Bat populations have declined by 90 percent due to white-nose syndrome, a fungal infection.
When a wild animal species becomes extinct, it affects the entire ecosystem. A new study puts an impressive link between infant and bat deaths.
If bats die, more human babies will soon die. This is the dramatic conclusion of a study from the USA recently published in the magazine “Science” which deals with the extinction of bats in the New England region in the north of the USA. In 2006, large numbers of bats there succumbed to a fungal disease known as white nose syndrome, which has no cure as yet.
The syndrome is characterized by a white fungal growth around the nose of the bats. It has now spread to numerous other US states and Canadian provinces. Millions of bats have already died as a result. And humans also suffer indirectly from it.
It’s a chain reaction: When there are fewer bats to eat beetles, flies and caterpillars, the number of insects increases. This in turn causes farmers to spray more insecticides. In New England, 31 percent more insecticides entered the environment, the researchers report. At the same time, infant mortality in the affected districts rose by 8 percent. The researchers link these deaths to the increase in insecticides, which are known to be particularly dangerous for fetuses and infants.
Insecticides increased, herbicides remained the same
Eyal Frank, an economist at the University of Chicago, realized that the bat extinction due to white-nose syndrome was something of a natural experiment. The disease appeared suddenly and spread quickly. Frank was therefore able to compare the results in districts where many bats were dying with those in similar districts that were not yet affected.
He found that farmers sprayed an average of about one additional kilogram of insecticide per square kilometer in the first year. After five years, they were spraying two kilograms more than before. The use of weed and fungicides, however, remained stable.
In counties where bat populations had collapsed, deaths from accidents or homicides remained the same. However, other deaths, such as those from disease or birth defects, increased by 8 percent. In counties with healthy bat populations, the numbers did not change in either direction.
The study cannot conclusively clarify whether there really are no other factors that influence infant mortality in New England. It is puzzling why, for example, the birth weight of infants does not correlate with the decline in bats.
“The increase in deaths is enormous”
The study is “the most compelling evidence to date” of the link between economic and health impacts and the loss of a wild species, Paul Ferraro told Science magazine. Ferraro is a sustainability scientist at Johns Hopkins University who was not involved in the study.
“The increase in deaths is enormous,” says environmental health scientist Tracey Woodruff of the University of California, San Francisco. She believes the connection is plausible and worrying. In an earlier study, she linked a similar increase in child mortality to air pollution.
Winifred Frick, chief scientist at the international NGO Bat Conservation, says her jaw dropped when she heard the results. There are signs that some bat populations in the region are recovering, but it could take decades for them to return to their former size. In the meantime, the white-nose fungus is spreading across the western United States, including California, a major agricultural region.
