Wind turbines blamed in deaths of migratory bats

BY BILL GRAVELAND The Canadian Press

CALGARY — New research is blaming tall wind turbines for the deaths of hun­dreds of migratory bats in the foothills of southwestern Alberta’s Rocky Mountains.

Robert Barclay, a University of Cal­gary biology professor and interna­tional bat expert, began a study in 2006 after large numbers of the flying mam­mals were found dead on wind farms near Pincher Creek.

More and more giant windmills tow­er over the landscape in southern Al­berta and across the country as Cana­dians look for greener sources of elec­tricity. But the swooping wind-catch­ing blades are proving fatal to bats.

The study says roughly 90 per cent of the animals that were found dead had severe respiratory injuries consistent with a sudden drop in air pressure that occurs when they get close to turbine blades.

“A large number of the bat carcasses we found had no (visible) injuries. It didn’t look like anything had happened to them," said project leader Erin Baer­wald.

“They were lying on the ground — no broken wings or injuries you would ex­pect to see if they were struck by these large blades."

The blades are 40 metres long and their tips can move at a speed of 250 kilometres an hour.

“We started looking inside and what we found was a large proportion of these bats internally had severe hem­orrhaging, so they were full of blood."

A veterinary pathologist found blood vessels in the bats had burst and the lungs were filling with blood.

“What happens when you fly through an area when the pressure drops dra­matically . . . is the lungs overexpand and it causes breakages in all the small vessels around the lungs," explained Baerwald.

The results of the study were to be published in the Aug. 26 online edition of Current Biology.

There are nine species of bats found in Alberta, three of which migrate through the province each year. The majority of bats killed by wind tur­bines are migratory and roost in trees. They include hoary bats, eastern red bats and silver-haired bats and have been known to migrate from as far away as Mexico and the southern Unit­ed States.

Bats typically reach ages of 30 or more and produce only one or two off­spring at a time, so researchers fear the deaths could have far-reaching conse­quences.

“Slow reproductive rates can limit a population’s ability to recover from crashes and thereby increase the risk of endangerment or extinction," said Barclay in a news release.

He said all three species of migratory bats eat thousands of insects, including crop pests, and large-scale losses of the nocturnal animals could have an im­pact on ecosystems along their routes. Prior to 2005 there were few bat deaths near the turbines, but the older units were about 20 metres lower than the towers now being erected.

Baerwald said there is no obvious way to reduce the pressure drop at wind turbines without severely limit­ing their use. But since bats are more active when wind speeds are low, one strategy she suggested might be to in­crease the rate at which turbine blades rotate during the fall migration.