The ocean and early-childhood mortality and development

Evidence on the exact mechanism linking in utero shocks with early-childhood outcomes remains scarce because biological factors are often tangled with changes in parental inputs. This paper addresses this issue by exploiting exogenous variation in the ocean's productivity resulting from water acidification, a consequence of climate change that is negatively affecting marine life and has been largely ignored in the literature. Ocean acidification provides a unique setting to study prenatal nutritional deprivation as water chemistry affects fish stocks, but is not directly observed or felt by mothers. This isolates the channel of transmission to the availability of resources. We estimate the causal impact of the ocean's acidity while in utero on early-childhood mortality and development at a global scale, analyzing more than 1.5 million geocoded births taking place over the last 50 years in 36 developing countries. We compare children, including siblings, born in the same location but on different dates, controlling for a set of high-dimensional fixed effects. In coastal areas, a 0.01 unit increase in acidity causes 2 additional neonatal deaths per 1,000 live births. Using a novel measure of fishing pressure that combines local and industrial fishing, we show that the effect is strictly related to reduced access to nutrients during gestation. We find no evidence of parental adaptation on other inputs. Deprivation selectively affects the weakest children, creating small differences in child development. These results provide the first quantitative evidence linking the exploitation of renewable natural resources with malnutrition and neonatal selection.