Study links declining bat population to more than 1,000 infant deaths
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Key takeaways:
- When insect-eating bat populations decline, farmers use insecticides to protect their crops.
- Increased insecticide use led to an estimated 1,334 infant deaths in affected counties from 2006 to 2017.
Insecticide use and infant mortality have increased in United States counties affected by declining bat populations, according to a study published in Science.
Bat populations in the U.S. are dying because of white-nose syndrome, a disease caused by an invasive fungus. White-nose syndrome has an average mortality rate of 73% and can cause local extinction within 5 to 6 years, according to Eyal Frank, PhD, MA, assistant professor at the University of Chicago Harris School of Public Policy, who authored the new study.
White-nose syndrome was first reported in Albany, New York, in 2006. Since then, 12 out of 50 bat species that eat insects have been affected, according to Frank.
“Bats are widely known to consume large numbers of pest insects, such that in the absence of pest control by bats, farmers might face crop losses unless they compensate with insecticides,” Frank wrote.
Frank investigated pesticide use in counties that have reported cases of white-nose syndrome, as well as infant mortality rates.
“To test for the potential health consequences of increased insecticide use, I used county-level data on annual infant mortality — commonly used to study negative health impacts of environmental pollution,” Frank wrote.
One year after white-nose syndrome was detected, pesticide use increased by 1 kg/km2 in affected counties compared with nonaffected counties, Frank found. After 5 years, farmers were using 2 kg/km2 more insecticides.
Frank found that pesticide use increased by an average of 2.7 kg/km2 — or 31% — in counties with white-nose syndrome, and internal infant mortality — deaths not caused by accidents or homicides — increased by 0.54 per 1,000 live births, or 7.9%. For every 1% increase in insecticide use, infant mortality rose by 0.25%, according to Frank.
Frank estimated that from 2006 to 2017, declining bat populations and increased pesticide use accounted for 1,334 infant deaths.
Bat die-offs had monetary costs as well, Frank found. After white-nose syndrome was detected, crop revenue decreased by $7.96 per km2, which is 28.9% lower than average. From 2006 to 2017, affected communities lost $26.9 billion in crop revenue and $12.4 billion in damages from infant mortality.
“When bats are no longer there to do their job in controlling insects, the costs to society are very large — but the cost of conserving bat populations is likely smaller,” Frank said in a press release. “More broadly, this study shows that wildlife adds value to society, and we need to better understand that value in order to inform policies to protect them.”
References:
- Frank EG. Science. 2024;doi:10.1126/science.adg0344.
- The collapse of bat populations led to more than a thousand infant deaths. https://www.eurekalert.org/news-releases/1056333. Published Sept. 5, 2024. Accessed Sept. 6, 2024.
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