• Energy Research

ABSTRACTPredicting species range shifts in response to environmental change requires the determination of regions where individuals maintain a positive energy budget. For hibernating animals, this budget depends on two physiological states (normothermy and torpor) that alternate in response to ambient temperature. To study range shifts of hibernators like the common noctule (Nyctalus noctula), we developed an ecophysiological approach that integrates metabolic rates, physiological states, and environmental conditions. Our model accurately hindcasted the northward range shift of this migratory bat over the past 50 years. Under climate change forecasts SSP1‐2.6, SSP2‐4.5, SSP3‐7.0, and SSP5‐8.5, for which winters will shorten by 1.4–41 days and warm by 0.11°C–2.3°C, the hibernation area is predicted to shift by 78–732 km and expand north‐eastward by 5.8%–14% by 2100. Mean ambient temperature and winter duration prove sufficient to approximate the hibernation niche and may be used to predict changes in hibernation areas where collecting physiological measurements is difficult.

ABSTRACTAerial migration is the fastest, yet most energetically demanding way of seasonal movement between habitats. However, for many taxa, and bats in particular, we lack a clear understanding of the energy requirements for migration. Here, we examined the energetic cost and flight speed of the long-distance migratory Nathusius’ bat (Pipistrellus nathusii). We measured flight metabolism in relation to airspeed in a wind tunnel, inferred the optimal traveling speed over long distances, i.e. maximum range speed, and compared this value with flight speed measured in wild conspecifics. Body mass and wing morphologies were similar in captive and wild bats, indicating that the body condition of captive bats was similar to that of migratory bats. Nine out of the 12 captive bats exhibited a U-shaped relationship between flight metabolic power and airspeed when flying in the wind tunnel. The flight metabolic rate across all airspeeds averaged 0.98±0.28 W, which corresponds well to established allometric relationships between flight metabolic rate and body mass for bats. During summer migration, P. nathusii traveled at an average speed of 6.9±0.7 m s−1, which was significantly higher than the minimum power speed (5.8±1.0 m s−1), yet within the range of expected maximum range speed inferred from wind tunnel experiments. This suggests that P. nathusii may migrate at an energetically optimal speed and that aerial refueling does not substantially lower migratory speed in P. nathusii.

Many countries are investing heavily in wind power generation,1 triggering a high demand for suitable land. As a result, wind energy facilities are increasingly being installed in forests,2,3 despite the fact that forests are crucial for the protection of terrestrial biodiversity.4 This green-green dilemma is particularly evident for bats, as most species at risk of colliding with wind turbines roost in trees.2 With some of these species reported to be declining,5,6,7,8 we see an urgent need to understand how bats respond to wind turbines in forested areas, especially in Europe where all bat species are legally protected. We used miniaturized global positioning system (GPS) units to study how European common noctule bats (Nyctalus noctula), a species that is highly vulnerable at turbines,9 respond to wind turbines in forests. Data from 60 tagged common noctules yielded a total of 8,129 positions, of which 2.3% were recorded at distances <100 m from the nearest turbine. Bats were particularly active at turbines <500 m near roosts, which may require such turbines to be shut down more frequently at times of high bat activity to reduce collision risk. Beyond roosts, bats avoided turbines over several kilometers, supporting earlier findings on habitat loss for forest-associated bats.10 This habitat loss should be compensated by developing parts of the forest as refugia for bats. Our study highlights that it can be particularly challenging to generate wind energy in forested areas in an ecologically sustainable manner with minimal impact on forests and the wildlife that inhabit them.

