Changes to prey availability
  1. Potential impacts on key prey species for razorbills breeding at Forth Islands SPA during the operation and maintenance phase have been assessed in volume 2, chapter 9 of the Offshore EIA Report using the appropriate maximum design scenarios for these receptors. Reduction or disruption to prey availability through temporary and long-term subtidal habitat loss/disturbance, increased SSC and deposition, reductions in water clarity, EMF from subsea electrical cabling, and colonisation of subsea structures, could affect razorbill survival and productivity in the Forth Islands SPA population.
  2. The same evidence basis and context in relation to this effect pathway for the operation and maintenance phase applies to the Forth Islands SPA razorbill population as to the St Abb’s Head to Fast Castle SPA razorbill population. This is detailed in the section on Project Alone: Operation and Maintenance – Changes to Prey Availability for the St Abb’s Head to Fast Castle SPA population.
  3. Given this, it is considered that there is relatively little potential for the Forth Islands SPA razorbill population to be affected by changes to prey availability during the operation and maintenance phase, with any such effects being largely intermittent across a relatively small spatial extent. Consequently, it is considered that there is no potential for operational or maintenance related changes in prey availability to lead to an adverse effect on the Forth Islands SPA razorbill population.
Project alone: population-level impacts
  1. As determined above, the effects from the Proposed Development alone which could lead to an adverse effect on the Forth Islands SPA razorbill population are limited to displacement (inclusive of barrier effects) during the operation and maintenance phase. For other effect pathways, there is considered to be no potential for an adverse effect on this population as a result of the Proposed Development alone, with any such effects likely to be small and of little, or no, consequence in terms of impacts at the population level.
  2. Given this, PVA was undertaken on the mortality to the adult and immature age classes predicted due to the displacement effects associated with the Proposed Development, as determined by both the Scoping and Developer Approaches (see Tables 5.71 above). The population model for the SPA population was a stochastic, density independent, matrix model, based upon the demographic parameters specified in Table 2.19 of volume 3, appendix 11.6 of the Offshore EIA Report. The starting population size was the 2017 – 2021 count for the SPA, with the projected population trends considered over a 35 year timescale (Offshore EIA Report, volume 3, appendix 11.5). The approach and methods to undertaking the PVA are as described in the section on Project Alone: Population-Level Impacts for the St Abb’s to Fast Castle SPA kittiwake population above (with further details provided in the Offshore EIA Report, volume 3, appendix 11.6).
  3. Outputs from the PVA are summarised according to the median predicted population-sizes at the end of the projection period, and the three metrics which the Scoping Opinion (volume 3, appendix 6.2 of the Offshore EIA Report) advised should be used for the interpretation of outputs and which have been shown to have relatively low sensitivity to factors such as varying population status and the mis-specification of the demographic rates underpinning the population model (Cook and Robinson 2015, Jitlal et al., 2017). These metrics are:
  • The CPS – the median of the ratio of the end-point size of the impacted to un-impacted (or baseline) population, expressed as a proportion;
  • The CPGR - the median of the ratio of the annual growth rate of the impacted to un-impacted population, expressed as a proportion; and
  • The centile of the un-impacted population that matches the median (i.e. 50th centile) of the impacted population (based upon the distribution of the end-point population-sizes generated by the multiple replications of the model runs, the value should always be less than 50 because the median for the impacted population is not expected to exceed that for the un-impacted population).

 

Table 5.72:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Forth Islands SPA Razorbill Population Under Different Impact Scenarios for the Proposed Development Alone

Table 5.72: Projected 35 Year Population Sizes and Associated PVA Metrics for the Forth Islands SPA Razorbill Population Under Different Impact Scenarios for the Proposed Development Alone

 

