The conservation calculus for wind energy changed dramatically in Fall 2003. Bird fatalities had been the primary environmental concern at the giant, spinning turbines, especially eagles, hawks and other raptors. Then a study commissioned by FPL Energy discovered many more bat carcasses than birds at FPL’s Mountaineer Wind Energy Center in West Virginia. The concerns about environmental impacts of wind power began to change across North America.
The Mountaineer finding caught everyone off guard. A planning session hosted by Bat Conservation International in December 2003 brought together U.S. government agencies and wind-industry representatives. That led in early 2004 to the first major bats-and-wind-energy workshop, which generated far more questions than answers. FPL Energy was host for the workshop. One outcome was the creation of the Bats and Wind Energy Cooperative (BWEC) of key agencies, wind-energy groups and international experts that is led by BCI.
In the years since those bat carcasses were found at Mountaineer, we have learned a great deal about this serious threat to bats. And none of that could have been accomplished without the direct involvement and serious financial support of the wind-energy industry. But now, as wind power continues to grow dramatically around the world, wind companies need to implement strategies that have been proven to reduce bat fatalities.
This is the story of one firm that stepped up.
Indeed, our own bats-and-wind research was initiated and championed by Canada’s largest wind-energy producer, TransAlta. In 2005, as wind energy was beginning to boom in Canada, we wondered if we would see bat fatalities at new wind facilities. We got the answer that fall, when hundreds of dead hoary bats (Lasiurus cinereus) and silver-haired bats (Lasionycteris noctivagans) were found at the new Summerview I Wind Farm in southern Alberta.
TransAlta was surprised and contacted us. We were also surprised. Few bat fatalities had been found at other wind facilities in the area, and Summerview is located in the prairies, smack in the middle of pastures and crops – hardly the place we expected to find so many migratory tree-roosting bats. The company asked us to help them investigate, and we gladly accepted.
So began a close working relationship that produced an undergraduate honors thesis (by Jesika Reimer), a Master’s thesis and a Ph.D. degree (by Erin Baerwald) and almost a dozen peer-reviewed publications. Of course, all this research does not happen in a bubble. Given the potential for fatalities at other wind facilities in southern Alberta, TransAlta formed a research consortium with fellow Canadian wind-energy firms Suncor, Enmax and Alberta Wind Energy Corporation.
This consortium, along with additional funding from BCI, the Alberta Conservation Association, the University of Calgary’s Institute for Sustainable Energy, Environment and Economy, the Natural Sciences and Engineering Research Council of Canada and Shell Canada, provided unprecedented access to wind sites and data, which led ultimately to a much better understanding of bat fatalities at wind-energy facilities.
By having access to multiple facilities, we were able to address questions that could not have been answered at single sites. For instance, we quickly learned that fatality rates vary tremendously from facility to facility. By analyzing data from across North America, we showed that one reason for this is that newer, taller turbines kill more bats than older, shorter ones.
As elsewhere in North America, the majority of bat fatalities at our study sites were of migratory species during the fall migration. We found that more bats were killed at sites on nights when echolocation activity, as measured with bat detectors, was greater, and that activity decreased among migrating bats the farther we moved from the eastern slopes of the Rocky Mountains into the mostly treeless prairies. This leads us to hypothesize that tree bats may be choosing migration routes based largely on the availability of tree roosts.
We also documented that weather influences the behavior of migrating bats much as it does migrating birds. More bats are killed when wind speeds are low (and bats are more likely to be flying), when barometric pressure is falling (which usually occurs before a storm), and when the moon is especially bright (which makes sense if, as hypothesized, bats are attracted to turbines and can see them more easily in moonlight).
BCI and BWEC, meanwhile, also explored the influence of wind speed on bat fatalities and, as early as 2005, proposed that bat-fatality rates might be reduced by adjusting the turbines so their blades do not spin during low-wind periods, when little or no electricity is being generated.
TransAlta suggested that we conduct the first large-scale test of this mitigation strategy. In the summer of 2007, we altered half the turbines at TransAlta’s Summerview site so their blades remained stationary at low wind speeds. We compared those to turbines that operated in the standard way.
The results were dramatic: bat fatalities fell by 60 percent at the experimental turbines. Since our study, other wind-energy facilities have tested this strategy and also report large reductions in bat fatalities with only modest reductions in energy production. BCI and BWEC have been leading this critical research, and we hope to see this effective strategy implemented by wind-energy operators throughout the world. Millions of bat fatalities could be prevented.
TransAlta, meanwhile, has demonstrated its continuing commitment to better understanding and reducing bat fatalities.
“Following the successful implementation of the bat mitigation program at Summerview I, TransAlta has continued to explore ways of reducing its environmental impacts across its wind fleet,” says Mike Peckford of TransAlta. “At Summerview II, we worked with the turbine manufacturer to test and refine a process that automatically changes the ‘cut-in speeds’ – the minimum wind speed at which turbine blades begin generating electricity – during particular times of the year and day when bats are known to be at a greater risk of interacting with turbines.”
Peckford said TransAlta is also experimenting with varied cut-in speeds at wind farms in Ontario and Alberta. And the company is working “to reduce its environmental impacts” by the continued implementation of these mitigation strategies at Summerview I and II and “through the creation of site-specific Operations Environmental Management Plans for each of our wind facilities.” TransAlta is also instituting a new WInd Stewardship Plan and Environmental Reporting (WISPER) initiative that includes long-term monitoring of bird and bat populations at its wind facilities.
While the collective efforts of many scientists, government agencies and industry partners have greatly increased our understanding of the wind-power threat to bats, key questions remain. And as more and more wind facilities are added to the energy mix in North America and elsewhere, widespread adoption of proven mitigation strategies that will reduce bat fatalities remains elusive. TransAlta is the exception rather than the rule, and bats by the tens of thousands are at risk at wind facilities as a result.
Perhaps recognizing those companies that voluntarily act to minimize damage to bats will encourage others to follow suit.
ERIN BAERWALD is completing her Ph.D. at the University of Calgary, where ROBERT BARCLAY is Professor and Head of the Department of Biological Sciences.