It's a bad time to be a bat.
This may seem like good news for people who fear them, but the wind-farm mortality rate is an example of how harnessing natural energy can lead to disruptions in the cycle of life - and the cycle of cost. When bat populations go down, bug populations go up, leaving farmers with bigger bills for pesticides and crops.
Wind-industry executives are shelling out millions of dollars on possible solutions, even as Pennsylvania wind farms are collaborating with the Game Commission to count dead bats.
Bats consume as many as 500 insects in an hour, or nearly 3,000 in a night, said Miguel Saviroff, agricultural financial manager at the Penn State Cooperative Extension in Somerset County.
"A colony of just 100 little brown bats may consume a quarter of a million mosquitoes and other small insects in a night," he said. "That benefits neighbors and reduces the insect problem with crops."
Bats save farmers as much as $74 per acre, according to an April report in Science magazine that calculated bats' economic value county by county. In Pennsylvania, the study put yearly savings in rural Somerset County at $6.7 million. Lancaster County? You owe bats $22 million. Statewide, bats saved farmers an estimated $277.9 million.
Initially, the "Economic Importance of Bats in Agriculture" article was meant to attract attention to the white-nose fungus virus, which is wiping out bat colonies across the country.
"We were getting a lot of questions about why we should care about white-nose syndrome," said author Justin Boyles, a postdoctoral fellow in bat research at the University of Tennessee. "Really, it's the economic impact that makes people listen."
The white-nose syndrome has killed more than a million bats in the Northeastern United States since 2006. It surfaced in Pennsylvania in 2008.
Meanwhile, bats are costing energy companies big bucks spent trying to stave off their deaths beneath wind-turbine blades.
Technology is being developed to equip turbines with sound generators that would drive bats away with a high-pitched noise that only they hear. Some studies suggest slowing down blades would also help.
But new technology is expensive, and a blade slowdown would reduce the megawatts produced.
"All these options cost money," said Tracey Librandi Mumma, the wildlife biologist who headed the Game Commission's March study on bird and bat mortality. She said it could be a tough sell to the industry handing over the information that helps in the research. "You don't want to penalize the hand that's giving you the data."
Companies that have signed a Game Commission cooperation agreement must foot the bill for the commission's preconstruction reconnaissance and postconstruction monitoring. The cost varies, and the research can last several months and involve extensive habitat monitoring.
Under the agreement, each site conducts two years of mortality monitoring, sending a lucky employee out every day from April to November to comb the ground around each turbine for bat carcasses.
Agents will leave a carcass on the ground and note how long it takes to disappear, the better to get a sense of how many carcasses are being eaten by predators.
Some wind companies with Pennsylvania operations have already seen seven-figure expenses related to the bat problem.
NextEra Energy Resources, which operates the Somerset wind farms visible from the Pennsylvania Turnpike, has five sites in Pennsylvania but did not participate in the Game Commission study.
The company monitors its mortality rates in-house and funds outside research to reduce bird and bat deaths at its sites, said Skelly Holmbeck, environmental business manager at the firm, which is based in Juno Beach, Fla.
The funding program, involving nine research facilities, is "in the millions overall," she said.
Migratory research that precedes any construction can employ bird-watchers, nets, or tape recorders designed to read the local ecosystem.
PPL Renewable Energy L.L.C. of Allentown had planned to install four turbines at its Lancaster County wind farm but went with only two after sensitive avian populations were found nearby.
"There were design aspects that we elected not to use," spokeswoman Mimi Mylin said. "Some construction sites use lattice towers, but those can become roosting sites" for birds.
Not just bats are dying around wind turbines. Turbines killed an estimated 1,680 birds in Pennsylvania last year, according to the Game Commission report.
Birds typically crash into the blade, while bats suffer from a condition called barotrauma. It's the bat equivalent of the "bends" that scuba divers can suffer if they surface too quickly.
The rapid drop in air pressure around the blades causes bats' lungs to burst, and they collapse with no lacerations or scars.
Bats must fly very close to the blades for their lungs to burst, and some researchers say the lights around the turbines may attract insects, which in turn attract bats.
Barotrauma in bats was discovered only in 2008, when a Canadian biologist dissected one of the unblemished bat carcasses turning up at wind farms.
"It was an 'aha' moment," Librandi Mumma said.
The turbine problem has yielded other, unexpected discoveries. A carcass hunter at a central Pennsylvania turbine found a Seminole bat felled by barotrauma. Seminole bats live in the Southeastern United States and rarely show up in Pennsylvania.
"It's like a double-edged sword," Librandi Mumma said. "You're excited because it's a new bat, but it's a dead one."