11.12. Cumulative Effects Assessment

11.12.1. Methodology

  1. The CEA assesses the impacts associated with the Array together with other relevant plans, projects and activities. Cumulative effects are defined as the combined effect of the Array in combination with the effects from a number of different projects, on the same receptor or resource. Further details on CEA methodology are provided in volume 1, chapter 6.
  2. The projects and plans selected as relevant to the CEA presented within this chapter are based upon the results of a screening exercise (see volume 3, appendix 6.4). Volume 3, appendix 6.4 further provides information regarding how information pertaining to other plans and projects is gained and applied to the assessment. Each project or plan has been considered on a case-by-case basis for screening in or out of this chapter's assessment based upon data confidence (the availability and accuracy of quantitative information, and the confidence that the information is likely to reflect the project’s consented design), impact-receptor pathways and the spatial/temporal scales involved. All projects screened out are detailed within volume 3, appendix 6.4.
  3. In undertaking the CEA for the Array, it should be noted that other projects and plans under consideration will have differing potential for proceeding to an operational stage and hence a differing potential to ultimately contribute to a cumulative impact alongside the Array. Therefore, a tiered approach has been adopted which provides a framework for placing relative weight upon the potential for each project/plan to be included in the CEA to ultimately be realised, based upon the project/plan’s current stage of maturity and certainty in the project’s parameters. The tiered approach which will be utilised within the Array CEA employs the following tiers:
  • tier 1 assessment – Array and Proposed offshore export cable corridor(s) and Proposed onshore transmission infrastructure and all plans/projects which became operational since baseline characterisation, those under construction, and those with consent and submitted but not yet determined;
  • tier 2 assessment – All plans/projects assessed under Tier 1, plus those projects with a Scoping Report; and
  • tier 3 assessment – All plans/projects assessed under Tier 2, which are reasonably foreseeable, plus those projects likely to come forward where an Agreement for Lease (AfL) has been granted.
  1. For consistency with the finalised CEA long list presented in volume 3, appendix 6.4, (which was finalised at the end of March 2024, three months prior to submission of the Array EIA Report), Table 11.36 provides a detailed overview of all screened in projects. However, it is important to note that where detailed quantitative analysis was undertaken, the cumulative assessment only considered project-specific data up to January 2024 (six months prior to submission of the Array EIA Report), as outlined in the Ossian Array EIA Scoping Report (Ossian OWFL, 2023) and agreed as part of the Ossian Array Scoping Opinion (MD-LOT, 2023). Project information available at the end of March 2024 has been considered qualitatively within the CEA.
  2. Table 11.36   Open ▸ only includes projects which have been assigned tier 1 or tier 2, with tier 3 projects not listed. This is due to tier 3 projects being predominantly ‘proposed’ or only identified in development plans, and so may not actually be taken forward. Projects under construction are likely to contribute to cumulative impacts (providing effect or spatial pathways exist), whereas those proposals (listed as tier 3 projects) not yet approved are less likely to contribute to such an impact, as some may not achieve approval or may not ultimately be built due to other factors. Tier 3 projects are detailed within volume 3, appendix 6.4.
  3. Some of the potential impacts considered within the Array alone assessment are specific to a particular phase of development (e.g. construction, operations and maintenance or decommissioning). Where the potential for cumulative effects with other plans or projects only have potential to occur where there is spatial or temporal overlap with the Array during certain phases of development, impacts associated with a certain phase may be omitted from further consideration where no plans or projects have been identified that have the potential for cumulative effects during this period.
  4. In addition, some of the projects considered cumulatively only have potential to impact species during a specific season (e.g. breeding or non-breeding seasons). During the breeding season, projects within a species’ foraging range were considered as there is the potential for individuals to have connectivity to the Array area and the other plans/projects specific to each species. Foraging ranges by Woodward et al., (2019) were used. Within the non-breeding season all developments within the BDMPS area relevant to a species (Furness, 2015) are included. As such, all ‘breeding season’ projects are also included within the non-breeding period given that the BDMPS areas defined by Furness (2015) are larger than the breeding foraging ranges. Additional projects not included within a breeding season assessment may be included within the non-breeding season assessment. Projects considered for each species during each season are presented within Table 11.36   Open ▸ .
  5. It should be noted that the Greater Gabbard, Gunfleet Sands 1 and 2, Inner Dowsing, Lynn, Methil Demo and Scroby Sands are currently operational however, the operational consents for these projects expires before the Array becomes operational. These projects are therefore discounted from the CEA as there is no temporal overlap between the operational phases of these projects and the Array.
  6. Other aspects, such as indirect impacts associated with prey distribution and availability, are very difficult to quantify. Although it is acknowledged that cumulative effects related to these impacts are possible, the magnitude of these impacts is not considered to be significant at a population level for any offshore ornithology receptor. It should further be noted that some activities which may contribute to a cumulative effect related to these impacts (e.g. fishing activities) are considered to already be captured within the baseline conditions established in section 11.7 and therefore already taken into account. These impacts are therefore not considered further within the CEA. The impacts included and excluded from the cumulative assessment are detailed within Table 11.37   Open ▸ . The impacts included in the CEA are:
  • disturbance and displacement from the physical presence of wind turbines and maintenance activities; and
  • collision with wind turbines.

 

Table 11.36:
List of Other Projects and Plans Considered Within the CEA for Offshore Ornithology

Table 11.36: List of Other Projects and Plans Considered Within the CEA for Offshore Ornithology

 

Table 11.37:
Potential Cumulative Effects for Ornithological Receptors

Table 11.37:  Potential Cumulative Effects for Ornithological Receptors

 

Figure 11.4:
Location of Projects/Plans Screened into the Cumulative Effects Assessment for Offshore Ornithology

Figure 11.4: Location of Projects/Plans Screened into the Cumulative Effects Assessment for Offshore Ornithology


11.12.2. Maximum Design Scenario

  1. The MDS for the cumulative assessment is defined as the combination of design parameters for both the Array and all other relevant projects that would result in the greatest impact on VORs. Normally the cumulative MDS is identical to the sum of the MDS of each relevant project individually, but this is not necessarily the case – for example, a longer construction phase may be the MDS for a single project, but if that means that there is a reduction in the overlap with other relevant projects of the operational phase, then the cumulative MDS may consider a shorter construction phase. The MDSs identified in Table 11.38   Open ▸ have been selected as those having the potential to result in the greatest effect on an identified receptor or receptor group. The cumulative effects presented and assessed in this section have been selected from the details provided in volume 1, chapter 3 of the Array EIA Report as well as the information available on other projects and plans (see volume 3, appendix 6.4). Effects of greater adverse significance are not predicted to arise should any other development scenario, based on details within the Project Description (volume 1, chapter 3) (e.g. different wind turbine layout), to that assessed here, be taken forward in the final design scheme.

