Mexico By 2050, climate change is expected to turn 1.7 million Mexicans into migrants. The arid north and low-lying southern regions of Mexico will be more prone to drought, wildfires, and flooding than the central plateau around Mexico City, so migration into urban areas will increase. Port workers and farmers from Veracruz and Tabasco will likely need to retrain for the urban economy of Mexico City. The World Bank Groundswell Report

These examples focus on migration within rather than between countries, because that’s what most of the existing models focus on. Why? Because when people move, they don’t usually go far— people forced into migrating typically don’t have a lot of money, and if people in a neighboring country speak a different language, that’s yet another disincentive to leaving the home country. And in some cases a potential destination country has physical or legal barriers that can compel people to stay close to home.

Bangladesh Researchers expect that 13.3 million Bangladeshis could be climate migrants in 2050. That’s close to 8% of the projected population. The most likely migrant is a rural rice farmer moving into the Ganges River Basin—but since that region is already overcrowded, the migrants are likely to have a hard time finding work and shelter. The World Bank Groundswell Report

Improving these models is crucial, because if governments know where people might go, they can prepare for what’s coming. For example, a city with great economic opportunities is likely to draw more migrants if a climate shock happens. If policymakers can get a better sense of how many people might arrive and when, they can prepare by directing investment to that area for affordable housing, hospitals, and schools.

“We’re never going to get exact numbers,” says Alex de Sherbinin of Columbia University, another of the report’s coauthors, “but if people understand what the model is doing, they can get very useful information out of it.”

Tate Ryan-Mosley contributed research for this story.