  1. The PVA predicted that the Forth Islands SPA razorbill population would increase over the 35 year projection period irrespective of the effects from the Proposed Development. Thus, the population is predicted to be almost four and three times larger than the current estimate of 7,878 adult birds under baseline conditions (i.e. no wind farm effects) and under the scenario of greatest annual mortality (i.e. Scoping Approach B), respectively (Table 5.72). Given that the PVAs are based on density independent models, which assume all mortality from the wind farm effects is additive and that there are no compensatory mechanisms operating within the population, the predicted increases are inevitably greatest for the baseline scenario and least for the scenario involving highest annual mortality (i.e. Scoping Approach B). Whilst the predicted levels of increase are unlikely to occur in reality (and are, in part, a consequence of the absence of any compensatory density dependence within the models – as discussed in the section on Project Alone: Population-level impacts for the St Abb’s Head to Fast Castle SPA kittiwake population), the prediction for an increasing trend is broadly consistent with the documented, overall, long-term trend for this SPA population (Figure 5.22).
  2. The PVA metrics suggest relatively small effects overall. Thus, the CPS value for the Developer Approach indicates that the displacement effects from the Proposed Development alone would result in a reduction of less than 2% in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects, whilst for the Scoping Approach the CPS values indicate reductions of 5 – 10% after 35 years, relative to that in the absence of any wind farm effects (Table 5.72). The associated reduction in annual population growth rate (relative to that predicted under baseline conditions) is estimated to be 0.1% for the Developer Approach and 0.2 – 0.3% for the Scoping Approach. The centile values indicate considerable overlap in the distributions of the predicted impacted and un-impacted population sizes and, hence, a high likelihood of the impacted population being of a similar size to the un-impacted population after 35 years (Table 5.72).
  3. For the same reasons as described in the section on Project-Alone: Population-Level Impacts for the St Abb’s Head to Fast Castle SPA razorbill population, the assessment of the Forth Islands SPA razorbill population incorporates high levels of precaution, which extend beyond the differences between the Developer and Scoping Approaches that are outlined above (and detailed in the Offshore EIA Report, volume 3, appendix 11.4). Notably, the concerns over the extent to which the seasonal mean peak abundances (which provide the basis for the displacement mortality estimates) are likely to be representative of the overall usage of the Proposed Development array and two kilometre buffer by razorbill are equally relevant to the Forth Islands SPA population as to the St Abb’s Head to Fast Castle SPA population. As for the St Abb’s Head to Fast Castle SPA population, the evidence available from tracking data suggests low levels of usage of the Proposed Development array area and two kilometre buffer during the breeding season by razorbills from the Forth Islands SPA, as outlined above (Cleasby et al. 2018, Bogdanova et al. 2022).
Project alone: conclusion
  1. It is considered that the predicted levels of impact from the Proposed Development alone on the Forth Islands SPA razorbill population are of a relatively small scale, as determined by both the Developer and Scoping Approaches. For both the Developer and Scoping Approaches it is also the case that the centile metric indicates a high likelihood of the impacted population being of similar size to the un-impacted population after 35 years. These levels of impact are within the context of an assessment which incorporates high levels of precaution (particularly as determined by the Scoping Approach) and a population for which the documented, long-term, trend is increasing, and which is considered to be in ‘favourable maintained’ condition. Given this, it is concluded that the effects from the Proposed Development alone (as determined by either the Developer or Scoping Approaches) would not result in an adverse effect on this SPA population.
Effects in-combination
Effects of relevance to the in-combination assessment
  1. As detailed above, any effects from the Proposed Development alone on the Forth Islands SPA razorbill population during construction and decommissioning and resulting from disturbance and changes to prey availability during operation and maintenance will be small and highly localised. As such, there is considered to be no potential for these effect pathways to add to impacts at the population-level that might result from other effects pathways associated with the Proposed Development or from the effects due to other plans and projects.
  2. Therefore, the potential for effects of the Proposed Development to act on the Forth Islands SPA razorbill population in-combination with other plans and projects is limited to the displacement (inclusive of barrier effects) effect pathway during operation and maintenance. Following advice from NatureScot provided through the Ornithology Roadmap process (at meeting 3, 8th December 2021), the following sections consider these potential effects for (i) the Proposed Development in-combination with the other Forth and Tay wind farms and (ii) the Proposed Development in-combination with the other UK North Sea wind farms (noting that scenario (ii) includes those plans and projects which comprise scenario (i)).
Displacement/barrier effects – operation and maintenance
  1. As described in annex E of the Offshore EIA Report, volume 3, appendix 11.6, estimates of breeding season displacement mortality which had been attributed to the Forth Islands SPA razorbill population were extracted from the existing assessments for offshore wind farms that are in planning, consented, under construction or in operation. As for the potential displacement mortality estimated for the Proposed Development, the mortality attributed to the SPA population from other offshore wind farms was estimated using the SNCB matrix approach, with details on the displacement and mortality rates that had been applied being available in each case. Thus, it was possible to adjust the estimated mortalities from each of the other projects to align with the displacement and mortality rates on which the Scoping and Developer Approaches are based.
  2. For the non-breeding periods, razorbill numbers associated with other offshore wind farms that are in planning, consented, under construction or in operation were extracted for each of the relevant seasonal periods from the cumulative totals collated for the East Anglia TWO and East Anglia ONE North submissions (MacArthur Green and Royal HaskoningDHV 2021, see annex E of the Offshore EIA Report, volume 3, appendix 11.6 for more details). The cumulative numbers for each of the non-breeding periods were apportioned to the Forth Islands SPA razorbill population according to the BDMPS approach (Furness 2015), with the subsequent displacement mortality calculated according to the displacement and mortality rates appropriate to each of the Scoping and Developer Approaches (Table 5.70). This was done separately for all of the other UK North Sea wind farms and for the subset represented by the other Forth and Tay wind farms.

