The Dark Knight vs. the wind

It's hard to pick a fight with a wind-power advocate. Aside from the problem of intermittency -- typical wind farms produce only a third of their theoretical capacity because of calm periods -- what's not to like about generating electricity from moving air?

An earlier generation of wind turbines did have the tendency to kill a lot of birds, but new models, with their larger blades that turn more slowly and solid towers that provide no attractive nesting sites, largely have dealt with that problem. But now comes research suggesting that wind farms are killing bats in worrisome numbers.

"Barotrauma is a significant cause of bat fatalities at wind turbines" appears in Current Biology (Volume 18, Issue 16). The authors, from the University of Calgary in Alberta, say that when they examined dead bats at the base of windmills, they found many of them had burst lungs. The cause, they speculate, is low-pressure pockets of air created by moving blades.

Bats are able to "see" moving targets with their sonar, so some experts had predicted they would be able to avoid windmills. But they can't detect these air pockets, and their lungs' blood vessels burst when suddenly exposed to the low pressure. This is big deal, because bats are critical species in many ecosystems, serving as pollinators for a large number of plants and eating agricultural pests.

New Scientist's Catherine Brahic writes that it might be possible to limit bat mortality by raising the minimum wind speed at which the turbines start spinning. But another solution is to simply build them away from bat habitat. Offshore, for example. Denmark, which already gets much of its electricity from windmills, has just approved another 400 MW of turbines in the North Sea. The Danes want the wind to supply half their power by 2025, most of that off-shore. (Of course, Denmark has more offshore territory available than it does land, but there's plenty of coastline in the U.S., too.)

It may also be possible to install "acoustic deterrents" that divert bats away from wind farms with annoying tones.

In the end, if we are going to have any hope of eliminating greenhouse-gas emissions, wind power will have to part of the mix. Let's hope we have the imagination to ensure bats don't have to be sacrificed in the process.

James Hrynyshyn's blog posts are provided by LifeWire, a part of The New York Times Company.