 

Table 11.38:
Maximum Design Scenario Considered for Each Impact as Part of the Assessment of Likely Significant Cumulative Effects on Offshore Ornithology

Table 11.38:  Maximum Design Scenario Considered for Each Impact as Part of the Assessment of Likely Significant Cumulative Effects on Offshore Ornithology

11.12.3. Cumulative Effects Assessment

  1. An assessment of the likely significance of the cumulative effects of the Array in combination with other plans and projects upon offshore ornithology receptors arising from each identified impact is given below.
  2. The CEA is limited by the data available upon which to base the assessment. Due to the age of developments in the North Sea and surrounding areas which have the potential to have a cumulative impact upon receptors, few have comparable datasets upon which to base an assessment. However, every effort has been made to obtain quantitative estimates for both displacement and collision from project-specific documentation. For displacement impacts this includes following the approach applied by many previous offshore wind farms using any available population data to calculate mean-pack or peak population estimates for use in displacement analyses.
  3. Additionally, older developments did not carry out certain impact assessments (e.g. displacement and/or collision risk) for species such as kittiwake, gannet, fulmar, Manx shearwater and gull species (herring gull, great black-backed gull and lesser black-backed gull) due to limited data at the time of assessment on the species’ behavioural response to the presence of offshore turbines. As such the CEA is carried out using data from offshore wind farms with available species data to do so. For projects in early stages (i.e. Tier 3), there was insufficient project information in the public domain to allow the effects to be reasonably understood and a cumulative assessment undertaken. Tier 3 projects have therefore not been included in the cumulative assessment below.
  4. For the cumulative assessment, impacts from Tier 1 and Tier 2 projects have been assessed together, with Tier 2 impacts included if there is sufficient data to do so. This provides the most precautionary impact on the population. If any Tier 2 project does not get consented/built, the assessment presented here still includes the impacts. The only Tier 2 projects with sufficient data, which therefore has been included within the assessment are Five Estuaries, North Falls and Outer Dowsing. All other Tier 2 projects ( Table 11.38   Open ▸ ) were at an early stage of planning at the time of writing, and there is therefore insufficient robust project information in the public domain to allow the effects to be reasonably understood and for them to be included within the cumulative assessment at this time. Impacts included from Five Estuaries, North Falls and Outer Dowsing may be subject to change following examination.

Disturbance and Displacement from the Physical Presence of Wind Turbines and Maintanence Activities

  1. There is potential for cumulative displacement as a result of operational activities associated with the Array cumulatively with other developments. Disturbance and subsequent displacement of seabirds during the construction phase is primarily centred around where construction vessels and piling activities are occurring. The activities may displace individuals that would normally reside within and around the area of sea where the Array is located. This in effect represents indirect habitat loss, which will potentially reduce the area available to those seabirds to forage, loaf and/or moult.
  2. The level of data available and the ease with which disturbance and displacement impacts can be combined across the wind farms is quite variable, reflecting the availability of relevant data for other projects and the approach to assessment taken. A maximum design approach would be to assume complete overlap in construction for all projects, while the minimum design approach would be to assume no overlap. The most realistic assumption is that at most there will be a degree of construction overlap (and hence increased vessel and helicopter activity), but that it will be limited to a small number of cumulative effects associated with projects and other activities and that the impact from construction and decommissioning will be small with no significant effects occurring.
  3. During the operations and maintenance phase, the presence of offshore wind turbines has the potential to directly disturb and displace seabirds that would normally reside within and around the area of sea where offshore wind farms are located. Displacement may contribute to individual birds experiencing fitness consequences, which at an extreme level could lead to the mortality of individuals. Cumulative displacement therefore has the potential to lead to effects on a wider scale.
  4. Impacts from tidal farms is still relatively unknown (Isaksson et al. 2020) due to the limited number and small spatial footprint of operational devices currently deployed in a few tidal lease sites (Fox et al., 2018). The study by Long (2017) stated that some displacement was detected during construction, but that numbers returned to around previous levels once turbines were installed and operational. Consequently, impacts from tidal farms is not considered in the cumulative assessment due to this uncertainty.
  5. The species assessed for cumulative displacement impacts were kittiwake, guillemot, puffin, razorbill and gannet. The predicted impact for fulmar from the Array represented less than 0.01% of the baseline mortality of all seasonal and annual regional populations. It is therefore considered that the Array will not materially contribute to any existing cumulative displacement impact on this species.
  6. There is no displacement impact from the Proposed onshore application. Whilst there may be a displacement resulting from maintenance/repair activities associated with the Proposed offshore export cable(s), any such displacement would be highly localised and temporary in nature, and is therefore expected to be negligible.

                        Tier 1 and Tier 2

                        Kittiwake
  1. The estimated abundance of kittiwake for the purpose of estimating displacement impacts is given in Table 11.39   Open ▸ . Estimated abundances for projects are those presented by Berwick Bank (SSE Renewables, 2022), for which NatureScot has not raised any concerns or noted any errors. In addition, estimates have been obtained from Green Volt Offshore Wind Farm (Green Volt, 2023), Pentland Floating Offshore Wind (Pentland Floating Offshore Wind Farm, 2022), West of Orkney (Offshore Wind Power Limited, 2023), North Falls (North Falls, 2023), Five Estuaries (Five Estuaries, 2023) and Outer Dowsing (Outer Dowsing, 2023) offshore wind farms, as those projects had not published their estimates at the time of the Berwick Bank application.

