Bats and wind power – introduction
posted on April 8, 2019
We know more than 1300 bats species around the world. In the IUCN red list 91 species was described as endangered, 199 as threatened and 5 as extinct. Populations of 231 species are not evaluated (IUCN 2019). The biggest species diversity is in equatorial area. The diversity of bat species is low or medium in area where the wind industry intensive growth. On the other hand the low numbers of species in low-bat-species-diversity-regions are the only species of bats there and their importance in ecosystems can’t be ignored. Bats mortality on wind farms is one of main anthropological factors of fatality in this group of animals (EUROBATS 2018).
Number of bat fatalities on wind turbines is changeable between seasons, wind farms and regions. In EMPEKO post-construction monitoring projects for wind farms in Poland we estimated 4,7-14,6 bats/turbine/year, on average 10 bats/turbine/year. Just for your knowledge I put in Table 1 a little bit numbers from publications I’ve found in internet.
Table 1. Number of bats fatalities in various studies.
|Doty, Martin 2012|
ca 0,1-ca 80
|Strickland et al. 2011|
As you can see the variability is relative high: from ca 0,1 to ca 80 bats/turbine/year. Let me stay by numbers from research I performed with B-finder Team: 10 bats/turbine/year.
The information about the number of all installed wind turbines in Europe is not available (if you find it, please share with B-finder Team), so just for rough numbers I get the 189GW (WindEurope 2019) and the average ca 2MW/turbine to receive ca 100 000 wind turbines in Europe operated today. The 10 carcasses/year combined with ca 100 000 wind turbines in Europe give the mortality ca 1 million bats/year. It concern 27 from among 36 European species because not all species are noted as victims of collision with wind turbines so far. In the U.S. and Canada, at least 24 from 45 species of bats have been reported as killed by wind turbines (Bat Conservation International 2019). The ca 65 000 windmills in North America can cause mortality of 600 000 bats/year.
What fatality rate should we use for estimation? How can we know real numbers of collision? Can it be significant for populations? Who knows?
The impact on population depends on many factors like:
– population size;
– reproduction rate;
– cumulation of fatality factors.
Population size is barely known even for common species. Bats are difficult to observe and census. The EIONET database informs about ca. 40 millions of individuals of 39 bat species from European Union countries in 2016. There is the only synthesis I have found for Europe, so let put it as reference having in mind that it is probably big undervaluation. Scattered data are available for some North American species. We can find for example detailed range 195 398 – 957 348 individuals of endangered Indiana bat (Wayne et al. 2009) as well estimation over 100 million Mexican free-tailed bats (Russel et al. 2011). But generally we don’t have systematic large-area censuses of bats population. We have weak frame of reference.
Reproduction rate. The avoidance of lethal factors is in bat’s world important issue due to low reproduction (especially in non-tropical species). Females in north-hemisphere bat species give usually one or two juvenile annually. The reproduction can’t be higher because the female body weight can’t be exceed without the loss of flight ability. The survival of population is possible because the balance between lethal factors and reproduction rate. High growth of lethal factors destroys this balance and can be the reason of extension of population if the population can’t be rebuilt due to low tempo of reproduction.
Cumulation of lethal factors. Again, detailed assessment of the scale and importance of each negative factor is impossible without input data. I list, what chiropterologists know today: loss and disturbance of roosts, landscape fragmentation, roads mortality, wind energy mortality; infections, starvation during long time weather changes.
Yes, bats have many problems. The lack of reliable data on number of bats makes it impossible to assess the impact of mortality on wind turbines on their populations. Systematic monitoring is the first step for reasonable management of populations.
Fig. 1. Bat during night flight in wind farm. Sample picture from B-finder system.
- Bat Conservation International 2019. Retrieved April 6, 2019 from: http://www.batcon.org/resources/for-specific-issues/wind-power
- Doty, A., Martin, A. 2012. Assessment of bat and avian mortality at a pilot wind turbine at Coega, Port Elizabeth, Eastern Cape, South Africa. New Zealand Journal of Zoology 40: 75-80.
- EIONET 2019. Retrieved April 8, 2019 from: http://bd.eionet.europa.eu/article17/reports2012/species/summary/
- Ellison L.E. 2012. Bats and wind energy – A literature synthesis and annotated bibliography: U.S. Geological Survey Open File Report 2012 – 1110, 57pp. https://pubs.usgs.gov/of/2012/1110/OF12-1110.pdf
- EUROBATS 2014. MoP7 .Record Annex 8 7th Session of the Meeting of the Parties. Brussels, Belgium, 15-17 September 2014. Resolution 7.5. Wind Turbines and Bat populations. https://www.eurobats.org/sites/default/files/documents/pdf/Meeting_of_Parties/Doc.MoP7_.13.DraftRes7.5WindturbinesandBatPopulations.pdf
- EUROBATS 2015. Guidelines for consideration of bats in wind farm projects Revision 2014. EUROBATS Publication Series No 6. UNEP/EUROBATS Secretariat, Bonn 133 pp.
- EUROBATS 2018. Action Plan for the Conservation of All Bat Species in the European Union 2018 – 2024. https://www.eurobats.org/sites/default/files/documents/news/EU%20Bats%20Action%20Plan_0.pdf
- IUCN 2019, Retrieved April 8, 2019 from: https://www.iucnredlist.org
- Ontario Ministry of Natural Resources 2011. Bats and bat habitats. Guidelines for Wind power Projects. First Edition.
- Russell A.L., Cox M.P., Brown V.A., McCracken G.F. 2011. Population growth of Mexican free-tailed bats (Tadarida brasiliensis mexicana) predates human agricultural activity. BMC Evol. Biol. 2011; 11: 88.
- Strickland M.D., Arnett E.B., Erickson W.P., Johnson D.H., Johnson G.D., Morrison M.L, Shaffer J.A., Warren-Hicks W. 2011. Comprehensive Guide to Studying Wind Energy/Wildlife Interactions. Prepared for the National Wind Coordinating Collaborative, Washington, D.C., USA.
- WindEurope 2019. Wind energy in Europe in 2018. Trends and statistics. https://windeurope.org/wp-content/uploads/files/about-wind/statistics/WindEurope-Annual-Statistics-2018.pdf