Renewable energy vs. wildlife conservation - Solar, Wind and Land: Conflicts in Renewable Energy Development - page 86

Wind energy vs. bats
Although conflicts between wind turbines and birds tend to garner more
headlines, wind turbines kill roughly as many bats as they do birds. By one
researcher's estimation, wind farms are responsible for more than 450,000
bat deaths each year. 85 Conflicts between wind energy development and bats
are similar in many respects to those involving birds, but some important
differences exist that are worthy of mention.
Bats' unique vulnerability to danger from wind farms
Bats are so elusive that most people know relatively little about them.
Roughly one fifth of all mammal species on earth are bats, and bats live
in nearly every corner of the globe. 86 Most bats residing in temperate
climates eat only insects and play an important role in the food chain and
in agriculture. According to one estimate, the natural pest control provided
by insectivorous bats saves United States farmers more than $3.7 billion
per year. 87 However, although numerous species of bats enjoy statutory
protections under the European Union's Habitats Directive, 88 few of the bat
species materially affected by wind energy development in the United States
are on the U.S. endangered species list. 89
Some bat species seem to be inexplicably attracted to wind turbines . 90
And even though bats make effective use of sound waves and echo location
to navigate and have little difficulty avoiding turbine blades themselves,
they can be defenseless against the major drops in air pressure behind
rotating turbine blades. 91 Research suggests that the majority of bat deaths
near wind farms are due to pulmonary barotrauma—fatal lung damage
from exposure to rapid air pressure decreases near the blades of massive,
spinning wind turbines. 92 Several mass killings of bats at wind farms over
relatively short time periods have been attributed to this effect. In one
documented case, between 1,500 and 4,000 bats died at a 44-turbine wind
farm in a single year. 93
A large proportion of bat fatalities at wind farms is believed to occur
during seasonal migrations. Although few bat species engage in cross-
continental migrations like those of many migratory birds, bats do
annually migrate across modest distances to caves or other underground
locations where they hibernate during the cold winter months. 94 Because
they tend to travel in the dark of night, relatively little is known about
bats' nocturnal migration patterns. 95 This lack of information complicates
wind farm operators' efforts to predict when such migrations may occur
and adjust accordingly. Bats also tend to have slower reproduction rates
and longer life expectancies than birds, making it more difficult for their
populations to rapidly recover from disruptions. 96 All of these factors
make certain species of bats particularly sensitive to having wind farms
nearby.