Wind turbines are responsible for hundreds of thousands of bat deaths every year across the U.S. Reuters

Wind turbines across the U.S. are killing America’s bats at an alarming rate. According to a study of bat deaths, more than 600,000 of the nocturnal fliers were killed by energy-producing wind turbines in 2012, and the largest number of bat deaths occurred in the Appalachian Mountains.

"Dead bats are found underneath wind turbines across North America," researchers from the University of Colorado wrote in the study, published Friday in the journal BioScience. "This estimate of bat fatalities is probably conservative." Researchers think that the number could be as much as 50 percent higher. There were holes in the data, and the assumption that some of the dead bats were scavenged by other animals before they could be counted.

According to the Los Angeles Times, scientists used data from dead bats found at 21 locations across the U.S. Researchers calculated the number of bat deaths on a per megawatt basis and found that the deadliest things for bats were the East Coast generators of the Appalachian Mountains.

Wind farms consist of clusters of wind turbines as tall as 30-story buildings. According to NBC News, their spinning rotors are as wide as a passenger jet’s wingspan, and the blades can reach speeds of up to 170 mph at the tips. This creates a tornado-like vortex behind the wind turbines that can cause sudden changes in air pressure that can traumatize bats flying through the vortex.

They believe the bats are not only killed by directly colliding with the massive generator propellers, but also by changes in air pressure created by the turbines. Another study of bird deaths linked to wind turbines estimated that wind farms kill around 600,000 birds in the U.S. every year, including nearly 70 bald eagles in the last five years, according to Forbes.

According to the U.S. Energy Information Administration, wind turbine generation increased 27 percent in 2011 from 2010. This is indicative of a growing trend in wind turbine production across the country, as energy producers increasingly turn to wind power as a renewable source of clean energy.

The dangers of wind turbines only add to the increasing vulnerability of U.S. bat populations. According to the U.S. Geological Survey, bat populations have declined worldwide over the past few decades. Bats have a very low reproductive rate – females give birth to only one pup per year -- and the mortality rate for young bats is high. This makes bats especially vulnerable to small changes in the environment.

Also, a certain fungus has killed around 6 million American bats since the fungus first debuted seven years ago in New York. Known as white-nose syndrome, the disease now infects bats in 22 U.S. states, according to The Huffington Post.

Bats provide an invaluable service to humans. First, bats eat an enormous number of flying insects. Second, bats help pollinate such crops as avocadoes and peaches.