 

Table 11.39:
Kittiwake Cumulative Abundance Estimates

Table 11.39: Kittiwake Cumulative Abundance Estimates

 

  1. The cumulative displacement mortality is given in Table 11.40   Open ▸ (with Berwick Bank included) and Table 11.41   Open ▸ (with Berwick Bank excluded). Mortality is calculated using 30% displacement and a range of 1% to 3% mortality in all seasons, in line with guidance (NatureScot, 2023h). Additionally, the Applicant’s Approach which utilises a 30% displacement rate and 1% mortality rate is presented.

 

Table 11.40:
Kittiwake Cumulative Displacement Mortality Estimates Inclusive of Berwick Bank

Table 11.40: Kittiwake Cumulative Displacement Mortality Estimates Inclusive of Berwick Bank

 

  1. With Berwick Bank, and using the NatureScot rates, the estimated displacement mortality for kittiwake is 204 to 613 individuals in the pre-breeding season, 189 to 566 individuals in the breeding season and 248 to 744 individuals in the post-breeding season. This is equivalent to an increase in baseline mortality of 0.21% to 0.63% in the pre-breeding season, 0.46% to 1.39% in the breeding season and 0.19% to 0.57% in the post-breeding season. On an annual basis, the number of mortalities is estimated as 641 to 1,923 individuals, which equates to an increase in baseline mortality of 0.49% to 1.48% ( Table 11.40   Open ▸ ).
  2. When following the Applicant’s Approach, the estimated displacement mortality with Berwick Bank, for kittiwake is 204 individuals in the pre-breeding season, 189 individuals in the breeding season and 248 individuals in the post-breeding season. This is equivalent to an increase in baseline mortality of 0.21% in the pre-breeding season, 0.46% in the breeding season and 0.19% in the non-breeding season. On an annual basis, the number of mortalities is estimated as 641 individuals, which equates to an increase in baseline mortality of 0.49%.

 

Table 11.41:
Kittiwake Cumulative Displacement Mortality Estimates Exclusive of Berwick Bank

Table 11.41:  Kittiwake Cumulative Displacement Mortality Estimates Exclusive of Berwick Bank

 

  1. Without Berwick Bank and using the NatureScot rates, the estimated displacement mortality for kittiwake is 163 to 489 individuals in the pre-breeding season, 125 to 375 individuals in the breeding season and 214 to 643 individuals in the post-breeding season. This is equivalent to an increase in baseline mortality of 0.17% to 0.50% in the pre-breeding season, 0.31% to 0.92% in the breeding season and 0.17% to 0.50% in the post-breeding season. On an annual basis, the number of mortalities is estimated as 503 to 1,508 individuals, which equates to an increase in baseline mortality of 0.39% to 1.16% ( Table 11.41   Open ▸ ).
  2. When following the Applicant’s Approach, the estimated displacement mortality without Berwick Bank, for kittiwake is 163 individuals in the pre-breeding season, 125 individuals in the breeding season and 214 individuals in the post-breeding season. This is equivalent to an increase in baseline mortality of 0.17% in the pre-breeding season, 0.31% in the breeding season and 0.17% in the non-breeding season. On an annual basis, the number of mortalities is estimated as 503 individuals, which equates to an increase in baseline mortality of 0.39%.
  3. The upper range of the NatureScot Approach represents an increase in mortality of over 1% of baseline mortality with Berwick Bank included for the breeding season. Impacts estimated both with and without Berwick Bank included surpasses the 1% increase on an annual basis using the NatureScot rates. Therefore, to further assess the significance of this effect, a PVA has been carried out for kittiwake as described in volume 3, appendix 11.5.
                        PVA Assessment Including Berwick Bank
  1. When considering the impact during the breeding season on the regional population defined for the breeding season, using the most extreme scenario of the NatureScot approach (30% displacement and 3% mortality) and with Berwick Bank included, the PVA predicted that the Counterfactual Population Size (CPS) was 0.841 ( Table 11.42   Open ▸ ). The median population size was therefore projected to be 15.87% smaller than the unimpacted population over a 35 year time period, with a 50th centile value of 38.24. In terms of the population size, this means that the median of the impacted population fell within the 38th percentile of the unimpacted population (a value of 50 would indicate that they are the same). This suggests that the impacted scenario was still within the margin of error of the non-impacted scenario, and therefore there would likely be no adverse effect to the population. However, as outlined within volume 3, appendix 11.5, the Counterfactual of Population Growth Rate (CPGR) is considered a more robust metric compared to the CPS in this analysis due to the models being conducted with density independence, in line with NatureScot (2023k) guidance. The PVA model predicted that the CPGR was 0.995 ( Table 11.42   Open ▸ ) which translates to a median reduction of 0.48% in population growth rate after 35 years. Such a decrease indicates that this level of impact would not adversely affect the population and would likely remain undetectable against natural population fluctuations. Furthermore, it is not expected to significantly alter the background mortality rate.

 

Table 11.42:
Kittiwake 35 Year Cumulative PVA Results for Displacement Impacts Including Berwick Bank during the Breeding Season

Table 11.42 Kittiwake 35 Year Cumulative PVA Results for Displacement Impacts Including Berwick Bank during the Breeding Season

 

  1. When considering the annual impact on the annual regional population (which is defined as the largest of the seasonal regional populations), under the most extreme scenario (30% displacement and 3% mortality) and with Berwick Bank included, the PVA predicted that the CPS was 0.843 (Table 11.43). The median population size was therefore projected to be 15.69% smaller than the unimpacted population over a 35 year time period, with a 50th centile value of 39.48. In terms of the population size, this means that the median of the impacted population fell within the 39th percentile of the unimpacted population (a value of 50 would indicate that they are the same). This suggests that the impacted scenario was still within the margin of error of the non-impacted scenario, and therefore there would likely be no adverse effect to the population. However, as stated, the CPGR is considered a more robust metric compared to the CPS in this analysis due to the models being conducted with density independence, in line with NatureScot (2023k) guidance. The PVA model predicted that the CPGR was 0.995 (Table 11.43) which translates to a median reduction of 0.47% in population growth rate after 35 years. Such a decrease indicates that this level of impact would not adversely affect the population and would only result in a slight reduction in the growth rate currently seen in the BDMPS population and would therefore be undetectable against natural population fluctuations. Furthermore, it is not expected to significantly alter the background mortality rate.

