Study: Bat carcasses linked to pesticides and spike in infant mortality

There are many well-known ways to keep your baby healthy, such as washing your hands frequently, getting vaccinated, and not smoking indoors.

But there's one thing you probably haven't heard of: bat conservation — literally flying bat conservation.

This is noteworthy New Researchpublished in the journal Science, This links the decline of bats to an increase in newborn deaths in the United States.

By collecting and analyzing vast amounts of government data, environmental economists Eyal FrankDr. Schneider, the study's sole author, found that areas affected by white-nose syndrome, a wildlife disease that can kill bats, experienced an approximately 8 percent increase in infant mortality compared with areas without the disease.

According to the study, there's a clear reason for this: Most North American bats eat insects, including moths and other pests that damage crops. With fewer bats flying around, farmers end up spraying their fields with more pesticides, the study shows, and exposure to these chemicals is known to have negative effects on the health of newborns.

“When there are fewer bats to eat insects, farmers compensate by increasing their use of pesticides,” Frank, an assistant professor at the University of Chicago Harris School of Public Policy, told Vox. “That has negative health effects. The damage from the loss of bats seems likely to be substantial.”

Frank's work adds to a growing body of research that supports the idea (which should probably be obvious by now) that healthy ecosystems are important to human well-being.

Previous research Wolves have been found to help reduce car accidents by keeping deer off roads. Other studiesThe group, led by Frank, links India's steep decline in vultures to rising human mortality rates: Vultures feed on dead animals, which as they rot pollute waterways and provide food for wild rats and dogs, causing rabies.

When the connections between human and environmental health are overlooked, industries enabled by short-sighted policies can destroy wildlife habitats without fully understanding what we lose in the process. This is exactly why studies like this are so important: they make clear, in terms most people can understand, how the ongoing destruction of biodiversity affects us all.

Not everyone thinks bats are cute — they are! — But these animals are undeniably amazing: They're the only mammals on Earth that can truly fly, and they eat an astonishing amount of insects; a single bat can catch hundreds of insects per hour, and thousands per night.

This is a good thing for us: Many of the creatures bats eat on their nocturnal hunts are insects we don't like, like blood-sucking mosquitoes and crop-eating moths and beetles. Bats are essentially natural pest control agents.

So it stands to reason that without bats, farmers would have to use more pesticides on their crops – the pesticides are doing the job the bats do for free.

There wasn't a good way to test this theory until very recently, when bats across North America began to die off in large numbers. In 2006, a fungal disease called White Nose Syndrome appeared in New York state and spread through bat colonies, killing an average of more than 70% of the bats. The scary thing is that White Nose Syndrome invades the bats' skin, causing white, fluffy tumors around their noses, waking up the hibernating bats when they should be resting. Infected bats burn through vital energy reserves and either freeze to death or starve to death.

While the sudden decline of bats could be devastating, it presents researchers with a rare opportunity to test what would happen if these animals disappeared from the landscape. In the new study, Frank, who works at the intersection of economics and conservation, analyzed data on pesticide use in counties with and without WNS, which until recently were mostly in the eastern U.S. Bat populations are likely much smaller in places with WNS.

His results were surprising: Farms in areas where bats live used 31 percent more pesticides on their crops than farms in disease-free counties, suggesting that when the bats are gone, farmers compensate by using more chemical pesticides.

First, it costs farmers: According to Frank's research, bat declines cost the agriculture industry about $27 billion between 2006 and 2017, with revenues dropping in areas with white-nose syndrome. The reasons for these losses aren't clear, but Frank said it could be due to lower crop quality in areas without bats.

a study A 2022 paper supports a similar conclusion, linking bat infestations to lower rental values ​​for farmland. The idea is that without bats providing free pest control, farmers would suffer lower yields or have to spend more on growing crops to buy pesticides, etc. (I interviewed Amy Andoh, one of the study's co-authors, for an episode of Vox's Science Show.) I can't explainYou can hear here.

Furthermore, there will be serious damage to human lives.

It is well known that when farmers spray their fields with pesticides, the chemicals seep into the environment and pose a danger to pests. Public Health1 Recent Reviews For example, newborn pesticide exposure is associated with lifelong abnormalities and disease, so given this, one might expect areas without bats to have more health problems because farmers use more pesticides.

Frank also tested this theory, overlaying government data on infant mortality with the prevalence of White Nose Syndrome. His analysis, the first of its kind, found that infant mortality rates (infants who died from causes other than accidents or homicide) increased by nearly 8% after White Nose Syndrome outbreaks compared to counties that didn't have the disease. In other words, a 1% increase in pesticide use was associated with a 0.25% increase in infant mortality, comparable to (but slightly lower than) the effects of air pollution.

“The signal [in the data] “It was very strong,” he said. Dale Manning“Those are big numbers in terms of monetary impact, but you're also talking about human lives, right? So the impact is pretty big,” said Dr. John F. Kennedy, an environmental economist at the University of Tennessee, Knoxville, who was not involved in the study.

Manning and Environmental economist Ando Ohio State's Ando, ​​who was not involved in the study, said the paper's conclusions are sound. (Ando and Manning were also involved in the 2022 study.)

While the study did not conclusively prove that bat declines caused increased pesticide use or infant mortality, it did rule out many other potential factors behind the trend. Frank also found that infant mortality rates were higher when bat declines were more severe — when there were more dead bats, more infected caves, or when the rate of decline was steeper.

Studies like this make it even more urgent to address declining bat populations: More than half of North American bat species are “at risk of significant population declines over the next 15 years,” according to one research organization. 2023 Report The trend is being highlighted by the North American Bat Conservation Alliance, a coalition of government agencies and groups including Bat Conservation International. Mirroring Globally.

WNS continues to spread westward, invading new areas. Climate change is also having a negative impact on these animals. Physiological adaptations for flight As we've reported before, bats are highly vulnerable to severe droughts and heatwaves. Moreover, wind turbines, an important climate solution, kill hundreds of thousands of bats every year in North America alone. Most of these bats are migratory birds, and they often die from collisions with turbine blades. The reason is unknown. These animals are drawn to them.

The news isn't all bad: There are ways to help bat colonies survive. Scientists I've been testing For example, a vaccine for WNS. And the study Slowing down wind turbine speeds at night during certain times of the year has been shown to reduce collisions.

But such approaches can be costly, highlighting the value of research that more clearly sheds light on the returns on conservation investments, both in terms of money and human lives.

“Ultimately, scientists and policymakers need to justify allocating resources to things like bridge repairs, school repairs, or bat 'restorations,'” Manning said. “All of these have different payoffs.”

“And if we don't make an effort to show the benefits of 'improving' bats, then those benefits will be discounted,” he said.