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Bats are facing a myriad of threats. In the northeastern U.S., white-nose syndrome, a fungal infection, has decimated populations. Habitat loss through deforestation and development are also stressors for bats. Even when we’re trying to fix an environmental problem, like carbon pollution, we cause another for them.

“Pretty much everywhere where wind turbines are installed, we see mortalities of bats at those facilities,” says Mylea Bayless. She is the Senior Director of Networking and Partnerships at Bat Conservation International. Among other things, the organization works with conservationists, governments, and energy companies to minimize the damage of wind energy on bats.

According to the Pennsylvania Game Commission, new wind energy projects have dramatically dropped off in Pennsylvania because federal tax credits for the industry expired. The commission even eliminated positions it created in the early 2000s to deal with the industry. Wind projects aren’t allowed on state game lands, but the commission has an agreement with energy companies operating on private property to consider how wildlife, like bats and eagles, will be impacted. But now that Pennsylvania’s climate plan calls for an increase in renewable energy, the wind might be changing, again.

The Allegheny Front’s Kara Holsopple talked with Mylea Bayless from her office in Texas to get a handle on how wind energy impacts bat species, and what’s being done about it.

LISTEN to the interview:

KH: As far as threats to bats go, how bad is wind energy?

MB: Wind energy is a relatively new threat to bats, as we’ve seen wind expand on the landscape over an 11 year period between 2000 and 2011. We had some estimates that ranged between a total of 840,000 bats to 1.6 million bats killed, and then the most recent study that we have, estimates between 200,000 and 400,000 bats were killed [in the U.S.] in 2012.

Those estimates sound high, but we expect them to become much higher. According to the Department of Energy, the wind energy capacity in the U.S. is expected to double in the next 10 years, and by 2050, the wind energy capacity is expected to be four times what it is today.

We also expect wind turbines to increase in both size and efficiency, which is basically going to allow them to capture energy at lower wind speeds. This is going to allow for more wind developments in areas of the country where currently it’s not economically viable, like the southeastern United States.

“We’re going to quadruple the number of turbines on the landscape by 2050, and that’s going to lead to a lot more bat mortalities.”

Not only are we going to see turbines become bigger and more efficient, and more widespread across the landscape, but we’re also going to quadruple the number of turbines on the landscape by 2050, and that’s going to lead to a lot more bat mortalities.

And the impacts to different species are pretty broad. Currently we have about 24 different species in the U.S. that we’ve documented have been killed by wind turbines, and of those reported, most are migratory tree roosting bats–about 78 percent. But within their range, Mexican free-tailed bats make up the majority of the fatalities, and that’s the species that’s best known for all those spectacular emergences in central Texas, like under the Congress Avenue Bridge.

There’s also documented fatalities of federally endangered or threatened bats, including the endangered Indiana bat, northern long-eared bats, Hawaiian hoary bats, and lesser long-nosed bats.

KH: What causes the bat fatalities at wind projects? What’s the actual physical thing that happens?

MB: The bats are coming into the airspace of the turbine blades, and they’re getting hit by the blades, falling to the ground, and dying.

“It really seems like they’re just getting hit by the turbine blades as they occupy the air space.”

There was some conversation a while ago about something called barotrauma, which is a pressure differential, and so for a while we were thinking that barotrauma contributed to some of those deaths. But upon further research, it really seems like they’re just getting hit by the turbine blades as they occupy the air space. The turbine blades look like they might be spinning fairly slowly from afar, but really the tips of those blades are spinning very fast.

KH: You mentioned endangered and threatened species. How does the designation impact where wind projects are sited, and the regulations around wind projects?

MB: There’s plenty of wind energy development within the range of federally protected species. Usually, the wind facilities conduct one or two years of post-construction monitoring to see what the impacts are. But beyond that first couple years, we really don’t know what the mortality rates are for the life of those projects, which can be 25 or 30 years.

If a wind company wants to build a project within the range of a federally listed species, they have to consult with the U.S. Fish and Wildlife Service. Developers can be issued a permit basically to impact the species, and if they get a habitat conservation plan approved, that plan has to demonstrate steps that they’ll take to minimize and mitigate that impact.

So there is a process that wind developers can use to develop within the range of the species, but they have to implement those conservation measures.

KH: So how does Bat Conservation International work with groups and industry to minimize bat deaths as a result of wind energy?

MB: Bat Conservation International as a founding member of the BWEC, which stands for the Bats and Wind Energy Cooperative. For the past 15 years, the BWEC has been a place for the wind industry, the U.S Department of Energy, state and federal wildlife agencies, NGOs and university professors and experts to really work together to find solutions to this problem of bats being killed by wind turbines.

This group develops ideas and technologies to save bats from being killed, and test them at real on-the-ground wind facilities. And it’s been pretty effective.

This collaboration has developed the only reliable tools for estimating and reducing fatalities that’s trusted by the Fish and Wildlife Service when they negotiate with wind companies to allow developments where endangered species live.

KH: Tell me a little bit about some of the tools that are used and how they’re used.

MB: The most effective way to keep bats from being killed right now is to modify the way that turbine blades operate, particularly at low wind speeds. This is called ‘curtailment,’ or sometimes ‘operational minimization.’

The reason it works is because bats are the most active when wind speeds are low, so on those low wind nights, most turbines begin generating electricity between three or four meters per second. And that’s called the ‘cut in speed.’ So the BWEC figured out that if we simply increase that ‘cut in speed’ a little bit, say to like five or six meters per second, and then ‘feather’ the turbine blades, which means to pitch them parallel to the wind, that’ll keep them from spinning at those lower wind speeds when they’re not producing very much electricity.

If we do that we can save about 50 to 75 percent of the bats from being killed, because the bats don’t really fly at those higher wind speeds. There’s some electricity production that’s lost, but by most estimates, it’s not very much–one percent.

There are also several kinds of bat deterrents that are being tested. One of them is an ultrasonic acoustic deterrent, which basically means it’s emitting sound above the hearing range of humans. These are mounted on the wind turbine, and they blast a broad spectrum sound to create an uncomfortable space for the bats. It really messes with their echolocation. These are still being tested, but the earlier results look pretty promising.

KH: And it’s in the best interests of wind companies to know about this technology to use it and implement it?

“Nobody wants to kill bats. It’s not good for business, it’s not good for conservation. It’s not good for their image as green energy.”

MB: Oh yeah, you bet. And they’re right there at the table working with us to try and find these solutions, because nobody wants to kill bats. It’s not good for business, it’s not good for conservation. It’s not good for their image as green energy, and so they’re really highly motivated to help us solve the problem. I’ve been pretty impressed.

Most of the wind companies are really trying hard to figure out a solution that works for them. It’s tricky because everything has a cost. So if we can find those solutions that are both recognized as having a high enough conservation value, and are also reasonable and cost effective for the wind industry to implement, then we’re going to get this thing figured out. That’s just going take a little bit of work, because some things are better for conservation, but there are big impediments to implementing them.

If we can’t implement them in a widespread way across the industry, we’re just not going to get that much traction and get the conservation work done.

This story is part of our series, Wild Pennsylvania, which is funded by the Richard King Mellon Foundation. To check out the other stories in the series, click here