"Bats eat tremendous quantities of flying pest insects, so the loss of bats is likely to have long-term effects on agricultural and ecological systems," said Justin Boyles, a researcher with the University of Pretoria and the lead author of the study. "Consequently, not only is the conservation of bats important for the well-being of ecosystems, but it is also in the best interest of national and international economies."

A single little brown bat, which has a body no bigger than an adult human thumb, can eat 4 to 8 grams (the weight of about a grape or two) of insects each night, the authors note. Although this may not sound like much, it adds up—the loss of one million bats in the Northeast has probably resulted in between 660 and 1,320 metric tons of insects no longer being eaten each year by bats in the region.

"Additionally, because the agricultural value of bats in the Northeast is small compared with other parts of the country, such losses could be even more substantial in the extensive agricultural regions in the Midwest and the Great Plains, where wind-energy development is booming and the fungus responsible for white-nose syndrome was recently detected," said Kunz.

Although these estimates include the costs of pesticide applications that are not needed because of the pest-control services bats provide, Boyles and his colleagues said they did not account for the detrimental effects of pesticides on ecosystems or the economic benefits of bats suppressing pest insects in forests, both of which may be considerable.