The notion of “planetary health” – that is, the close links between the health of ecosystems and that of human societies – is notoriously difficult to quantify. Difficult, but not impossible. This is the meaning of the innovative work that the journal Science The Friday 6 September issue highlights the fact that environmental economist Eyal Franck (University of Chicago) shows that the collapse of American insectivorous bat populations was marked by a drop in agricultural production and offset by a considerable increase in the use of insecticides. Sufficient, in any case, for the consequences on infant mortality to be measurable locally.
The estimates are staggering. Farmers’ income and production losses amounted to nearly $2.7 billion (€2.4 billion) per year between 2006 and 2017 in 245 of the counties included in the study. As for excess newborn mortality directly attributable to excessive pesticide use, it is estimated at around 1,300 deaths in all affected counties, during the same period.
To carry out his analysis, Franck took advantage of a formidable epizootic that appeared in 2006 in the north-east of the United States and which affected bats. Caused by a pathogenic fungus, the “white nose syndrome” precipitates abrupt declines in these animals: as soon as the disease is detected in an area, their populations can decrease by more than 70% in a few months. After its appearance in 2006, explains the American economist, “The disease continued to spread in a stepwise manner, with each year more and more counties moving from being “unaffected” to being “affected” by the disease.”.
Falling agricultural income
The researcher was thus able to compare data from affected areas with those from areas free of the pathogen. “An important finding of the analysis is that both types of counties, affected and unaffected, saw their insecticide use and infant mortality outcomes move in parallel in the years leading up to disease onset.explains Franck. But the data begins to diverge once bats start dying in counties where the disease takes hold. » On average, affected counties see an increase in insecticide use of 31%, as farmers compensate for the pest-killing service provided by bats. Locally, average farm income per square kilometer drops by 28.9%.
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