Thresholds for bats killed by wind turbines
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Thresholds for bats killed by wind turbines 171 Edward B Arnett Director of Energy Programs, Theodore Roosevelt Conservation Partnership, Loveland, CO GUEST EDITORIAL GUEST EDITORIAL GUEST EDITORIAL © The Ecological Society of America www.frontiersinecology.org W ind turbines kill bats, often in high numbers. Minimizing bat deaths is critically important for both conservation of bats and the wind energy industry’s public image, making this an issue that should be of concern to all stakeholders. Luckily, new studies have shown that bat fatalities can be reduced sub- stantially if turbine blade speed and operating time are reduced on low-wind nights in summer and fall, when bats are most active (eg Front Ecol Environ 2011; 9: 209–14). Although these strategies for cur- tailing turbines hold great promise, developing thresholds – those values that trigger mitigation of bat fatalities – is difficult. This is especially true when supporting data are limited or unreliable. Wildlife regulators are trying to remedy the turbine–bat problem by setting fixed thresholds, in the absence of scientific evidence. Recently, the Canadian province of Ontario set thresholds for initiating curtailment based on the annual mean number of bats killed per turbine (10 per turbine), and the state of Pennsylvania is proposing a similar approach (possibly up to 28 per turbine). However, we believe the set- ting of arbitrary thresholds establishes a dangerous precedent and has several flaws, not the least of which is the assumption that bat populations are currently stable and are likely to remain so. This approach also ignores expanding development of wind turbines that will lead to increasing numbers of bat fatalities per population or region. Currently, each wind facility and its kill rate are assessed in isolation without regard to other facilities, or to future facilities that may affect populations. Many species of bats are known to be in decline due to habitat loss, white-nose syndrome, and other factors, so static thresholds using mean annual turbine kills are short-sighted and fail to recognize additional causes of mortality and cumulative impacts. If we think about places where mean bat kills are already high, such as in Pennsylvania, the mean that triggers curtailment might never be reached if populations are actually declining. An analogy with game management seems appropriate. Managing wildlife such as waterfowl or deer requires an understanding of population boundaries, sizes, and trends based on extensive data. Quotas are set for the maximum take per management unit that ensures sustainable harvest. A per-hunter take limit is established, and the number of hunters is strictly regulated. An adaptive management approach means that allowable take and number of hunters vary between years and regions, based on concurrent popula- tion monitoring. If bat populations were managed in a similar way, comparable biological data would be required, as are available for game species, and the total allowable “take” of bats that triggers mitigation such as curtailment would be established from population data, rather than set on an average per-turbine basis. The number of turbines (analogous to “hunters”) or the take per turbine would also be regulated and adjusted to ensure that bat fatalities are sustainable. If game populations were managed the way that some jurisdictions are managing bat populations with regard to fatalities at wind turbines, many game species might long be extinct. So what are managers to do? We do not support using mean kills to trigger curtailment given the pauci- ty of data regarding the numbers and trends seen in bat populations and until we can quantify these, determining a sustainable level of bat fatalities at wind power sites will be impossible. It is also important to remember that the species most vulnerable to wind development, the migratory tree-roosting bats, are not restricted by geopolitical boundaries and do not reside solely in one state, province, or country. Because these species migrate to or through multiple jurisdictions, managers must consider much broad- er, continent-wide impacts of wind development on bats. Two things we do know: bat fatalities should be mitigated, and curtailing turbine operations is current- ly the only proven way to reduce kills. We suggest that a more meaningful approach is for stakeholders to collaborate on a site-by-site basis to implement a mitigation strategy that meets objectives for both indus- try and conservation. For example, if the goal is to reduce bat fatalities by 50%, then let each company decide on the best curtailment strategy to implement at their facility, for example by altering turbine oper- ation at low wind speeds or incorporating other weather variables (eg temperature) into an automated cur- tailment program, designed to maximize energy production while minimizing bat fatalities. Providing incentives – such as forgoing costly post-construction monitoring studies for sites willing to implement mitigation programs – may encourage industry participants when mitigation efforts are purely voluntary. Considering the gravity and scale of the situation, efforts to conserve bat populations affected by wind turbines should be proactive and based on science rather than being reactive and arbitrary. Robert MR Barclay Professor, Department of Biological Sciences, University of Calgary, Calgary, Canada Cris D Hein Conservation Scientist, Bat Conservation International, Austin, TX
Transcript of Thresholds for bats killed by wind turbines
Thresholds for bats killed by windturbines
171
Edward B ArnettDirector of EnergyPrograms, Theodore RooseveltConservationPartnership, Loveland, CO
GUEST EDITORIAL GUEST EDITORIAL GUEST EDITORIAL
© The Ecological Society of America www.frontiersinecology.org
Wind turbines kill bats, often in high numbers. Minimizing bat deaths is critically important for bothconservation of bats and the wind energy industry’s public image, making this an issue that should
be of concern to all stakeholders. Luckily, new studies have shown that bat fatalities can be reduced sub-stantially if turbine blade speed and operating time are reduced on low-wind nights in summer and fall,when bats are most active (eg Front Ecol Environ 2011; 9: 209–14). Although these strategies for cur-tailing turbines hold great promise, developing thresholds – those values that trigger mitigation of batfatalities – is difficult. This is especially true when supporting data are limited or unreliable.