 

Table 5.73:
Estimated Annual Mortality of Forth Islands SPA Razorbills as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach, In-Combination with other Forth and Tay Wind Farms and other UK North Sea Wind Farms

Table 5.73: Estimated Annual Mortality of Forth Islands SPA Razorbills as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach, In-Combination with other Forth and Tay Wind Farms and other UK North Sea Wind Farms

 

  1. The potential mortality resulting from the predicted displacement effects associated with the Proposed Development in-combination with the other Forth and Tay wind farms represents an approximate fourfold increase in that predicted for the Proposed Development alone (for both Developer and Scoping Approaches), whilst for the Proposed Development in-combination with the other UK North Sea wind farms there is an almost fivefold increase in the predicted mortality compared to that for the Proposed Development alone (Tables 5.71 and 5.73). For all scenarios the predicted mortality is concentrated in the breeding season. Thus, for the Proposed Development in-combination with the other Forth and Tay wind farms, 91 – 96% of the predicted mortality is attributed to the breeding season, whilst for the Proposed Development in-combination with the other UK North Sea wind farms 70 – 87% of the predicted mortality is attributed to the breeding season (with the percentages being higher for the Scoping Approach than the Developer Approach).
  2. For the Proposed Development in-combination with the other Forth and Tay wind farms, the additional annual mortality of adult razorbills from the Forth Islands SPA population predicted due to displacement represents 0.16% of the current adult breeding population at this colony (i.e. 7,878 individuals – Table 3.3 in volume 3, appendix 11.5) as determined by the Developer Approach, and between approximately 0.57 – 0.97% of this population as determined by the lower and upper estimates from the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.090 – see Table 2.19 in the Offshore EIA Report, volume 3, appendix 11.6), the estimates of adult displacement mortality equate to an increase of 1.9% for the Developer Approach and of 6.3 – 10.8% for the lower and upper estimates from the Scoping Approach.
  3. For the Proposed Development in-combination with the other UK North Sea wind farms, the additional annual mortality of adult razorbills from the Forth Islands SPA population predicted due to displacement represents 0.22% of the current adult breeding population at this colony as determined by the Developer Approach, and between approximately 0.63 – 1.15% of the current adult breeding population at this colony as determined by the lower and upper estimates from the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population, the estimates of adult displacement mortality equate to an increase of 2.4% for the Developer Approach and of 7.0 – 12.8% for the lower and upper estimates from the Scoping Approach.
  4. The potential levels of impact on the Forth Islands SPA razorbill population resulting from the mortality predicted from displacement and barrier effects associated with the Proposed Development in-combination with other wind farms in the Forth and Tay or in-combination with other wind farms in the UK North Sea during the operation and maintenance phase are considered in more detail below in the Effects In-Combination: Population-Level Impacts section. This presents the outputs from PVAs of the potential effects of predicted displacement mortality on the SPA population.
In-combination: population-level impacts
  1. As for the Proposed Development alone, PVA was undertaken on the mortality to the adult and immature age classes predicted due to the displacement effects associated with the Proposed Development in-combination with the other Forth and Tay wind farms and the Proposed Development in-combination with the other UK North Sea wind farms. This was on the basis of the potential mortality as determined by both the Scoping and Developer Approaches (see Table 5.73 above).
  2. The approach to the PVA and the metrics used to summarise the PVA outputs are as described for the Proposed Development alone (see Project Alone: Population-Level Impacts section above).