 

Table 11.43.:
Kittiwake 35 Year Cumulative PVA Results for Displacement Impacts Including Berwick Bank on an Annual Basis

Table 11.43. Kittiwake 35 Year Cumulative PVA Results for Displacement Impacts Including Berwick Bank on an Annual Basis

 

  1. Based on the PVA results using the 30% displacement and 3% mortality rate of the NatureScot Approach, the magnitude of impact on the kittiwake population during the breeding season is considered to be of low magnitude.
  2. Based on the PVA results using the 30% displacement and 3% mortality rate of the NatureScot Approach, the magnitude of impact on the kittiwake population annually is considered to be of low magnitude.
                        PVA Assessment Excluding Berwick Bank
  1. When considering the annual impact on the annual regional population, under the most extreme scenario (30% displacement and 3% mortality) and with Berwick Bank excluded, the PVA predicted that the CPS was 0.875 ( Table 11.44   Open ▸ ). The median population size was therefore projected to be 12.53% smaller than the unimpacted population over a 35 year time period, with a 50th centile value of 41.88. In terms of the population size, this means that the median of the impacted population fell within the 41st percentile of the unimpacted population (a value of 50 would indicate that they are the same). This suggests that the impacted scenario was still well within the margin of error of the non-impacted scenario, and therefore there would likely be no adverse effect to the population. However, as stated the CPGR is considered a more robust metric compared to the CPS in this analysis due to the models being conducted with density independence, in line with NatureScot (2023k) guidance. The PVA model predicted that the CPGR was 0.996 ( Table 11.44   Open ▸ ) which translates to a median reduction of 0.37% in population growth rate after 35 years. Such a decrease indicates that this level of impact would not adversely affect the population and would only result in a slight reduction in the growth rate currently seen in the BDMPS population and would therefore be undetectable against natural population fluctuations. Furthermore, it is not expected to significantly alter the background mortality rate.

 

Table 11.44:
Kittiwake 35 Year Cumulative PVA Results for Displacement Impacts Excluding Berwick Bank on an Annual Basis

Table 11.44 Kittiwake 35 Year Cumulative PVA Results for Displacement Impacts Excluding Berwick Bank on an Annual Basis

 

  1. Based on the PVA results using the 30% displacement and 3% mortality rate of the NatureScot Approach, the magnitude of impact on the kittiwake population annually is considered to be of low magnitude.
                        Magnitude of impact
  1. The estimated mortality resulting from displacement during operation and maintenance was assessed for each season, and also on an annual basis by combining seasonal impacts and comparing them against the largest regional seasonal population (as set out in volume 3, appendix 11.3, and summarised in Table 11.20   Open ▸ ).
  2. Based on the displacement assessment, for the pre-breeding and post-breeding season with Berwick Bank included and following the NatureScot Approach using a 30% displacement and 1% mortality rate, the cumulative impact was perceived as low magnitude.
  3. Based on the displacement assessment, for the pre-breeding and post-breeding season with Berwick Bank included and following the NatureScot Approach using a 30% displacement and 3% mortality rate, the cumulative impact was perceived as low magnitude.
  4. Based on the displacement assessment, for the pre-breeding and post-breeding season with Berwick Bank included and following the Applicant Approach using a 30% displacement and 1% mortality rate, the cumulative impact was perceived as low magnitude.
  5. Based on the PVA results for the breeding season with Berwick Bank included and following the NatureScot Approach using a 30% displacement and 3% mortality rate, the impact from the cumulative assessment was perceived as low magnitude.
  6. Based on the displacement assessment, for the breeding season with Berwick Bank included and following the NatureScot Approach using a 30% displacement and 1% mortality rate, the cumulative impact was perceived as low magnitude.
  7. Based on the displacement assessment, for the breeding season with Berwick Bank included and following the Applicant Approach using a 30% displacement and 1% mortality rate, the impact from the cumulative assessment was perceived as low magnitude.
  8. Based on the  PVA results, on an annual basis with Berwick Bank included and following the NatureScot Approach using a 30% displacement and 3% mortality rate, the impact from the cumulative assessment was perceived as low magnitude.
  9. Based on the displacement assessment, on an annual basis with Berwick Bank included and following the NatureScot Approach using a 30% displacement and 1% mortality rate, the impact from the cumulative assessment was perceived as low magnitude.
  10. Based on the displacement assessment, on an annual basis with Berwick Bank included and following the Applicant Approach using a 30% displacement and 1% mortality rate, the impact from the cumulative assessment was perceived as low magnitude.
  11. Based on the displacement assessment, for the pre-breeding, breeding and post-breeding season with Berwick Bank excluded and following the NatureScot Approach using a 30% displacement and 3% mortality rate, the cumulative impact was perceived as low magnitude.
  12. Based on the displacement assessment, for the pre-breeding, breeding and post-breeding season with Berwick Bank excluded and following the NatureScot Approach using a 30% displacement and 1% mortality rate, the cumulative impact was perceived as low magnitude.
  13. Based on the displacement assessment, for the pre-breeding, breeding and post-breeding season with Berwick Bank excluded and following the Applicant Approach using a 30% displacement and 1% mortality rate, the cumulative impact was perceived as low magnitude.
  14. Based on the  PVA results, on an annual basis with Berwick Bank excluded and following the NatureScot Approach using a 30% displacement and 3% mortality rate, the impact from the cumulative assessment was perceived as low magnitude.
  15. Based on the displacement assessment, on an annual basis with Berwick Bank excluded and following the NatureScot Approach using a 30% displacement and 1% mortality rate, the impact from the cumulative assessment was perceived as low magnitude.
  16. Based on the displacement assessment, on an annual basis with Berwick Bank excluded and following the Applicant Approach using a 30% displacement and 1% mortality rate, the impact from the cumulative assessment was perceived as low magnitude.
  17. Kittiwake populations have been declining within the UK with Burnell et al. (2023) reporting that the population has decreased by 21%. However it is evident that this decline is attributed to the presence of other pressures such as poor prey resources which can impact productivity (Furness & Tasker, 2000; Frederiksen et al., 2008; Carroll et al., 2017) and challenges from climate change (Heath et al, 2012). The PVA indicated that cumulative mortality attributed to offshore wind farms would have a minimal impact on the overall population trajectory.
  18. The cumulative effect is predicted to be of national spatial extent, long-term duration, continuous and high reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore, considered to be low.
                        Sensitivity of the receptor
  1. In terms of behavioural response to offshore vessel traffic and helicopters, kittiwake are considered have a low vulnerability (Wade et al., 2016).
  2. Kittiwake is a qualifying interest for several SPAs likely to be connected to the Array (within the mean-max + SD foraging range), with several non-SPA colonies also within range and so the species is considered to be of international value. Refer to Table 6.2 of volume 3, appendix 11.1 for details of SPAs with connectivity to the Array with regards to kittiwake.
  3. Kittiwake lay two eggs and breed from the age of three onwards, typically living on average for 12 years (Burnell et al., 2023). Kittiwake have undergone decreases of approximately 57% in Scotland since the early 2000s. Surveys managed by the RSPB in 2023 have recorded indicative increases of 8% across a number of sites in Britain in 2023 when compared against a pre-HPAI baseline (Tremlett et al., 2024). Overall, kittiwake is deemed to have low recoverability.
  4. Kittiwake is deemed to be of low vulnerability, low recoverability and international value. The sensitivity of the receptor is therefore considered to be high.

