” under severe threat due to ... wind turbine facilities (... in ... Europe)”

Of course, there could be certain areas with features that lead to mortality in bat populations (caused by wind-mills), otherwise it could be risky to generalise a local-specific aspect/situation to continental level.

I am interested in the subject, not necessarily because we carried out some impact-studies in the previous years, but mostly because in our region there are several hundreds of wind-mills built in the last few years, so it is a proper site for testing (various) hypotheses.

Dear Zsolt,

Thanks for your response. I agree that there are various places with efficient promotion of wind power facilties throughout Europe. It would be surely promising to look into how such measures affect local bat populations in particular and local or regional ecosystems in general. The most demanding issue with wind turbine related fatalities is that most bat species killed by wind farms are migratory species; at least in Central Europe. Therefore, biased top-down effects on e.g. altered rates of herbivory (as it was shown in Boehm et al. 2011 PlosONE) are difficult to demonstrate given the missing information on connectivity between breeding sites and fatality sites. Yet, I was wondering if there are other studies besides Boehm et al. 2011 that show a significant ecological effect of bat population on local ecosystems. As a side not, it would be great to engage into a larger network of collaborators looking in the whole complex of bat fatalities, changes in bat populations and ecological consequences. What is the best study design for such a project?

Best,

Christian

Hi

Bats apparently are increasing in Europe even if turbines and other are a growing type of threat http://www.unep.org/newscentre/Default.aspx?DocumentID=2762&ArticleID=10704&l=en

Best

Hi Jorge,

Thanks for the input, yet I must disagree with the general nature of this statement. I am aware of this publication and I find the various trends quite interesting. However, this survey is mostly based on counting bats in hibernacula such as caves and therefore this study ignores population trends in many of the tree-dwelling bats. This is sad enough because many of these species such as Nyctalus noctula, N. leisleri and Pipistrellus nathusii represent the majority of bat fatalities at wind turbines, at least in Central and Northwest Europe (see for example Rydell et al. 2010 Acta Chiropterology). Therefore, populations of these turbine-affected species are not included in the report!

Secondly, one has to be careful with generalizations of findings, because - although I appreciate the large effort behind the numbers of this report -, it covers only a fraction of the area of the E.U. Whole Fennoscandinavia is ignored and the vast area of the mediterranean region (except for Portugal) is ignored. Therefore, I would be cautious with simple and generalized statements.

If European bat populations are increasing in size - which I hope -, it would mean that they are recovering from an alltime low population size in the sixties and seventies. Therefore, reports about modest increases are not comforting in the sense that we should no longer be concerned about bat populations. Currently, bat populations strive to go back to the level where they used to be.

My take-home message here is: This report is interesting and valuable for the species that are included, yet it does not apply for the majority of bat species killed at European wind turbines. Therefore, the report is irrelevant or even misleading when used in the discussion of wind turbine related bat fatatliies. Does anyone disagree?

By the way, it would be great to look into populations trends of the abovementioned species. In case anyone is interested to contribute to a larger project, please contact me at [email protected] .

Cheers,

Christian

Of course, if a general increase of bat does happen, that doesn't mean that every species increases its numbers.

On the other hand, I posted a question on mortality causes of birds, in order to know the ranking of the different causes. It seems that in some countries cats are, by far, the number 1 cause ( http://goo.gl/E8mxVM) followed by collision against windows and others. I'm sure that bats are sensitive to other causes (although cats also predate on them http://goo.gl/wSDnf0).

Cheers

I agree with Christian,

I think it's a good report given its scope, but this report doesn’t add much knowledge for the discussion of wind turbine related bat fatalities.

For example, in Portugal this survey was only based on counting bats in hibernacula, ignoring all must tree-dwelling bats. In fact from 2001 in Portugal, we are found only 2 cave-dwelling bats (2 Minioterus schreibersii), representing 0,2% of fatality at wind turbines (see Agreement on the conservation of populations of european bats report on implementation of the agreement in Portugal – 2013).

36 % of the species present in Portugal are classified as “Data Deficient” (DD). A taxon is classified as DD when the available information is not sufficient to establish a proper assessment of its conservation status. This does not necessarily indicate that the species has not been extensively studied, only indicates that little or no information is available on the abundance and distribution of the species.

I think we are increasingly the gap knowledge between tree-dwelling bats (mostly classified DD) and cave-dwelling.

