A deadly pandemic decimated bats across North America, ultimately having detrimental effects on humans, including higher infant mortality rates, according to a new study.
The research is part of growing evidence that humans depend on the animal and plant species around them and suffer when these species decline or become extinct.
White-nose syndrome is a deadly fungal disease that kills an average of 70 percent of infected bats. Since it was first reported on the continent in 2006, the disease has spread to new areas.
The disease awakens bats during hibernation, often causing them to freeze and starve to death.
What happens when farmers don’t have access to bats?
Conservationists know that bats play a key role in controlling and controlling insect pests.
So Eyal Frank, an environmental economist at the University of Chicago, decided to look at what happens when white-nose syndrome spreads to new counties in the eastern U.S., decimating bat populations.
He found that farmers responded to insect plagues by increasing their use of pesticides by 31 percent. Pesticides are toxic and are often associated with health impacts on humans, such as increased infant deaths.
According to his research, Frank found that infant mortality increased by eight percent after white-nose syndrome appeared in a given county. published today in the journal Science.
“I was surprised at first,” Frank said, noting that the increases were “big effects.”
He noticed, however, that in regions affected by white-nose syndrome, the bat population not only decreases, but declines rapidly, and often completely dies out.
“It really shuts down biological pest control in some of these counties,” he said.
This forces farmers to compensate with “significantly more insecticides,” which he notes are toxic.
Frank also found evidence that pesticides were not only expensive, but also not as effective at controlling insects as bats—farmers’ income from selling crops fell by 29 percent in areas affected by the bat pandemic.
He estimates that farmers in communities affected by bat die-offs lost a total of $26.9 billion between 2006 and 2017. Including infant mortality, the societal cost of bat loss was $39.6 billion.
Scientists in British Columbia are monitoring bats to protect them from a deadly disease called white-nose syndrome, which causes the animals to emerge from hibernation in winter when food is scarce, often leading to their death.
The importance of biodiversity
The study shows how interactions between species such as bats and insects stabilize ecosystems that other species depend on, including humans, who could be harmed if those species go extinct, Frank said.
“These ecosystems are very complex systems with many interactions between species. We don’t fully understand what to expect or what happens when we allow the population of one species to fall below a certain viability level or become extinct,” said Frank, who previously linked the deaths of half a million people in India to the collapse of the local vulture population due to accidental poisoning.
He added that protecting more species and greater biodiversity can provide redundancy, so that if one species declines, another can take over.
Jianping Xu, a professor at McMaster University who studies white-nose syndrome in North American bats, said the new study shows that bats are important “not only for the ecosystem, but also for agriculture and human health.”
Xu, who was not involved in the study, said the “data looks pretty solid.” While the study focused on the eastern United States, Xu said white-nose syndrome occurs in all 10 Canadian provinces, and bats here are even more affected because it’s colder and they hibernate longer.
He would like to see similar Canadian data on the link between bat population declines, pesticides and infant mortality.
“I wouldn’t be surprised if the Canadian data showed a similar pattern,” he said.
Xu added that increased pesticide use is also associated with a decline in bat populations, creating a “vicious cycle.” He believes pesticide use should be limited to areas without bats.
Bruce Lanphear, a professor of health sciences and a pesticide expert at Simon Fraser University, said the study “elegantly” uses the pandemic among bats as a natural experiment to show the impact of pesticides on human health. He noted, however, that the study has limitations in determining which pesticides were involved in those health effects.
Lanphear, who has criticized the federal government’s transparency on pesticides, said the findings should also prompt us to “ask ourselves questions like, ‘Why aren’t our governments looking for ways to reduce pesticide use?'”
