Understanding Wind Power Systems - Wind Power: Politics and Policy - page 51

ten million birds pass through the site each year, the mortality rate is less
signiicant. In order to evaluate the bigger picture, a statistic known as bird
risk is commonly used. Bird risk is deined as the number of bird fatalities as
a percentage of the total number of birds observed in the area. 75
Unfortunately this metric exhibits all of the potential problems associ-
ated with estimating bird mortality plus a host of other confounding threats
associated with estimating the number of birds passing through an area.
First, birds migrate into and out of habitats. Accordingly, bird numbers are
rarely consistent throughout the day, month, or year. Second, some birds
are nocturnal. his poses obvious enumeration challenges. hird, diferent
birds ly at diferent heights and so the threat posed is not the same for all
species. Finally, as implied earlier, avoiding fatalities of endangered birds
should take priority. herefore, enumeration eforts should ideally endeavor
to separate endangered species from commonly found species. In practice,
this is hard to accomplish. 76
here are two useful lessons to draw from these observations. First, mor-
tality studies can provide insight into the potential for public opposition
from groups that are concerned about avian welfare. However, such studies
are only useful if they avoid the threats to validity outlined earlier. Second,
policymakers who reference avian mortality studies in order to gain insight
into the threat that a wind energy project poses to the avian population
should do so with a critical mindset. he methodology supporting the data
should be clearly understood in order to ascertain the limitations associated
with the study's conclusions. Absolute declarations of safety based on sub-
jective assumptions can inadvertently inlame public opposition. Similarly,
estimates of harm can be overstated.
2.6.3 Degradation of Animal Habitat
Disruptions to animal habitats associated with construction and operation
of a wind facility can signiicantly inluence foraging patterns and under-
mine the continued viability of the area to support resident species. 77 More
efective planning can signiicantly mitigate threats to ecosystem integrity
at the site preparation, construction, and operation stages.
Ecosystem-friendly site design requires a reassessment of the traditional
approach to site development, which typically begins by clearing all vegeta-
tion from a site and leveling the site with bulldozers. Clearing a site in this
manner creates ecologically barren wastelands that uproot animal habitats,
disrupt foraging patterns and fragment animal populations. 78 his is true
even if new vegetation is planted once construction is completed. he level