Extreme weather is contributing to undocumented migration and returns between Mexico and the United States, new study suggests, suggesting more migrants could risk their lives crossing the border as climate change fuels droughts, storms and other difficulties.

People in agricultural areas of Mexico were more likely to cross the border illegally after droughts and less likely to return to their home communities when extreme weather persisted, according to a study published this week in the journal Proceedings of the National Academy of Sciences.

Around the world, climate change – caused by the burning of fossil fuels such as coal and natural gas – is exacerbating extreme weather. Droughts are longer and drier, heat is deadlier, and storms are rapidly intensifying and dumping record rainfall.

In Mexico, a country of nearly 130 million people, drought has dried up reservoirs, caused severe water shortages and dramatically reduced corn production, threatening livelihoods.

The researchers said Mexico is a notable country for studying the links between migration, return and weather stressors. Its average annual temperature is expected to rise as much as 5.4 degrees Fahrenheit by 2060, and extreme weather risks economically devastating rural communities dependent on rain-fed agriculture. The United States and Mexico also experience the largest international migration flows in the world.

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Scientists predict that migration will increase as the planet warms. Over the next 30 years, 143 million people worldwide will likely be uprooted by rising seas, drought, scorching temperatures and other climate disasters, according to a report by the Intergovernmental Panel on Climate Change. United Nations climate.

This new study on migration comes as Republican Donald Trump was re-elected to the US presidency this week. Trump has called climate change a “hoax” and promised mass, illegal evictions of an estimated 11 million people in the United States.

The researchers said their results highlight how extreme weather conditions drive migration.

Filiz Garip, a researcher and professor of sociology and international affairs at Princeton University, said advanced countries have contributed far more to climate change than developing countries who bear the brunt.

Migration “is not a decision that people make lightly…and yet they are forced to do it more, and they are forced to stay longer in the United States” due to extreme weather conditions, he said. Garip said.

Researchers analyzed daily weather data as well as survey responses from 48,313 people between 1992 and 2018, focusing on about 3,700 people who crossed the border undocumented for the first time.

They examined 84 agricultural communities in Mexico where corn cultivation depended on weather conditions. They correlated a person’s decision to migrate and then return with abnormal changes in temperature and precipitation in their home communities during the corn growing season, from May to August.

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The study found that communities experiencing drought had higher migration rates than communities experiencing normal rainfall. And people were less likely to return to Mexico from the United States when their communities were unusually dry or wet. This was true for recent arrivals to the United States and for people who had been there longer.

People who were better off financially were also more likely to migrate. The same was true for people from communities with established migration histories, where friends, neighbors or family members who had previously emigrated could offer information and assistance.

These social and economic factors that influence migration are well understood, but Garip said the study’s findings highlight the inequalities of climate adaptation. During extreme weather events, not everyone is affected or reacts in the same way, she said, “and typical social and economic advantages or disadvantages also shape how people experience these events”.

For Kerilyn Schewel, co-director of Duke University’s Climate, Resilience and Mobility Program, economic factors underscore that some of the most vulnerable people are not those displaced by climate extremes, but rather are “stuck in place.” or lacking the resources to travel.” “.

Schewel, who was not involved in the study, said analyzing regions with a history of migration could help predict where migrants will come from and who is most likely to migrate due to climate shocks. “In places where people are already leaving, where there is a high degree of migration, that’s where we can expect more people to leave in the future,” she said.

The survey data used in the Mexican Migration Project makes this study unique, according to Hélène Benveniste, a professor in the Department of Environmental Social Sciences at Stanford University. Migration data on this scale, community-specific, is “rarely available,” she said in an email. The same applies to information on a person’s complete migration journey, including their return.

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The finding that return migration decisions were delayed by climate stress in communities of origin is “important and novel,” said Benveniste, who studies climate-related human migration and was not involved in the ‘study. “Few datasets allow us to analyze this question.”

But increased monitoring and enforcement along the U.S.-Mexico border is making returning home — and traveling there and back — more difficult, said Michael Méndez, assistant professor of environmental policy and planning at the University of California at Irvine. And once undocumented migrants arrive in the United States, they often live in dilapidated housing, lack health care, or work in industries such as construction or agriculture, making them vulnerable to others climate impacts, he said. Méndez was not involved in the study.

As climate change threatens social, political and economic stability around the world, experts said the study highlights the need for global collaboration around migration and climate resilience.

“In some ways, a lot of our focus has been on the border and securing the border,” Duke’s Schewel said. “But we need a lot more attention, not only to why people are leaving, but also to the demand for immigrant workers in the United States.”