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What Makes an Area Vulnerable to Disasters?

How do basic variables in demography shape disaster impacts?

 Ilan Kelman
How do population numbers and densities impact disaster vulnerabilities?
Source: Ilan Kelman

A disaster does not happen without society—such as people, infrastructure, livelihoods, and heritage—being impacted. How might population numbers and densities affect a disaster’s scale? The unequivocal answer is, as always, “it depends."

Starting with population numbers, the general definition of a disaster typically implies that, as more people are affected, the disaster becomes worse. This statement is fair, but presents only one portion of the picture.

An example comes from the volcanic island of Montserrat in the Caribbean, which is a UK Overseas Territory. In 1995, around 12,000 people lived there when eruptions began. Ash and gas emissions continued regularly until recent years, destroying most of the isle’s infrastructure and forcing the entire population to leave their homes.

Some went to the north of the island to rebuild while perhaps two-thirds left Montserrat at some point, although many returned eventually. Hot ash and gas clouds rolling down the mountain, called pyroclastic flows or pyroclastic density currents, killed at least 19 people on June 25, 1997.

This total of immediate deaths is often low for disasters, although the total number of all deaths is hard to calculate since long-term mortality might occur due to years of, for example, inhaling volcanic ash. Nonetheless, 100 percent of Montserrat’s population experienced some form of major impacts, including disruption, from the disaster. This number is less than half the number of people killed in Bam, Iran during an earthquake on December 26, 2003.

Is Montserrat’s disaster irrelevant compared to Iran’s? Not for Montserratians. In any case, by country/territory population, the proportion of people killed in Montserrat in 1997 is around four times the proportion of people killed in Iran in 2003. Using proportional numbers, Iran’s disaster is not as bad as Montserrat’s.

So which disaster was actually worse? Should we even be asking this question on the basis of a few demographic variables? Both were horrible disasters, both populations suffered immensely, the negative impacts in both cases could have been reduced through better action beforehand, and each represents different characteristics of affected populations, as reflected in the deaths, death rates, and other impacts.

Similar patterns of “it depends” appear when examining how population densities affect disasters. A popular statement is that cities make disasters worse and urbanisation drives disaster vulnerability, attributed to population densities being higher with more infrastructure to be damaged. These factors do mean that a hazard covering a specific land area can potentially affect more people and cause more damage, subject to prevention, mitigation, preparedness, and other pre-hazard measures.

Conversely, more people in a city means that their skills and equipment can assist, if available. More infrastructure sometimes (not all the time) means more emergency and health services, including staff with the most diverse experience, the most equipment, and the best training. An urban location’s population is generally spread over a smaller area than non-urban places, which can have advantages for planning, logistics, transportation, and supply chains.

But not always. Numerous counterexamples exist due to lack of investment or interest in having an urban area be disaster-ready, compared to less urban places deciding that they wish to save lives. The state of infrastructure, warning systems, evacuation routes, governance, inequities, discrimination, resource distribution, and options for the population to deal with potential hazards have much more influence on disaster outcomes than urban characteristics—although correlations do exist.

Certainly, less urban settlements are typically not paved over as much as cities, leading to larger runoff and flood problems in urban areas. Yet cities could and do use permeable surfaces and green spaces to absorb water. Population numbers and densities become far less important than how a place is planned, designed, landscaped, maintained, and governed.

The influence of population numbers and densities on disasters should never be neglected. Much more comes from societal choices on dealing with people who are in a location, so that they are not vulnerable to hazards.


Kelman, I. 2020. Disaster vulnerability by demographics? The Journal of Population and Sustainability, online

Nadim, F., Moghtaderi-Zadeh, M., Lindholm, C., Andresen, A., Remseth, S., Bolourchi, M.J., Mokhtari, M., & Tvedt, E. 2004. The Bam Earthquake of 26 December 2003. Bulletin of Earthquake Engineering, vol. 2, pp. 119-153.

Pattullo, P. 2000. Fire from the Mountain: The Tragedy of Montserrat and the Betrayal of its People. London: Constable and Robinson.