                        Significance of the effect

  1. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of minor to moderate adverse significance. However, due to the pre-breeding season and post-breeding season falling below 1% and due to PVA results concluding there to be a low impact both with and without Berwick Bank and following both the NatureScot and Applicant’s Approach, it is considered that minor adverse significance is appropriate, which is not significant in EIA terms.
                        Guillemot
  1. The estimated abundance of guillemot for the purpose of estimating displacement impacts is given in Table 11.45   Open ▸ . Estimated abundances for projects are those presented by Berwick Bank (SSE Renewables, 2022), for which NatureScot has not raised any concerns or noted any errors. In addition, estimates have been obtained from Green Volt Offshore Wind Farm (Green Volt, 2023), Pentland Floating Offshore Wind (Pentland Floating Offshore Wind Farm, 2022), West of Orkney (Offshore Wind Power Limited, 2023), North Falls (North Falls, 2023), Five Estuaries (Five Estuaries, 2023) and Outer Dowsing (Outer Dowsing, 2023) offshore wind farms, as those projects had not published their estimates at the time of the Berwick Bank application.

 

Table 11.45:
Guillemot Cumulative Abundance Estimates

Table 11.45: Guillemot Cumulative Abundance Estimates

 

  1. The cumulative displacement mortality is given in Table 11.46   Open ▸ (with Berwick Bank included) and Table 11.47   Open ▸ (with Berwick Bank excluded). Mortality is calculated using 60% displacement and a range of 3% to 5% mortality in the breeding season and 1% to 3% mortality in the non-breeding season, in line with guidance (NatureScot, 2023h). Additionally, the Applicant’s Approach which utilises a 50% displacement rate and 1% mortality rate is presented.
Table 11.46:
Guillemot Cumulative Displacement Mortality Estimates Inclusive of Berwick Bank

Table 11.46: Guillemot Cumulative Displacement Mortality Estimates Inclusive of Berwick Bank

 

  1. With Berwick Bank, the estimated displacement mortality for guillemot, following the NatureScot Approach, is 2,406 to 4,010 individuals in the breeding season and 2,395 to 7,184 individuals in the non-breeding season. This is equivalent to an increase in baseline mortality of 1.98% to 3.29% in the breeding season and 1.12% to 3.35% in the non-breeding season. On an annual basis, the number of mortalities is estimated as 4,801 to 11,194 individuals, which equates to an increase in baseline mortality of 2.24% to 5.21% ( Table 11.46   Open ▸ ).
  2. When following the Applicant’s Approach, the estimated displacement mortality with Berwick Bank, for guillemot is 668 individuals in the breeding season and 1,995 individuals in the non-breeding season. This is equivalent to an increase in baseline mortality of 0.55% in the breeding season and 0.93% in the non-breeding season. On an annual basis, the number of mortalities is estimated as 2,664 individuals, which equates to an increase in baseline mortality of 1.24%.
  3. Without Berwick Bank, the estimated displacement mortality for guillemot, following the NatureScot Approach, is 1,071 to 1,786 individuals in the breeding season and 2,130 to 6,389 individuals in the non-breeding season. This is equivalent to an increase in baseline mortality of 0.88% to 1,47% in the breeding season and 0.92% to 2.98% in the post-breeding season. On an annual basis, the number of mortalities is estimated as 3,201 to 8,175 individuals, which equates to an increase in baseline mortality of 1.50% to 3.81% ( Table 11.47   Open ▸ ).

 

Table 11.47:
Guillemot Cumulative Displacement Mortality Estimates Exclusive of Berwick Bank

Table 11.47: Guillemot Cumulative Displacement Mortality Estimates Exclusive of Berwick Bank

 

  1. When following the Applicant’s Approach, the estimated displacement mortality with Berwick Bank, for guillemot is 298 individuals in the breeding season and 1,775 individuals in the non-breeding season. This is equivalent to an increase in baseline mortality of 0.25% in the breeding season and 0.83% in the non-breeding season. On an annual basis, the number of mortalities is estimated as 2,073 individuals, which equates to an increase in baseline mortality of 0.97%.
  2. The estimated cumulative displacement mortality therefore represents an increase in mortality of over 1% of baseline mortality, when including Berwick Bank or applying the NatureScot Approach range without Berwick Bank. Therefore, to further assess the significance of this effect, a PVA has been carried out for guillemot during the breeding season, non-breeding season and on an annual basis as described in volume 3, appendix 11.5.
                        PVA Assessment Including Berwick Bank
  1. When considering the impact during the breeding season on the regional population defined for the breeding season, using the NatureScot approach (60% displacement and 3% to 5% mortality) and with Berwick Bank included, the PVA predicted that the CPS was 0.299 to 0.130 (Table 11.48:). The median population size was therefore projected to be between 70.14% to 86.97% smaller than the unimpacted population over a 35 year time period, with a 50th centile value of 0. In terms of the population size, this implies that the median of the impacted population falls outside the percentile range of the unimpacted population (a value of 50 would indicate that they are the same). This suggests that this level of impact would have an adverse effect on the population, with an impact rate of 60% displacement and 3% to 5% mortality causing a population decline. However, as stated, the CPGR is considered a more robust metric compared to the CPS in this analysis due to the models being conducted with density independence, in line with NatureScot (2023k) guidance. The PVA model predicted that the CPGR was between 0.967 to 0.945 (Table 11.48:) which translates to a median reduction of 3.30% to 5.50% in population growth rate after 35 years. Such a decrease indicates that this level of impact would adversely affect the population. However, as noted earlier within section 11.11, research examining the displacement effects on guillemots indicates that a 50% displacement rate is more reflective, with this rate still regarded as precautionary (RoyalHaskoning, 2013; Peschko et al. 2020; APEM, 2022; MacArthur Green, 2023). Consequently, it is anticipated that the Applicant’s approach (incorporating a 50% displacement rate alongside a 1% mortality rate) leads to an estimate that aligns more closely with actual conditions. If the Applicant’s approach is followed, the increase in baseline mortality would be 0.55%. This level of impact would likely remain undetectable against natural population fluctuations. Furthermore, it would not significantly alter the background mortality rate.

