How do you measure a wind turbine’s impact on birds? Experts are addressing that question now as they weigh the turbines’ direct effect of collisions and habitat loss with indirect effects such as habitat loss and deaths caused by fossil fuels the wind energy might replace, or global warming that a reduction in carbon dioxide emissions might mitigate.
“It’s not going to be easy. It’s very difficult to get all parties to agree on an appropriate level of environmental assessment,” said Taber Allison, Massachusetts Audubon Society Vice President for Conservation Science and recent appointee to the Wind Turbine Guidelines Advisory Committee to advise the U.S. Fish and Wildlife Service on mitigation measures to minimize impacts to wildlife.
Allison spoke on the impact of wind power on wildlife Nov. 14 at the Audubon’s Wellfleet Bay Sanctuary during a meeting of the Cape and Islands Renewable Energy Collaborative.
In 2004, the National Audubon Society reported that about half the bird species in the United States and Canada were in decline due to habitat loss by development, incompatible human use such as driving on the beaches where birds nest, and climate change.
“(Climate change) is perhaps the biggest conundrum, especially when we talk in terms of wind energy development,” said Allison.
For instance, melting Artic ice means a loss of habitat for many species such as winter sea ducks. “Their habitat will disappear,” Allison said.
Species ranges are shifting northward at a rate of about 6.1 km per decade, according to some studies. The most extreme predictions foresee no summer ice in the Artic by the year 2013.
“All of this, the rise in carbon dioxide levels, is directly attributed to our use of fossil fuels,” said Allison.
He said fossil fuels not only raise carbon dioxide levels, but their production, including such methods as mountain-top mining, which typically encompasses between 1,0000 and 4,000 acres of ridgeline, also contribute to habitat loss.
Buildings and windows are the biggest killers of birds, causing nearly one billion deaths annually, while wind turbine collisions kill between 10,000 and 40,000 birds annually, measured at three birds per megawatt installed capacity annually, according to a National Academy of Sciences report.
There have been recorded instances of 30,000 birds killed in one night at a communications tower, Allison said.
“On the one hand you might look at that and say, ‘Well, the impact of collision and wind turbines is negligible relative to all sources of impact.’ Then you’ll also hear people say it’s cumulative impact that matters.”
Possibly more at danger from the turbines are bats, according to Allison. They seem to be attracted to wind turbines, possibly by the whooshing sound or because they don’t see very well and think the turbines are trees.
“In my opinion, it’s a more serious concern than potential bird mortality because of this potential attraction factor,” he said. “Mortality seems to be much higher and we know less about bats other than that they are long-lived and have low reproduction rates.”
In the end, Allison’s recommendation was to reduce energy consumption. “You can’t use energy without having an environmental impact,” he said.
By Linda Culhane
16 November 2007
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