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What is killing the bats of Pincher Creek?

Bats are dying as they fly into low-pressure zones around wind turbines. The sudden low pressure causes the air in their lungs to expand and cause tissue damage, called barotrauma. Low-pressure area: most severe immediately out from the blades and decreases as it gets closer to the centre of the turbine. There is also a low-pressure area down the shaft.

A mystery surrounding the large number of dead animals on a wind farm in Alberta prompted a groundbreaking study at the University of Calgary that found the drop in air pressure around some turbines resulted in fatal respiratory injuries

Alberta proudly leads the country when it comes to producing wind energy, but in 2005, a troubling mystery began to emerge at a newly opened wind farm near Pincher Creek.

A large number of migratory bats were being found dead at the bottom of wind turbines, and many didn't show signs of actually coming into contact with the turbine blades.

TransAlta Corp., a Calgary-based energy firm that owns the wind farm, quickly approached bat experts at the University of Calgary in search of answers.

Sean Whittaker, vice-president of policy with the Canadian Wind Energy Association, said the fact that large numbers of dead bats have been found at only a few wind farms around North America at a time when hundreds are in operation made the deaths more perplexing.

After a two-year study, University of Calgary researchers have found that most of the bats suffered severe injuries to their respiratory systems consistent with a sudden drop in air... more [truncated due to possible copyright]  

A mystery surrounding the large number of dead animals on a wind farm in Alberta prompted a groundbreaking study at the University of Calgary that found the drop in air pressure around some turbines resulted in fatal respiratory injuries

Alberta proudly leads the country when it comes to producing wind energy, but in 2005, a troubling mystery began to emerge at a newly opened wind farm near Pincher Creek.

A large number of migratory bats were being found dead at the bottom of wind turbines, and many didn't show signs of actually coming into contact with the turbine blades.

TransAlta Corp., a Calgary-based energy firm that owns the wind farm, quickly approached bat experts at the University of Calgary in search of answers.

Sean Whittaker, vice-president of policy with the Canadian Wind Energy Association, said the fact that large numbers of dead bats have been found at only a few wind farms around North America at a time when hundreds are in operation made the deaths more perplexing.

After a two-year study, University of Calgary researchers have found that most of the bats suffered severe injuries to their respiratory systems consistent with a sudden drop in air pressure - called barotrauma - that occurs near the turbine blades.

The study will be released today in the online edition of the journal Current Biology.

Erin Baerwald, the research's project leader and a University of Calgary graduate student, said that bats rarely run into manmade structures because the flying mammals can detect objects with echolocation, the location of objects by reflected sound.

"An atmospheric pressure drop at wind turbine blades is an undetectable - and potentially unforeseeable - hazard for bats, thus partially explaining the large number of bat fatalities at these specific structures," she said.

Bats, unlike birds, do not have a respiratory system that can withstand sudden pressure changes in the air.

Ms. Baerwald said that one way in which energy companies could reduce or prevent bat fatalities is to increase the wind speed at which turbine blades begin to rotate during the bats' migration period, which runs annually from mid-July to mid-September in Alberta. This strategy would work, she added, because bats are more active when wind speeds are low.

While the University of Calgary is well known for its bat research, Ms. Baerwald said there is still a dearth of knowledge about these animals, and conducting this study was difficult but ground-breaking for the field. The researchers examined the carcasses of nearly 190 bats killed at turbines in southern Alberta.

"They aren't seen as sexy animals," she said. "People love to sit in their backyards and watch birds. It's much harder to watch bats because they are nocturnal."

She said the animals - nine species of bats are found in Alberta - are important because they play a major role in pest control. An average bat can gobble up its body weight in insects every night.

Ms. Baerwald plans to expand on the latest study, which was funded by government, industry and conservation groups, by researching bat migration.

Jason Edworthy, director of stakeholder relations at TransAlta Corp.'s wind arm in Calgary, said the company welcomes the study's findings. "It was important for us to determine as much as we could about this issue," he said.

Mr. Edworthy said even before the research was finished, the company began experimenting with ways to reduce bat fatalities, and that they've already seen results.

He said lack of information about bats was initially a barrier. "We had to be quite patient, mainly because we were started from a knowledge base that wasn't quite zero but very, very low."

There are 473 commercial wind turbines operating in Alberta, the vast majority in the southern portion of the province.

Deadly whirl

Bats are dying as they fly into low-pressure zones around wind turbines. The sudden low pressure causes the air in their lungs to expand and cause tissue damage, called barotrauma.

Low-pressure area: most severe immediately out from the blades and decreases as it gets closer to the centre of the turbine.

There is also a low-pressure area down the shaft.

WHY BATS FARE WORSE THAN BIRDS

Bats have large, pliable lungs and hearts that expand, causing tissue damage when exposed to a sudden drop in pressure.

Birds have compact, rigid lungs that do not expand in the same conditions.


Source: http://www.theglobeandmail....

AUG 26 2008
http://www.windaction.org/posts/16745-what-is-killing-the-bats-of-pincher-creek
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