 

Table 11.48:
Guillemot 35 Year Cumulative PVA Results for Displacement Impacts Including Berwick Bank during the Breeding Season

Table 11.48: Guillemot 35 Year Cumulative PVA Results for Displacement Impacts Including Berwick Bank during the Breeding Season

 

  1. When considering the impact during the non-breeding season on the regional population defined for the non-breeding season, using the NatureScot approach (60% displacement and 1% to 3% mortality) and with Berwick Bank included, the PVA predicted that the CPS was 0.904 to 0.739 ( Table 11.49   Open ▸ ). The median population size was therefore projected to be between 9.58% to 26.15% smaller than the unimpacted population over a 35 year time period, with a 50th centile value of 32.92 to 8.32. In terms of the population size, this implies that the median of the impacted population fell within the 32nd and 8th percentile of the unimpacted population (a value of 50 would indicate that they are the same). This suggests that, if a 60% displacement and 3% mortality rate was applied, this level of impact could have an adverse effect on the population. However, as stated, the CPGR is considered a more robust metric compared to the CPS in this analysis due to the models being conducted with density independence, in line with NatureScot (2023k) guidance. The PVA model predicted that the CPGR was between 0.997 to 0.992 ( Table 11.49   Open ▸ ) which translates to a median reduction of 0.28% to 0.84% in population growth rate after 35 years. Such a decrease indicates that this level of impact would not adversely affect the population and would likely remain undetectable against natural population fluctuations. Furthermore, it is not expected to significantly alter the background mortality rate. Additionally, as stated above, it is anticipated that the Applicant’s approach (incorporating a 50% displacement rate alongside a 1% mortality rate) leads to an estimate that aligns more closely with actual conditions. If the Applicant’s approach is followed, the increase in baseline mortality would be 0.93%. In addition, the guillemot population in the UK North Sea & Channel waters BDMPS is observed to be growing and the population is still expected to continue to grow and will be larger after 35 years than that which is currently recorded, even in the event of the largest impact.

 

Table 11.49:
Guillemot 35 Year Cumulative PVA Results for Displacement Impacts Including Berwick Bank during the Non-breeding Season

Table 11.49: Guillemot 35 Year Cumulative PVA Results for Displacement Impacts Including Berwick Bank during the Non-breeding Season

 

  1. When considering the annual impact on the annual regional population, under the NatureScot Approach (60% displacement and 1% to 3% mortality) and with Berwick Bank included, the PVA predicted that the CPS was 0.817 to 0.623 ( Table 11.50   Open ▸ ). The median population size was therefore projected to be between 18.31% to 37.71% smaller than the unimpacted population over a 35 year time period, with a 50th centile value of 17.72 to 1.52. In terms of the population size, this implies that the median of the impacted population fell within the 17th and 1st percentile of the unimpacted population (a value of 50 would indicate that they are the same). This suggests that, if a 60% displacement and 3% mortality rate was applied, this level of impact could have an adverse effect on the population. However, as stated, the CPGR is considered a more robust metric compared to the CPS in this analysis due to the models being conducted with density independence, in line with NatureScot (2023) guidance. The PVA model predicted that the CPGR was between 0.994 to 0.987 ( Table 11.50   Open ▸ ) which translates to a median reduction of 0.56% to 1.31% in population growth rate after 35 years. Such a decrease indicates that this level of impact could adversely affect the population. As stated previously, it is anticipated that the Applicant’s approach (incorporating a 50% displacement rate alongside a 1% mortality rate) leads to an estimate that aligns more closely with actual conditions. In addition, the guillemot population in the UK North Sea & Channel waters BDMPS is observed to be growing and the population is still expected to continue to grow and will be larger after 35 years than that which is currently recorded, even in the event of the largest impact.
  2. When following the Applicant’s Approach, the PVA predicted that the CPS was 0.894 ( Table 11.50   Open ▸ ). The median population size was therefore projected to be 10.60% smaller than the unimpacted population over a 35 year time period, with a 50th centile value of 31.04. In terms of the population size, this implies that the median of the impacted population fell within the 31st percentile of the unimpacted population (a value of 50 would indicate that they are the same). This suggests that the impacted scenario was still within the margin of error of the non-impacted scenario, and therefore there would likely be no adverse effect to the population. As stated the CPGR is considered a more robust metric compared to the CPS in this analysis due to the models being conducted with density independence, in line with NatureScot (2023) guidance. The PVA model predicted that the CPGR was 0.997 ( Table 11.50   Open ▸ ) which translates to a median reduction of 0.31% in population growth rate after 35 years. Such a decrease indicates that this level of impact would not adversely affect the population and would not trigger a risk of population decline and would only result in a slight reduction in the growth rate currently seen in the BDMPS population and would therefore be undetectable against natural population fluctuations. Furthermore, it is not expected to significantly alter the background mortality rate. In addition, the guillemot population in the UK North Sea & Channel waters BDMPS is observed to be growing and the population is still expected to continue to grow and will be larger after 35 years than that which is currently recorded, even in the event of the largest impact.

