Article

Bats surpassing birds as ecological concern

New research shows that the study of bat mortality at wind turbines should be the primary ecological concern for developers. ...TransAlta has about 189 MW of wind farms operating in southern Alberta and another 162 MW under construction. By analyzing specimens found on one of TransAlta's farms, Robert Barclay, a biological sciences professor at the university, discovered that the vast majority of bats died not as a result of colliding into the turbines, but as a result of a sudden drop in air pressure in the airspace around the turbines - which destroys their lungs.

New research shows that the study of bat mortality at wind turbines should be the primary ecological concern for developers.

Night-vision goggles, thermal imaging equipment, echolocation radar detectors and marine radar are not the usual tools found on wind farms, but in the eastern U.S. and western Canada, scientists and developers seeking to prevent bat fatalities are using this equipment to track the elusive creatures.

Since 2004, when the 2,095 bat deaths reported at West Virginia's Mountaineer Project sent alarms ringing, wind farm developers, scientists and conservationists have been working together to pinpoint and prevent fatalities. This summer, one such partnership, between TransAlta Wind and the University of Calgary, debunked one of the popular beliefs about bat deaths and will help steer future work in this area.

TransAlta has about 189 MW of wind farms operating in southern Alberta and another 162 MW under construction. By analyzing specimens found on one of TransAlta's farms, Robert Barclay, a biological sciences professor at the university, discovered that the vast majority of bats died not as a result of colliding into the turbines, but as a result of a sudden drop in air pressure in the airspace... more [truncated due to possible copyright]  

New research shows that the study of bat mortality at wind turbines should be the primary ecological concern for developers.

Night-vision goggles, thermal imaging equipment, echolocation radar detectors and marine radar are not the usual tools found on wind farms, but in the eastern U.S. and western Canada, scientists and developers seeking to prevent bat fatalities are using this equipment to track the elusive creatures.

Since 2004, when the 2,095 bat deaths reported at West Virginia's Mountaineer Project sent alarms ringing, wind farm developers, scientists and conservationists have been working together to pinpoint and prevent fatalities. This summer, one such partnership, between TransAlta Wind and the University of Calgary, debunked one of the popular beliefs about bat deaths and will help steer future work in this area.

TransAlta has about 189 MW of wind farms operating in southern Alberta and another 162 MW under construction. By analyzing specimens found on one of TransAlta's farms, Robert Barclay, a biological sciences professor at the university, discovered that the vast majority of bats died not as a result of colliding into the turbines, but as a result of a sudden drop in air pressure in the airspace around the turbines - which destroys their lungs.

The results were staggering. Ninety percent of the bats found around TransAlta's Summerview wind farm near Pincher Creek, Alberta, died from internal injuries to their respiratory systems.

Called barotraumas, this type of fatality is similar to a human condition called the bends - when divers' lungs fill with fluid because they surface from a dive too quickly. Bats' balloon-like lungs are made up of two-way airflows ending in thin, flexible sacs surrounded by capillaries. When outside pressure drops, the sacs can overexpand, bursting the capillaries around them.

Study leader Erin Baerwald says the results show that bats - not birds - should be the top ecological concern for wind developers.

"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," Baerwald says. Because bats are mammals, their lungs arc totally different from the more robust respiratory system of birds, which is designed to hold out in sudden drops in air pressure.

The study is part of a longer partnership between TransAlta and Barclay's group that began after company officials approached Barclay - a leading bat expert - a few years ago, when the company began noticing bat fatalities at some of its Alberta wind farms.

It was important for us to determine as much as we could about this issue," says Jason Edworthy, director of stakeholder relations for TransAlta. "Ultimately, it's a situation we're working hard to alleviate. Ongoing research with the university is seeing some real results in terms of mitigation of collisions."

The TransAlta study drew worldwide media attention from researchers and the wind industry. Other groups will likely replicate the study to see if it holds true in different parts of North America.

Prevention

But Barclay, who views the results as conclusive, is moving forward with new research aimed at preventing the deaths altogether.

"What we've found doesn't change the numbers that are killed - it just explains why they're killed. But why are they there in the first place?" he asks.

