The loss of bats to white-nose syndrome has largely occurred during the past 4 years, after the disease first appeared in upstate New York. Since then, the fungus thought to cause white-nose syndrome has spread southward and westward and has now been found in 15 states and in eastern Canada. Bat declines in the Northeast, the most severely affected region in the U.S. thus far, have exceeded 70 percent. Populations of at least one species, the little brown bat, have declined so precipitously that scientists expect the species to disappear from the region within the next 20 years.

The losses of bats at wind-power facilities, however, pose a different kind of problem, according to the authors. Although several species of migratory tree-dwelling bats are particularly susceptible to wind turbines, continental-scale monitoring programs are not in place and reasons for the particular susceptibility of some bat species to turbines remain a mystery, Cryan said.

By one estimate, published by Kunz and colleagues in 2007, about 33,000 to 111,000 bats will die each year by 2020 just in the mountainous region of the Mid-Atlantic Highlands from direct collisions with wind turbines as well from lung damage caused by pressure changes bats experience when flying near moving turbine blades. In addition, surprisingly large numbers of bats are dying at wind-energy facilities in other regions of North America.

"We hope that our analysis gets people thinking more about the value of bats and why their conservation is important," said Gary McCracken, a University of Tennessee professor and co-author of the analysis. "The bottom line is that the natural pest-control services provided by bats save farmers a lot of money."

The authors conclude that solutions to reduce the impacts of white-nose syndrome and fatalities from wind turbines may be possible in the coming years, but that such work is most likely to be driven by public support that will require a wider awareness of the benefits of insectivorous bats.

The article, "Economic importance of bats in agriculture," appears in the April 1 edition of Science. Authors are J.G. Boyles, P. Cryan, G. McCracken and T. Kunz.