February 3, 2025 – Environmental disasters disrupt lives across entire regions, layering disproportionate burdens faced by communities that already face social and economic hardship. Extreme events like the flooding caused by Hurricane Helene in Tennessee and North Carolina illustrate this phenomenon in real time.
A new study led by UT Knoxville Professor Paul Armsworth offers a comprehensive analysis of how multi-hazard environmental risks impact US communities. Through a pairing of Social Vulnerability Index data from the Centers for Disease Control and Prevention and hazard-exposure data, the study reveals that over 37 million people—more than 11 percent of the US population—are at high risk from compounded effects of environmental hazards such as water shortages, air pollution, wildfires, flooding, and impaired water quality.
Their findings show how socially vulnerable populations—in particular low-income households and those with limited access to healthcare—are far more likely to experience compounded risks from multiple severe hazards. These risks add to the immediate threat and hamper their ability to recover from future extreme environmental events.
“We can expect extreme events to become more frequent and for more people to be exposed to them,” said Armsworth. “This also means we can expect compounded hazards to become more common.”
Armsworth, an expert in spatial conservation planning and human-nature interactions, is a distinguished service professor in the Department of Ecology and Evolutionary Biology and a fellow in the Baker School of Public Policy and Public Affairs. He partnered for this study with researchers at Colorado State University, Fort Collins, and the US Forest Service’s Rocky Mountain Research Station. The study, “Multi-hazard risk in socially vulnerable communities across the United States,” published in Environmental Research Letters, was funded by the Pew Charitable Trusts.
“By mapping the intersection of social vulnerability and environmental hazards, this study underscores how these overlapping risks can create a cycle of disadvantage, making it more difficult for already vulnerable communities to adapt and recover,” said Armsworth.
The scope of their study, focused on the contiguous US, reveals widespread environmental risk accumulation. Work to address these complex issues requires coordinated efforts that go beyond isolated interventions. The study also emphasizes regional differences in environmental and demographic risk factors that amplify the importance of addressing the unique challenges faced by people in different communities.
“Solutions still need to be tailored to the particular social vulnerabilities that a community is experiencing,” said Armsworth. “Is it a lack of access to services, lower income and economic vulnerability, or something else?”
These insights are crucial for policymakers and resource managers working to reduce multi-hazard risks and build resilience in the most vulnerable communities. The data in the study offers a useful tool and reference for field experts who track these issues.
“What makes this study so valuable is its identification of exactly which American communities are exposed to which combinations of hazards,” said Robert McDonald, lead scientist for nature-based solutions at The Nature Conservancy. “This helps us target our efforts to reduce environmental hazards in the communities that need that help the most.”