Why Immigration Opponents Should Worry About Climate Change

The Americans who want to keep immigrants out will be dismayed by the latest climate report.

Migrant woman and child sitting on concrete bridge.
A migrant waits along the border bridge with her family after being denied entry into the U.S. from Mexico on June 25.
Spencer Platt/Getty Images

Climate change is a hoax. If it’s not a hoax, it’s overrated. If it’s not overrated, it’s a problem for other countries, not for us. It’s just a pet issue for panicky liberals.

If you believe any of these things, I have bad news: The Intergovernmental Panel on Climate Change—basically, the world’s best weather and earth scientists—has just issued a report on rising temperatures and the problems they’re causing around the world. One of the problems is migration. People are fleeing the hotter parts of the world. If we keep burning coal and oil, we won’t be able to build a wall high enough to keep out the millions of refugees heading north.

The IPCC report outlines this threat and the research behind it. From 2008 to 2015, more than 100 million people were displaced by floods, 60 million by storms, and nearly 1 million by extreme temperatures. Over the past four decades, the rate of such dislocations has increased by 60 percent. The number of likely “environmental migrants” or “environmental refugees” is projected at 50 million to 200 million.

Scientists are documenting the precise effects of temperature on migration. Two years ago, a worldwide study based on 30 years of data found that in countries reliant on agriculture, every one-degree increase in temperature on the Celsius scale—that’s about 1.8 degrees Fahrenheit—correlated with a 5 percent increase in migration to other countries. A study published in 2015 found that in 142 countries, a one-degree rise in Celsius was “associated with a 1.9 percentage increase in migration flows” to the United States, Western Europe, and a few other highly industrialized nations.

The principal factor seems to be agriculture. “Extreme heat is correlated both with lower crop yields and higher outmigration flows,” says the 2016 study. A separate report, published last year by scientists in Germany, explains that heat destroys rice and wheat, causes diseases in animals, and accelerates soil degradation. In Pakistan, a study published four years ago found that high temperatures drove migration by “wiping out over a third of farming income.”

The temperatures in Pakistan triggered an 11-fold increase in migration within that country, often from villages to cities, as men sought easier places to make a living. Similar effects, albeit less dramatic, have been reported in Bangladesh, India, Indonesia, and sub-Saharan Africa. Borders can slow this movement, but they can’t stop it. In 2010, researchers found that a 10 percent decline in Mexican crop yields correlated with a 2 percent increase in emigration. Based on climate projections, they calculated that by 2080, climate-induced effects on agriculture would cause a significant share of Mexico’s working population—2 to 10 percent—to leave the country. That’s on top of the number who would leave Mexico for other reasons. And they won’t be heading south.

The 2015 global study calculated that on an annual basis, each degree of increase in temperature would produce 100,000 additional migrants to the United States, Europe, and other highly industrialized countries. But that figure doesn’t take account of illegal migrants, since their movements weren’t documented. Migration estimates also understate the effects of “slow-onset natural disasters,” such as rising heat, drought, and sea levels, since, as the German report notes, these problems “cause people to migrate alone or in small groups, making it more difficult to identify them as environmental migrants.”

The effects of temperature on global population movement are likely to accelerate for several reasons. One is that we’ve already degraded soil in much of the world, and more heat could finish the job. Fifty million people live in Africa near Lake Chad, which was nearly depleted 30 years ago and remains threatened by “advancing desertification in the entire Sahel region.” Twenty million live in drought-prone areas of East Africa (in Ethiopia, Kenya, Somalia, South Sudan, and Yemen). These regions are projected to suffer some of the worst damage and violence as droughts worsen. A lot of the inhabitants will leave.

Another reason to expect acceleration is secondary migration. Today, most people who flee climate change move to nearby cities, particularly on the coast. But as temperatures and sea levels rise, we can expect many of these people, who have already migrated within their countries, to be driven out of their countries altogether. One emerging threat to these cities of temporary refuge is coastal flooding, which is already a major driver of climate migration. Another threat is the urban heat differential. Due to population density, energy use, and sparsity of vegetation—all of which are exacerbated by climate change—cities run hotter than surrounding areas do. Heat waves there can be life-threatening. Even if we limit the average global temperature rise to two degrees, the increase in some big cities will double that.

All of these mediating factors—soil erosion, population density, coastal flooding, and the exponentially increasing misery of rising heat—imply that the rate at which climate change drives international migration will escalate. People who can’t make a living in nearby plains, mountains, or cities will find their way to other countries. Probably to your country, if you’re already a favored destination. That’s the pattern shown in studies of climate migration.

Unlike people who have fled the temporary droughts or floods of the past, these migrants will stay. “Climate disaster refugees generally tend to migrate back to the regions they were force to leave as soon as conditions allow it,” says a 2015 report from the University of Hamburg. But when “the physical environment is vanishing or permanently becoming uninhabitable”—due, for example, to desertification or rising sea levels—displaced people become “permanent disaster refugees.”

So if you worry, as President Donald Trump does, about people “pouring into our country,” it’s time to wake up. A two-degree increase in global temperatures could trigger “significant population displacement concentrated in the tropics,” says the IPCC report. “Tropical populations may have to move at distances greater than 1000 [kilometers],” and a “rapid evacuation from the tropics could lead [to] concentration of population in tropical margins and the subtropics, where population densities could increase by 300% or more.” As temperatures continue to rise, these people won’t stop in the overcrowded subtropics. And no wall will keep them out.