Abstract
ORJIP Offshore Wind launched its second stage with the objective of identifying, prioritising and selecting research to reduce consenting risk for offshore wind. The application of seabird mortality rates associated with predicted displacement from offshore wind farms was identified as an important area for research, as the mortality rate values currently used for displaced birds lack sufficient evidence base and poorly communicate any associated uncertainty, which reduces their defensibility. This project aims to review the ranges of mortality rates currently used for displaced birds and provide recommendations for their improvement.
The Joint SNCB (Statutory Nature Conservation Bodies) Interim Displacement Advice Note provides advice on how to present assessment information on the extent and potential consequences of seabird displacement from Offshore Wind Farm (OWF) developments (JointSNCB 2017). This advice requires assessments to use published indices of disturbance (e.g., Furness et al. 2013; Wade et al. 2016) to assign a range of displacement levels for each species individually, with consideration of modifications arising from emerging new evidence and discussions with SNCBs to agree appropriate levels of likely adult mortality associated with particular displacement levels, for each species individually (acknowledging that data are very limited at this time). Assessments should then use these two metrics (displacement rate and displacement mortality rate) to estimate displacement impacts. The advice specifies that this table should be presented from 0-100%, in 10% increments for displacement levels. Percentage increments for mortality should also be presented between 0-100% but including smaller increments at lower values (e.g., 0%, 1%, 2%, 5%, 10%, 20%, etc).
The estimation of displacement mortality rates is therefore a critical component of the assessment process, with large influence upon resulting offshore wind farm impacts on affected populations. However, there is very little empirical evidence upon which this rate may be based. Importantly, a recent Marine Scotland project, Scottish waters east region – regional sectoral marine plan - SEANSE, suggested that the use of an individual-based model, SeabORD (Searle et al. 2014, 2018), indicates mortality rates from displacement and barrier effects are likely to be higher than those used in the displacement matrix for Round 3 sites (Searle et al. 2020). The displacement matrix outputs are based on SNCB advice on, what are assumed to be, precautionary values. However, the outputs from SeabORD are based on “the latest available data and understanding of the ecology of seabirds”. Neither approach has been compared to empirical values of displacement or mortality as a consequence of displacement.
This report reviews the displacement mortality rates used to determine the mortality of birds displaced by offshore wind farms in the United Kingdom, the key factors influencing mortality rates from displacement, the tools and methods for estimating displacement mortality and identifies relevant datasets that could be used to estimate empirical values for the demographic consequences of displacement.
This study focuses on six key species considered to be at greater potential risk of displacement and displacement mortality in future offshore wind farm development in the UK:
• Black-legged kittiwake Rissa tridactyla (hereafter ‘kittiwake’),
• Common guillemot Uria aalge (hereafter ‘guillemot’),
• Razorbill Alca torda,
• Atlantic Puffin Fratercula arctica (hereafter ‘puffin’),
• Red-throated diver Gavia stellata, and
• Northern Gannet Morus bassanus (hereafter ‘gannet’).