Action Synopsis: Bat Conservation About Actions

Slow rotation of turbine blades at low wind speeds

How is the evidence assessed?
  • Effectiveness
  • Certainty
  • Harms

Study locations

Key messages

  • One study evaluated the effects of slowing the rotation of turbine blades at low wind speeds on bat populations. The study was in Canada.




About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A replicated, randomized, controlled study in 2006–2007 at a wind farm in an agricultural area of Alberta, Canada (Baerwald et al 2009) found that slowing the rotation of turbine blades at low wind speeds resulted in fewer bat fatalities than at conventional turbines. Average bat fatality estimates were lower at experimental turbines with altered blade angles (8 bats/turbine) than at conventional control turbines (19 bats/turbine). Average bat fatality estimates did not differ significantly between turbines before the experiment (‘experimental’ turbines: 19 bats/turbine; ‘control’ turbines: 24 bats/turbine). Most bats identified during carcass searches were hoary bats Lasiurus cinerus and silver-haired bats Lasionycteris noctivagans (see original paper for data). In 2006, all of 14 turbines were operated using conventional methods (blades rotated freely at low wind speeds). In 2007, six randomly chosen turbines were altered by changing the pitch angle of the rotor blades to slow rotation at low wind speeds (<4 m/s). Eight control turbines were left unaltered. Carcass searches were conducted weekly along spiral transects up to 52 m around each of the 14 turbines in July–September 2006 and 2007. Carcass counts were corrected to account for searcher efficiency and removal by scavengers.

    Study and other actions tested
Please cite as:

Berthinussen, A., Richardson O.C. and Altringham J.D. (2021) Bat Conservation: Global Evidence for the Effects of Interventions. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.


Where has this evidence come from?

List of journals searched by synopsis

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Bat Conservation

This Action forms part of the Action Synopsis:

Bat Conservation
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