Wildlife and renewable energy: German politics cross migratory bats
- First Online:
- Cite this article as:
- Voigt, C.C., Lehnert, L.S., Petersons, G. et al. Eur J Wildl Res (2015) 61: 213. doi:10.1007/s10344-015-0903-y
- 598 Views
The catastrophic nuclear meltdowns at Fukushima triggered a worldwide demand for renewable energy. As one of the few countries, Germany decided on an accelerated shift towards green energy, resulting in substantial conflicts with international conservation goals. Currently, large numbers of wind power facilities are erected in Germany, yet with unforeseen consequences for wildlife, particularly for endangered and protected bats. Presumably, more than 250,000 bats are killed annually due to interactions with German wind turbines, and total losses may account for more than two million killed bats over the past 10 years, if mitigation measures were not practiced. More than 70 % of killed bats are migrants, because major migratory routes cross Germany. Consequently, Germany’s environmental policy is key to the conservation of migratory bats in Europe. Prospective increases in wind power will lead to the installation of larger wind turbines with potentially devastating consequences for bats. The higher net energy production of modern wind turbines at low wind speeds may exacerbate the conflict between green energy and conservation goals since revenue losses for companies increase. We conclude that evidence-based action plans are urgently needed to mitigate the negative effects of the operation of wind energy facilities on wildlife populations in order to reconcile environmental and conservation goals.
KeywordsAlternative energyChiropteraConservationMigratory speciesWind energy facilitiesWind parksGreen energy
Over the past two decades, wind turbines have been promoted in many North American and European countries, particularly after the galvanizing event of Fukushima when several nuclear power plants were destroyed by a tsunami. In response to this traumatic event and in consideration of greenhouse gas emissions known to affect global climate, German politicians decided against the continuation of nuclear and conventional power production and for the promotion of renewable energy with a strong emphasis on wind power. Currently, a major domain of renewable energy production stems from wind power facilities in Germany, which already makes up about 34 % of the national renewable electricity production (Berkhout et al. 2014).Yet, the total wind power-generating capacity is estimated to increase by about 30 % from 35 GW in 2013 (Berkhout et al. 2014) to 46 GW until 2020 (BRD 2010a). Accordingly, numerous wind power facilities are currently erected in Germany. By 2014, about 24,000 on-shore wind turbines had been installed in Germany (Berkhout et al. 2014), and Germany ranks third worldwide with respect to net energy production derived from wind power, outnumbered only by China and the USA (Berkhout et al. 2014). Yet, considering its smaller geographical size, Germany exceeds China and the USA by a factor of about 10 and 16, respectively, when it comes to net energy production per kilometer squared (0.096 MW km−2 for Germany compared with 0.0095 MW km−2 for China and 0.006 for the USA). Recent studies highlight that renewable, so-called green energy may come at environmental costs as well (Rydell et al. 2010; Voigt et al. 2012; Northrup and Wittemyer 2013; Lehnert et al. 2014), raising concerns about whether German energy politics are in conflict with international legislation such as the EU Habitats Directive 92/32/CEE (Annexes II and IV) and also international conservation goals such as the “UN Convention on Migratory Species of Wild Animals” (conventions dated Bonn 1979 and London 1991).
Consequences of German environmental policy for protected wildlife species
How many bats are killed at German wind turbines?
