To navigate the intricate intersection of climate change, migration, and urbanization, we need a holistic approach.

When crops fail, or when floods rise, sometimes the only option is to leave home. Climate hazards are already driving migration, as tens of millions of people are displaced every year, most of them drawn to cities. In turn, growing cities affect climate change, and create new environmental risks – especially for migrants. The message from recent IIASA research is that this complex nexus of climate, migration, and urbanization requires a holistic approach, bringing together separate strands of science and policy.

“To address this we need to bring everyone to the table,” says Roman Hoffmann, who leads the Social Cohesion, Health, and Wellbeing Research Group at IIASA.             

Climate change increases the risks of drought, famine, flooding, and conflict, all of which can drive migration – but as IIASA research shows, migration also depends on many other factors, such as job opportunities. In a 2020 study, Hoffmann and his colleagues examined some of these factors.

Analyzing statistical evidence from 30 country-level studies, they found that local economic, social and political conditions shape the extent to which people are affected by environmental changes, as well as their abilities to protect themselves, adapt, and migrate. Understanding these effects can help to identify potential migration hotspots.

When people move to cities, their vulnerability to climate hazards can increase. Storms and floods generally have more severe impacts in cities than in the countryside. A lack of resources makes migrants less resilient to disasters. What’s more, migrants tend to live in slums or poorly-planned neighborhoods that are more exposed to extreme weather, often in low-lying flood-prone areas.              

On top of all this, migration to cities may harm the environment. Globally, urban consumption patterns mean higher demand for energy and other resources. Locally, rising city populations produce more waste and change the landscape, for example, increasing flood risk by replacing natural environments with concrete.

So how can we find a way through this tangle of issues? Hoffmann and Raya Muttarak, Principal Research Scholar in the Migration and Sustainable Development Research Group, explored this topic in a 2021 briefing document for Think20, the research and policy advice network of the G20. As well as laying out the intricacy of the problem, this report concludes that it can be tackled with a holistic approach.

“Domains like migration and urban planning operate separately today,” says Hoffmann. To bring these policy areas together, the authors suggest using multi-stakeholder partnerships and participatory approaches. For example, urban planning could simultaneously address energy efficiency, transport access, and resilience to flooding.      

Policy must also consider those left behind, as Muttarak pointed out in a recent talk at a panel discussion, “Climate crisis boosts displacement”, organized by IIASA and the Vienna Institute for International Dialogue and Cooperation. Migration is expensive, so it is not an option for everyone. People in middle-income groups are most likely to migrate after a climatic shock; the rich can afford to remain, probably because they are able to adapt in situ, while the poor do not have the resources to move. Muttarak’s research on South Africa shows that households headed by women are particularly vulnerable to climatic shocks, due to their relative shortage of economic and other resources.

“These highly vulnerable groups deserve particular attention from policymakers,” says Hoffmann.

IIASA is now working with policy actors including the Intergovernmental Authority on Development to improve climate migration modeling and better understand the implications for cities across the world.