A Fungus Killing Bats Could Be Indirectly Killing Human Babies

Halloween or not, bats play a crucial role in our ecosystem. From natural pest control to plant pollination to seed dispersion, bats are one of the most important yet misunderstood animals, according to the U.S. Fish & Wildlife Service.

A new study published in the journal Science found a strong link between bat mortality and human infant mortality. The scientists speculate it has to do with white-nose syndrome, a fungal disease killing millions of bats. It’s an incredible-sounding finding: When bats die off, so do human babies.

“Bats are a fantastic example of a species that we like to keep a distance from, but are really impactful in terms of the role they play in ecosystems,” said Eyal Frank, an environmental economist at the University of Chicago and author of the study.

Frank speculates that the less bats we have, the more insecticides farmers will use to keep bugs away from their crops—and the more health complications those insecticides might trigger in humans. More pesticide use, they said, leads to an increase in infant deaths. 

Of course, there are many other factors we could attribute to the increase in infant deaths. But researchers also spent an entire year ruling out other causes, including the opioid epidemic, unemployment rates, genetically modified crops, and more.

White-nose syndrome kills millions of bats

White-nose syndrome is a continuous threat to bats across the U.S. and is responsible for millions of deaths. Frank found it important to understand how this will continue to impact humans.

“Reading how this disease is spreading from county to county, decimating bat populations, made my economist senses go, ‘Oh, this is probably the best natural experiment you can have,’” Frank told The New York Times. “It’s the closest we’re going to get to just going out there into the wild and randomly manipulating bat population levels to see what happens at a large, meaningful spatial scale.”

The study found that farmers in counties experiencing white-nose syndrome outbreaks used 31% more toxic chemicals than those in other counties. That response, Frank said, “had an adverse health impact on human infants.”

Eli Fenichel, an environmental economist at Yale, also weighed in on the study findings, praising Frank’s work and the link between bat and human mortality rates.

“Fungal disease killed bats, bats stopped eating enough insects, farmers applied more pesticide to maximize profit and keep food plentiful and cheap, the extra pesticide use led to more babies dying,” said Fenichel. “It is a sobering result.”

It sounds like a classic butterfly effect. Speaking of which, earlier this year conservationists declared a “nature emergency” in the UK after the 2024 Big Butterfly Count found the lowest number of butterflies in 14 years, likely due to factors like habitat loss, climate change, and—you guessed it—pesticide use.