Wildlife regulators are trying to remedy the turbine–bat problem by setting fixed thresholds, in theabsence of scientific evidence. Recently, the Canadian province of Ontario set thresholds for initiatingcurtailment based on the annual mean number of bats killed per turbine (10 per turbine), and the state ofPennsylvania is proposing a similar approach (possibly up to 28 per turbine). However, we believe the set-ting of arbitrary thresholds establishes a dangerous precedent and has several flaws, not the least of whichis the assumption that bat populations are currently stable and are likely to remain so. This approach alsoignores expanding development of wind turbines that will lead to increasing numbers of bat fatalities perpopulation or region. Currently, each wind facility and its kill rate are assessed in isolation without regardto other facilities, or to future facilities that may affect populations. Many species of bats are known to bein decline due to habitat loss, white-nose syndrome, and other factors, so static thresholds using meanannual turbine kills are short-sighted and fail to recognize additional causes of mortality and cumulativeimpacts. If we think about places where mean bat kills are already high, such as in Pennsylvania, the meanthat triggers curtailment might never be reached if populations are actually declining.
An analogy with game management seems appropriate. Managing wildlife such as waterfowl or deerrequires an understanding of population boundaries, sizes, and trends based on extensive data. Quotas areset for the maximum take per management unit that ensures sustainable harvest. A per-hunter take limitis established, and the number of hunters is strictly regulated. An adaptive management approach meansthat allowable take and number of hunters vary between years and regions, based on concurrent popula-tion monitoring. If bat populations were managed in a similar way, comparable biological data would berequired, as are available for game species, and the total allowable “take” of bats that triggers mitigationsuch as curtailment would be established from population data, rather than set on an average per-turbinebasis. The number of turbines (analogous to “hunters”) or the take per turbine would also be regulatedand adjusted to ensure that bat fatalities are sustainable. If game populations were managed the way thatsome jurisdictions are managing bat populations with regard to fatalities at wind turbines, many gamespecies might long be extinct.
So what are managers to do? We do not support using mean kills to trigger curtailment given the pauci-ty of data regarding the numbers and trends seen in bat populations and until we can quantify these,determining a sustainable level of bat fatalities at wind power sites will be impossible. It is also importantto remember that the species most vulnerable to wind development, the migratory tree-roosting bats, arenot restricted by geopolitical boundaries and do not reside solely in one state, province, or country.Because these species migrate to or through multiple jurisdictions, managers must consider much broad-er, continent-wide impacts of wind development on bats.
Two things we do know: bat fatalities should be mitigated, and curtailing turbine operations is current-ly the only proven way to reduce kills. We suggest that a more meaningful approach is for stakeholders tocollaborate on a site-by-site basis to implement a mitigation strategy that meets objectives for both indus-try and conservation. For example, if the goal is to reduce bat fatalities by 50%, then let each companydecide on the best curtailment strategy to implement at their facility, for example by altering turbine oper-ation at low wind speeds or incorporating other weather variables (eg temperature) into an automated cur-tailment program, designed to maximize energy production while minimizing bat fatalities. Providingincentives – such as forgoing costly post-construction monitoring studies for sites willing to implementmitigation programs – may encourage industry participants when mitigation efforts are purely voluntary.Considering the gravity and scale of the situation, efforts to conserve bat populations affected by windturbines should be proactive and based on science rather than being reactive and arbitrary.
Robert MR BarclayProfessor, Departmentof Biological Sciences, University of Calgary,Calgary, Canada
Cris D HeinConservation Scientist, Bat ConservationInternational, Austin, TX
