Marine Heatwaves and Undernutrition in Low- and Middle-Income Countries

Marine heatwaves are accelerating under climate change and increasingly threaten the lives and livelihoods of coastal populations, particularly in low and middle-income countries where many households directly depend on local marine fisheries for protein, micronutrients and income. To quantify this threat, we link individual-level data on child and maternal health from 9,813 coastal sites in 36 low or middle-income countries to heatwave exposures in the nearby ocean, and use this linked dataset to estimate fixed-effects logistic regression models that test for heatwave effects on child mortality, child wasting, child stunting, and adult underweight. We find that a 1 SD increase in the number of heatwaves over a 24-month period increases the odds of child mortality by 5.4%, child wasting by 6.5% and child stunting by 8.8%, and that these effects also extend to other dimensions of heatwaves such as maximum sea surface temperature and cumulative intensity. Urban populations, unexpectedly, are most strongly affected, which may reflect their position as purchasers rather than producers of protein-rich foods. Taken together, these results document that marine heatwaves directly undermine human health and emphasize the continued importance of global monitoring for child and maternal health as well as oceanic conditions.