Potential for spatial coexistence of a transboundary migratory species and wind energy development

Global expansion in wind energy development is a notable achievement of the international community's effort to reduce carbon emissions during energy production. However, the increasing number of wind turbines have unintended consequences for migratory birds and bats. Wind turbine curtailment and other mitigation strategies can reduce fatalities, but improved spatial and temporal data are needed to identify the most effective way for wind energy development and volant migratory species to coexist. Mexican free-tailed bats (Tadarida brasiliensis mexicana) account for a large proportion of known bat fatalities at wind facilities in the southwestern US. We examined the geographic concordance between existing wind energy generation facilities, areas of high wind potential amenable for future deployment of wind facilities, and seasonally suitable habitat for these bats. We used ecological niche modeling to determine species distribution during each of 4 seasons. We used a multi-criteria GIS-based approach to produce a wind turbine siting suitability map. We identified seasonal locations with highest and lowest potential for the species' probability of occurrence, providing a potential explanation for the higher observed fatalities during fall migration. Thirty percent of 33,606 wind turbines within the southwestern US occurred in highly suitable areas for Mexican free-tailed bats, primarily in west Texas. There is also broad spatial overlap between areas of high wind potential and areas of suitable habitat for Mexican free-tailed bats. Because of this high degree of overlap, our results indicate that post-construction strategies, such as curtailing the timing of operations and deterrents, would be more effective for bat conservation than strategic siting of new wind energy installations.

Changes in diversity and species composition in the assemblage of live and dead bats at wind farms in a highly diverse region

Besides direct mortality, wind farms also affect aerial fauna by modifying their communities, reducing species diversity and richness through disturbance. During three consecutive years, we used mist nets and acoustic recorders, and conducted carcass searches, to characterize the assemblage of bat species and to estimate bat mortality at two nearby wind farms sited <5 km apart in a highly biodiverse region. We asked whether the diversity, richness and evenness of the assemblages varied yearly, predicting it would decrease through time. Richness and evenness did not change, but the diversity of species recorded acoustically, 96% being aerial insectivores, was significantly lower the third year. We estimate 4 - 15.7 fatalities/MW/year by wind farm, with 63% of species found as carcasses being aerial insectivores. We found >40% of dissimilarity in the species composition of bat assemblages between wind farms despite the short distance between them, with species turnover accounting for more than half of the dissimilarity every year. Similarly, species turnover accounted for >15% of the dissimilarity in the composition of the assemblage of live bats (captured and recorded acoustically) and the assemblage obtained through carcass searches. Our findings suggest that nearby wind farms impact bat communities differentially and aerial insectivores disproportionally. Long term, multi-method surveys are needed to characterize bat communities in highly diverse regions and to evaluate the post-construction effects that wind farms have on them.

Considerations on environmental, economic, and energy impacts of wind energy generation: Projections towards sustainability initiatives

The energy sector contributes significantly to the emission of greenhouse gases (GHGs) due to the use of fossil fuels which leads to climate change problems. Worldwide, there is a shift from fossil fuel-based energy to cleaner energy sources such as solar, wind, geothermal, and biomass. Wind energy is one of the promising cleaner energy sources as it is feasible and cost-effective. However, the development of wind farms causes impacts on sustainability aspects. This article aims to review the impacts of wind energy generation on environmental, economic, and social aspects of sustainability and their mitigation strategies. The aim was achieved by reviewing recent research papers on different aspects of wind energy sustainability. The environmental impacts reviewed include the effects on avian life, noise pollution, visual impacts, microclimate and vegetation. Apart from environmental impacts, wind energy generation faces issues in energy and financial sustainability, such as the wind power fluctuation, technology lagging and use of fixed feed-in tariff contracts that do not consider wind energy advancement and end-of-life management. We discussed that turbine deterrents, automatic curtailment, low gloss blades and sustainable siting of wind farms as some of the effective ways to combat wind energy environmental impacts. In addition, we discussed that energy storage systems, setting up microgrids, combination of solar, wind and energy storage, and renewable energies policies are some of the ways to combat wind energy's economic and energy impacts. Lastly, the recommendations, and future perspectives on wind energy generation sustainability are discussed.

A review of raptor carcass persistence trials and the practical implications for fatality estimation at wind farms

Bird and bat turbine collision fatalities are a principal biodiversity impact at wind energy facilities. Raptors are a group at particular risk and often the focus of post-construction fatality monitoring programs. To estimate fatalities from detected carcasses requires correction for biases, including for carcasses that are removed or decompose before the following search. This is addressed through persistence trials, where carcasses are monitored until no longer detectable or the trial ends. Sourcing sufficient raptor carcasses for trials is challenging and surrogates that are typically used often have shorter persistence times than raptors. We collated information from raptor carcass persistence trials to evaluate consistencies between trials and assess the implications of using persistence values from other studies in wind facility fatality estimates. We compiled individual raptor carcass persistence times from published sources along with information on methods and location, estimated carcass persistence using GenEst and ran full fatality estimates using the carcass persistence estimates and mock datasets for other information. We compiled results from 22 trials from 17 sites across four terrestrial biomes, with trials lasting between 7 and 365 days and involving between 11 and 115 carcasses. Median carcass persistence was estimated at 420 days (90% confidence interval (CI) of 290 to 607 days) for the full dataset. Persistence time varied significantly between trials (trial-specific persistence estimates of 14 (5-42) days to 1,586 (816-3,084) days) but not between terrestrial biomes. We also found no significant relationship between either the number of carcasses in the trial or trial duration and estimated carcass persistence. Using a mock dataset with 12 observed fatalities, we estimated annual fatalities of 25 (16-33) or 26 (17-36) individuals using a 14- or 28-day search interval respectively using global dataset. When using trial-specific carcass persistence estimates and the same mock dataset, estimated annual fatalities ranged from 22 (14-30) to 37 (21-63) individuals for a 14-day search interval, and from 22 (15-31) to 47 (26-84) individuals for a 28-day search interval. The different raptor carcass persistence rates between trials translated to small effects on fatality estimates when using recommended search frequencies, since persistence rates were generally much longer than the search interval. When threatened raptor species, or raptors of particular concern to stakeholders are present, and no site-specific carcass persistence estimates are available, projects should use the lowest median carcass persistence estimate from this study to provide precautionary estimates of fatalities. At sites without threatened species, or where the risk of collision to raptors is low, the global median carcass persistence estimate from this review could be used to provide a plausible estimate for annual raptor fatalities.