Bats are often seen as a nuisance — a scary one at that — but a new study shines a light on the unsung heroes they may have been all along.
Bat populations have been declining because of white-nose syndrome, a fungus-caused disease that strikes while they hibernate. The study, published by Eyal Frank, an assistant professor at the Harris School of Public Policy at the University of Chicago, found farmers had to increase the use of pesticides to make up for this. This, in turn, leads to an increase of infant mortality, a common marker of health impacts of a type of environmental pollution, according to Frank.
“Bats have gained a bad reputation as being something to fear, especially after reports of a possible linkage with the origins Covid-19,” Frank said in a news release. “But bats do add value to society in their role as natural pesticides, and this study shows that their decline can be harmful to humans.”
White-nose syndrome is caused by the fungus Pseudogymnoascus destructans, which grows in cold, damp places like caves. It forms a white fuzz on bats’ noses as they sleep and causes them to do odd things like fly outside in winter and burn the fat needed to survive, according to the White Nose Syndrome Response Team.
Biologists first noticed bats getting sick and dying from the fungus in 2007, and since then it has spread rapidly throughout the United States and Canada. It has killed millions of bats in America, according to the team, with some sites having 90% or 100% of their bat population succumb to the disease.
How does a disease that primarily affects bats have an effect on infant mortality rates among humans? In his study, Frank found that farmers in counties with a decline in the bat population have, in turn, had to increase their use of pesticides on crops. Bats are often considered a “natural pesticide.”
Frank’s study found pesticide use increased by 31%, which coincided with a rise in infant mortality rates by almost 8%.
This means that for every 1% increase in pesticide use, there was a 0.25% increase in infant mortality rates.
The study also found a financial hit taken by farmers, because pesticides are not as effective as bats. Some farmers’ revenue declined by 29% percent due to the quality because of the decrease in their crop quality. Farmers who experienced this bat die-off suffered a combined loss of $26.9 billion from 2007 to 2017 as a result of decline in revenue and the expense of pesticides, Frank determined.
“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 the 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.”
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