• People are five times as likely to move following drought conditions as they are after floods or periods of excess water.
  • In low-income countries, most people in a drought-stricken region do not migrate, either because they do not want to or they cannot afford to, according to the World Bank.
  • The greatest environmental pressures are exerted on people in rural areas who rely on farming for their livelihood.

After a year of extreme weather, people in the drylands of northern California and the hurricane-drenched bayous of southern Louisiana are brooding on the same question: should we leave?

New global research suggests that one of these “water shock” scenarios is more likely to result in migration. World Bank researchers found that people are five times as likely to move following drought conditions as they are after floods or periods of excess water.

The finding is part of a lengthy report on water and migration released on Monday during the opening day of World Water Week, an annual conference. The report details the nuanced relationship between changes in water availability and the movement of people.

“Water has the power to shape these migration patterns, perhaps more than you think,” said the World Bank’s Esha Zaveri, the lead author on the report. People have always settled near rivers, lakes, oases, and coasts. It makes sense, she said, that lack of water in a place would drive people away.

These stay-or-go decisions are troubling not just rich-world Californians and Louisianans. Climate change is making rainfall more variable across the planet. In the Mediterranean, southern Africa, the southwestern United States and Mexico, droughts are already more severe than they were six decades ago. If society continues to burn fossil fuels and clear forests, those dry cycles are expected to intensify and spread across wetter areas like the Caribbean and Amazon, potentially affecting hundreds of millions of people a year. Meanwhile, diversions for agriculture, industry, or fast-growing cities can end up being a hydrological own goal, contributing to local water deficits.

Tempting as it is to blame climate change alone for the mass movement of Central Americans northward into Mexico or the exodus of Yemenis, the report urges restraint when it comes to attributing causes. There is a lot of variation across countries and regions and migration has not only environmental roots, but political and social ones as well. The distinction between a climate migrant and a migrant is often quite blurry. “This really cautions against making any sweeping conclusions,” Zaveri said.

Even so, the researchers sought to answer three questions related to water shocks: Why do people migrate? Who migrates? Where do they migrate to?

To answer these questions, they assembled a database showing the in-country movements of hundreds of millions of people in 150 countries over three decades. To that trove they added data on precipitation patterns, urban drinking water sources, and demographics.

People move because they feel their lives will improve and they have the means to do so. Usually migration occurs within a country and not across international borders. The greatest environmental pressures are exerted on people in rural areas who rely on farming for their livelihood. After a few failed harvests, migration can be perceived as an exit ramp to a better life.

But that exit ramp is not available to everyone. Rainfall affects income, but income also influences migration. Zaveri notes that, in low-income countries, most people in a drought-stricken region do not migrate, either because they do not want to or they cannot afford to. More often than not it is the poorest who remain, stuck in a place with diminished economic prospects.

“These populations who are left behind are often omitted from media headlines, yet they represent a policy concern that is just as serious,” Zaveri said.

Flooding was not as likely to induce migration as drought for several potential reasons. Communities may be more capable of adapting to periodic inundation. Or, flooding seeds fields with the prospect of better future harvests.

Richard Elelman, head of politics at Eurecat, the Technology Center of Catalonia, said that the report raises key questions about whether migration is a survival mechanism that is open only to a privileged few and what happens to those who can’t leave. “These are essential issues which need to be addressed, which, I think, this report brings to light really effectively,” he said.

Ana María Ibáñez, principal economic adviser for the Interamerican Development Bank, reacted similarly, if not more poetically, about the migration field’s blind spots: “The research concentrates on the movers and we need to know about the stayers.”

Big city lights

The answer to the third question — where people migrate to — is more straightforward. Cities are often the destination. The life that awaits them, though, may not match the skills they have. Farmers generally are displaced in droughts and their field-honed labor and fewer educational credentials are a bad pairing for the urban jobs market. The study found that they face not only lower wages once they move to cities, but also less access to housing and basic social services.

To stem migration, rural areas could be fortified, the report argues. Building water storage to smooth peaks and troughs in rainfall is a form of insurance, as is irrigation. Restoring forests and preserving wetlands can buffer an ecosystem in dry times. Another option, Zaveri said, are safety net programs like crop insurance or food aid. To ease the transition for those who move to urban areas, there ought to be investments in education, infrastructure, and services.

The options have drawbacks, though. Water storage can lure people to ecologically risky areas and potentially stretch local supplies, upsetting an already tenuous resource balance and spurring conflict. For migrants fleeing rural drought, cities themselves are not immune to water shortages. They might trade one bad situation for another.

“What we find is that such water shortages can significantly slow urban growth, compounding the vulnerability of migrants,” Zaveri said. Sharp droughts in Cape Town and Chennai in recent years show that, just like their rural counterparts, urban areas are subjected to stressful water crises. “Paradoxically, migrants who travel to cities to avoid the impacts of rainfall variability may in fact find themselves in cities that offer fewer economic opportunities and critical services due to these deficits.”

The challenge ahead, Zaveri said, is to recognize the complexity of human migration and acknowledge that the ebb and flow of people, always in search of water, binds the future of rural and urban areas.