A recent study indicates that when communities faced a significant decline in insect-eating bat populations, there was a notable increase in pesticide usage among farmers, which consequently led to a rise in infant mortality rates.
Bats function as a natural form of pest control, serving as an alternative to chemical pesticides that farmers utilize to safeguard their crops from insects. However, starting in 2006, several bat populations in North America have faced severe declines due to an invasive fungus found in their caves, which causes a condition called White-Nose Syndrome. A new research article published in Science examines whether farmers resorted to using more chemical pesticides following the decline of bat populations, and the effects this had on human health. The study reveals a significant increase in pesticide use among farmers, resulting in over 1,000 infant deaths.
“Bats have often been viewed negatively, especially after speculations regarding their possible connection to the origins of Covid-19,” explains study author Eyal Frank, an assistant professor at the Harris School of Public Policy. “However, bats benefit society by serving as natural pest controllers, and this research highlights that their decrease can pose risks to human health.”
Frank analyzed the impact of bat population declines on pesticide use by comparing counties where bat die-offs occurred to those that were unaffected by the disease affecting bats. His findings show that in areas with declining bat populations, farmers increased their pesticide applications by approximately 31 percent. Due to the established links between pesticide use and adverse health effects, Frank further investigated whether this escalation in pesticide usage correlated with a rise in infant mortality—a frequently used indicator for assessing the health effects of environmental pollutants. Indeed, there was an almost 8 percent increase in infant mortality rates, equating to around 1,334 additional infant deaths. Specifically, for every 1 percent increase in pesticide use, the infant mortality rate increased by 0.25 percent.
Additionally, the study found that pesticides are less effective at managing pest populations compared to bats. As a result, the quality of crops deteriorated, leading to a nearly 29 percent drop in farmers’ revenue from crop sales. When combining the revenue loss with the costs incurred from pesticides, farmers in communities affected by the bat die-offs faced a staggering total loss of $26.9 billion from 2006 to 2017. Factoring in the $12.4 billion in damages associated with infant mortality, the overall societal cost of the bat declines in these areas reached $39.6 billion.
“The absence of bats, which play a vital role in pest control, translates to significant costs for society; however, the expenses related to conserving bat populations are probably much lower,” states Frank. “This study, in a broader context, demonstrates that wildlife contributes valuable services to society, emphasizing the need for better understanding of this value to shape effective conservation policies.”
