Wind turbines are hailed as a environmentally friendly source of renewable energy. And while gales will continue to blow and generate power, there are hidden costs. One criticism of wind turbines is their aesthetic impact on the view. But they are also lethal to flying animals. Annually, in the US alone, 20,000-37,000 birds are killed through collision with turbines.
Songbirds are one hard-hit group. A recent study shows that nocturnal birds are particularly susceptible to mortality. In some areas, the species at risk are raptors, whose populations are typically long-lived and slow to recover. In addition, bats are caught in the blades where wind turbines are placed in forested ridges. In the Mid-Atlantic Highlands, a large greenbelt area straddling a number of eastern US states, an average of 22-60 bats are killed per turbine each year.
Many bird species migrate along traditional routes, known as flyways; birds expend less energy flying where winds updraft, making longer distances more manageable. The same strong wind conditions that characterize many parts of flyways make them good candidates for wind turbine placement.
The problem with wind turbines is site-specific. If wind-energy projects are located in sensitive habitat, the damage is magnified. Well-considered locations reduce the hazards for wildlife. But poorly chosen sites can cause significant habitat disruption and direct injury.
In most areas considering wind power, recommendations are being drafted in order to mitigate the effect of wind-power generation on wildlife. No one denies the rationale for shifting to new energy sources, but it is a relatively new field and the full range of environmental repercussions are still being discovered.
To put it into perspective, the impact of wind turbines is only one human-related cause of mortality, joining collision with windows, power lines and communication towers, as well as pesticide poisoning, and death at the paws of domestic cats.
