If you think wind energy is a good alternative to fossil fuels, but you also care about wildlife, you’ve probably worried about the possible "lawnmower" effect of spinning wind turbines on birds and bats.
At least some of that
concern is justified. In the mid-1980s, people reported seeing
piles of dead raptors at Altamont Pass Wind Resource Area near San
Francisco, one of the nation’s first wind farms. When a
Sierra Club employee later described wind turbines as the
"Cuisinarts of the sky," newspapers went wild with reports of
hashed-up hawks, and opponents of alternative energy seized on this
new excuse to halt wind-farm development. Another alarm was set off
in 2003, when it came to light that turbines at the Mountaineer
Wind Energy Center in West Virginia had killed about 2,000 bats in
a two-month period.
Wind turbines do kill birds and bats,
but the scale of damage varies widely, depending on several
factors, including the wind farm’s location, its turbine
design, and the species of birds and bats that live nearby or
migrate through. However, compared to the many other ways that
humans kill winged animals, turbine blades generally cut only a
sliver out of the pie.
According to the American Wind
Energy Association, wind turbines account for only one out of every
5,000 to 10,000 human-caused bird kills nationwide. Many bird
deaths are caused by communications towers, automobiles and
domestic cats. The worst killers are glass windows: Researchers
estimate that every year, 900 million birds die after slamming into
these invisible barriers. But most of these victims are common city
birds like pigeons and house sparrows.
farms, like California’s Altamont, do pose a significant
threat to raptors. Altamont, a cluster of wind projects begun in
1981, was built "in the absolute worst place to put a wind farm,"
says Jeff Miller, a spokesman for the Center for Biological
Diversity. The Center is suing Altamont to force it to replace many
of its older, less-efficient turbines with fewer and taller
powerhouses; this would reduce the blade gantlet, Miller says, and
at the same time increase energy production.
Jodziewicz, communications and policy specialist for the American
Wind Energy Association, says Altamont is unique. Not only is the
wind farm located in the middle of a major migration route, it has
7,000 turbines that spin at the same elevation at which hunting
raptors normally soar. Modern wind farmers have learned from
Altamont, and now try to build outside bird migration routes,
minimizing habitat destruction by choosing areas that have already
been altered by industry. And the new cylindrical towers are harder
for birds to nest on than the old ladder-like structures.
The U.S. currently generates only about one-half of 1 percent of
its energy from wind, according to Jodziewicz. Comparing the new
wind technology to other sources of bird mortality — such as
the Exxon Valdez oil spill in the 1990s, which killed an estimated
500,000 birds — she says, "Even if the U.S. got all its
energy from wind, the percentage of birds killed by turbines would
Merlin Tuttle, executive director of Bat
Conservation International, says scientists know almost nothing
about the relationship between bats and wind energy, except that
the wind farms reporting high numbers of dead bats are located
close to forested areas, which are used by certain migratory bats.
Some researchers speculate that the bats’ sonar may perceive
the turbines’ rotating blades as flying insects. But so far,
he says, wind energy companies are reluctant to give bat biologists
the permits they need to research turbine-related bat kills.
Until scientists do more research, new wind farms may not
know how to be bat-friendly. Even so, Ed Arnett, a conservation
scientist with Bat Conservation International, believes that "wind
energy is a great thing," and notes that better siting and turbine
design may solve the bat-blade dilemma.