 

Table 11.50:
Guillemot 35 Year Cumulative PVA Results for Displacement Impacts Including Berwick Bank on an Annual Basis

Table 11.50: Guillemot 35 Year Cumulative PVA Results for Displacement Impacts Including Berwick Bank on an Annual Basis

 

                        PVA Assessment Excluding Berwick Bank
  1. When considering the impact during the breeding season on the regional population defined for the breeding season, using the NatureScot approach (60% displacement and 5% mortality) and with Berwick Bank excluded, the PVA predicted that the CPS was 0.409 ( Table 11.51   Open ▸ ). The median population size was therefore projected to be 59.08% smaller than the unimpacted population over a 35 year time period, with a 50th centile value of 0. In terms of the population size, this implies that the median of the impacted population falls outside the percentile range of the unimpacted population (a value of 50 would indicate that they are the same). This suggests that this level of impact would have an adverse effect on the population, with an impact rate of 60% displacement and 5% mortality causing a population decline. However, as outlined within volume 3, appendix 11.5, the CPGR is considered a more robust metric compared to the CPS in this analysis due to the models being conducted with density independence, in line with NatureScot (2023k) guidance. The PVA model predicted that the CPGR was 0.976 ( Table 11.51   Open ▸ ) which translates to a median reduction of 2.45% in population growth rate after 35 years. Such a decrease indicates that this level of impact would adversely affect the population. However, as noted earlier within section 11.11, it is anticipated that the Applicant’s approach (incorporating a 50% displacement rate alongside a 1% mortality rate) leads to an estimate that aligns more closely with actual conditions. If the Applicant’s approach is followed, the increase in baseline mortality would be 0.25%. This level of impact would likely remain undetectable against natural population fluctuations. Furthermore, it would not significantly alter the background mortality rate.

 

Table 11.51:
Guillemot 35 Year Cumulative PVA Results for Displacement Impacts Excluding Berwick Bank during the Breeding Season

Table 11.51: Guillemot 35 Year Cumulative PVA Results for Displacement Impacts Excluding Berwick Bank during the Breeding Season

 

  1. When considering the impact during the non-breeding season on the regional population defined for the non-breeding season, using the NatureScot approach (60% displacement and 3% mortality) and with Berwick Bank excluded, the PVA predicted that the CPS was 0.749 ( Table 11.52   Open ▸ ). The median population size was therefore projected to be 25.06% smaller than the unimpacted population over a 35 year time period, with a 50th centile value of 9.00. In terms of the population size, this implies that the median of the impacted population fell within the 9th percentile of the unimpacted population (a value of 50 would indicate that they are the same). This level of impact could have an adverse effect on the population. However, as stated, the CPGR is considered a more robust metric compared to the CPS in this analysis due to the models being conducted with density independence, in line with NatureScot (2023k) guidance. The PVA model predicted that the CPGR was 0.992 ( Table 11.52   Open ▸ ) which translates to a median reduction of 0.80% in population growth rate after 35 years. Such a decrease indicates that this level of impact would not adversely affect the population and would not trigger a risk of population decline and would only result in a slight reduction in the growth rate currently seen in the BDMPS population and would therefore be undetectable against natural population fluctuations. Furthermore, it is not expected to significantly alter the background mortality rate. As stated, it is anticipated that the Applicant’s approach (incorporating a 50% displacement rate alongside a 1% mortality rate) leads to an estimate that aligns more closely with actual conditions. If the Applicant’s approach is followed, the increase in baseline mortality would be 0.83%. In addition, the guillemot population in the UK North Sea & Channel waters BDMPS is observed to be growing and the population is still expected to continue to grow and will be larger after 35 years than that which is currently recorded, even in the event of the largest impact.

 

Table 11.52:
Guillemot 35 Year Cumulative PVA Results for Displacement Impacts Excluding Berwick Bank during the Non-breeding Season

Table 11.52: Guillemot 35 Year Cumulative PVA Results for Displacement Impacts Excluding Berwick Bank during the Non-breeding Season

 

  1. When considering the annual impact on the annual regional population, under the range of scenarios considered (60% displacement, 1% to 3% mortality) and with Berwick Bank excluded, the PVA predicted that the CPS was 0.874 to 0.708 ( Table 11.53   Open ▸ ). The median population size was therefore projected to be between 12.60% to 29.19% smaller than the unimpacted population over a 35 year time period, with a 50th centile value of 27.56 to 5.04. In terms of the population size, this implies that the median of the impacted population fell within the 27th and 5th percentile of the unimpacted population (a value of 50 would indicate that they are the same). This suggests that, if a 60% displacement and 3% mortality rate was applied, this level of impact could have an adverse effect on the population. However, as outlined within volume 3, appendix 11.5, the CPGR is considered a more robust metric compared to the CPS in this analysis due to the models being conducted with density independence, in line with NatureScot (2023) guidance. The PVA model predicted that the CPGR was between 0.996 to 0.991 ( Table 11.53   Open ▸ ) which translates to a median reduction of 0.37% to 0.95% in population growth rate after 35 years. Such a decrease indicates that this level of impact would not adversely affect the population and would not trigger a risk of population decline and would only result in a slight reduction in the growth rate currently seen in the BDMPS population and would therefore be undetectable against natural population fluctuations. Furthermore, it is not expected to significantly alter the background mortality rate. As stated, it is anticipated that the Applicant’s approach (incorporating a 50% displacement rate alongside a 1% mortality rate) leads to an estimate that aligns more closely with actual conditions. If the Applicant’s approach is followed, the increase in baseline mortality would be 0.97%. In addition, the guillemot population in the UK North Sea & Channel waters BDMPS is observed to be growing and the population is still expected to continue to grow and will be larger after 35 years than that which is currently recorded, even in the event of the largest impact.

