OFW: Harbour Porpoises in German Bight Unaffected by Pile Driving

Pile driving during construction of offshore wind farms in the German North Sea has little to no effect on local harbour porpoise population, according to a study commissioned by the Offshore-Forum Windenergie (OFW) in partnership with the offshore wind industry leaders. 

“The study shows that offshore wind farms have no negative consequences for the harbor porpoise population,” said Ursula Prall, chairwoman of OFW.

Indeed, despite constantly increasing foundation work, the porpoise population remained constant, and two subzones even saw an increase in the population throughout the course of the project, even though noise mitigation measures were just beginning to be developed and implemented during the study period, OFW said.

In 2014, the OFW – together with several companies from the offshore wind energy sector and the German OFFSHORE WIND ENERGY Foundation – commissioned three research companies and institutes, BioConsult SH, IBL Umweltplanung, and IfAÖ, to study the disruptive effects of pile driving noise on harbor porpoises in the German exclusive economic zone of the North Sea.

A number of wind farm operators and developers, who built eight offshore wind farms with a total of 400 foundations in the German Bight between 2009 and 2013 and/or are currently planning wind farms, provided details from studies conducted for the construction of the wind farms. The researchers also looked at porpoise counts for seven other projects being planned at the time.

Details of foundation installations, data from underwater noise measurements, and harbor porpoise population numbers determined via C-POD and aerial surveys served as the basis of the analyses. For the first time, a large amount of data from individual wind farm projects in the German Bight was collated in one joint database.

The results show that while pile driving occurs, the animals tend to avoid the area for a short time, with a clear distance-based gradient. This reaction was observed for all pile driving work with and without noise mitigation starting at 143 decibels (SEL) for a distance of up to 17 kilometers, according to the study.

When taking into account only pile driving with noise mitigation measures, the animals avoided up to 14 kilometers around the area. Even in near areas with noise levels of more than 155 decibels (SEL), not all of the animals went elsewhere, according to the study. Instances of porpoises becoming more or less sensitive as a result of increased pile driving in the studied time period were not observed or were observed only to a very small extent, the study has shown.

OFW commissioned the study in co-operation with Dong Energy Wind Power A/S, EnBW Energie Baden-Württemberg AG, E.ON Climate and Renewables GmbH, Global Tech I Offshore Wind GmbH, Horizont II Renewable GmbH, Iberdrola Renovables Offshore Deutschland GmbH, Nordsee Offshore MEG I GmbH, Ocean Breeze Energy GmbH & Co. KG, Offshore Deutschland GmbH, Offshore Windpark RIFFGAT GmbH & Co. KG, OWP Butendiek GmbH & Co. KG, PNE WIND AG, innogy SE, STRABAG OW EVS GmbH, Tennet Offshore GmbH, Trianel Windkraftwerk Borkum GmbH & Co. KG, Vattenfall Europe Windkraft GmBH, WindMW GmbH, wpd offshore solutions GmbH, and the German OFFSHORE WIND ENERGY Foundation.

Earlier this month, World Wildlife Fund UK released a study which suggested that using noise reduction measures to bring down noise levels by the equivalent of around 8dB would reduce the risk of a 1% annual decline in the North Sea population of harbour porpoises by up to 96%.