In Dutch. Instituut voor Natuur- en Bosonderzoek (Nature and Forest Institute), Brussels, Belgium. English Abstract:
Effects of wind turbines on fauna in Flanders
Birds and bats can collide with wind turbines, or encounter the vortex wake behind the turbines. They can also become disturbed in their breeding, resting, and foraging areas, or during migration. Therefore, the impact on fauna was studied on 7 wind farm locations in Flanders (=northern part of Belgium). At 2 additional locations, a reduced random test was also performed. The study results are presented in this report and discussed with foreign results. Recommendations for further study and the selection of new wind farm locations, are also included.
The collision numbers in Flanders, with applied necessary correction factors, varied from 0 to around 125 birds per individual wind turbine per year. No bats were found. The mean number for the 7 wind farms (with correction factors) varied substantially with resp. 1, 3, 7, 12, 21, 26 and 42 birds per wind turbine per year. Wind farms in The Netherlands (comparable locations and species) had similar results.
Most of the collision fatalities in Flanders were local relatively common birds like Black-headed Gull, Herring Gull, Lesser Black-backed Gull, Mallard, Wood Pigeon and Starling, but also rarer or even endangered species were found such as Grey Heron, Common Shelduck, Common Pochard, Wigeon, Common Teal, Kittiwake, Mediterranean Gull, Eurasian Sparrowhawk, Peregrine Falcon, Kestrel, Redshank, Black-tailed Godwit, Oystercatcher, Kentish Plover, Common Tern, Sandwich Tern, Little Tern, Woodcock, Swift and Meadow Pipit. For Common Tern, Sandwich Tern and Little Tern, the number of fatalities was also high. The large number of collided gulls and terns in the Brugge and Zeebrugge wind farms was striking, all the more because these birds are largely diurnally active. This will be the result of local migration of gulls towards a large sleeping place (Brugge) and foraging flights of gulls and terns in the vicinity of a breeding colony (Zeebrugge). It is not clear whether this resulted in a significant impact on the local gull population. The large number of tern collision fatalities during the breeding season in the Zeebrugge wind farm, resulted in a significant impact on the breeding colony of Common Tern, Sandwich Tern and Little Tern. The planned repowering of the Zeebrugge turbines by larger ones with more free space at the height where most terns are flying, must result in less fatalities in the future. A study will determine if additional measures will be needed.
At some foreign wind farm locations, significant numbers of collided birds and bats are also found, including raptors and several rare species. Whether this current impact is significant for national populations, is unclear. At least in some cases, a certain or probable significant impact on local and/or regional populations has been determined. More research is needed to have better clarity on that subject. But at the same time, with a persistent very important impact (including local), effective measures must be taken. This should also include switching off the wind turbines during certain risk periods, or even in some extreme cases the dismantling of turbines.
From the research in Flanders, it was found that modern large wind turbines can also have relatively large numbers of collision fatalities among birds, just like small wind turbines. In several foreign locations, this was also the case, even for bats. The number of tern and gull collision fatalities in Flanders seems to depend largely on the number of present and/or flying birds at the wind farms. For the locations near waterbodies in Flanders, The Netherlands and France, on average for all species, the size of the wind turbine (hub height and/or rotor area) seems to be a less important factor, although there is a tendency (not significant) towards slightly more collision fatalities with larger turbines (numbers per turbine). The calculated collision chances at rotor height for gulls in wind farms with small and large turbines in Flanders seem to confirm this trend. Obviously, factors like species, flight height, flight behavior, and properties of the wind farm and surroundings, will also be very important. When the results are presented per megawatt installed capacity, a wind farm with large wind turbines would have on average less collision fatalities then a wind farm with more smaller turbines. Of course, local differences can play a very important role (for example ‘inland‘ vs. ‘coast’), therefore the results cannot simply be generalized.
The research on disturbance at the wind farm locations in Flanders was rather limited, partly due to the lack of reliable reference situations (highly changing surrounding area in industrial zones). Nevertheless, it was clear that foraging and roosting waterfowl and waders outside the breeding season, experienced some disturbance. Breeding birds had less or no clear disturbance. There are however large differences between species and locations, and still many open questions. Gulls and terns experienced no barrier effect during their local foraging flights in the breeding season, resulting in a large number of birds that crossed the turbines at close distance and consequently also more collisions. Outside the breeding season, for gulls flying towards the sleeping place, the situation was not that clear with only an indication for a partly (small) barrier effect.
An analysis of many foreign studies, confirms that certainly foraging and resting waterfowl like geese, ducks and some wader species outside the breeding season, can experience a disturbance of up to 500m from wind turbines (in some exceptional cases possibly 600-800m). Depending on the local situation, this can result in an important degradation of nature areas. Breeding birds are less disturbed, but still quite important for at least some waders.
In contrast to breeding birds, it was found that for most studied bird species outside the breeding season, the disturbance increased with wind turbine height.
Disturbance of local migration routes can happen, but this will depend on several factors. Many seasonal migrating birds do experience an important barrier effect during the day, but the situation during the night is less known.
Study results in Flanders and from foreign locations clearly show that, under certain circumstances, wind turbines can cause an important negative impact on birds and bats. Cumulative effects because of the expansive growth of wind farms, must be taken into account seriously. More wind turbines will result in extra pressure on top of the already existing sources of negative impact, like power lines, roads, disruption of nature areas, etc. In a densely populated region like Flanders, this degrades the total suitability for ecological functions such as the presence of bird and bat populations and the guarantee for regional or international migration routes.
The right policy for wind farm planning, should include a strategic planning on regional, national and certainly also for the offshore wind farms on an international scale. Based on all information like the amount of wind, residences, protected and other important nature areas and migration routes, maps for potential wind farms can be created.
In general, from the study results, it is recommended not to build new wind farms near important breeding, resting and foraging areas and local or seasonal migration routes. Although the possible impact for planned wind farms can be estimated, in an important number of cases, there can be a substantial lack of data to make a reliable assessment of the potential impact. Certainly in case of a potential impact on the fauna in nature areas that are protected or meet the criteria to be protected, including important migration corridors, the precautionary principle must be applied. Despite all studies and possible proposed mitigation measures, proper site selection (“macro-siting”) is still the best and certain way to reduce the impact. So, this should be the first stage in the search for new wind farm locations. Depending on the quality of the area (for example industrial vs. open undisturbed) and the importance for fauna, other methods can be investigated like mitigation measures and/or compensation measures.
On several levels, there is still an important lack of knowledge concerning the impact of wind turbines of birds and bats. Considering the further expansion of wind energy, more research is urgently needed. This is best performed by independent long-term study in which specific points of interest are conducted.
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