The Great Interdependence: Populations and a Warming Planet

Climate change is not just an environmental issue; it is a profound demographic force. It influences where people can live, how they make a living, their health, and their survival. Simultaneously, the size, distribution, and consumption patterns of human populations drive greenhouse gas emissions and environmental degradation. The Institute of Experimental Demography has established a dedicated research cluster to study this critical nexus. Our goal is to move beyond speculative scenarios and generate causal evidence on the demographic impacts of climate change and the feedback loops that exist. We focus particularly on human mobility as an adaptation strategy, the differential vulnerability of population subgroups, and the long-term demographic consequences of environmental stress.

Causal Identification in a Complex System

Isolating the 'climate signal' in demographic behavior is methodologically challenging, as environmental factors are intertwined with economic and political ones. We overcome this by focusing on clear environmental shocks that can be treated as natural experiments. For example, we study the demographic aftermath of specific, unexpected extreme weather events—like a typhoon of unusual intensity or a localized multi-year drought—comparing affected communities to statistically similar unaffected ones. This allows us to estimate the causal effect of the shock on mortality, fertility, and, crucially, migration. Our research has shown that migration is often a last-resort adaptation; many households become trapped in place due to resource loss, a finding critical for humanitarian planning.

We also use spatial and temporal gradients in climate exposure. By exploiting the fact that global warming affects regions differently and has accelerated over time, we can use advanced panel data methods to estimate how gradual changes in temperature and precipitation influence agricultural yields, rural livelihoods, and subsequent urbanward migration flows. We link climate model projections with demographic models to produce probabilistic forecasts of future climate-related displacement under different emissions scenarios.

Another key area is differential vulnerability. Not everyone is affected equally. We investigate how pre-existing social inequalities—based on gender, age, ethnicity, or wealth—shape who is harmed most by climate impacts and who has the capacity to adapt or move. We use household survey data from disaster-prone areas to model these intersecting vulnerabilities, providing a map of where targeted support is most needed.

• Sea-Level Rise and Coastal Depopulation Project: Tracks population change in low-lying coastal zones using satellite and census data, modeling the point at which protective migration becomes likely.
• Climate, Conflict, and Demography Study: Uses rigorous methods to test whether climate-induced resource scarcity causally increases the risk of localized conflict, which in turn drives displacement.
• Urban Heat Vulnerability Index: Develops a fine-grained index combining demographic data (age, poverty) with land-surface temperature data to identify city neighborhoods at highest risk during heatwaves.
• Agricultural Adaptation Experiments: Partners with development agencies to run RCTs evaluating new drought-resistant crops or insurance schemes, measuring their impact on household food security and migration decisions.

Informing Equitable Adaptation and Mitigation

The policy implications of our work are twofold. For adaptation, we provide evidence for designing effective, targeted support systems for vulnerable populations, whether through social protection, disaster risk reduction, or planned relocation programs that respect community rights. We argue that supporting voluntary, informed migration can be a legitimate adaptation strategy and should be facilitated by policy. For mitigation, our research contributes to understanding the demographic drivers of emissions. We study how changes in household size, urbanization, and consumption patterns associated with demographic transitions influence carbon footprints. This helps identify high-impact behavioral levers for reducing emissions. The institute actively engages in international climate negotiations, ensuring that demographic evidence is incorporated into frameworks like the UNFCCC's Loss and Damage mechanism. By illuminating the human face of climate change, our research underscores the urgency of action and provides a roadmap for building demographic resilience in an era of environmental uncertainty.