Resource Documents: Wildlife (294 items)
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Activity of forest specialist bats decreases towards wind turbines at forest sites
Author: Ellerbrok, Julia; Delius, Anna; Peter, Franziska; Farwig, Nina; and Voigt, Christian
Abstract
Worldwide, wind turbines are increasingly being built at forest sites to meet the goals of national climate strategies. Yet, the impact on biodiversity is barely understood. Bats may be heavily affected by wind turbines in forests, because many species depend on forest ecosystems for roosting and hunting and can experience high fatality rates at wind turbines.
We performed acoustic surveys in 24 temperate forests in the low mountain ranges of Central Germany to monitor changes in the acoustic activity of bats in relation to wind turbine proximity, rotor size, vegetation structure and season. Call sequences were identified and assigned to one of three functional guilds: open-space, edge-space and narrow-space foragers, the latter being mainly forest specialists.
Based on the response behaviour of bats towards wind turbines in open landscapes, we predicted decreasing bat activity towards wind turbines at forest sites, especially for narrow-space foragers.
Vertical vegetation heterogeneity had a strong positive effect on all bats, yet responses to wind turbines in forests varied across foraging guilds. Activity of narrow-space foragers decreased towards turbines over distances of several hundred metres, especially towards turbines with large rotors and during mid-summer months. The activity of edge-space foragers did not change with distance to turbines or season, whereas the activity of open-space foragers increased close to turbines in late summer.
Synthesis and applications. Forest specialist bats avoid wind turbines in forests over distances of several hundred metres. This avoidance was most apparent towards turbines with large rotors. Since forests are an important habitat for these bats, we advise to exclude forests with diverse vegetation structure as potential wind turbine sites and to consider compensation measures to account for habitat degradation associated with the operation of wind turbines in forests.
Julia S. Ellerbrok, Conservation Ecology, Department of Biology, University of Marburg, and Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
Anna Delius, Conservation Ecology, Department of Biology, University of Marburg, Germany
Franziska Peter, Natural Resource Conservation, University Kiel, Germany
Nina Farwig, Conservation Ecology, Department of Biology, University of Marburg, Germany
Christian C. Voigt, Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
Journal of Applied Biology: 09 July 2022, doi:10.1111/1365-2664.14249
Download original document: “Activity of forest specialist bats decreases towards wind turbines at forest sites”
Curtailment and acoustic deterrents reduce bat mortality at wind farms
Author: Good, Rhett; et al.
Abstract – The impacts of wind energy on bat populations is a growing concern because wind turbine blades can strike and kill bats, and wind turbine development is increasing. We tested the effectiveness of 2 management actions at 2 wind-energy facilities for reducing bat fatalities: curtailing turbine operation when wind speeds were <5.0 m/second and combining curtailment with an acoustic bat deterrent developed by NRG Systems. We measured the effectiveness of the management actions using differences in counts of bat carcasses quantified by daily and twice-per-week standardized carcass searches of cleared plots below turbines, and field trials that estimated searcher efficiency and carcass persistence. We studied turbines located at 2 adjacent wind-energy facilities in northeast Illinois, USA, during fall migration (1 Aug–15 Oct) in 2018. We estimated the effectiveness of each management action using a generalized linear mixed-effects model with several covariates. Curtailment alone reduced overall bat mortality by 42.5% but did not reduce silver-haired bat (Lasionycteris noctivagans) mortality. Overall bat fatality rates were 66.9% lower at curtailed turbines with acoustic deterrents compared to turbines that operated at manufacturer cut-in speed. Curtailment and the deterrent reduced bat mortality to varying degrees between species, ranging from 58.1% for eastern red bats (Lasiurus borealis) to 94.4 for big brown bats (Eptesicus fuscus). Hoary (Lasiurus cinereus) and silver-haired bat mortality was reduced by 71.4% and 71.6%, respectively. Our study lacked a deterrent-only treatment group because of the expense of acoustic deterrents. We estimated the additional reduction in mortality with concurrent deployment of the acoustic deterrent and curtailment under the assumption that curtailment and the acoustic deterrent would have reduced mortality by the same percentage at adjacent wind-energy facilities. Acoustic deterrents resulted in 31.6%, 17.4%, and 66.7% additional reductions of bat mortality compared to curtailment alone for eastern red bat, hoary bat, and silver-haired bat, respectively. The effectiveness of acoustic deterrents for reducing bat mortality at turbines with rotor-swept area diameters >110 m is unknown because high frequency sound attenuates quickly, which reduces coverage of rotor-swept areas. Management actions should consider species differences in the ability of curtailment and deterrents to reduce bat mortality and increase energy production.
