Why Do People Move? Research on Environmental Migration Coming of Age | Wilson Center
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Why Do People Move? Research on Environmental Migration Coming of Age

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When she finished her dissertation on migration as a response to climate change in 2003, it was one of only a handful of scholarly papers published on the topic that year, said Susana Adamo, an associate research scientist at Columbia University’s Center for International Earth Science Information Network. But in the decade since, interest in climate migration has exploded – in 2012, more than 10 times as many papers were published.

The topic is mired in debate, however. Some influential observers have warned that climate change will create vast numbers of environmental refugees that will flood developed countries, while others suggest there’s little evidence for such alarmism and the term “refugee” is not appropriate for such migrants.

What is clear, said Adamo at the Wilson Center on May 14, is that “the geography of vulnerability is changing because of the effect of high migration.” And while fresh thinking is needed to better understand how demographic and climatic factors interact, unsubstantiated claims must be challenged, said Marcel Leroy, a senior researcher at the University for Peace’s Africa Program.

Urbanization and Vulnerability

Migration, compared to other demographic factors, can concentrate large numbers of people over relatively short periods of time, making it particularly relevant to climate change, said Adamo. But there is no consensus on how exactly climate change will influence migration in the future – in part because “the impacts of climate change are complex and could be direct and indirect.”

The developing world is rapidly becoming more urban, with Asia urbanizing at the fastest pace and Africa following closely behind. According to the United Nations, the total number of people living in cities surpassed the number of people living in rural areas around 2008.

“As the population transition and the urbanization transitions advance, people start moving around, and when they are doing this they start moving also between and within different ecosystems,” said Adamo. Currently, many dry ecosystems are losing populations, and “coastal ecosystems – where most of the urban areas are – are increasingly having more and more in-migration.”

Most cities are currently destinations, and climate impacts are likely to increase rural to urban flows. However, “we also see that a lot of the cities are on the coast, and coasts could be affected not only from sea-level rise – that is a very slow onset event – but also from storm surge coming from increasing frequency of hurricanes or increasing number of storms,” said Adamo. As a result, as vulnerability increases, there may be more movement away from some cities.

Distinguishing Between Factors

“Now the problem is how to determine the relevance or the exact weight of the environmental factors,” said Adamo.

This requires questioning some common assumptions, said Leroy. “Very often when you talk of problems that are induced by climate change – even in articles done by scholars who do, or should, know better – there is no attempt to disaggregate the effect of climate change and population increase.”

In the Horn of Africa, for example, migration patterns are shaped more by population growth than by climate change, yet much of the attention focuses on decreasing precipitation, said Leroy. The region is urbanizing, but slowly, and growing resource competition will ensure that migration – particularly within state boundaries – remains high:

Most people are subsistence farmers, and if a farmer has eight children he cannot keep subdividing his land…So people will have to move to cities and there will be no possibility for return because there’s nothing to go back to. They cannot have a livelihood in the areas where they came from.

2009 study from Tufts University, which Leroy called “less wrong than most,” supports this argument, suggesting migration is more related to population growth and land degradation than climate change.

“Some of the areas that have had decreases in precipitation are areas that have had the highest population increase,” said Leroy. Parts of Ethiopia and Kenya, some of the most densely populated in Africa, are prime examples:

We often observe scarcity in these regions, and the scarcity results from the effects of climate change combined with the effects of population increase, because even if the climate wasn’t changing but the population rises at three percent a year, as it does in many of these countries, per capita availability of resources is going to decline.

The Darfur conflict is another case in point for the disruptive effect of population growth, said Leroy, who served as the political advisor to the European Union special representative for Sudan. “It’s not a climate war; it’s not an environmental war; it’s a war that was caused by elites making decisions about resources.” Between 1980 and 2000, the population roughly doubled and the livestock population quadrupled, he said. “This simply became untenable.”

And population growth is not likely to subside any time soon, “even if fertility continues to decline,” said Leroy. Ethiopia’s population may reach 200 million – more than twice its current size – by 2050, he said. “You will, in 20 or 30 years, have more young adults than you have now because these children have already been born, and as they form families, even if those families are smaller, the birth rate on a population basis will essentially remain unchanged.”

“Don’t Believe Anything if You Can Avoid It”

Even the commonly assumed physical effects of climate change deserve a critical eye, suggested Leroy. “We base assumptions on how to adapt to climate change on what we observe – or what we think we observe – which isn’t always that well-founded.” Many believe Africa is drying up, he said, but some areas have actually experienced increased precipitation since 1979, as demonstrated by the so-called greening of the Sahel. “I’m not denying the idea that Africa is suffering, but I think that the rest of the world is going to suffer at least as much.”

The connections between climate change and demography are becoming more widely recognized, and the research inspired by this attention is welcome, said Adamo. But more and better data is needed to understand exactly what’s happening, why, and how it affects both host communities and migrants.

“Don’t believe anything if you can avoid it,” said Leroy. “Don’t take things at face value, because usually that is the wrong way to go.”

Event Resources:

Drafted by Moses Jackson, edited by Schuyler Null and Roger-Mark De Souza.


  • Susana Adamo

    Associate Research Scientist, Center for International Earth Science Information Network, Columbia University
  • Roger-Mark De Souza

    Global Fellow and Advisor
    Former Director of Population, Environmental Security, and Resilience
  • Marcel Leroy

    Senior Researcher, University for Peace Africa Program