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Κοινωνικό δίκτυο της Πάρου και Αντιπάρου

Source: REVOLT, The Worldwatch Institute's Climate and Energy Blog

Author: Sam Shrank

The most recent issue of the magazine new energy contains an article describing the initial findings of a collection of studies commissioned by the German Environment Ministry on the subject of “Birds of Prey and Wind Turbines: Problem Analysis and Suggested Solutions.” I had always thought of this issue as somewhat of a sideshow, but understood that a small but vocal community took it very seriously and succeeded in keeping it in the public eye.

Although the article (and by extension, the studies) may not have completely changed my outlook, it did point out that aggregate, top-line numbers are not the best way to judge wind turbines’ effects on bird populations. The article also highlights some relatively painless measures that developers and landowners can take to help partially mitigate the situation.

At first glance, wind turbines seem like a spectacularly insignificant cause of death among birds. Although turbines kill anywhere from 100,000 to 440,000 birds each year in the United States, and there are many grisly photos to prove it, this is less than one-tenth of 1 percent of unnatural bird deaths. Up to 1 billion birds die each year in the U.S. from crashing into windows, and 60–80 million are killed by automobiles.

But even for bird enthusiasts, not all birds are created equal, and wind turbines have a disproportionate effect on some species that are either especially treasured or endangered. Birds of prey have long suffered at the hands of turbines, beginning with the now-infamous Altamont Pass Wind Resource Area that was once responsible for 4,700 bird deaths a year, including over 1,000 raptors and dozens of golden eagles. (Altamont Pass has since taken steps to reduce the number of bird deaths and will soon be installing newer, more bird-friendly turbines.) Just last year, four wind generation projects on U.S. public lands with a combined capacity of 416 megawatts were put on indefinite hold after the Fish and Wildlife Service raised concerns about their effects on golden eagles.

The Altamont Pass Wind Farm has been notorious for causing bird deaths

This brings us to the German studies, which focus on three birds of prey thought to be particularly threatened: red kites, white-tailed eagles, and Montagu’s harriers. Birds of prey account for 41 percent of recorded bird deaths in Germany, and these species are no exception. Sixty white-tailed eagles are known to have been killed in Germany since 2002, out of a total of only 600 pairs. Turbine collisions are now the bird’s number-one cause of death. Montagu’s harrier is even rarer, with just over 400 pairs, but has so far proven less susceptible to turbines, with only two known deaths since 2002. This can, however, be attributed in part to the fact that permits for turbines have been declined due to proximity to harriers’ nests.

The multi-year study involved researchers following individual birds to analyze their most basic behavior. They tracked the birds’ flight height, the extent of their home range, and their behavior around wind farms and individual turbines. The research showed that while none of the birds changed their behavior to avoid wind farms, over 90 percent turned away in time to miss individual turbines. Even for those birds that flew through the rotors, only a small number were killed (varying from below 10 percent for Montagu’s harrier to above 15 percent for the white-tailed eagle).

Perhaps the most useful information concerned the birds’ ranges and flight patterns. Both the kite and harrier stayed largely within 2 kilometers of their nests, while the eagle regularly ranged throughout 150 square kilometers. The harrier also stays within 20 meters distance during the vast majority of its flights, lowering its susceptibility to turbine encounters.

Ultimately, the study concludes that the most practical way to ensure minimal bird deaths is to require turbines to be sited away from nests, as they already must be. However, other measures can be taken as well. Farmers often conduct test cuts on fields where wind turbines are located before harvesting the rest of their crop, and this draws birds of prey like a magnet. Because tall plants make it harder for the birds to see their prey, they gravitate toward newly cut fields. If the fields around wind farms are mowed later (and in cases where the turbines are not on farmland, perhaps not mowed at all), birds will spend less time around turbines. Birds also tend to nest in specific areas—Montagu’s harrier, for example, favors winter barley fields—so planting crops to avoid having turbines in the way of the birds’ hunting grounds could have a positive impact.

To some extent, birds and wind turbines will always be in conflict, and we must decide how to balance competing priorities. It is pretty easy to make the case that wind power overall poses less risk to wildlife than conventional power generation is. But while some might be frustrated when they see concerns about birds slowing the transition to a clean energy system, surely strategies for helping turbines and birds better coexist are welcome.



REVOLT, The Worldwatch Institute's Climate and Energy Blog

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Comment by Shenpen Rinpoche on March 14, 2011 at 15:00

Most efficient wind turbines are the vertical ones (helical), while people continue to install the classic ones which need wind from specific direction to work well (while helical ones turn from any wind or even breeze). The helical ones have less impact also on ecosystem and birds...

I won't say "then why?" because I suspect the helical to be slightly more expensive (but with much better efficiency!) ... Aaaaah humans! ;)


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