Rhett E. Good, Goniela Iskali, John Lombardi, Trent McDonald, Karl Dubridge, Andrew Tredennick, Western EcoSystems Technology
Michael Azeka, EDF Renewables
The Journal of Wildlife Management, 08 May 2022, doi:10.1002/jwmg.22244
Wind turbines without curtailment produce large numbers of bat fatalities throughout their lifetime: A call against ignorance and neglect
Author: Voight, Christian, et al.
Abstract – Bats are protected by national and international legislation in European countries, yet many species, particularly migratory aerial insectivores, collide with wind turbines which counteracts conservation efforts. Within the European Union it is legally required to curtail the operation of wind turbines at periods of high bat activity, yet this is not practiced at old wind turbines. Based on data from the national carcass repository in Germany and from our own carcass searches at a wind park with three turbines west of Berlin, we evaluated the magnitude of bat casualties at old, potentially poor-sited wind turbines operating without curtailment. We report 88 documented bat carcasses collected by various searchers over the 20-year operation period of this wind park from 2001 to 2021. Common noctule bats (Nyctalus noctula) and common pipistrelles (Pipistrellus pipistrellus) were most often found dead at these turbines. Our search campaign in August and September 2021 yielded a total of 18 carcasses. We estimated that at least 209 bats were likely killed during our field survey, yielding more than 70 casualties/wind turbine or 39 casualties/MW in two months. Since our campaign covered only part of the migration season, we consider this value as an underestimate. The 20-year period of the wind park emphasises the substantial impact old turbines may have on bat individuals and populations when operating without curtailments. We call for reconsidering the operation procedures of old wind turbines to stop the continuous loss of bats in Germany and other countries where turbine curtailments are even less practiced than in Germany.
Christian C. Voigt, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
Klara Kaiser, Samantha Look, Freie Universitäat Berlin, Germany
Kristin Scharnweber, Carolin Scholz, Universität Potsdam, Germany
Global Ecology and Conservation, Volume 37, September 2022, e02149
doi:j.gecco.2022.e02149
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Impact assessments of wind farms on seabird populations that overlook existing drivers of demographic change should be treated with caution
Abstract – Population viability analyses (PVA) are now routinely used during the consenting process for offshore wind energy developments to assess potential impacts to vulnerable species, such as seabirds. These models are typically based on mean vital rates, such as survival and fecundity, with some level of environmental stochasticity (i.e., temporal variation). However, many species of seabird are experiencing population decline due to temporal (i.e., directional) trends in their vital rates. We assess the prevalence of temporal trends in rates of fecundity for a sentinel species of seabird, the black-legged kittiwake Rissa tridactyla, and examine how accounting for these relationships affects the predictive accuracy of PVA, as well as the projected population response to an extrinsic threat. We found that temporal trends in kittiwake rates of fecundity are widespread, and that including these trends in PVA assessments dramatically influences the projected rate of population decline. We advocate that model validation become a prerequisite step in seabird PVA assessments to identify potential biases influencing the projected population response. We also argue that environmental factors driving current population dynamics need to be incorporated in PVA impact assessments as potential “worst-case” scenarios. These findings have immediate application for improving and reducing uncertainty in impact assessments conducted as part of the consenting process for offshore wind energy developments.
a) Temporal (i.e., directional) trends in rates of fecundity are widespread amongst populations of kittiwakes in the UK and Ireland. Colonies with significant temporal trends in fecundity shown as red circles, those with stable fecundity shown as blue triangles. Skomer (South Wales) shown as an open red circle. (b) Fecundity of kittiwakes on Skomer Island declined at a constant rate between 1989 and 2020. Dashed line shows a linear regression fitted through the data. (c) We found high variation in the strength of temporal trends estimated using colony-specific Poisson GLMs. Slope coefficient values shown with standard error. Colonies with directional fecundity shown as red circles, those with stable fecundity shown as blue triangles. Skomer shown as open red circle. Gray dashed line at zero for reference.
Catharine Horswill, ZSL Institute of Zoology, London, Centre for Biodiversity and Environmental Research, Department of Genetics, Evolution and Environment, University College London, and Department of Zoology, University of Cambridge, UK
Julie A.O. Miller, Marine Scotland Science, Marine Laboratory, Aberdeen, UK
Matt J. Wood, School of Natural and Social Sciences, University of Gloucestershire, Cheltenham, UK
Conservation Science and Practice. 13 March 2022. doi: 10.1111/csp2.12644
Download original document: “Impact assessments of wind farms on seabird populations that overlook existing drivers of demographic change should be treated with caution”
