I have always maintained that every action justified by sustainability has side effects, and that it becomes a values-based judgement as to whether the value of the sustainability improvement outweighs negative impacts of the side effects. Being a values-based judgement means that not everyone will view the cost-benefit tradeoff the same way. Further complicating matters is the fact that the tradeoffs are apples versus oranges, as in the case of compact florescent light bulbs, that have much better energy efficiency than our historical incandescent bulbs, but also have embedded mercury that poses other threats if not handled appropriately.
One such cost-benefit tradeoff that deserves far more attention is the threat of wind power to birds and bats. The fact that giant wind turbines kill birds isn’t a surprise, but we (the US public) don’t know how many. The problem is that the data of has been kept secret, though its value is questionable since collecting the data has not been a requirement for wind energy providers. However, we can get a hint from US Government decisions, and what is revealed is not pretty.
On the 14th of December the Department of the Interior (DOI) finalized a rule that absolves wind generation companies from penalties and prosecution for killing protected birds for the next 30 years (news coverage by AP here), overriding the Bald and Golden Eagle Protection Act that us normal Americans are governed by. The rule allows up to 4,200 deaths per year of bald eagles, or roughly 3% of the total population. It also waives penalties for killing the rarer golden eagles.
While the number of eagles killed each year is kept secret by the DOI, we have some insight into the number, since this DOI rule raised the cap on bald eagles by nearly 4x, indicating that the wind turbine owners were nervous that they were at or above the current limits.
Personally I'm appalled by the death of these beautiful birds. However, more appalling are the lack of good, public data on bird deaths by wind farms, and the lack of an open discussion about the relative value of wind power and birds. How many dead bald eagles per year are an "acceptable" side effect of our growing wind power? How many golden eagles? The DOI has decided that this is a discussion they are not going to allow to happen.