In Europe, reported cases of bat fatalities at wind turbines vary largely with respect to number and species composition (Rydell et al. 2010). This variation is most likely associated with local variation in species richness, but may also be caused by differences in habitats (high or low elevations, forested, and open habitats) as well as differences in applied search protocols. For example, studies covering the whole annual activity period of bats are rare, and most of them tolerate relatively large gaps between search events, despite the fact that several days or even weeks of daily searches per month are more appropriate. In addition, surveys have only recently begun to consider carcass removal by scavengers and search efficiency in the estimation of annual bat fatalities at wind turbines (Arnett et al. 2008). Currently, standardized protocols are recommended that control for these biases (Rodrigues et al. 2008), thus avoiding systematic underestimations when numbers of bat carcasses at wind turbines are reported. When controlling for such biases, surveys revealed that about 10–12 bats are killed annually at each wind turbine in Germany where no mitigation measures have been implemented (Brinkmann et al. 2011). Assuming that these numbers are representative for all types of wind turbines and for all of Germany, it can be inferred that in each of the past 5 years more than 200,000 bats were killed at on-shore wind turbines in Germany if mitigation measures were not practiced. This is equivalent to 6–8 killed bats annually per MW installed net energy production (Berkhout et al. 2014). For the contiguous United States of the America, it is estimated that wind farm facilities caused about 600,000 bat fatalities in 2012 (Hayes 2013), which is equal to 10 killed bats annually per MW installed net energy production. Thus, our estimate for wind turbine-related bat fatalities in Germany is in a similar range as the one suggested for the contiguous USA. Summarizing, cumulative numbers of wind turbine-related bat fatalities suggest that more than 2,000,000 bats could have been killed by wind turbines over the past 10 years in Germany if no mitigation measures were implemented.
What kills bats at wind turbines?
Do bat populations suffer from increased mortality at wind turbines?
Considering the massive losses of bats at wind turbines, a key question for conservationists is as follows: Are bat colonies or populations affected by the increased mortality risk of individual bats at wind turbines? In theory, bat populations should be quite susceptible to additional causes of mortality because of their low fecundity (Jones et al. 2003). Additionally, fatalities of pregnant bats during spring migration in Germany could aggravate a negative effect of wind turbines on bat populations. Although urgently required, conclusive studies on the population level effect of wind turbines have not yet been conducted (but see Roscini et al. 2013), because they require collection of baseline demographic data such as age structure, dispersal, and recruitment in multiple colonies over a prolonged period of time and most importantly some knowledge about the location of source populations from which killed bats originated from. Affected bat populations could be as far away from Germany as Fenno-Scandinavia, Baltic Countries, Belarus, and Russia (Voigt et al. 2012; Lehnert et al. 2014). Lastly, it is important to note that the question of population effects is not relevant from a legislative point of view, because effects at the individual level (i.e., the killing of an individual of a legally protected species), and not the population level, are the subject of EU legislation.
Avoidance, mitigation, or compensation?
According to legal requirements in Germany, wind turbines should not be erected when bat activity is high at the designated location. Pre-construction surveys require substantial monitoring efforts, but even if monitoring is commissioned, efforts are limited in time because of limited funding for more comprehensive surveys. A recent study highlights that bats may even be attracted to wind turbines (Cryan et al. 2014), which makes pre-construction surveys of limited use for predicting the mortality risk for bats at an operating wind turbine. In summary, avoidance measures may prove difficult and thus inefficient, because surveying techniques are prone to bias. Even if wind turbine sites may prove unsuitable because of high bat activity, we have not heard of cases in Germany where turbines were forced to stop operation or where they were even deconstructed. Also, to the best of our knowledge, measures for repelling bats from wind turbines have not proven to be efficient or practical. For example, bats avoided wind turbines when exposed to the high electromagnetic fields (>2 V/m) of radar (Nicholls and Racey 2007, 2009), yet such measure may not be practical for several reasons. Electromagnetic radiation may impose a health risk on bats, causing thermal overheating, and possibly also on humans in proximity to the radar. Accordingly, this avoidance measure may not be acceptable for the public, for authorities, for conservationists, and for animal welfare groups. Compensation measures for increased bat fatalities at wind turbines, e.g., improving habitat or roost quality, are inefficient, because source populations of killed bats may be far away and difficult to locate (Voigt et al. 2012). Also, trading bat fatalities at wind turbines against habitat improvements (e.g., installation of bat boxes) is not consistent with the EU legislation.
