Identifying and Mapping Vulnerable Populations

Introduction: Defining Vulnerable Populations

The first step in identifying populations of concern is to define “vulnerability” and how it applies to public health impacts in the context of global warming.

Merriam Webster’s Dictionary defines “vulnerability” as “the quality or state of having little resistance to some outside agent (vulnerability to infection)” (Merriam Webster, 2017). In the context of climate change threats to health, vulnerability is the tendency or predisposition to be adversely affected by these threats. Vulnerability to climate-related health effects comprises three elements: exposure, susceptibility to harm, and adaptive capacity. In the Introduction to The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment, Balbus et al. (2016) define the three elements as follows:

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  Exposure is contact between a person and one or more biological, psychosocial, chemical, or physical stressors, including stressors affected by climate change. Contact may occur in a single instance or repeatedly over time, and may occur in one location or over a wider geographic area.

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  Susceptibility to harm (or sensitivity) is the degree to which people or communities are affected, either adversely or beneficially, by climate variability or change.

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  Adaptive capacity is the ability of communities, institutions, or people to adjust to potential hazards, to take advantage of opportunities, or to respond to consequences. A related term, resilience, is the ability to prepare and plan for, absorb, recover from, and more successfully adapt to adverse events (Balbus et al., 2016, adapted from IPCC, 2014 and NRC, 2012).

Vulnerability occurs on an individual level, affected by the person’s health status (e.g., presence of underlying medical condition such as asthma), age, gender, educational level, income, family support, and access to healthcare. It also occurs at the societal level, where adaptive capacity is influenced strongly by the natural and built environments (for example, the infrastructure), governance and management (health-protective surveillance programs, regulations and enforcement, or community health programs), and institutions. Exposure to extreme weather events is in part a function of geography, (e.g., coastal areas and islands are especially at risk of storms and flooding). Exposure to pathogens is a function of location (near vector habitats) but can be greatly reduced through integrated pest management. Susceptibility to harm, or sensitivity, may be increased by a pre-existing condition (e.g., asthma or other lung disease), age (i.e., very young or elderly), pregnancy, occupation. The greatest predisposing factor for vulnerability is poverty. Racial, religious, ethnic, or gender discrimination is another risk factor for vulnerability.

Maplethorpe’s Climate Change Vulnerability Index 2016 ranks 186 nations’ vulnerability to the adverse impacts of climate change according to their risk for exposure (50 percent), sensitivity (25 percent), and adaptive capacity (25 percent). The 2016 Index deemed Chad as the country most vulnerable to the impacts of global warming; the second most vulnerable country was Bangladesh. The 2016 Index rated Africa as the most vulnerable region because it is exceptionally exposed to unpredictable rainfall patterns and prolonged drought, suffers from extreme levels of poverty, hunger, and lack of clean water, and is racked by conflicts and an inability to implement climate adaptation policies. The second most vulnerable regions are Central America and Asia (Ranada, 2016).

In Chapter 9 of The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment (Gamble et al., 2016), the following key findings are noted: