Monday, February 12, 2007

Wind Turbines and Seabirds

A report out of Denmark suggests that wind turbines may not threaten seabirds as much as we feared. The report was based on a study using infrared cameras to monitor seabird movements around a Danish wind farm.

TADS [Thermal Animal Detection System] was developed to solve a problem specific to monitoring bird collisions at offshore wind farms, in this case the 80-turbine Horns Rev wind farm off Denmark's North Sea coast and the 72-turbine Nysted wind farm in the Baltic. The Danish researchers at Horns Rev and Nysted used visual monitoring and radar tracking, which showed that most birds avoided the farms altogether or flew down the half-kilometer-wide gaps between the wind farms' orderly rows of turbines. But the researchers still could not rule out the possibility that some birds were flying close enough to strike the turbine blades, which spin as fast as 80 meters per second at the tip. Of particular concern were larger seabirds, especially the common eiders that migrate through the area. "We were concerned that these large, rather clumsy birds might not be able to maneuver around the turbines," says Danish environmental institute researcher Mark Desholm, who designed TADS. ...

TADS was mounted on a Nysted wind-farm turbine that was situated in the most common flight path, and during more than 2,400 hours of monitoring that concluded last fall, it spotted only fifteen birds and bats and one moth flying near the turbine, and it recorded one collision involving a small bird or bat. Furness says that this provides confidence in estimations by Danish researchers that the Nysted wind farm would kill few common eiders.
The results will make it easier for energy companies and local governments to argue that wind power is safe, and should ease the consciences of conservationists. However, two things were not addressed, at least in the article. One, why are the results so different from some inland sites, like California's Altamont Pass, where birds are killed regularly? Perhaps the birds had more room to maneuver or the site had less of a choke point effect. Second, does the farm's presence have long-term effects beyond simply killing birds? It may be that the change in flight path is so slight that it does not make a difference, but if the shift involves hundreds of miles, it will mean extra energy expended between feeding stops.

Read the rest.