At a recent evening “batwalk” at the University of California’s Sedgwick Reserve conducted by vertebrate biologist Paul W. Collins, curator of vertebrate zoology at the Santa Barbara Museum of Natural History, I learned that a lot of bats are dying from turbines used to produce renewable energy.
I emphasize this was my own discovery because a quick Google search reveals the problem is well-known to bat fanciers; there’s even a 9-year-old Bats and Wind Energy Cooperative. That birds and windmills don’t always mix is something I knew, thanks in part to active inbox lobbying from groups like the American Bird Conservancy and even those sub rosa environmentalists at The Heartland Institute.
However, in the last four years, bat mortality has exceeded bird mortality at wind farms in the U.S.
Birds seem more likely to be the victim of spinning blades since their navigation – little magnets in their heads aside—is more visual than bats’ snazzy sonar systems. Shouldn’t a bat, which after all can find a mosquito in midair, be able to locate and then whip around a giant wind turbine like they do other structures? Piles of bats at the bottom of turbines suggest the answer is no.
As the U.S. Geological Survey notes:
Dead bats are turning up beneath wind turbines all over the world. Bat fatalities have now been documented at nearly every wind facility in North America where adequate surveys for bats have been conducted, and several of these sites are estimated to cause the deaths of thousands of bats per year.
The USGS and a slew of researchers are trying to figure out what’s up with these deaths and what can be done to prevent them short of stopping the turbines spinning on the world’s current best-hope for renewable electricity.
While they are stumbling around in the dark on lots of the potential answers, researchers do know a few things. For one, the types of bats that die are predominately bats that both migrate and that roost in trees, such as the Hoary Bat, the Eastern Red Bat, and the Silver‐haired Bat–none of which are currently threatened. They also know that deaths increase when the bats are migrating in the spring and fall, and that not all turbines kills bats at the same rate (Buffalo Mountain in Tennessee is murder on bats, while those turbines operated by the Sacramento Municipal Utility District statistically are much more benign).
They also know that bats aren’t necessarily being turned into bat suey. As the University of Calgary’s Erin Baerwald told Discovery News in 2008, "When people were first starting to talk about the issue, it was 'bats running into the turbine blades.' We always said, 'No, bats don't run into things.' Bats can detect and avoid all kinds of structures," and are even better at detecting stuff that’s moving. No, they're exploding.
Baerwald and her colleagues discovered that bats' “large, pliable lungs” blow up from change in air pressure created by moving blades. Up the 90 percent of the dead bats they examined showed the internal bleeding consistent with their argument. Birds, by the way, have different kinds of lungs so their deaths are from the more predictable blunt-force trauma.
Scientists are beavering away on saving bats, hoping to replicate some of the success they’ve seen in saving birds. Deterring bats from frequenting wind farms hasn’t been the most active area of inquiry. Instead, operational changes are the busiest avenue – making the structures higher or lower, changing when turbines spin, maybe only running them when it’s too windy for bats to be about, changing their speed, or maybe even shutting them down during crucial migration periods or moving them completely out of popular migration corridors. Wired reported in June on a test in Wisconsin that listens for bats’ sonar and can alert operators to power down turbines in response. The system, known as ReBAT, has been approved in a few places like New York and Ontario.
In California, other researchers with the USDA, also listening in on bats’ echolocation, have suggested including weather and season information in the algorithm on when to curtail operations. To see how all these variables might play out, click here for an interactive model that mimics a Riverside, California wind farm.
My batwalk also taught me that bats are long-lived—up to 30 years—but slow to reproduce. With the flying mammals already under siege from white-nose syndrome, I hope I’m not the last person to get on board with helping them.