 

Table 11.53:
Guillemot 35 Year Cumulative PVA Results for Displacement Impacts Excluding Berwick Bank on an Annual Basis

Table 11.53: Guillemot 35 Year Cumulative PVA Results for Displacement Impacts Excluding Berwick Bank on an Annual Basis

 

                        Magnitude of impact
  1. The estimated mortality resulting from displacement during operation and maintenance was assessed for each season, and also on an annual basis by combining seasonal impacts and comparing them against the largest regional seasonal population (as set out in volume 3, appendix 11.3, and summarised in Table 11.21   Open ▸ ).
  2. Based on the PVA results for the breeding season with Berwick Bank included and following the NatureScot Approach using the 60% displacement, 5% mortality rate, the magnitude of impact on the guillemot population during the breeding season is considered to be of medium magnitude.
  3. Based on the PVA results for the breeding season with Berwick Bank included and following the NatureScot Approach using the 60% displacement, 3% mortality rate the magnitude of impact on the guillemot population during the breeding season is considered to be of medium magnitude.
  4. Based on the displacement assessment, for the breeding season with Berwick Bank included and following the Applicant Approach using a 50% displacement and 1% mortality rate, the cumulative impact was perceived as low magnitude.
  5. Based on the PVA results for the non-breeding season with Berwick Bank included and following the NatureScot Approach using the 60% displacement, 3% mortality rate, the magnitude of impact on the guillemot population during the non-breeding season is considered to be of low magnitude.
  6. Based on the PVA results for the non-breeding season with Berwick Bank included and following the NatureScot Approach using the 60% displacement, 1% mortality rate, the magnitude of impact on the guillemot population during the non-breeding season is considered to be of low magnitude.
  7. Based on the displacement assessment, for the non-breeding season with Berwick Bank included and following the Applicant Approach using a 50% displacement and 1% mortality rate, the cumulative impact was perceived as low magnitude.
  8. Based on the PVA results using the 60% displacement and 3% mortality rate of the NatureScot Approach and with Berwick Bank included the magnitude of impact on the guillemot population on an annual basis is considered to be of low magnitude.
  9. Based on the PVA results using the 60% displacement and 1% mortality rate of the NatureScot Approach and with Berwick Bank included the magnitude of impact on the guillemot population on an annual basis is considered to be of low magnitude.
  10. Based on the PVA results using the Applicant’s Approach of 50% displacement and 1% mortality and with Berwick Bank included the magnitude of impact on guillemot population on an annual basis is considered to be of low magnitude.
  11. Based on the PVA results for the breeding season with Berwick Bank excluded and following the NatureScot Approach using the 60% displacement, 5% mortality rate, the magnitude of impact on the guillemot population during the breeding season is considered to be of medium magnitude.
  12. Based on the displacement assessment for the breeding season with Berwick Bank excluded and following the NatureScot Approach using the 60% displacement and 3% mortality, the magnitude of impact on guillemot population during the breeding season is considered to be of low magnitude.
  13. Based on the displacement assessment, for the breeding season with Berwick Bank excluded and following the Applicant Approach using a 50% displacement and 1% mortality rate, the cumulative impact was perceived as low magnitude.
  14. Based on the PVA results for the non-breeding season with Berwick Bank excluded and following the NatureScot Approach using the 60% displacement, 3% mortality rate, the magnitude of impact on the guillemot population during the non-breeding season is considered to be of low magnitude.
  15. Based on the displacement assessment for the non-breeding season with Berwick Bank excluded and following the NatureScot Approach using the 60% displacement and 1% mortality, the magnitude of impact on guillemot population during the non-breeding season is considered to be of low magnitude.
  16. Based on the displacement assessment, for the non-breeding season with Berwick Bank and following the Applicant Approach using a 50% displacement and 1% mortality rate, the cumulative impact was perceived as low magnitude.
  17. Based on the PVA results using the 60% displacement and 3% mortality rate of the NatureScot Approach and with Berwick Bank excluded, the magnitude of impact on the guillemot population on an annual basis is considered to be of low magnitude.
  18. Based on the PVA results using the 60% displacement and 1% mortality rate of the NatureScot Approach and with Berwick Bank excluded, the magnitude of impact on the guillemot population on an annual basis is considered to be of low magnitude.
  19. Based on the displacement assessment using the Applicant’s Approach of 50% displacement and 1% mortality and with Berwick Bank excluded, the magnitude of impact on guillemot population on an annual basis is considered to be of low magnitude.
  20. For all seasons, the Applicant Approach is regarded as informative, particularly because the rates utilised are derived from post-construction studies conducted over multiple years (see paragraph 144 to 147). The impact is considered to be of low magnitude, irrespective of whether Berwick Bank is included or excluded from the analysis.
  21. Due to the minimal level of change to baseline conditions, the cumulative effect is predicted to be of national spatial extent, long-term duration, continuous and high reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore, considered to be low.

                        Sensitivity of the receptor

  1. Guillemot are considered to be moderately vulnerable to disturbance (Wade et al., 2016). Whilst there is evidence from studies that guillemot respond adversely to vessel traffic (Rojek et al., 2007), behavioural response to underwater and airborne sounds resulting from construction activities are unknown. Although guillemot are likely to respond to visual stimuli during the construction phase, the impacts of disturbance/displacement are short-term and guillemot have the ability to return to the baseline abundance and distribution after construction.
  2. Guillemot raise a single chick per year and breed from the age of six onwards, typically living on average for 23 years (Burnell et al., 2023). Guillemot have undergone decreases of approximately 31% in Scotland since the early 2000s. Surveys managed by the RSPB in 2023 have recorded indicative decreases of 6% across a number of sites in Britain in 2023 when compared against a pre-HPAI baseline (Tremlett et al., 2024). Overall, Guillemot is deemed to have low recoverability.
  3. Guillemot is a qualifying interest for several SPAs likely to be connected to the Array (within the mean-max + SD foraging range), with several non-SPA colonies also within range and so the species is considered to be of international value. The population recorded during baseline surveys of the Array was found to be of regional importance. Therefore, guillemot is considered to be of international value.
  4. Guillemot is deemed to be of medium vulnerability, low recoverability and international value. The sensitivity of the receptor is therefore, considered to be high.

                        Significance of the effect

  1. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of minor to moderate adverse significance. However, due to the PVA results concluding there to be a low impact both with and without Berwick Bank and following the Applicant’s Approach (the approach deemed more in line with displacement effects observed by the species based on evidence; Dierschke et al., 2016; APEM, 2022; MacArthur Green, 2023; RoyalHaskoning, 2013; Leopold and Verdaat, 2018; Peschko et al., 2020) it is considered that minor adverse significance is appropriate, which is not significant in EIA terms.