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Wind turbines to blame for bat deaths: study

Sudden air pressure changes around wind turbines is likely behind the large numbers of migratory bats found dead in southern Alberta, according to a new University of Calgary study. The two-year study found 90 per cent of the studied bats found dead below turbines near Pincher Creek suffered severe injuries to their respiratory systems consistent with a sudden drop in air pressure that occurs near the turbine blades.

Sudden air pressure changes around wind turbines is likely behind the large numbers of migratory bats found dead in southern Alberta, according to a new University of Calgary study.

The two-year study found 90 per cent of the studied bats found dead below turbines near Pincher Creek suffered severe injuries to their respiratory systems consistent with a sudden drop in air pressure that occurs near the turbine blades. Few of the bats showed signs of coming into contact with the turbine blades.

Unlike birds, bats do not have a rigid respiratory system and are therefore less able to withstand sudden pressure changes in the air. When outside pressure drops, the bats' air sac over-expands, bursting the capillaries around it. Their lungs fill with blood and fluid - similar to drowing, the researchers said.

"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," said project leader Erin Baerwald.

Three of the nine bat species found in Alberta migrate through the province each year. The majority of bats killed at... more [truncated due to possible copyright]  

Sudden air pressure changes around wind turbines is likely behind the large numbers of migratory bats found dead in southern Alberta, according to a new University of Calgary study.

The two-year study found 90 per cent of the studied bats found dead below turbines near Pincher Creek suffered severe injuries to their respiratory systems consistent with a sudden drop in air pressure that occurs near the turbine blades. Few of the bats showed signs of coming into contact with the turbine blades.

Unlike birds, bats do not have a rigid respiratory system and are therefore less able to withstand sudden pressure changes in the air. When outside pressure drops, the bats' air sac over-expands, bursting the capillaries around it. Their lungs fill with blood and fluid - similar to drowing, the researchers said.

"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," said project leader Erin Baerwald.

Three of the nine bat species found in Alberta migrate through the province each year. The majority of bats killed at wind turbines are the migratory species - hoary bats, eastern red bats and silver-haired bats.

The study was begun after TransAlta wind farm operators began noticing bat carcasses below their turbines.

Baerwald acknowledged that while the deaths related to wind turbines could have a significant impact on bat populations, given slow reproductive rates, there is no obvious way to reduce pressure drops without curtailing their use.

One possibility, Baerwald said, is to change the speeds at which turbine blades are activated during the bats' fall migration period.


Source: http://www.canada.com/calga...

AUG 25 2008
http://www.windaction.org/posts/16739-wind-turbines-to-blame-for-bat-deaths-study
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