Best regards

Paulo Barros

Christian, it seems to me that an ecosystem would need to have been carefully studied in the first place. At least we'd need to know the kinds and numbers of nocturnal insects in a large geographical area. THEN we'd need to measurably reduce bat numbers in that area.

I doubt this has been done, and I doubt any government would allow an intentional kill off of bats. However, wherever a measured decrease in bat numbers has been observed (evidently in Europe), if sufficient data about insect populations has a baseline back before bat numbers were reduced, then a current insect survey could answer your question.

Hi Joseph,

Thanks for your suggestion. It may be difficult to obtain baseline data of insect abundance and diversity from the last century for various habitats across Europe (or North America) as a reference. Your other suggestions about experimentally lowering the density of bat populations does not sound feasible given the status of bats as endangered and protected species in many countries, e.g. within whole E.U. Certainly, I would not support such an invasive approach.

Instead, I would suggest turning around the experimental design, i.e. instead of lowering bat population densities, why not increasing bat population densities by setting up artifical bat boxes and then study if increased bat population densities lower the degree of insect herbivory in plants? Many studies have shown that roosts are very prominent limiting factors in bat population densities and that introducing artifical roosts may support local bat populations. Clearly, this approach makes only sense in species with local populations, i.e. not in migratory species.

Besides that there are other and more elegant experimental approaches without the need to reduce local bat numbers. For example, similar to the study by Kalka et al. (2008), Williams-Guillen et al. (2008) or Boehm et al. (2011), one could restrict the access of bats to plants or small patches of habitats by establishing nocturnal cage exclosure. Then, one could quanitify the extent of herbivory in relation to whether or not bats had access to plants. Such experiments have so far been done in forest environments (Kalka et al. 2008 and Boehm et al. 2011) and coffee plantations (Williams-Guillen et al. (2008) but not in any other habitat; At least to the best of my knowledge. Please correct me if I am wrong. Yet, such experiments would be worthwhile to conduct in grassland habitats and in agricultural areas of the temperate zone.

Is there any other experimental approach possible?

Best,

Christian

hejhej Christian,

I very much like your idea!! Maybe you know the studies of Carles Flaquer and Xavier Puig-Montserrat in Barcelona? In the last European Bat Meeting in Vilnius they showed data on how rice farmers had to do less against pest species after an increase in artificial roost supply and growing population size of P. nathusii in the rice field area.Though, I don't think its published yet.

Tata, Frauke

Christian & Frauke, my main point is that we need good baseline data on both bats and insect populations against which we could then compare data when bat numbers change significantly -- up or down. And if we can bring bat numbers up with artificial bat boxes, great.

But if windmills kill off a significant number of bats, thus resulting in lower bat numbers, that is still information that can be used to answer your question.

Hi Frauke,

Thanks for pointing out the study. I haven't seen anything like that. I am aware that Sara Bumrungsri is working on related topics in tropical rice fields.

Joseph, I agree that we need good baseline data. That would be awesome for a quantitative study, i.e. to what extent do bat populations alter insect populations, or insect species richness. The experimental approach I was talking about earlier is more of qualitative or semi-quantiative nature. Unfortunately, I think that there may be not a whole of opportunities for obtaining good baseline data. The other pitfall in this approach is that over years many other things are changing and therefore, changes in insect population densities or species compositions could not only be attributed to changes in bat numbers but also changes in e.g. other predators densities, forest structure, landscape use etc. I haven't found a good approach that would control for such confounding factors, any suggesitons?

Christian

Hi. In the Canary Islands we know that an endemic bat species, Plecotus teneriffae, is an important predator of many moths, and between its preys there is one which cause, from time to time, defoliation in Canary Pines (Pinus canariensis): Calliteara fortunata (= Macaronesia fortunata). So the ecological value of this bat species in the ecosystem (Canary Pine forest) is presumably high, together with the key role of several birds as predators of larvae of such moth. Fortunately, the present conservation status of this bat is good, as some volcanic caves (typical refugia of the species) are protected with special fences for bats and its populations seem to be stable or even increasing, at least locally. On the other hand, Plecotus teneriffae is protected by law. You can find some information on the subject in the book of D. TRUJILLO (1991): Murciélagos de las Islas Canarias, published by ICONA (Madrid, Spain).