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Add as preferred source Marine heat waves—periods of abnormally warm ocean temperatures—may have negative health effects on children who live in coastal communities in low- and middle-income countries, according to a study led by researchers at Penn State and the University of North Carolina at Chapel Hill.
The study—recently published in the Proceedings of the National Academy of Sciences —found that exposure to marine heat waves is associated with an increased risk of children experiencing acute malnutrition; thinness; chronic malnutrition, as indicated by low height for their age; and mortality.
Study co-author Brian Thiede, a professor of rural sociology, sociology and demography at Penn State's College of Agricultural Sciences and director of the university's Population Research Institute, said this may be because fish are an important source of protein and micronutrients among many coastal populations, and marine heat waves have the potential to hurt fish supplies through changes in fish populations' range, nutrient quality and mortality.
"Such disruptions can have direct impacts on food supplies and also may have secondary impacts by affecting income among fishers and food prices for consumers," he said. "These factors may shape households' ability to purchase food or to have the economic resources needed to access other critical services, such as health care."
Thiede added that the findings emphasize that climate change is affecting many Earth systems critical to human health and survival, including coastal communities that depend on the ocean for food or financial support.
"Researchers and practitioners should place renewed focus on coastal populations and better differentiate between the sources of vulnerability faced by coastal and inland populations," he said. "Coastal populations face unique climate-related risks due to their environment and livelihoods."
Marine heat waves are increasing in both frequency and severity as the global climate shifts, according to the researchers. These heat waves can trigger many additional ecological changes, including those that directly affect human society, with coastal populations in low- and middle-income countries being particularly vulnerable.
Thiede said attention to the human health impacts of these marine heat waves is important for several reasons, including the fact that, globally, human populations tend to be concentrated in and around coastal environments.
"Ocean temperatures are warming rapidly , making these heat waves more common and severe," he said. "Additionally, poor health has widespread and multidimensional consequences, from the immediate human costs of illness and death to adverse impacts on education and employment that can slow economic growth in poor countries."
For the study, the researchers linked nationally representative data on children's and women's health and survival from more than 9,800 coastal sites in 36 low- and middle-income countries to global data on sea surface temperatures.
Next, they identified marine heat waves that occurred in ocean waters near individuals in the months and years before their health was measured. The team then applied statistical techniques to isolate the relationship between marine heat wave exposure and health and survival outcomes.
The team found that a standard deviation increase in the number of heat waves over the two-year period increased the odds of child mortality by 5.4%, child wasting—or being too thin for their height—by 6.5% and child stunting—or being too short for their age—by 8.8%.
The researchers also found that these impacts are largest in countries dependent on small-scale fishing —versus more industrialized, commercial sectors—and in urban areas.
"While the impacts in urban areas may be somewhat unexpected, it is consistent with fairly widespread evidence that city-dwelling populations can be quite vulnerable to environmental change," Thiede said. "Their populations may be less involved in agriculture and aquaculture than rural populations, but they may still be vulnerable to shocks through market mechanisms, such as increases in fish prices."
The researchers said the findings suggest the need to target populations affected by marine heat waves with nutrition-improving interventions or other safety-net programs.
Practitioners might also use marine temperature forecasts in their early-warning systems to anticipate where resources will need to be allocated. They added that more research focusing on the links between climate change and health in coastal areas is also needed.
Clark Gray, Sally Dowd, Noah Shaul and Janet Nye, all of the University of North Carolina at Chapel Hill, co-authored the paper.
Clark Gray et al, Marine heatwaves and undernutrition in low- and middle-income countries, Proceedings of the National Academy of Sciences (2026). DOI: 10.1073/pnas.2528506123
Journal information: Proceedings of the National Academy of Sciences
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