Scottish Government's Energy Strategy (Dec 2017) set a 2030 target for 50% of the energy for Scotland's heat, transport, and electricity consumption to be supplied by renewable sources, and the Climate Change (Emissions Reduction Targets) (Scotland) Act 2019 sets a target of net-zero greenhouse gas emissions by 2045. These targets will require the development of extensive areas for marine renewable energy extraction. In October 2020, the Scottish Government published the Sectoral Marine Plan for Offshore Wind (SMP; Scottish Government, 2020), which identified the most sustainable plan options for the future development of commercial-scale offshore wind energy in Scotland. With six operational offshore wind farms in Scotland, and a further eight having received consent, in January 2022 the Crown Estate Scotland announced the results of a further leasing round ('ScotWind'). Seventeen proposed projects within 14 of the 15 Plan Options now have lease option agreements, covering over 7,000 km2 of seabed in Scotland, with a total generating capacity of nearly 25 GW. These projects are predominantly off the north and east coasts of mainland Scotland, in waters beyond the 12 nm territorial limit (Figure 1; Crown Estate Scotland, 2022).Unleased areas, including Plan Option NE1, underwent a Clearing process which closed on 10 May 2022, and resulting Option Agreements from the Clearing process will be signed in Autumn 2022. In February 2022, Marine Scotland published an Initial Plan Framework for a Sectoral Marine Plan for Innovation and Targeted Oil and Gas Decarbonisation (INTOG; Scottish Government, 2022). This provides potential areas for future seabed leasing for small scale innovation and offshore wind farms specifically for the purpose of providing low carbon electricity to power oil and gas installations and help to decarbonise the sector. These areas are all in the north and east of Scotland, therefore potential new offshore wind farm projects could come forward in these locations in the future.
The need to ensure that future offshore developments do not adversely impact Scotland's internationally important marine environment is embedded in the aims of both the National Marine Plan (NMP; Scottish Government, 2015) and SMP. In addition, Habitat Regulation Appraisals and Strategic Environmental Assessments require evaluation of potential impacts of proposed marine developments on marine biodiversity, and on other marine users. The SMP, which assessed for up to 10 GW maximum installed capacity at a national level, identified the key risk factors of development in all Plan Option regions include "risks to bird species, including collision risk and displacement, as well as potential impacts to birds on migratory pathways".
A number of frameworks and tools have been developed to assess the vulnerability and sensitivity of seabird species to marine pressures (e.g. Williams et al., 1995, Furness and Wade, 2012, Furness et al., 2013, Bradbury et al., 2014, Certain et al., 2015, Rogerson et al., 2021), to quantify risk of collision with offshore turbines (Band et al., 2007, McGregor et al., 2018), to apportion impacts of marine development to particular breeding populations (NatureScot, 2018) and to estimate survival consequences for seabirds of displacement from former foraging areas (Searle et al., 2018, Searle et al., 2019). Implementing these frameworks and tools requires key information about the distribution, ecology, morphology, behaviour, and population status of the species of interest. For example, knowledge of species' population sizes and marine distributions is required to assess overlap with licensing areas for offshore wind farms, and the density of birds within these areas of overlap; factors such as flight height and levels of nocturnal activity will influence a species' vulnerability to collision, and an understanding of a species' behaviour is important for determining the probability and scale of avoidance of an offshore development, and therefore the levels of displacement or barrier effects. In addition, seabird species that are nocturnally active, such as Manx Shearwaters, European and Leach's Storm-petrels are potentially vulnerable to attraction to artificial lighting (Rodríguez et al., 2019) such as that associated with offshore wind structures and related shipping. Structures associated with offshore wind farms in UK waters are required to display illumination to meet the lighting requirements of the Air Navigation Order 2009 (CAA, 2016), the Northern Lighthouse Board, and the Maritime and Coastguard Agency. Attraction to illumination associated with offshore wind farms may affect the risk of collision for these nocturnally active procellariiform seabird species. This key information is not currently synthesised for Procellariiformes in Scotland and, given the rapidly increasing activity relating to offshore wind farms in the country, there is a clear and urgent need to do so. The current ScotWind leasing round, and potential future rounds, are likely to include areas to the north and west of Scotland not previously developed, and in closer proximity to the breeding colonies and foraging areas of procellariform seabirds.
Here we present a review of the published literature to collate and synthesise the existing evidence base for the assessment of the impacts of offshore wind farms and associated activities on three focal species: Manx Shearwater Puffinus puffinus, European Storm-petrel Hydrobates pelagicus and Leach's Storm-petrel Hydrobates leucorhous. We have included less detailed accounts for two additional procellariiform species: Northern Fulmar Fulmaris glacialis and Sooty Shearwater Ardenna grisea. We identify critical gaps in existing knowledge, outline the challenges to filling data gaps, and make recommendations for possible approaches for improving the existing evidence base. Preliminary findings were shared with subject experts, and through two online workshop we clarified the state of existing knowledge and critical knowledge gaps, especially in relation to the attraction of focal species to artificial lighting of offshore renewable structures and support vessels. We include particular reference to Scotland's Sectoral Marine Plan Options, the specific risks posed to nocturnally active petrels and shearwaters by artificial lighting, and how light attraction may influence assessment of other risks (e.g. collision). We outline potential mitigation methods.