 

Table 5.74:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Forth Islands SPA Razorbill Population Under Different Impact Scenarios for the Proposed Development in-Combination with the Other Forth and Tay Wind Farms

Table 5.74: Projected 35 Year Population Sizes and Associated PVA Metrics for the Forth Islands SPA Razorbill Population Under Different Impact Scenarios for the Proposed Development in-Combination with the Other Forth and Tay Wind Farms

 

Table 5.75:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Forth Islands SPA Razorbill Population Under Different Impact Scenarios for the Proposed Development in-Combination with the other UK North Sea Wind Farms

Table 5.75: Projected 35 Year Population Sizes and Associated PVA Metrics for the Forth Islands SPA Razorbill Population Under Different Impact Scenarios for the Proposed Development in-Combination with the other UK North Sea Wind Farms

 

  1. Given that the in-combination effects are inevitably greater than those for the Proposed Development alone, the PVA metrics for the Proposed Development in-combination with either the other Forth and Tay wind farms or the other UK North Sea wind farms suggest greater population-level impacts than as predicted for the Proposed Development alone (compare Table 5.72 with Tables 5.74 and 5.75). However, on the basis of the effects as determined by the Developer Approach, the predicted levels of impact remain relatively small. Thus, the CPS value for the Proposed Development in-combination with the other UK North Sea wind farms indicates that the SPA population size would be reduced by 8% after 35 years relative to that in the absence of any wind farm effects (Table 5.75). The centile value of 39.4 indicates a considerable overlap in the distributions of the predicted impacted and un-impacted population sizes and, hence, a reasonably high likelihood of the impacted population being of a similar size to the un-impacted population after 35 years. The PVA metrics for the Proposed Development in-combination with the other Forth and Tay wind farms indicate lower levels of impact (as determined by the Developer Approach), as would be expected from the lower predicted mortalities (Table 5.74).
  2. The predicted levels of impact as determined by the Scoping Approach are considerably greater, with the CPS values indicating reductions of 21 – 33% and of 22 – 37% in the size of the SPA population after 35 years (relative to that in the absence of any wind farm effects) for the other Forth and Tay in-combination scenario and the other UK North Sea in-combination scenario, respectively (Tables 5.74 and 5.75). The centile values range from 11.0 – 23.6 for the Proposed Development in-combination with the other Forth and Tay wind farms and from 8.1 – 21.9 for the Proposed Development in-combination with the other UK North Sea wind farms. These suggest low to, at most, moderate overlap in the distributions of the predicted impacted and un-impacted population sizes and, hence, a reasonably high likelihood of the impacted population being smaller than the un-impacted population after 35 years.
In-combination: conclusion
  1. On the basis of the Developer Approach, it is considered that the potential effects from the Proposed Development in-combination with the other Forth and Tay wind farms or the other UK North Sea wind farms would not result in an adverse effect on the Forth Islands SPA razorbill population. The predicted population-level impacts are relatively small, whilst there remains a reasonably high likelihood of the population being of a similar size to that which would occur in the absence of the Proposed Development after 35 years. Furthermore, this level of impact is within the context of an assessment which incorporates high levels of precaution and a population for which the documented, long-term, trend is increasing and which is considered to be in ‘favourable maintained’ condition.
  2. For the Scoping Approach, the predicted levels of impact are markedly greater and are considered to be of a level for which the possibility of an adverse effect on the SPA population cannot be excluded. This conclusion is considered to apply to the effects from the Proposed Development in-combination with either the other Forth and Tay wind farms or the other UK North Sea wind farms, and as determined by either the lower or upper range of the Scoping Approach. However, as detailed above, it is considered that the displacement and mortality rates used in the Scoping Approach are overly precautionary and are not supported by the available evidence (volume 3, appendix 11.4, annex G of the Offshore EIA Report). Therefore, it is considered that greater weight should be given to the conclusions as determined by the Developer Approach.

