June 20, 2005

Migrating birds forced to lengthen migration to avoid wind turbines

New Scientist has reported the results of a recently published study of a goose and a duck species flying in the area of the wind facility off shore from Nysted, Denmark. The results show that almost all of them avoid the turbines. The industry and their apologists have naturally leapt on it as vindication, but here are some qualifying remarks from the paper (Desholm & Kahlert, Avian collision risk at offshore wind farm, Biology Letters, early online publication, 2005).
"... data collection was conducted only in calm winds (less than 10 m/s) and no-precipitation situations."
Considering that the 2.3-MW Bonus turbines don't start turning until the wind is 6 m/s, how much of the time were they actually turning? It is much easier to avoid a large blade that is still than one whose tip is moving at 164 mph (82.4-m rotor diameter at 17 rpm).
"... data collected during twilight were excluded from the analysis."
Twilight is a particularly confusing time for assessing visual cues. The stated reason for excluding it is "to compare situations with good and poor visibility only," but at night the turbines are clearly lit and this comparison could be done without throwing out the twilight data, which might be crucial to an honest assessment of the facility's impact on the birds.
"During the initial operation, frequent visits of maintenance vessels may have influenced the avian avoidance response to the sweeping turbines in an uncertain way. Before solid conclusions can be reached, complementary studies at other sites are needed to confirm these findings, to include possible habituation behaviour over the years to come, and to cover other focal species such as divers (Gavia sp.) and common scoter (Melanitta nigra)."
This study was done in "autumn" of 2003 (the paper is not more specific and does not even specify how many days and nights of observation are included). But the facility was not completed until the end of November and began to generate electricity in December (except for 10 of the 72 turbines, which had begun operation in July and for all we know may have been among the 12 that were out of range of this study). It seems likely that the facility was not fully active during the study.

The researchers compare their results with an earlier study of the same area before construction began, but describing the lower percentage of birds flying through the turbine array as due to "operation" rather than construction seems quite inaccurate.

In addition, as countries desperate to salvage their misguided commitments to large-scale wind power look to build more of them off shore, the cumulative effect of facility after facility that must be dodged must be considered.

Also, I was unable to find any data on the actual output from the Nysted facility (let alone how often it corresponded to an actual need on the grid), which is central to the question of whether it is worth even the slightest risk to birds (and marine mammals -- see the recent story about dead baby seals at the Scroby Sands wind facility off the U.K. shore), not to mention the very high cost not only of manufacture and construction but also of maintenance and integration in the grid.

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