The butterfly effect suggests the flapping of a tiny insect's wings in Africa can lead to a tornado in Kansas.
Call this the bat effect: A bat killed by a wind turbine in Somerset can lead to higher tomato prices at the Wichita farmers market.
Bats are something of a one-species stimulus program for farmers, every year gobbling up millions of bugs that could ruin a harvest. But the same biology that allows the winged creatures to sweep the night sky for fine dining also has made them susceptible to one of Pennsylvania's fastest-growing energy tools.
The 420 wind turbines now in use across Pennsylvania killed more than 10,000 bats last year -- mostly in the late summer months, according to the state Game Commission. That's an average of 25 bats per turbine per year, and the Nature Conservancy predicts as many as 2,900 turbines will be set up across the state by 2030.
This is a bad time to be a bat.
It may seem like a good thing to those who fear the flying mammals, but the wind farm mortality rate is an acute example of how harnessing natural energy can lead to disruptions in the circle of life -- and the cycle of business. This chain of events mixes biology and economics: Bat populations go down, bug populations go up and farmers are left with the bill for more pesticide and crops (which accounts for those pricey tomatoes in Kansas).
Wind industry executives are shelling out millions of dollars on possible solutions that don't ruin their bottom line, even as wind farms in the area are collaborating with the state Game Commission to work carcass-combing into daily operations.
"If you look at a map and see where the mountains are, everything funnels through Somerset," said Tracey Librandi Mumma, the wildlife biologist who led the March commission report on bird and bat mortality. "If I'm out driving ... I wonder, 'How many are being killed at that one?' "
Bats are nature's pesticide, consuming as many as 500 insects in one hour, or nearly 3,000 insects in one night, said Miguel Saviroff, the 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."
If one turbine kills 25 bats in a year, that means one turbine accounted for about 17 million uneaten bugs in 2010.
Bats save farmers a lot of money: About $74 per acre, according to an April report in Science magazine that calculated the economic value of bats on a county-by-county basis.
In Allegheny County, bats save farmers an estimated $642,986 in a year. That's nothing compared with more agricultural counties in the region such as Somerset ($6.7 million saved), Washington ($5.5 million) or Westmoreland ($6.1 million).
Lancaster County? You owe bats $22 million.
In all of Pennsylvania, bats saved farmers $277.9 million in estimated avoided costs.
Initially, the "Economic Importance of Bats in Agriculture" article was meant to attract attention to the white-nose fungus virus that is wiping out entire colonies of bats across the country.
"We were getting a lot of questions about why we should care about white-nose syndrome," said author Justin Boyles, a post-doctoral fellow in bat research at the University of Tennessee. "Really, it's the economic impact that makes people listen."
The white-nose syndrome is compounding the wind turbine problems, having killed more than a million bats in the northeastern United States since 2006. It surfaced in Pennsylvania in 2008 and has killed thousands of in-state bats.
Meanwhile, the same creatures that save Pennsylvania farmers millions of dollars each year are also costing energy companies some big bucks as they try to stave off a mass execution beneath the blades.
Technology is being developed on sound generators that would deter the creatures from getting too close with a high-pitched noise only heard by bats. Some studies suggest that a slowdown in blade speed would reduce mortality.
But new technology is expensive and a blade slowdown would reduce the number of megawatts produced.
"All these options cost money," said Ms. Librandi Mumma, and it can be a tough sell to the private 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 pre-construction reconnaissance and post-construction monitoring. The cost of the process varies, but 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 six meters around each turbine for carcasses. The employees are tested to see "how good they are at finding dead things," said Ms. Librandi Mumma.
"We got a dead snake once, because it was on the road and they were just collecting everything dead," she said. "It wasn't because the wind turbine killed it. The guy was just being thorough."
Some retrievers aren't so good.
"The average person finds 30 percent of the carcasses that are under a turbine," said Ms. Librandi Mumma, so the commission has come up with an algorithm that accounts for the missing bodies.
Agents will leave a carcass on the ground and note how long it takes to disappear -- this provides some insight on how many carcasses are unaccounted for because of living animals that have a taste for decomposing flesh.
Some wind companies with Pennsylvania operations have already seen seven-figure expenses on account of the bat problem.
NextEra Energy Resources, which operates the Somerset wind farms visible from the Pennsylvania Turnpike, has five active 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 Juno Beach, Fla.-based firm.
The funding program involving nine different 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 LLC of Allentown had planned on installing 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," said spokeswoman Mimi Mylin. "Some construction sites use lattice towers, but those can become roosting sites" for birds.
It's not just bats that are dying around wind turbines. An estimated 1,680 birds were killed by turbines last year, according to the state Game Commission report.
The disparity in mortality stems from biology. Birds typically crash into the blade and die from blunt force trauma, 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 the bats' lungs to burst, and they collapse with no ostensible lacerations or scars on the body.
"They just look like they're sleeping," said Ms. Librandi Mumma.
Bats must fly very close to the blades for their lungs to burst, and some researchers say the lights around the turbines might attract insects, which in turn attract bats.
Barotrauma in bats was only discovered in 2008, when a Canadian biologist thought to dissect one of the unblemished carcasses turning up at wind farms across North America.
"It was an 'a-ha' moment," said Ms. Librandi Mumma.
The turbine problem has yielded some other, unexpected contributions to bat research.
One carcass hunter in central Pennsylvania found a Seminole bat felled by barotrauma under the blades. Seminole bats live in the southeastern United States and rarely show up in Pennsylvania.
"It's like a double-edged sword," said Ms. Librandi Mumma. "You're excited because it's a new bat, but it's a dead one."
The Seminole specimen was kept on dry ice in a small styrofoam container by a commission employee and handed over to Suzanne McLaren, the collection manager at the Carnegie Museum of Natural History's research center in East Liberty. They met in the Ligonier Diamond town square -- home to a postcard-perfect gazebo and lots of sunlight -- for the transfer.
The bat, which may have traveled here from as far as Florida, found its final resting place in a freezer in East Liberty.
Erich Schwartzel: firstname.lastname@example.org or 412-263-1455.