Barclay says a number of factors could be pushing migratory bats to the wind turbine sites, including good weather conditions, the location of the turbines or attraction to insects in the area. Or, maybe they are not especially attracted to the turbines at all, he says. "Maybe there are just lots of them flying all over the airspace."

How can an internationally renowned bat expert, who is also the lead scientific advisor to the Bat and Wind Energy Cooperative (BWEC), know so little about the problem?

Mainly, very little is known about some elusive species of bats, including hoary, silver-haired and eastern red bats, that are killed by turbines. For one thing, they are all migratory species - an exception in the bat world, where most species hibernate and stay in the same area, making them much easier to study than their fly-by-night counterparts. Because these solitary creatures move in total darkness, scientists have not been able to study them - even their population sizes arc unknown, leaving researchers and developers with no benchmark to gauge if their deaths actually pose an ecological problem.

Barclay says it could take a long time to nail down the population size. It's likely that developers could find ways to significantly reduce fatalities before researchers figure out if the quantity being killed is ecologically problematic.

"The ecological impact of bat deaths could be limited if the number of mortalities isn't biologically significant," says Barclay. "But these are insect-eating bats, and they play an important ecological role as consumers of night-flying insects that otherwise feed on our crops and forests. The only predators for these insects at night are bats, and they eat an awful lot." In fact, migratory bats gobble at least half of their entire body weight in insects each night.

The wind power industry has partnered with researchers and conservationists to test out a number of mitigation solutions. TransAlta Wind, for example, began post-construction monitoring for birds in 1999, just two years after it installed its first wind turbines. And BWEC, North America's leading research consortium on bat fatalities, is backed by more than 16 companies, including BP, Vestas, Invenergy, FPL Energy, PPM Energy and Horizon Wind Energy.

Founded in 2003 by Bat Conservation International, the U.S. Fish and Wildlife Service, the American Wind Energy Association and the National Renewable Energy Laboratory of the U.S. Department of Energy, the cooperative is running a series of studies across pre- and post-construction phases and trialing mitigation techniques. All of the cooperative's publications and studies can be found on its Web site.

Bats and wind

The wind power industry has been dedicated to solving the problem, says Barclay. His university team works with a number of developers, such as TransAlta, Suncor, Enmax and the Alberta Wind Energy Cooperative.

"They've been very helpful in funding, designing experiments and testing ways to reduce fatalities," says Barclay. "The companies we work with have been very proactive, and they have the same goals we do: to find out if this is an issue to be concerned with and if it is, how can we reduce the impact?"

Results from recent studies are already beginning to give developers clues on how to prevent some fatalities. Earlier this year, Barclay and TransAlta published results of another study from the Summerview Wind Farm, which upped the cut-in speed of half of its 38 80-meter wind turbines.

"A number of studies show that bats don't like to fly when it's windy," says Barclay, "so we thought changing the cut-in speed of turbines - so they don't start generating electricity until wind speed gets higher - [and that] gives bats more of an opportunity to move through at lower wind speeds."

Results of the study show bat deaths were reduced by 52%.

Barclay's group wants to perform the same test in other places and is working to determine the optimal cut-in speed. The optimal speed will have to be a compromise of lost generation costs and reduced bat deaths.

"The cost in terms of energy production needs to be weighted against bat fatalities," Barclay says. For example, TransAlta estimated it cost $50,000 in lost production as a result of altering cut-in wind speeds for its 2007 experiment.

Another promising mitigation method is emitting sounds to warn or steer bats away from turbines. BWEC has carried out laboratory studies that showed that bats avoided the area where an ultrasound device was operating. While humans are unable to hear ultrasound, it is "uncomfortable" for bats, according to BWEC coordinator Ed Arnett.

BWEC was testing speaker-sized ultrasound devices on some U.S. wind farms during the busy migratory period from July to September - the time when most bat deaths occur. Dr. Tom Kunz, a bat expert from Boston University who is involved with this study, was concerned about the ability to make the ultrasounds heard over the huge airspace that the turbines dominate. High-frequency sounds tend to fade quickly. And as the wind industry grows, so do turbine sizes. The sounds have to compete with increasingly larger turbines.


Source: http://www.nawindpower.com/...

JAN 11 2009
https://www.windaction.org/posts/18545-bats-surpassing-birds-as-ecological-concern
back to top