WMOD00469

• Title: Environmental Impact of Large Windpower Farms
• Weather Modification - Doc Type: Report

As a framework for analyzing the impact of land-use changes on
animals, a workshop group of animal biologists has adopted
consideration of "indicator species" selected as typical of a
class of animal/habitat relationships (Bureau of Reclamation,
1977). Among large mammals, they identified pronghorn antelopE~
and elk as indicator species for the high plains and Rocky Mountains
and likewise the most important species in their respective
classes. Both classes are affected by changes in food supply Clnd
availability of shelter. The pronghorn class is affected, in
addition, by encroachment of civilization and human artifacts.
If wi ndfarms were to occupy areas that are now pronghorn range,.
the distribution and population of these animals \'/ould be adver'sely
affected. Elk and other animals of their class (including mule
deer) are relatively tolerant of such encroachment and would
probably not be adversely affected.

Three classes of birds may be consider'ed in their relationship to
windfarms: birds that nest in the area, birds that migrate
through the area, and birds of prey. Birds that nest in the area
are primarily affected by changes in food supply and shelter or
nesti ng si tes. Si nee wi ndfarm use woul d not affect these primalry
elements, and since these birds do not ordinarily fly high enough
to be in conflict with the moving blades of windpowered generators,
no considerable impact is to be expected.

For migrating birds, the situation may be different, especially
for species accustomed to migrate by night at elevations above
the ground where the moving blades might strike them. Field
experience is limited. Bird kills have been carefully monitored
at the Plum Brook, Ohio installation of the NASA Mod 0 windpowered
generator with generally negative results. This experience may
not be representative of windfarm conditions, however, where the
presence of many machines might add to the birds' confusion and
where windfarm locations might coincide with flyways of particular
migratory species. One can calculate from crude assumptions what
losses might be suffered by a flock of birds flying through a
certa in number of rows of wi nd machi nes if they took no evasive'
action. The result, loss of one bird in fifty, serves only to
suggest that windfarms as a hazard to migrating birds will be
small in comparison with existing natural hazards, especially
severe storms, and that they pose no danger to survival of the
species. The actual outcome will be affected by whether flyways
tend to avoid especially windy locations, whether the birds stay
grounded or fly beneath blade level during periods of stronger
winds, and even whether they are flying upwind, downwind, or
crosswind. Better knowledge of the impact will come only from
experience at individual windfarm locations.

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