The 'Death Map': Some Perspective for Emergency Managers

A recent article I co-wrote with colleague Susan Cutter titled Spatial Patterns of Natural Hazard Mortality in the United States was published last winter in the International Journal of Health Geographics. It discussed research on natural-hazard mortality and sparked considerable national media interest. The work was soon dubbed the "Death Map."

For sure, a quantitative assessment of natural-hazard deaths presented in visual form made for compelling special-interest news. Before long, the media began running stories in print and online, and information about the Death Map appeared in high-visibility outlets, such as the Los Angeles Times, MSNBC.com and Yahoo News.

Video: Death Map Reveals Most Dangerous Natural Hazards

With such widespread coverage, it was inevitable that information would be taken out of context or misrepresented. We, the authors, thought it prudent to provide some perspective. What does this map of natural-hazards mortality really tell us? How can emergency managers use it to mitigate future hazard deaths?

The article, based on research performed at the Hazards and Vulnerability Research Institute at the University of South Carolina, analyzed natural-hazard mortality data from the Spatial Hazard Events and Losses Database for the United States (SHELDUS). Specifically we used natural-hazard mortality information from SHELDUS that covered the past 35 years to calculate the relative risk of death from natural events at the county level. We employed standardized mortality ratios (SMRs) that indirectly adjusted for variability in the age structure of county populations.

The research's purpose was to reveal the categorical and spatial distribution of natural-hazard deaths over time for a variety of natural events. The SHELDUS database is one of the most comprehensive publicly available sources of natural-hazard mortality. Furthermore, all the information contained in the SHELDUS database is geographically referenced to the county level, so we could compare mortality not only across types of hazards, but also by places. The article presented a way to visualize the national landscape of historical hazard mortality.

This data set represents a huge step forward in the collection, storage and manipulation of spatially referenced hazard-mortality information. However, in its current form the direct applications in planning and mitigation for emergency managers are limited. Our paper's analysis represents a tool that emergency managers can use to identify regional hot spots of hazard mortality. It's crucial to point out that local-level analyses of any county (or counties) should be performed to verify the suspected mortality anomalies. Our research paper revealed broad spatial trends, but it doesn't provide a detailed analysis of reasons that explain the individual county patterns within a state.

Media coverage of this work showed that the maps portrayed in the International Journal of Health Geographics article can be easily misinterpreted and misused by the public. For example, despite some claims by the media, the Death Map isn't predictive. The spatial patterns in natural-hazard mortality in the paper do not define future deaths from natural events, only what has happened during the past 35 years. Therefore, these maps won't reveal where people will die in the next hurricane, earthquake or heat wave.

Another reaction many people have is they expect to gain some insight into how many people will die and from what causes in the county in which they live. Unfortunately this work isn't very useful for analyzing a single county. We aggregated deaths from all natural hazards in SHELDUS when calculating SMRs by county, so some level of detail is unavailable in the final map. We know very little, for example, about the contextual and causal factors surrounding each individual death.

These unanswered questions don't lessen the contribution of this research. Rather, the maps and analysis create opportunities for future research to answer some of these questions and provide detailed analyses for local emergency managers on the distribution and nature of deaths from natural hazards. Ultimately we hope our work will contribute to decision-making and emergency management that lessens the human toll of natural hazards.