The threat of wind turbines to bat mortality

Piorkowski, M.D. and O'Connell, T.J. 2010. Spatial pattern of summer bat mortality from collisions with wind turbines in mixed-grass prairie. The American Midland Naturalist 164:260-269.

http://www.bioone.org.ezproxy.tru.ca/doi/full/10.1674/0003-0031-164.2.260

Wind turbine developments are increasing in number across North America as an alternative energy source, however, their potential risks on bat & bird mortality has been recognized. A recent study, conducted by Piorkowski and O'Connell (2010), included a spatial analysis at the Oklahoma Wind Energy Center (OWEC), in Great Plains, Oklahoma, USA, to find evidence of reduced mortality rates as a result of birds or bats colliding with wind turbines. More specifically, due to the presence of two different bat colonies within 15km of OWEC, the influence of wind turbines in close proximity to large maternity colonies was also of interest. The main objectives were: (1) to determine the rate of bat collision mortality per turbine during the summer, and (2) to discover if the spatial distribution of collision mortality was linked to local topography, vegetation, and flight corridors used by bats to and from their roost. In 2004 and 2005, during May and July of each year, various carcass surveys for bats and birds killed by turbines were conducted. The results showed that mortality was spread throughout 68% of the turbines at OWEC. Most of those carcasses were of various bat species; Brazilian free-tailed bats (Tadarida brasiliensis) accounted for most of the bat fatalities (85%). Spatial analyses did not show a strong pattern of mortality estimates, but collision mortality was higher at turbines close to eroded ravines –referred to as ‘hot spots’ of collision mortality in this study. Further research would be required to gather information about: parameters for predicting hot spots of wind turbines in association with seasons and years; identifying specific characteristics of hot spots; and examining whether factors like wind strength and direction could account for collision mortality in these areas. For species management issues, if continued monitoring shows the persistence of the presently identified hot spots at OWEC, Piorkowski and O'Connell recommend re-establishing the turbines and, ultimately, finding a balance between the goals to reduce collision mortality and the economic and environmental goals of power generation. Also, for future developments of wind farms, it was advised to examine the potential risks to individuals within colonies in close proximity to the areas, taking into consideration the daily foraging routes to and from roosts that may intersect with proposed developments.

Piorkowski and O'Connell reflect on a very important issue of yet another man-made threat that is still under research to implicate the best measures for appropriate management. In fact, organizations such as the Bats and Wind Energy Cooperative (BWEC) (formed in 2003 as a branch of alliance of Bat Conservation International, the US Fish and Wildlife Service, the American Wind Energy Association and the National Renewable Energy Laboratory of the US Department of Energy) have been formed to provide more data on the issues of bat collision mortality (Bat Conservation International, 2010).

Bats and Wind Energy:

http://www.batcon.org/index.php/what-we-do/bats-and-wind-energy.html

Words: 465