Recently, situation-dependant operation protocols, so-called algorithms, were developed for the operation of wind turbines. These algorithms consider a number of parameters such as temperature, wind speed, season, and time of day as well as recorded bat activities for defining a set of operation rules for wind turbines. When using such algorithms, operation of wind turbines is only stopped when some parameters, such as ambient temperature and wind speed, fall above or below pre-defined threshold values in 10-min intervals. From a company perspective, these algorithms come at a lower revenue loss compared with aforementioned more static operation protocols. From a conservation perspective, algorithms promise to reduce bat fatalities by more than 80 %, from about 10–12 to two bats killed per year per wind turbine (e.g., Brinkmann et al. 2011). However, these algorithms have been formulated for a single type of turbine (E-70; Enercon 2012) and for a limited number of sites of varying geographical background, and therefore, their efficiency is questionable for other types of wind turbines and geographical areas, for example these algorithms seem to work reasonably for N. noctula, but not necessarily for species of the genus Pipistrellus. It has also been criticized that the abrasion of wind turbines is larger when operation is frequently switched on and off. Finally, the widely recommended acceptance of an arbitrary number of two bat fatalities annually per wind turbine may not necessarily be consistent with national and EU legislation, which prohibits killing of single individuals of a protected mammalian species. Also, with increasing numbers of wind turbines, fixed “per capita” fatality rates, i.e., defined numbers of tolerated bat fatalities per year and wind turbine are unacceptable because of limited bat population sizes.
Unfortunately, we cannot compare the efficacy of mitigation measures and its dependency on, for example, geographical location, habitat structure, and wind turbine type, because we lack comparative data on wind turbine-related bat fatalities on a larger scale. This unsatisfying situation originates from a combination of factors such as a large heterogeneity in the quality of surveys, lack of central documentation of raw data, and the fact that some authorities do not even request post-construction surveys for bat carcasses. Because of this, we are missing the decisive parameters to establish algorithms and cut-in speeds that result in the least number of bat fatalities.
The most effective reduction in bat fatalities results from cut-in wind speeds at which bats stop flying and/or at which bat fatalities at wind turbines cease to occur. This may come at a larger revenue loss for companies, but may better conform to EU legislation and national conservation goals. Novel wind turbines with higher net energy production may produce larger revenues at even low wind speeds (Fig. 3), and such a development may complicate the implementation of cut-in speeds, because absolute and relative monetary losses for energy companies may increase at the same cut-in speed with increasing wind turbine size (Fig. 3). This may exacerbate the conflict between the wind energy industry and conservationists in the future.
Whence do migratory bats killed at German wind turbines originate? Are source populations suffering from increased fatalities at wind turbines?
Do European bats use specific habitats as migratory corridors? If so, where are these corridors and how are they best protected?
Are bats suffering from mild barotrauma at wind turbines and does this postpone death? Are reported bat fatalities underestimated because of unrecognized bat fatalities?
Lastly, we urge companies to reveal original data generated by pre- and post-construction surveys for meta-analysis. Also, it is essential to reconsider operation permits of older wind turbines, when bat and bird fatalities were not considered, and to pay careful attention to the repowering of such wind turbines. Because of Germany’s central location in Europe, Germany’s environmental policy is crucial for the conservation not only of local sedentary bats but particularly also for the conservation of migratory bats from northeastern populations. Thus, we argue for an evidence-based action plan that parallels or preferably precedes future developments of wind power production in Germany. Finally, we appeal to policy makers to reconcile environmental and conservation goals in order to develop Germany’s investment in renewable energy as a trend-setting model example for other countries.
We would like to acknowledge the support of the banding center at the Museum König in Bonn and in Dresden for providing the recovery data of banded bats. We thank Gudrun Wibbelt for the allowance to use her pictures and Paul Racey and Marie-Jo Dubourg-Savage and an anonymous reviewer for commenting on an earlier version of this manuscript.
Conflicts of interest
The authors declare no conflict of interest or financial constraints that would influence the objectivity of the paper.