Wind turbines may provide green energy, but what is the true cost to bats and birds?

Imagine that at the flick of a switch, you could not only turn a light on or off but select which power source you were going to use. Would an eco warrior choose wind power or coal? Surely this is a no-brainer.

Not necessarily. While Nimbys (Not-in-My-Backyarders) are often cast as agents of self interest (prioritising the preservation of the view from their own window above progress), in reality they're often motivated by a deep belief in wildlife conservation. There is no denying that wind turbines are inextricably linked to bird and bat mortality. The prominent US wildlife ecologist and ornithologist Albert Manville claims that as many as 440,000 birds are killed by existing wind turbines in the US every year. The numbers are thought to be big because the wind currents most beneficial for producing wind energy also happen to be the ones that billions of birds use to migrate across the US. This is more than an unhappy coincidence, as it adds huge pressure to species already at risk from habitat degradation. And while wind turbines are such great hulking symbols of wildlife slaying, traditional forms of fossil-fuel electricity generation tend to be let off the hook, despite actually killing more animals. A recent US study, Comparison of Reported Effects and Risks to Vertebrate Wildlife - which appears to be the only comparative study of electricity generation to factor in wildlife mortality - concludes that thanks to emissions of sulphur dioxide, nitrogen oxide, carbon dioxide and mercury, coal-fired generation is a far greater killer. But it's also worth mentioning that birds and bats fly into oil platforms and cooling towers, too.

As more research is conducted, so more ways are found to reduce wind-power casualties. As bats rarely fly over the ocean, offshore wind turbines have negligible effect on their mortality. Offshore turbines also seem to cause low bird mortality. The Nysted Offshore Wind Farm, in Denmark, was actually built in a duck flyway, yet mortality was discovered to be just 1.2 birds per year per tower. Other techniques include slowing turbine blades at night - the time when wind speeds are lowest anyway but bats happen to be most active - shown by US research at the Casselman Wind Power Project to cut wildlife deaths by 73%. Researchers at Aberdeen University, funded by the People's Trust for Endangered Species (ptes.org) are currently making good progress on using radar to deter bats from becoming entangled in the turbine's blades. Meanwhile we need to know more about migration patterns and exactly why bats and birds are attracted to spinning blades. Nor should any wind turbine be given the go ahead without a conservation plan. Notably the RSPB - once a vehement opponent of wind power - put up its first turbine earlier this summer after consultation on finding an appropriate site. The answer, as they say, is blowing in the wind. The complication is figuring out how to avoid a collision.