the room: How would the climate push people to migrate across international borders?
For all the ways in which human migration is hard to predict, one trend is clear: Around the world, as people run short of food and abandon farms, they gravitate toward cities, which quickly grow overcrowded.
It’s in these cities, where waves of new people stretch infrastructure, resources and services to their limits, that migration researchers warn that the most severe strains on society will unfold. Food has to be imported — stretching reliance on already-struggling farms and increasing its cost. People will congregate in slums, with little water or electricity, where they are more vulnerable to flooding or other disasters. The slums fuel extremism and chaos.
It is a shift that is already well underway, which is why the World Bank has raised concerns about the mind-boggling influx of people into East African cities like Addis Ababa, in Ethiopia, where the population has doubled since 2000 and is expected to nearly double again by 2035.
In Mexico, the World Bank estimates, as many as 1.7 million people may migrate away from the hottest and driest regions, many of them winding up in Mexico City.
But like so much of the rest of the climate story, the urbanization trend is also just the beginning. Right now a little more than half of the planet’s population lives in urban areas, but by the middle of the century, the World Bank estimates, 67% will.
In just a decade, four out of every 10 urban residents — two billion people around the world — will live in slums. The International Committee of the Red Cross warns that 96 percent of future urban growth will happen in some of the world’s most fragile cities, which already face a heightened risk of conflict and have governments that are least capable of dealing with it.
Some cities will be unable to sustain the influx. In the case of Addis Ababa, the World Bank suggests that in the second half of the century, many of the people who fled there will be forced to move again, leaving that city as local agriculture around it dries up.
People move to cities because they can seem like a refuge, offering the facade of order — tall buildings and government presence — and the mirage of wealth. I met several men who left their farm fields seeking extremely dangerous work as security guards in San Salvador and Guatemala City.
I met a 10-year-old boy washing car windows at a stoplight, convinced that the coins in his jar would help buy back his parents’ farmland. Cities offer choices and a sense that you can control your destiny.
These same cities, though, can just as easily become traps, as the challenges that go along with rapid urbanization quickly pile up. Since 2000, San Salvador’s population has ballooned by more than a third as it has absorbed migrants from the rural areas, even as tens of thousands of people continue to leave the country and migrate north.
By midcentury, the UN estimates that El Salvador — which has 6.4 million people and is the most densely populated country in Central America — will be 86% urban.
Yet around the world, nations are choosing walls. Even before the pandemic, Hungary fenced off its boundary with Serbia, part of more than 1,000 kilometers of border walls erected around the European Union states since 1990.
India has built a fence along most of its 2,500-mile border with Bangladesh, whose people are among the most vulnerable in the world to sea-level rise.
The United States, of course, has its own wall-building agenda — literal ones, and the figurative ones that can have a greater effect.
On a walk last August from one of El Paso’s migrant shelters, an inconspicuous brick home called Casa Vides, the Rev. Peter Hinde told me that El Paso’s security-oriented economy had created a cultural barrier that didn’t exist when he moved here 25 years earlier.
Hinde, who is 97, helps run the Carmelite order in Juárez but was traveling to volunteer at Casa Vides on a near-daily basis. A former Army Air Forces captain and fighter pilot who grew up in Chicago, Hinde said the United States is turning its own fears into reality when it comes to immigration, something he witnesses in a growing distrust of everyone who crosses the border.
That fear creates other walls. The United States refused to join 164 other countries in signing a global migration treaty in 2018, the first such agreement to recognize climate as a cause of future displacement. At the same time, the US is cutting off foreign aid — money for everything from water infrastructure to greenhouse agriculture — that has been proved to help starving families like Jorge A.’s in Guatemala produce food, and ultimately stay in their homes.
Even those migrants who legally make their way into El Paso have been turned back, relegated to cramped and dangerous shelters in Juárez to wait for the hearings they are owed under law.
There is no more natural and fundamental adaptation to a changing climate than to migrate. It is the obvious progression the earliest Homo sapiens pursued out of Africa, and the same one the Mayans tried 1,200 years ago.
As Lorenzo Guadagno at the UN’s International Organisation for Migration told me recently, “Mobility is resilience.” Every policy choice that allows people the flexibility to decide for themselves where they live helps make them safer.
But it isn’t always so simple, and relocating across borders doesn’t have to be inevitable. I thought about Jorge A. from Guatemala. He made it to the United States last spring, climbing the steel border barrier and dropping his 7-year-old son 20 feet down the other side into the California desert. (We are abbreviating his last name in this article because of his undocumented status.)
Now they live in Houston, where until the pandemic, Jorge found steady work in construction, earning enough to pay his debts and send some money home. But the separation from his wife and family has proved intolerable; home or away, he can’t win, and as of early July, he was wondering if he should go back to Guatemala.
And therein lies the basis for what may be the worst-case scenario: one in which the developed world refuse to welcome migrants but also fail to help them at home. As our model demonstrated, closing borders while stinting on development creates a somewhat counterintuitive population surge even as temperatures rise, trapping more and more people in places that are increasingly unsuited to human life.
In that scenario, the global trend toward building walls could have a profound and lethal effect. Researchers suggest that the annual death toll, globally, from heat alone will eventually rise by 1.5 million. But in this scenario, untold more will also die from starvation, or in the conflicts that arise over tensions that food and water insecurity will bring.
If this happens, the United States and Europe risk walling themselves in, as much as walling others out. And so the question then is: What are policymakers and planners prepared to do about that?
Wealthy countries can help vulnerable people where they live, by funding development that modernises agriculture and water infrastructure. A UN World Food Program effort to help farmers build irrigated greenhouses in El Salvador, for instance, has drastically reduced crop losses and improved farmers’ incomes. It can’t reverse climate change, but it can buy time.
Thus far, the United States has done very little at all. Even as the scientific consensus around climate change and climate migration builds in some circles the topic has become taboo.
Earlier this year, after Proceedings of the National Academy of Sciences published the explosive study estimating that, barring migration, one-third of the planet’s population may eventually live outside the traditional ecological niche for civilization, Marten Scheffer, one of the study’s authors, told me that he was asked to tone down some of his conclusions through the peer-review process and that he felt pushed to “understate” the implications in order to get the research published. The result: Migration is only superficially explored in the paper. (A spokeswoman for the journal declined to comment because the review process is confidential.)
“There’s flat-out resistance,” Scheffer told me, acknowledging what he now sees as inevitable, that migration is going to be a part of the global climate crisis.
“We have to face it.”
Our modeling and the consensus of academics point to the same bottom line: If societies respond aggressively to climate change and migration and increase their resilience to it, food production will be shored up, poverty reduced and international migration slowed — factors that could help the world remain more stable and more peaceful.
If leaders take fewer actions against climate change, or more punitive ones against migrants, food insecurity will deepen, as will poverty. Populations will surge, and cross-border movement will be restricted, leading to greater suffering. Whatever actions governments take next — and when they do it — makes a difference.
The window for action is closing. The world can now expect that with every degree of temperature increase, roughly a billion people will be pushed outside the zone in which humans have lived for thousands of years.
For a long time, the climate alarm has been sounded in terms of its economic toll, but now it can increasingly be counted in people harmed. The worst danger, Hinde warned on our walk, is believing that something so frail and ephemeral as a wall can ever be an effective shield against the tide of history.
“If we don’t develop a different attitude,” he said, “we’re going to be like people in the lifeboat, beating on those that are trying to climb in.”