When bats suffer from white nose syndrome, people suffer, too

Declines in bat populations affect agriculture, even infant mortality

New research into the fungus known as white-nose syndrome (WNS) finds there are human costs from this bat pandemic. Farmers have increased their use of pesticides, and in some places infant mortality has gone up.

There was evidence of North American bats showing signs WNS back in 2006. In 2007 biologist first took note of bats getting sick and dying from it. The fungus often looks like white fuzz on bats’ faces, hence the name. Hibernating bats will gather closely for warmth and security, allowing for easy spread of the disease. It also spreads easily in cold, damp places, like the caves bats live in.

WNS is most likely an introduced pathogen from Europe or Asia, where bats seem to have some resistance to the affliction. When bats have the syndrome, they become more active, which causes them to burn fat they need to survive winters. Bats afflicted with WNS will fly during the day and behave strangely in other ways. A recent study found that in under ten years, WNS has killed over 90 percent of three North American bat species: the northern long-eared, tri-colored, and little brown bat. The syndrome has also severely affected the Indiana bat and populations of other bat species.

It is a common assumption that viable ecosystems perform functions beneficial to humankind, but to fully assess the benefits the natural world confers on us is difficult and sometimes impossible to measure. The challenge arises because there is no ethical way to run experiments—manipulating species populations, interrupting food chains, etc.—to adequately test these hypotheses. Further, being creatures of the night, bats tend to go unnoticed, and we don’t consider the ecological niches they fill or how they may affect our lives. But it turns out the WNS pandemic has affected human populations everywhere it has infected bats.

Eyal G. Frank, an environmental economist and Assistant Professor at the Harris School of Public Policy, University of Chicago, looked into the effects the bat pandemic has had on agriculture and subsequent human health. His findings were published in the journal Science this month.

Collecting data from 2006 through 2017, Frank looked at counties in which there had been WNS outbreaks throughout the East Coast, Appalachian Mountains, and Midwest. He hypothesized that plummeting populations of bats, many of which are insectivorous, would lead to increases in insects, including agricultural pests. Oriental fruit flies, Mexican fruit flies, and other similar flies can destroy entire crops. And these are only a few of the insect pests that plague American farmers.

His guess was also that farmers would increase their use of pesticides, and these chemicals were being washed off fields, flowing into watersheds, and increasing in the general environment, leading to a rise in infant mortality. It’s well-documented that pesticides can make people sick and that individuals have died from exposure to these toxins, but there has not been any strong link connecting them with infant mortality.

Charting the use of insecticides, Frank found their use went up as soon as WNS was detected in 2007; infant mortality started rising at that time, too. Ultimately, farmers increased their use of pesticides by over 31 percent. Infant mortality rose by almost eight percent. For the mortality figures, Frank controlled for external factors, such as accidents and homicides.

We don’t know further ramifications from all these phenomena, but we can almost certainly conclude that increasing the use of pesticides most certainly affected the health and well-being of organisms in the watersheds where WNS has afflicted bats. Besides infant mortality, the pesticides probably affected the health of many individuals who live in the counties where WNS has spread. There may have been increases in the number of people with nagging coughs, irritated skin, nausea, vomiting, and diarrhea.

This study reveals how reliant we are on the natural world to provide us with pest control. Other parts of the natural world sequester carbon, give us clean water, cool our cities, and offer other benefits to humans. Obviously, we need to keep ourselves from destroying even more of the natural world. That being said, I would hate for us to value nature only for its utility. Some insectivorous bats help us a lot by regulating pests. Other bat species fill different niches. I feel that we should appreciate these other species just as much.

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