Assessment for the puffin population

  1. Puffins are a burrow nesting colonial seabird that occurs around the coasts of the North Atlantic region, mostly on islands. In Europe, colonies occur along the Atlantic coasts of Brittany, offshore islands in the British and Ireland, Faroes, Iceland, Norway and Russia. They forage entirely at sea, diving for small shoaling fish, particularly Ammodytidae, Clupeidae and Gadidae (Mitchell et al. 2004). In winter, puffins are very widespread across north-west European seas (Stone et al. 1995) and the Atlantic (Jessopp et al. 2013).
  2. The Forth Islands SPA puffin population occurs on several islands in the Firth of Forth. The largest colony occurs on the Isle of May, with smaller colonies on Craigleith, Fidra, Inchmickery, and The Lamb. The Isle of May colony represents approximately 89% of the total SPA population. The SPA puffin population is only counted sporadically and there are very few counts across all the colonies in the SPA in any one year. Therefore, count data are shown only for the Isle of May, where the population is counted approximately every five years (Figure 5.23). This has shown an overall increase since 1984 but with evidence of a decline in more recent years from a peak in abundance in the early 2000s. The numbers breeding on the Isle of May remain well above the citation population size of 14,000 breeding pairs and the current population estimate for the whole SPA is 43,620 apparently occupied burrows (which is taken to equate to 87,240 breeding individuals – volume 3, appendix 11.5 of the Offshore EIA Report). The Forth Islands SPA puffin population is considered to be in ‘favourable declining’ condition.

Figure 523:
Puffin Population Trend on the Isle of May (Which Holds Almost 90% of the Forth Islands SPA Population) between 1984 and 2017. The Red Line Shows the Citation Population Size for the Forth Islands SPA (14,000 Breeding Pairs). Data are from the Seabird Monitoring Programme Database (Seabird Monitoring Programme | JNCC (bto.org))

Figure 523: Puffin Population Trend on the Isle of May (Which Holds Almost 90% of the Forth Islands SPA Population) between 1984 and 2017. The Red Line Shows the Citation Population Size for the Forth Islands SPA (14,000 Breeding Pairs). Data are from the Seabird Monitoring Programme Database (Seabird Monitoring Programme | JNCC (bto.org))

 

