Environmental Engineering Reference
In-Depth Information
Chapter 5
Barry Nicholls and Paul A. Racey
INTRODUCTION
Large numbers of bats are killed by collisions with wind turbines and there is at
present no accepted method of reducing or preventing this mortality. Following our
demonstration that bat activity is reduced in the vicinity of large air traffic control and
weather radars, we tested the hypothesis that an electromagnetic signal from a small
portable radar can act as a deterrent to foraging bats. From June to September, 2007
bat activity was compared at 20 foraging sites in northeast Scotland during experimen-
tal trials (radar switched on) and control trials (no radar signal). Starting 45 min after
sunset, bat activity was recorded for a period of 30 min during each trial and the order
of trials were alternated between nights. From July to September, 2008 aerial insects
at 16 of these sites were sampled using two miniature light-suction traps. At each site
one of the traps was exposed to a radar signal and the other functioned as a control.
Bat activity and foraging effort per unit time were significantly reduced during ex-
perimental trials when the radar antenna was fixed to produce a unidirectional signal
therefore maximizing exposure of foraging bats to the radar beam. However, although
bat activity was significantly reduced during such trials, the radar had no significant
effect on the abundance of insects captured by the traps.
The UK government is committed to ensure that 10% of the country's electricity
will be generated from renewable sources by 2010 with an aspiration to double this
fi gure by 2020. Unfortunately, the drive to ameliorate the indirect impact of energy
production on the environment has led to a more immediate impact on local fauna. The
exploitation of wind as a renewable and pollution-free source of energy has led to the
proliferation of wind farms across the UK where 206 are currently operational, com-
prising 2,381 turbines and with an estimated 444 sites proposed for future develop-
ment [1]. Several studies have highlighted the problem of birds colliding with turbines
placed along traditional migratory routes [2-6] but until recently the impact of wind
turbines on bats has received little attention.
The scale of the problem became apparent in 2004 when, during a 6-week pe-
riod, an estimated 1,764 and 2,900 bat fatalities were recorded at two wind farms in
Pennsylvania and West Virginia respectively [7]. The number of collision mortalities
reported in America are greater than in Europe, where surveys have begun more re-
cently. However, 15 of the 35 species of European bat have been recorded as regular
victims of turbine collisions, and an Intersessional Working Group of Eurobats listed
20 species thought to be at risk of collision due to their foraging and commuting
behavior [8]. Currently, research in Europe is concentrated on arriving at scientifi -
cally credible mortality estimates to assess the extent of the problem. Although this
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