Extreme weather is contributing to undocumented migration and returns between Mexico and the United States, a modern study says, suggesting more migrants could risk their lives crossing the border as climate change fuels droughts, storms and other hardships.
People from agricultural areas in Mexico were more likely to cross the border illegally after droughts and less likely to return to their original communities when the extreme weather continued, according to a study this week in the journal Proceedings of the National Academy of Sciences.
Across the world, climate change – caused by the burning of fossil fuels such as coal and natural gas – is exacerbating extreme weather events. Droughts are longer and drier, heat is deadlier, and storms are rapidly intensifying and dumping record-breaking rainfall.
In Mexico, a country of nearly 130 million people, drought has drained reservoirs, caused severe water shortages and drastically reduced corn production, threatening livelihoods.
Researchers said Mexico is a notable country for studying the links between migration, return and weather stressors. By 2060, average annual temperatures are expected to rise by up to 3 degrees Celsius (5.4 degrees Fahrenheit), and extreme weather is expected to economically devastate rural communities that rely on rain-fed agriculture. The United States and Mexico also have the largest international migration flows in the world.
Scientists expect migration to escalate as the planet gets hotter. Over the next 30 years, 143 million people worldwide are expected to lose their homes due to rising sea levels, drought, scorching temperatures and other climate-related disasters, according to a report from the United Nations Intergovernmental Panel on Climate Change.
The modern migration research comes at a time when Republican Donald Trump was re-elected US president this week. Trump called climate change a “hoax” and promised the illegal mass deportation of an estimated 11 million people in the United States.
The researchers said their findings highlight how extreme weather conditions drive migration.
Filiz Garip, study researcher and professor of sociology and international affairs at Princeton University, said advanced nations have contributed far more to climate change than developing countries, which are bearing the brunt.
Migration “is not a decision that people make lightly … and yet extreme weather forces them to do more and stay longer in the United States,” Garip said.
Researchers analyzed daily weather data and survey responses from 48,313 people between 1992 and 2018, focusing on about 3,700 people who crossed the border for the first time without documents.
They studied 84 agricultural communities in Mexico where corn production was dependent on the weather. They correlated an individual’s decision to emigrate and then return to abnormal temperature and precipitation fluctuations in their communities of origin during the corn growing season from May to August.
The study found that communities affected by drought had higher migration rates compared to communities with normal rainfall. And people from the U.S. were less likely to return to Mexico if their communities were unusually parched or humid. This applied to both newcomers to the United States and people who had been there for a long time.
People who were financially better off were also more likely to emigrate. This also applied to people from communities with established migration histories, to whom friends, neighbors or family members who had previously emigrated could offer information and support.
These social and economic factors that influence migration are well understood, but Garip said the study’s findings highlight the inequalities of climate adaptation. Not everyone is affected by extreme weather events or reacts the same way, she said, “and the typical social and economic advantages or disadvantages also shape the way people experience these events.”
For Kerilyn Schewel, co-director of Duke University’s Climate, Resilience and Mobility Program, the economic factors illustrate that some of the most vulnerable people are not those displaced by climate extremes, but rather “stuck in place or.” not having the resources to get around.”
Schewel, who was not involved in the study, said analyzing regions with migration histories can support predict where migrants come from and who is more likely to emigrate due to climate shocks. “In places where people are already leaving, where there is a high level of migration prevalence, … we can expect even more people to leave in the future,” she said.
According to Hélène Benveniste, a professor in the Department of Environmental Social Sciences at Stanford University, the survey data from the Mexican Migration Project make this study unique. Migration data of this magnitude that is community-specific is “rarely available,” she said in an email. This also applies to information about a person’s entire migration journey, including their return.
The finding that return migration decisions were delayed by weather stress in communities of origin is “important and new,” said Benveniste, who studies climate-related human migration and was not involved in the study. “Only a few data sets allow an analysis of this question.”
But increasing surveillance and enforcement along the U.S.-Mexico border makes returning home — and moving back and forth — more hard, said Michael Méndez, an assistant professor of environmental policy and planning at the University of California, Irvine. And once undocumented migrants are in the U.S., they often live in shabby housing, lack health care or work in industries like construction or agriculture that make them vulnerable to other climate impacts, he said. Méndez was not involved in the study.
As climate change threatens social, political and economic stability around the world, experts say the study highlights the need for global cooperation on migration and climate resilience.
“In some ways, our main focus has been on the border and securing it,” Duke’s Schewel said. “But we need to pay much more attention not only to the reasons people are leaving, but also to the demand for migrant workers in the United States.”
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