Wind - Energy Policy Analysis: A Conceptual Framework - page 122

year (Erickson et al. 2001). Areas cleared of trees and brush around the base of wind turbines
in the Altamont Pass of California may establish a more open habitat than currently exists that
constitutes an “attractive nuisance” for raptors seeking ground-dwelling prey (Smallwood and
Thelander 2005).
By far the greatest number of fatalities at onshore wind facilities is songbirds and bats (NWCC
2010). Taller turbines reach higher above the ground than smaller, shorter turbine towers, have
much larger rotor sweep areas, and thus further overlap the normal flight heights of nocturnal
migrating songbirds and bats (Manville 2009). Larger, taller turbines and their wider and longer
blades also produce far greater blade-tip vortices and blade wake turbulence, the potential influ-
ence of which on collisions with birds and bats and barotrauma (damage to internal organs from
severe changes in air pressure) to bats is uncertain (Manville 2009).
Bats appear to be attracted to wind turbines (Horn, Arnett, and Kunz 2008), but reasons
for such attraction are unknown and deserve additional research. Bats are long-lived and have
low reproductive rates, making populations susceptible to localized extinction (Barclay and
Harder 2003). Bat populations may not be able to withstand the existing rate of wind turbine
fatalities (Arnett et al. 2008) or increased fatalities as the wind industry continues to grow.
Because North American bat population sizes are poorly known, it is difficult to determine
whether bat fatalities at wind facilities represent a significant threat of extinction, although
cumulative impacts raise concern and more studies are needed to assess population impacts
(Arnett et al. 2008).
The Wildlife Society has noted that fatalities of birds and bats have been reported at wind en-
ergy facilities worldwide, but baseline or systematically collected data against which to compare
studies of particular sites proposed for development are lacking. Large numbers of raptor kills in
California and bat kills in the eastern United States have heightened concern for some species and
sites. The Wildlife Society maintains that loss of wildlife habitat due to construction of turbines,
access roads, and power transmission networks, the footprint of turbine facilities, and increased
human access is an important issue that should be considered in the wind energy development
process (Wildlife Society 2008, 1).
Although wind power plants have relatively little impact on the natural environment compared
to other conventional power plants, there is increasing concern over noise produced by the rotor
blades, aesthetic (visual) impacts, and birds killed by flying into the rotors. On days with a light
breeze, a repetitive swoosh, high-pitched whistle, and stroboscopic flicker of light came from
220-foot-tall wind machines located less than 1,500 yards from a home in Maine, stimulating a
proposal for a local Dixmont ordinance requiring a one-mile setback from homes (Turkel 2009).
Such concerns have stimulated development of new ordinances in hundreds of U.S. communities,
often requiring performance bonds and site restoration upon decommissioning and establishing
noise standards, setback requirements, and regulation of “shadow flicker,” or shadows cast on
nearby surfaces by rotating turbine blades (USDOE 2011d).
Offshore Impacts
Similar difficulties attend offshore development of wind resources, where conflicts with commer-
cial fishing interests may influence location decisions so as to avoid entanglements with fishing
gear. Since offshore wind installations must be anchored to the seabed, they may create obstacles
to migration of marine mammals such as whales. Whether large offshore wind developments that
alter the topography of the coastline may have an impact on migration of birds in major flyways
is not well understood. Moreover, views of the “open ocean” may not appear so open and natural