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Environmental Impact of W ind Projects 249

birds. As the examples illustrate, putting the environmental impact of
wind farm in context will help all stakeholders make better informed
decisions.

Temporal and Spatial Scale
Environmental impact of a wind farm is easier to assess locally and
for a short duration. For instance, the impact of a wind farm over a
few years into the future and over tens of kilometers from the wind
farmisroutinelydone.However,windfarmshaveimpactoveramuch
larger timeframe, for example, loss of birds and bats that have long life
span and do not reproduce frequently can have a significant impact
over a longer timeframe. As a second example, consider the spatial
scale, fossil fuel-based energy-generation plants have a global impact
because of climate change caused by greenhouse gas emissions. In
the final example, consider the impact of wind turbines on a larger
spatial scale: Turbines placed in the path of migratory birds can have
impacts on bird populations that live thousands of kilometers away.
As the examples illustrate, an EIA must be performed over several
temporal and spatial scales in order to obtain a more comprehensive
understanding of the impact.

Cumulative Effects
Understanding the impact of single actions is an easier task than un-
derstanding the impact of past, current, and future actions. For ex-
ample, the impact of installing a few turbines on a wildlife habitat
may not be large, but past or subsequent wind developments in the
sameregionmayfragmentthehabitattoanextentthatthesurvivalofa
species in that region may be at risk. Another example is development
of wind farms along the migratory path of birds that cover hundreds
to thousands of miles. In regions where migratory bird paths coin-
cide with high-wind areas, a single wind farm may be acceptable, but
the cumulative effect of wind farms dotted along the migratory bird
path may cause harm that is an order of magnitude higher that pre-
dicted by single installation. As the two examples illustrate, an EIA
must examine the combined impact of multiple wind projects on the
environment.

Quick Comparison of Wind Versus Fossil Fuel–Based
Electricity Production
In the United States, the amount of greenhouse gases (CO 2 ,NO x , and
SO 2 ) emitted by coal and natural gas power plants is presented in
Table 12-1.