It is unclear what impacts repowering can have on total mortality of birds and bats. Researchers asked whether, after controlling for confounding factors, turbine-caused mortality of wildlife differed among turbines of different sizes and production capacity. They found that benefits to wildlife of replacing older turbines with newer ones in the same location will depend largely on the relative amount of energy produced, not on the size of the replacement turbines, which challenges a frequent assumption of repowering efforts. In a given location, newer turbines would be expected to be less harmful to wildlife only if they produced less energy than the older models they replace. The implications are far-reaching as 18 percent of U.S. and eight percent of world-wide wind power capacity will likely be considered for repowering within roughly five years. A USGS press release describing this paper was published on March 31 to coincide with the release of the Journal of Applied Ecology manuscript. 

Huso, M.M., Conkling, T.J., Dalthorp, D.H., Davis, M., Smith, H., Fesnock, A., Katzner, T.E., 2021, Relative energy production determines effect of repowering on wildlife mortality at wind energy facilities: Journal of Applied Ecology, p. online, https://doi.org/10.1111/1365-2664.13853.