Avoidance of wind farms by harbour seals is limited to pile driving activities

Abstract

Summary As part of global efforts to reduce dependence on carbon‐based energy sources there has been a rapid increase in the installation of renewable energy devices. The installation and operation of these devices can result in conflicts with wildlife. In the marine environment, mammals may avoid wind farms that are under construction or operating. Such avoidance may lead to more time spent travelling or displacement from key habitats. A paucity of data on at‐sea movements of marine mammals around wind farms limits our understanding of the nature of their potential impacts.Here, we present the results of a telemetry study on harbour seals Phoca vitulina in The Wash, south‐east England, an area where wind farms are being constructed using impact pile driving. We investigated whether seals avoid wind farms during operation, construction in its entirety, or during piling activity. The study was carried out using historical telemetry data collected prior to any wind farm development and telemetry data collected in 2012 during the construction of one wind farm and the operation of another.Within an operational wind farm, there was a close‐to‐significant increase in seal usage compared to prior to wind farm development. However, the wind farm was at the edge of a large area of increased usage, so the presence of the wind farm was unlikely to be the cause.There was no significant displacement during construction as a whole. However, during piling, seal usage (abundance) was significantly reduced up to 25 km from the piling activity; within 25 km of the centre of the wind farm, there was a 19 to 83% (95% confidence intervals) decrease in usage compared to during breaks in piling, equating to a mean estimated displacement of 440 individuals. This amounts to significant displacement starting from predicted received levels of between 166 and 178 dB re 1 μPa(p‐p). Displacement was limited to piling activity; within 2 h of cessation of pile driving, seals were distributed as per the non‐piling scenario. Synthesis and applications. Our spatial and temporal quantification of avoidance of wind farms by harbour seals is critical to reduce uncertainty and increase robustness in environmental impact assessments of future developments. Specifically, the results will allow policymakers to produce industry guidance on the likelihood of displacement of seals in response to pile driving; the relationship between sound levels and avoidance rates; and the duration of any avoidance, thus allowing far more accurate environmental assessments to be carried out during the consenting process. Further, our results can be used to inform mitigation strategies in terms of both the sound levels likely to cause displacement and what temporal patterns of piling would minimize the magnitude of the energetic impacts of displacement.

Seal monitoring and evaluation for the Gemini offshore windfarm: Tconstruction - 2015 report

“…Potentially, a significant contribution to understanding the long-term responses of harbour seals to wind farm construction, and possibly operation could be made (like for example in Russell et al 2016). …”

“…The nearest large port to Gemini windfarm is Eemshaven and a submarine power-cable was installed during 2015 to connect the windfarm to this port. Of all the activities involved with offshore windfarms, pile driving has the largest expected immediate, but short term, impact on marine fauna (Madsen et al 2006;Russell et al 2016). Pile driving into the sediment of monopiles produces high-impact, broadband noise and pressure waves.…”

Aerial low-frequency hearing in captive and free-ranging harbour seals (Phoca vitulina) measured using auditory brainstem responses

“…Seals have been found to use anthropogenic structures (Russell et al 2014) and anthropogenic signals that indicate locations of interest (Stansbury et al 2015). It is likely that they also developed strategies to minimise noise exposure by avoiding high exposure locations (Russell et al 2016). However, such choices may only be viable if there are alternative, suitable habitats available.…”

A decision framework to identify populations that are most vulnerable to the population level effects of disturbance

“…As a result, assessment of the population-level effects of disturbance caused by human activities is a component of many impact assessments for example, under the European Habitats Directive 92/43/EEC. Behavioral responses can result in changes in habitat use (e.g., Russell et al, 2016), vigilance (e.g., Armitage, 2004), and movement patterns (e.g., Fortin et al, 2005). Behavioral responses can result in changes in habitat use (e.g., Russell et al, 2016), vigilance (e.g., Armitage, 2004), and movement patterns (e.g., Fortin et al, 2005).…”