Large Bat Kills
Found at Wind Generating Facilities on Forested Ridges
Bat fatalities at wind generation facilities has been documented world wide in all sorts of habitats. Although the studies to date are incomplete, there appears to be a correlation between eastern wooded sites especially on high ridges and higher than usual bat moralities. Below are the resulting estimates for the three eastern sites where bats were studied. Researchers point out that actual numbers are likely to be much higher.
Mountaineer, WV 2003 (44 turbines) 47.53 2090 total
Mountaineer, WV 2004 (44 turbines) 38.0 1672 total
Buffalo Mt. Tennessee (3 turbines) 20.8 62 total
Meyersdale, Pa. 2005 (20 turbines) 23.0 460 total
For the Mountaineer and Meyersdale sites figures for bats killed per turbine are over a 6 week study period during migration, and can not accurately be converted to a yearly rate.
Why are scientists so concerned?
In a Washington Post article, Merlin D. Tuttle, president and founder of Bat Conservation International was quoted “ Take the most conservative estimates of mortality and multiply them out by the number of turbines planned and you get very large, probably unsustainable kill rates. One year from now we could have a gigantic problem”
How many wind turbines?
As reported by the recent GAO report the Department of Energy is aggressively promoting wind power. They are proposing that 15 times the current installed capacity be in place by the year 2020. This increase would be equivalent to 62,000 additional turbines added to the existing 16,000 turbines in operation making a total of 78,000 wind turbines. It is difficult to predict due to the lack of research on the subject what the national average kill rate per tower is for either bats or birds. However even if you use a fairly low projected estimate the total mortality to bats and birds is enormous.
Why bats are more at risk
Bats are an essential element in the environment. As predators of disease-carrying insects like mosquitoes they safeguard human life. They also consume large quantities of moths that damage plant life and transmit tree diseases. A bat can consume an impressive quantity of insects, as many as 3000 mosquitoes in a night.
Contrary to popular belief, bats are not flying mice. Mice are capable of having many litters with multiple offspring. Bats however typically have only one or two offspring per year. Bats compensate for low reproductive rates by having longer life spans. Many populations of bats are already showing declines. Twenty five percent of all bat species worldwide are considered threatened. By the introduction of wind turbines as an additional cause of mortality bat populations will have an even harder time surviving.
Protection of bats
Bats as a group are given no special status or protection. In theory the Fish and Wildlife Service is charged with the protection of all wildlife species however it is only when bats have the dubious distinction of being threatened or endangered that they are given any real protective status. The question has to be asked, will unprotected species of bats being impacted by wind turbine installations have to have their numbers dwindle to a point that they become a listed (endangered or threatened) species before any action is taken? What action will be possible at that point in time? At Altamont Pass in California post construction studies revealed some of the highest bird moralities ever recorded. Many of the birds collected were Golden eagles and Red-tailed hawks. That was 20 some years ago. Though attempts have been made to mitigate collisions, turbines still spin and birds are still being killed at high rates. Once in place turbines will remain as long they are making their owners a profit. Mortality of wildlife even protected species is considered an “incidental taking” by an otherwise legal action and while the problem may be noted by regulatory agencies there does not appear to be the political will to take much action.
Endangered species
Given the existing laws and the political climate for regulation it is up to those species of bats that have already been designated as threatened or endangered to represent, in a legal sense, the interests of bats as a whole. If an endangered species is at risk then regulators have a legal responsibility to act. While no endangered bat species have been collected in mortality surveys so far we must view this evidence in light of the fact that very few bat surveys have been conducted. Of the total number of bats killed by wind turbines only a small percentage have been collected and identified. If a species has been designated as endangered it goes without saying that that species numbers have already declined and that this decline decreases the probability of detection. It appears that migratory bat species are the most likely to collide with turbines. In southeastern Appalachia the Indiana myotis a migratory bat is the most probable endangered bat species to be effected at wind turbine facilities.
The problems with existing studies
Most mortality studies at wind generating facilities have been designed to
track mortality of birds. Estimates for bats have been less precise or
incidental. Overall there is just not much quality information on bat
mortality resulting from wind turbines. Bat Conservation International publication states that only 12 of the 200 U.S. turbine facilities (with a nationwide total of 16,000 turbines) had been examined for bat kills- and only six of those attempted to estimate total bat mortality. The post-construction mortality study at the Mountaineer project in Tucker County WV did look specifically at bat mortality at the urging of WV DNR biologist. Is the outcome of that study, high mortality of bats, the result of its focus being the mortality of bats as well as birds? An important factor in these studies is whether scavenger removal rates and searcher efficiency rates are incorporated. The mountaineer study did address these contingencies while in many other studies on record they were overlooked. When these factors are overlooked or underestimated, numbers for both birds and bats appear lower than they actually are. Finally it must be noted that most studies to date are conducted by and for wind generating companies with little or no peer review. The resulting bias is inevitable. There is a definite need for more thorough studies that are long term, ongoing and properly peer reviewed.
Bibliography:
Arnett, E. B. technical editor. Relationships between bats and wind turbines in Pennsylvania and West Virginia. A final report submitted to the Bats and Wind Energy Cooperative, Bat Conservation International, 2005
Bat Conservation International Inc., publication, Wind Energy; A Lethal Crisis. October 2005
Bat Conservation International Inc., publication, Wind Energy and Bats, August 2004, Vol.2, No.9
Blum, Justin, Washington Post, Researchers alarmed by bat deaths from wind turbines, January 2005
Johnson, G.D. What is known and not known about bat collision mortality at wind plants? In R.L. Carlton, editor Avian interactions with wind power structures. Proceedings of a workshop in Jackson Hole, Wyoming, USA, October 16-17, 2002. Electric Power Research Institute Technical Report, Concord, Ca.
Kerns, J. and P. Kerlinger. 2004 A study of bird and bat collision fatalities at Mountaineer Wind Energy Center, Tucker County, West Virginia: annual report for 2003. Technical report prepared by Curry and Kerlinger, LLC. For FPL Energy and Mountaineer Wind Energy Center Technical Review Committee.
U.S. Accountability Office, Impacts on wildlife and government responsibility for regulating development and protection of wildlife. September 2005
U.S. Department of Energy, National Renewable Energy Laboratory, Keeping up with the rapidly growing wind industry
Williams, W. 2004. When blades meet bats: Unexpected bat kills threaten future wind farms. Scientific American. February 2004