Abstract Wind turbines used to combat climate change pose a green-green dilemma when endangered and protected wildlife species are killed by collisions with spinning blades. Here, we investigated the geographic origin of bats killed by wind turbines along an east-west transect in France to determine the spatial extent of this conflict in Western Europe. We analysed stable hydrogen isotopes in the fur keratin of 60 common noctule bats ( Nyctalus noctula ) killed by wind turbines during summer migration in four regions of France to predict their geographic origin using models based on precipitation isoscapes. We first separated migratory from regional individuals based on fur isotope ratios of local bats. Across all regions, 71.7% of common noctules killed by turbines were of regional and 28.3% of distant origin, the latter being predominantly females from northeastern Europe. We observed a higher proportion of migratory individuals from western sites compared to eastern sites. Our study suggests that wind-turbine-related losses of common noctule bats may impact distant breeding populations across whole Eurasia, confirming that migratory bats are highly vulnerable at wind turbines and that effective conservation measures, such as temporary curtailment of turbine operation, should be mandatory to protect them from collisions with wind turbines.

(Uploaded by Plazi for the Bat Literature Project) S Wind energy production is particularly rewarding along coastlines, yet coastlines are often important as migratory corridors for wildlife. This creates a conflict between energy production from renewable sources and conservation goals, which needs to be considered during environmental planning. To shed light on the spatial interactions of a high collision risk bat species with coastal wind turbines (WT), we analysed 32 tracks of 11 common noctule bats (Nyctalus noctula) in Northern Germany with miniaturized global positioning system units yielding 6266 locations. We used three spatial models to infer on the preferred and avoided landscape features in interaction with WT. We found 3.4% of all locations close to WT, with bats preferring areas with high levels of impervious surface, identified as farmhouses. Common noctule bats were also more present close to WT adjacent to paths and waterbodies. At the local scale, >70% of common noctule bats avoided WT, yet if bats approached WT we counted more positions at large WT, specifically close to known roosts. Our study highlights that coastal WT should not be placed next to feeding grounds and bat roosts. Additionally, avoidance of WT by bats indicates that foraging bats may suffer from habitat loss in coastal landscapes with high turbine densities. To mitigate the conflict between wind energy power production and conservation goals at coastal sites, wind turbines should be placed at distance to habitat features preferred by bats and turbine densities should be limited.

Although renewable energy production is widely accepted as clean, it is not necessarily environmental neutral since, for example, wind turbines kill large numbers of airborne animals such as bats. Consequently, stakeholders involved in the planning and operation of wind turbines are often in conflict when trying to reconcile both goals, namely, promoting wind energy production and protecting bats. We report the responses to an online questionnaire sent out to stakeholders to assess this conflict. More than 80% of stakeholders acknowledged the conflict between bat conservation and wind energy production; yet, the majority was confident about solutions and all desired an ecologically sustainable energy transition. All groups, except members of the wind energy sector, disagreed with the statements that wind energy production is of higher priority than biodiversity protection and that global warming is more critical than the biodiversity crisis. All groups agreed that more measures have to be taken to make wind energy production ecologically sustainable and that the society should be included to pay for the implementation of these measures. All stakeholders except for members of the wind energy sector agreed on that revenue losses from wind energy production and delays in the transition process should be acceptable to resolve the green–green dilemma. Among offered choices, most stakeholders suggested engaging in more research, improving the efficiency of energy use and implementing context dependent cut-in speed during wind turbine operation. The suggestion to weaken the legal protection of wildlife species was dismissed by all, underlining the consensus to protect biodiversity.

Abstract Wind energy production is growing rapidly worldwide in an effort to reduce greenhouse gas emissions. However, wind energy production is not environmentally neutral. Negative impacts on volant animals, such as bats, include fatalities at turbines and habitat loss due to land-use change and displacement. Siting turbines away from ecologically sensitive areas and implementing measures to reduce fatalities are critical to protecting bat populations. Restricting turbine operations during periods of high bat activity is the most effective form of mitigation currently available to reduce fatalities. Compensating for habitat loss and offsetting mortality are not often practiced, because meaningful offsets are lacking. Legal frameworks to prevent or mitigate the negative impacts of wind energy on bats are absent in most countries, especially in emerging markets. Therefore, governments and lending institutions are key in reconciling wind energy production with biodiversity goals by requiring sufficient environmental standards for wind energy projects.