While wind developers downplay the impact of such huge spinning "green" machines on humans, bats and birds, even to the point of denying there is
a problem, the facts tell us a different story. The following story is from The Discovery Channel's website, but the same story appears on the New Scientist website (CLICK HERE.)
Or to read about it in Scientific American (CLICK HERE
TO READ SEPTEMBER 1st UPDATE CLICK HERE
Wind Turbines Kill Bats Without Impact
Aug. 25, 2008 -- Researchers have found the cause behind mysterious bat deaths near wind turbines, in which many bat carcasses appeared uninjured.
The explanation to this puzzle is that the bats' lungs effectively blow up from the rapid pressure drop that occurs as air flows over the turbine blades.
"The idea had kind of been floating around, because people had
noticed these bats with no injuries," said Erin Baerwald of the
University of Calgary and lead author of a study about the finding in
the journal Current Biology.
Researchers examined a large sample size of hoary and silver-haired bats found under wind turbines, performing necropsies on the bats within hours of their death.
The damage from rapidly expanding air in the lungs caused by the
sudden drop in pressure was clear. Ninety percent of the bat deaths at
the southern Alberta site involved internal hemorrhaging consistent
with such damage, called barotrauma, while only 50 percent showed signs
of collision with turbine blades.
For those overlapping cases, it may be that the bats flew through
the pressure drop, suffered barotrauma, and then were struck by a
blade. It is also possible that they were struck first, causing
But, Baerwald said, "When people were first starting to talk about
the issue, it was 'bats running into the turbine blades.' We always
said, 'No, bats don't run into things.' Bat's can detect and avoid all kinds of structures."
In fact, they are even better at detecting moving objects, Baerwald said.
"This kind of answers that mystery," she added. "It was something nobody could have predicted."
The bat fatalities appear to be a more significant problem than bird
deaths from wind turbines in most locations. "Here we're picking up ten
bats for every bird," Baerwald said.
"I can pick up nine different species of bird. I can pick up two
species of bat," she added. "The impact on the populations is very
Whether these deaths are having a significant effect on the bat
populations in Alberta or elsewhere is difficult to gauge because so
little is known about the bats.
All species are susceptible to
death by sudden change in air pressure, Baerwald said. "But the larger
the animal is, the bigger the air pressure drop has to be. We know that
four kilopascals [a unit of pressure] is enough to kill a rat. Bats are
much smaller. We found that these wind turbines produce a five to 10
Birds are less vulnerable to the drop, because they have rigid,
tubular lungs, compared to the balloon-like structures of bat lungs,
which are much like human lungs.
"It's one of those things we have speculated on for a long time," conservation scientist Edward Arnett of Bat Conservation International in Austin, Texas, told Discovery News.
"It's an important finding on the cause of the fatalities. They're
not offered much room for error. If they avoid being struck at the last
minute, they still may be killed by this rapid change in air pressure."
However, he added, "It may not lead us directly to any solution.
Whether they're getting struck or they're dying from the barotrauma may
or may not make any difference. We have to find ways to keep them away
from the turbines."
"There are a lot of people testing different forms of mitigation,"
Baerwald said. "Right now the most promising one is to shut turbines
down during slow wind speeds during the fall migration at night." These
are the conditions when bats are most active.
Tests of this approach at her site in Alberta and elsewhere are promising, she said.Wind Power Victim
A hoary bat is shown. This bat, along with the silver-haired bat, is a
frequent victim of wind turbines. Research shows the animals are killed
by the sudden drop in air pressure created around wind turbine blades.
To read a more detailed (and more upsetting) article on this subject rom New Scientist CLICK HERE.
Or to read about it in Scientific American CLICK HERE
Below, a third article from Canada's Globe And Mail(Click here for to read the following story at its source)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
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
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.
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.