Explaining Wind Turbine Lethality

By Willis Eschenbach – Re-Blogged From WUWT

For reasons that will soon be evident, the comments on my previous wind turbine post reminded me of a long-ago sunset dinner with my gorgeous ex-fiancée on the verandah of a lovely treetop restaurant on Pohnpei island in the tropical Pacific.

The only “fly in the ointment”, as is often the case in the tropics, was … the flies. And various other tropical flying insects. So the owners had thoughtfully installed one of those insect electrocution devices with the exposed power wires that go BZZZT every time another fly hits the wires, is electrocuted, and falls out of the sky.

In the lovely twilight, I thought little more about the occasional BZZZT! of the fly-killer until the owner of the restaurant said, “You should look over the edge of the verandah.”

We stood up, went to the edge, and looked down. And way down there on the ground, in the gathering darkness, was a group of very large tropical toads gazing straight upwards … and as we gazed down at their toadiness, BZZZT! went the fly-killer.

The freshly barbecued corpse of the fly fell straight downwards … but it never made it back to the earth …

I realized then that in nature nothing goes to waste. There’s always something waiting to consume any form of food, at times before it even hits the ground.

I bring this up because I’ve been thinking about the unexpectedly lethal habits of wind turbines. In the US, if someone kills a bald eagle they get slapped with a big fine … but wind turbines can kill the national bird, the Bald Eagle, by the dozens and absolutely nothing happens to them. They kill so many birds and bats that the US government has had to give them special exemption from all environmental rules and regulations about bird and bat deaths … and that’s a lot of deaths. It’s bizarre just how lethal wind turbines are.

So for example, it’s estimated that the wind farm at Altamont Pass in California not far from my home has killed 2,900 golden eagles in the quarter-century since it was built … and that’s just golden eagles. And estimates are that 600,000 bats are killed annually in the US alone.

I was thinking about my evening in the Pohnpei restaurant because someone said to me on Twitter “But … but … cats and tall buildings kill lots of birds, too” … and it’s a fact, they do.

However, there’s a huge difference with wind turbines, and I say that the difference, curiously, is bugs. Here is my theory as to why wind turbines kill so many bats and birds big and small, many more than anyone expected.

Wind turbines are surprisingly lethal because they kill bugs.

And not just a few bugs. Based on observations and model calculations, German researchers calculated that each wind turbine kills on the order of 12,000 insects per day, which is some 12,000 tonnes of dead insects per year in Germany alone. And for each bug that is killed, perhaps ten bugs are injured or dazed. Plus I suspect their calculations are too low.

First, a bit of background. Most folks don’t realize that the tips of those big slow-turning wind turbine blades are typically moving at 175 miles per hour (280 km/hr, an average of 21 different models), with some going as fast as 230 miles per hour (370 km/hr). YIKES! There’s no way to dodge something moving that fast.

It gets worse. At that speed, the blade tip doesn’t even have to hit an insect, bird, or bat to kill it or daze it. There is a large overpressure of air directly in front of the leading edge of the blade. And there is a near-vacuum on the back side of the blade. Just going suddenly from the high overpressure to near-vacuum can cause a variety of injuries, including bursting the lungs of bats and birds.

So let’s follow the story, starting with the bugs. The turbine is acting like a giant bug-mincer. It is smashing bugs on the leading edges of the blades, just like the smashed bugs you get when you drive down the highway. It is injuring bugs through both turbulence and pressure changes. And it is constantly and invisibly spinning hundreds of both dead and wounded bugs, and lots of smelly bug-juice from the smashed insects, up into the sky.

What happens first, of course, is that the smell of the dead and wounded insects attract lots of other insects. Many insects are scavengers, and so more insects come to feed on the dead insects just like flies drawn to sh … well, you get the idea. So in addition to the bugs killed and wounded, we have all of the other very live bugs eating on them, and flying around between meals.

Now, remember what I said about the frogs eating the flies “before they hit the ground”? What happens next is that large numbers of both bats and insectivorous birds are drawn by the smell of thousands of dead and wounded insects. They do their very best to eat the dead and wounded insects before they hit the ground.

And when you mix large numbers of bats and insectivorous birds on the hunt, somewhat oblivious to their surroundings in pursuit of insect prey, with turbine blade tips going 230 miles an hour, that’s 370 km/hr, the outcome is unavoidable—large numbers of dead and wounded bats and birds.

Of course, wherever you have large numbers of dead and wounded bats and birds, you’ll inevitably attract numbers of the large predatory or scavenging birds such as owls, buzzards, vultures, falcons, eagles, kites, buteos, accipiters, or harriers. They come in to eat the living, wounded, or dead birds and bats that came in to eat the living, wounded, or dead bugs … and of course, since these large predators too are on the hunt and somewhat oblivious to their surroundings, when you mix in the high-speed turbine blades the raptors suffer the same fate as the smaller birds, the bats, and the thousands of bugs. Killed and wounded.

How many birds die this way? The simple answer is … too many. But it’s hard to tell because the wind industry folks consider that a trade secret, and they won’t reveal their figures. The Audobon Society says:

Wind turbines kill an estimated 140,000 to 328,000 birds each year in North America.

Hundreds of thousands … however, this is just a guess, and the guesses keep getting revised upwards. In Hawaii, one of the few places where they’re legally required to measure the losses, I find articles like this one from 2017, “Wind farms killing more bats than expected“, or this one, “Hawaii windmills take a toll on endangered animals

Right … I bet they are killing more than expected …

Me, I say that the reason people continually underestimate the number of birds and bats killed by wind turbines is that they never thought about the bugs. They think that a random bat or bird will only intersect with a turbine blade every once in a while as it flies through the landscape, so not many will die … they don’t realize that instead, the bats and birds are attracted to the turbines by easy prey and are chasing one of many dead or injured insects, birds, or bats through the lethal turbinespace, with the tragically predictable outcome.

Anyhow, that’s my own theory of why wind turbines kill so many birds and bats—because of bugs. As always, YMMV.

Here, I’ve been packing. I’m leaving tomorrow for a couple-week vacation in the Nevada desert, so I’ll be out of touch with you good folks for a bit.

Sea fog is rolling back in, stay well,


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