“When we try to pick out anything by itself, we find it hitched to everything else in the Universe.”–John Muir
A recent study by researchers at the University of Calgary and published in Current Biology (subscription required) reminds us of the truthfulness of Muir’s statement and of how careful we must be even when implementing “green” solutions.
According to an article on the research in Science News:
Ninety percent of the bats [the researchers] examined after death showed signs of internal hemorrhaging consistent with trauma from the sudden drop in air pressure (a condition known as barotrauma) at turbine blades. Only about half of the bats showed any evidence of direct contact with the blades.
“Because bats can detect objects with echolocation, they seldom collide with man-made structures,” said Erin Baerwald of the University of Calgary in Canada. “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.
“Given that bats are more susceptible to barotrauma than birds, and that bat fatalities at wind turbines far outnumber bird fatalities at most sites, wildlife fatalities at wind turbines are now a bat issue, not a bird issue.”
The greater vulnerability of bats than birds to wind towers can be understood in terms of their differing respiratory systems.
Bats’ lungs, like those of other mammals, are balloon-like, with two-way airflow ending in thin flexible sacs surrounded by capillaries, the researchers explained. When outside pressure drops, those sacs can over-expand, bursting the capillaries around them. Bird lungs, on the other hand, are more rigid and tube-like, with one-way circular airflow passing over and around capillaries. That rigid system can more easily withstand sudden drops in air pressure.
The Canadian Wind Energy Association responded positively to the research:
This study and the new information it provides will contribute to the development and implementation of initiatives to reduce the risk of bat mortality around wind farm projects.
Watch a short video on the Calgary researchers work: