posted: November 19, 2007 • Noise, U.K., Wildlife

Conservation of British Cetaceans

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Author: Parsons, E.C.M.; Clark, J.; and Ross, A.

The Conservation of British Cetaceans: A Review of the Threats and Protection Afforded to Whales, Dolphins and Porpoises in UK Waters

(EXTRACT)

1.3.2.1.7. Windfarms

In order to provide a source of renewable energy for the UK, there has been considerable investment in the development of alternative technologies and, in particular, windfarms. Due to competition over land use, land-based windfarms are becoming harder to site, therefore attention has become focused on marine windfarms. Although, on the one hand, being a renewable source of energy, windfarms have a positive environmental impact, on the other they could possibly have a negative impact on cetaceans due to the noise they produce and possible impacts on habitats and the marine ecosystem in general. Their potential to displace animals is one concern and one that it is particularly difficult to gauge, since so little is known about current cetacean distributions around the UK.

When in operation, windfarms produce a considerable amount of low frequency noise, which research has calculated increases background levels of marine noise by 80-110 dB. However, the construction of windfarms also produces considerable amounts of marine noise (260 dB), likewise the laying of submarine cables to service the windfarm site (176 dB). In fact, a study funded by a UK statutory authority investigated the possible effects on cetaceans (and marine fish) from noise and vibrations of offshore windfarms and determined that there would be significant effects during construction, with disturbance reactions likely to a distance of several kilometers. Close to windfarm construction (within 100 m) it was estimated that noise levels might be so severe that cetaceans may suffer acoustic trauma.

Disturbance reactions by cetaceans to noises produced by windfarms have also been documented. Researchers played back recordings of noises produced by a 2 MW wind turbine (frequency <800 Hz) and reported that the distance between harbour porpoise surfacings and the sound source significantly increased, and there was a significant increase in porpoise echolocation rates, thus indicating disturbance of the harbour porpoises by windfarm noise. This disturbance occurred even though, according to hearing sensitivity tests conducted on captive porpoises, the animals should not have been able to detect these low frequency sounds.

Another study monitored harbour porpoise acoustics both before and during construction of a 166 MW wind farm in the western Baltic Sea. The research discovered that porpoises were less frequently encountered by acoustic methods during the construction of the wind farm. In addition, during the pile driving phase of construction, porpoises were excluded from the study area for 27 hours, before returning. This study demonstrated a significant effect of windfarm construction on porpoises, in particular an extremely negative reaction to the noise produced by pile driving activity.

The complete 4-MB report (with references) is available from the Whale and Dolphin Conservation Society (click here).

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