Severe Climate Disasters May Lead to Lasting Drops in Fertility, Global Research Finds

A global study finds that climate disasters affect fertility mainly when they cause high mortality, with deadly events linked to long-term declines in birth rates. Disasters that affect many people but cause fewer deaths show little lasting impact on fertility trends.

Scientists are beginning to understand how climate disasters may influence one of the most fundamental human decisions: whether to have children. A new global study by researchers from the World Bank’s Development Economics Global Indicators Group, Banco de la República in Colombia, the University of Gothenburg in Sweden, Universidad Iberoamericana in Mexico, and Universidad EAFIT in Colombia explores how climate-related hazards affect fertility across countries. Using data covering more than seventy years, the research examines whether disasters linked to climate change shape long-term birth trends.

The findings come at a time when two major global shifts are happening simultaneously: climate hazards are becoming more frequent and severe, while fertility rates around the world continue to decline. The study provides new insights into how these two trends might interact.

A World with Fewer Births

Global fertility has changed dramatically over the past several decades. In the 1950s, many countries in Africa, Asia, and Latin America had fertility rates above five births per woman. Europe and North America averaged around three births per woman. Today, the situation is very different. Most regions now have fertility rates below two births per woman, which is considered below the level needed to maintain population size.

Several factors have driven this long-term decline. Education levels have risen, especially for women, and more women are joining the workforce. People are marrying later and gaining greater access to contraception. At the same time, the cost of raising children has increased in many countries.

Recently, climate change has also entered the discussion. Surveys suggest that some people are reconsidering having children because of worries about climate change, environmental degradation, and the uncertain future their children might face. But until now, it has been unclear whether climate events themselves actually influence fertility.

A Global Dataset Covering 70 Years

To explore this question, researchers compiled a large global dataset combining fertility statistics with records of natural disasters between 1950 and 2023. Fertility data came from the United Nations, while disaster information was drawn from an international disaster database that records events such as storms, droughts, floods, heat waves, cold waves, and wildfires.

The researchers also included non-climate disasters like earthquakes and biological crises to provide a comparison.

What makes this study unique is how it measures disaster impacts. Instead of simply counting disasters, the researchers focused on two key aspects of their impact. The first is population disruption, measured by the number of people affected by a disaster. The second is lethality, measured by the number of deaths caused by the disaster.

This distinction helped researchers understand whether fertility changes more when many people are affected or when disasters cause high loss of life.

Deadlier Disasters Lead to Fewer Births

The results show that climate disasters do not always influence fertility in the same way. When disasters are measured by the number of people affected, the study finds no clear long-term impact on fertility rates. Even events that disrupt the lives of many people do not necessarily lead to lasting changes in birth patterns.

However, the situation changes when disasters are measured by their lethality. Highly deadly disasters are linked to persistent declines in fertility. The study shows that fertility typically falls within five years after a lethal disaster and continues to decline gradually over the following decade.

The research also reveals that different types of hazards produce different fertility responses. Storms and drought-related disasters are strongly linked to lower birth rates. These events often damage livelihoods, destroy crops, and create economic uncertainty, which may lead families to delay or avoid having children.

Heat waves and cold waves, on the other hand, show small increases in fertility. The reasons for this are still not fully understood, but the findings highlight that different climate events can produce different demographic effects.

Why the Type of Disaster Matters

Another key insight from the study is that not all disasters affect countries in the same way. Floods and other water-related disasters tend to reduce fertility when they cause significant loss of life. Meanwhile, non-climate disasters such as earthquakes and biological crises consistently lead to fertility declines.

The researchers also found that the relationship between disasters and fertility has weakened slightly in recent decades. This may reflect improvements in disaster preparedness, healthcare systems, and emergency response capabilities that help societies recover more quickly from disasters.

Interestingly, the differences between rich and poor countries were relatively small. While fertility declines after deadly disasters were slightly larger in lower-income countries, the overall patterns were similar across both rich and poor nations.

Understanding Population Trends in a Changing Climate

Overall, the study suggests that climate disasters do not have a uniform impact on fertility. The type of disaster and the severity of its consequences appear to matter more than the number of people affected.

As climate change continues to intensify extreme weather events, understanding how these shocks influence population trends will become increasingly important. While climate anxiety may influence personal decisions about parenthood, the research suggests that the most significant demographic changes occur after severe disasters that threaten lives and long-term stability.