Colorado biologist scopes out bat, radar study
| July 23, 2009 | 10:02 AM
More journal entries from John Moore »
Could radar help save bats from wind turbines?
A Colorado biologist who has studied the effects of wind farms on the flying mammals is intrigued by new research out of Scotland that suggests the possibility.
A team from the University of Aberdeen has found that radar signals appear to drive bats away. That could prove helpful in keeping the little animals from being killed by wind turbines. While no exact numbers are available, scientists say that many bats fly into the spinning blades, or die when the sudden drop in air pressure caused by the rotors damages their lungs.
While Dr. Paul Cryan, a Colorado-based scientist, finds the study fascinating, he said more research is needed.
“One difficulty I see with the concept is that, if radar does indeed keep bats away from wind turbines, it would take a tremendous amount of electrical energy to blanket most wind energy facilities with radar energy,” he told the Rocky Mountain Independent on Wednesday. “Many wind sites cover tens of thousands of acres.”
Cryan, who was not involved in the Scottish study, is a research biologist at the U.S. Geological Survey’s Fort Collins Science Center.
In the study, researchers installed portable marine radar units at 20 sites where bats were known to forage for insects and found that bat activity there dropped by up to 40 percent over 58 days. Why the radar appeared to drive the animals away was not determined.
Bats use sonar to navigate, and some experts think the drop in air pressure near a wind turbine’s rotating blades may throw off their ability to avoid obstacles using echolocation. Losing too many bats would be bad for farming and the environment. Considering the number of wind farms springing up in Colorado and elsewhere, the RMI asked Cryan about the scope of the threat and about his reaction to the study. Here are his thoughts, from an interview conducted with the RMI via e-mail:
RMI: How big of a problem is this in the U.S.?
Cryan: Wind turbines are causing unprecedented mortality in at least three of the 45 species of bats that occur in the United States. The three species that compose the majority of fatalities in North America are the hoary bat, eastern red bat and silver-haired bat. These species differ from most others in the U.S. because they rely on trees as roosts throughout the year and migrate long distances across the continent — we call them migratory tree bats.
Fatality rates of bats at turbines vary by region, with estimates ranging from about one bat per megawatt of energy produced per year to over 50 bats (per megawatt per year). Most bat fatalities at turbines are found between about mid-July through October, which coincides with their fall migration, as well as likely mating period. In general, we see higher fatality rates at sites in or close to mountains and near the Great Lakes, and fewer fatalities in the flatlands, but our sample is fairly limited.
RMI: How many bats are found dead around wind turbines in an average month or year?
Cryan: If you download a presentation I put together for a Federal Advisory Committee a few years ago, you can view a map showing the distribution of wind sites in the U.S. and Canada as of a couple years ago. We have information on bats from proportionally few. This is mostly due to the fact that most turbine facilities are on private land, and when monitoring does occur, the resulting data are not always publically available.
Because of this, we do not yet have a very complete picture of which bat species are susceptible and how serious the problem might be. There is no evidence of human-induced impacts to the affected species that are of similar magnitude to mortality at turbines. Another complicating factor is that we currently don’t know how many of these bats are out there, so the length of time that their populations can sustain turbine-induced mortality is not known.
I am not aware of any data that are available to the public on fatality estimates for bats at wind energy facilities in Colorado, although Colorado has about 1000 (megawatts) of turbines installed statewide. However, I do know that bat fatalities (mostly hoary bats) were found at a wind site in northern Colorado several years ago when it was briefly monitored.
RMI: Do you see any alternatives to the radar idea that the researchers are looking at in Scotland?
Cryan: Three studies recently completed in the U.S., Canada and Europe (where similar problems are occurring with bats and turbines) offer a potentially more practical mitigation solution — all three studies have shown that shutting down turbines on low-wind nights during the period of bat migration significantly decreases fatalities. We don’t know exactly why, but it seems to be a promising technique in situations where bat fatality rates are otherwise high, but again, more study is needed to confirm the efficacy of that technique.
RMI: What are some of the possible solutions you’ve been looking at in your research?
Cryan: I have not been working at wind energy facilities in Colorado for lack of access. My research has been focusing on turbine facilities in New York and Texas. Last summer, I did a study to assess whether mating or feeding behaviors might cause bat fatalities at turbines. There is evidence that migratory tree bats may be attracted to wind turbines, and I am hoping to establish if attraction is occurring and what might be causing it, with the hope of somehow eliminating the attraction. I am also analyzing the organic chemicals (stable isotope ratios) in bat fur to try and infer where migratory bats killed at turbines began their journey.
RMI: Are there any breakthroughs or revelations from your research that you’d like to share?
Cryan: Not yet. I am still in the analysis phase but hope to have results available in the coming months. My involvement with the growing crisis of White-Nose Syndrome in bats has delayed my turbine-related work in the past year.
RMI: There are also concerns about the effects of wind turbines on birds. What about those who would say we shouldn’t build more wind farms until we know they are safe for wildlife?
Cryan: Bird fatalities are regularly found beneath wind turbines, but except in certain situations such as with raptors (e.g., eagles, hawks) at older lattice-tower turbines like Altamont Pass in California, there is not much evidence that certain species of birds collide with turbines at the rates approaching those we see with migratory tree bats. Birds are also known to regularly collide with other tall structures like buildings and communication towers, and often in larger numbers than are seen at wind turbines, but this is not the case with bats. I am optimistic that if biologists and wind energy developers work together, the current issues we are seeing with bats and wind turbines can be resolved. The patterns I see in bat fatalities at turbines are compelling enough to make me think that some answers might be just around the corner.
Read more at MSNBC.
bats, birds, colorado, fort collins science center, radar, scotland, u.s. geological survey, university of aberdeen, usgs, wind turbines
