Abstract
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 experimental trials (radar switched on) and control trials (no radar signal). Starting 45 minutes after sunset, bat activity was recorded for a period of 30 minutes 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 experimental trials when the radar antenna was fixed to produce a unidirectional signal therefore maximising 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.
Highlights
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 figure by 2020
All foraging sites were located within a 100 km radius of Aberdeen in northeast Scotland and were separated by a minimum straight-line distance of .1 km to ensure independence. Twelve of these sites were located within riparian habitats and the remainder along the edge of woodland where the radar signal would not be attenuated by any obstruction
When the radar antenna was fixed to emit a unidirectional signal a fourfold increase in field strength was observed at all distances (Table 1)
Summary
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 figure by 2020. 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, comprising 2381 turbines and with an estimated 444 sites proposed for future development [1]. The scale of the problem became apparent in 2004 when, during a six-week period, an estimated 1,764 and 2,900 bat fatalities were recorded at two wind farms in Pennsylvania and West Virginia respectively [7]. Research in Europe is concentrated on arriving at scientifically credible mortality estimates to assess the extent of the problem. This is clearly important, the rapid proliferation of wind turbines requires a more urgent response. Research has to be focussed on the underlying reasons behind these collisions and potential methods of mitigation to prevent what is undoubtedly an increasing threat to bat populations
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