The potential for impacts on the puffin population
  1. The Proposed Development and two kilometre buffer around the Proposed Development array area7 do not overlap with the Forth Islands SPA, so that potential impacts on its puffin population will only occur as a result of individuals from the colony occurring in the area (or vicinity) of the Proposed Development. Consequently, the main focus of the assessment for this SPA population is concerned with the Conservation Objective to maintain, in the long term, the population of the species as a viable component of the site because the other conservation objectives either apply to the site itself, and not to areas beyond the boundary, or are encompassed by the assessment of this first Conservation Objective (as for the maintain in the long term no significant disturbance of the species, because disturbance would only be considered significant if it caused an adverse effect on the population viability of the qualifying features).
  2. From published information on puffin foraging ranges generally (Woodward et al. 2019) and tracking from the SPA specifically (Bogdanova et al. 2022), it is highly likely that during the breeding period puffin from the Forth Islands SPA occur within the area of the Proposed Development and of the two km buffer around the Proposed Development array area. This is supported by the findings of the apportioning exercise, which estimates that 50% of the puffin occurring on the Proposed Development array area during the breeding season derive from this SPA colony (Offshore EIA Report, volume 3, appendix 11.5). The breeding period for puffin is defined as April to mid-August, following the NatureScot (2020) guidance.
  3. After the breeding season puffin migrate rapidly from their UK breeding areas, leaving the seas immediately adjacent to their colonies by late August and dispersing widely across north-west European seas and the Atlantic (Wernham et al. 2002, Harris and Wanless 2011, Stone et al. 1995, Jessopp et al. 2013). Consequently (and as advised in the NatureScot scoping advice - volume 3, appendix 6.2 of the Offshore EIA Report), no assessment of impacts during the non-breeding period is undertaken for puffin.
Project alone: construction and decommissioning
Disturbance
  1. Direct disturbance to puffins during the construction phase may arise within the Proposed Development array area (and its immediate vicinity) as a result of increased vessel movements and helicopter activity, as well as from other activities directly associated with the installation of the wind turbine foundations and other infrastructure, whilst there will also be increased vessel activity along the Proposed Development export cable corridor due to the cable laying activities. The levels of such activities that could arise are outlined in Table 4.1, with these activities occurring during construction campaigns within a construction period of at most eight years duration.
  2. A total of up to 11,482 vessel round trips may occur over the construction phase, whilst it is estimated that a maximum of 134 vessels could occur within the area of the Proposed Development at any one time (Table 4.1). However, this is within the context of high baseline levels of vessel traffic within this area (e.g. surveys recorded an average of 14 vessels per day within a 10 nm buffer around the Proposed Development over a 14-day period in August 2022, whilst also showing an average of three to four vessels intersecting the Proposed Development array area per day over summer - Offshore EIA Report, volume 2, chapter 13).
  3. When using the marine environment (and not at the breeding colony), puffins are considered to have a relatively low sensitivity to such sources of direct disturbance. Thus, reviews of the sensitivity of different seabird species to disturbance from vessels and helicopter traffic assign puffin as ‘2’ on a five-scale ranking system, where 1 indicates hardly any or limited escape/avoidance behaviour and very short flight distance when approached and 5 indicates strong escape/avoidance behaviour and a large response distance (Garthe and Hüppop 2004, Furness et al. 2013).
  4. The total area to be affected by such disturbance over the full eight years of the construction phase also represents a small proportion of the total area of marine habitat available to puffins from the Forth Islands SPA. Thus, the Proposed Development array area encompasses 1,010 km2, whilst the Proposed Development export cable corridor encompasses 168 km2. Together these areas represent approximately 1% of the total breeding season foraging area that is potentially available to the SPA puffin population, as defined by the generic measure of the species’ mean maximum breeding season foraging range plus 1 SD (i.e. 137.1±128.3 km - Woodward et al. 2019) and assuming that this range is represented by a semicircle to the seaward side of the colony. Similarly, the Proposed Development array and export cable corridor represent approximately 4% of the breeding season foraging area if considering the mean maximum foraging range only.
  5. Tracking data for puffin from the Forth Islands SPA indicate that the Proposed Development array area and Proposed Development export cable corridor have little overlap with waters that are heavily used during the breeding season (Bogdanova et al. 2022). Based on the data from 24 birds tracked from this SPA population during the 2021 breeding season, there is no overlap between the core areas used by these birds for foraging and ‘resting at sea’ (as defined by the 50% utilisation distribution of the tracked birds when exhibiting these behaviours) and the Proposed Development array area, whilst only 1.5% of the wider area used for these behaviours (as defined by the 90% utilisation distribution of the tracked birds when exhibiting these behaviours) overlapped with the Proposed Development array area (Bogdanova et al. 2022). Similarly, only four of the tracked birds and 2% of the 713 individual flight tracks that were recorded from these birds passed through the Proposed Development array area. The areas used by the tracked birds (both whilst in flight and when foraging and/or resting) showed some, limited, overlap with the Proposed Development export cable corridor, although this was not quantified (Bogdanova et al. 2022).
  6. In addition to the above, it is important to consider that the construction activities will not occur simultaneously across the entirety of the Proposed Development array area or the Proposed Development export cable corridor but, rather, will be carried out in different areas at different times. Thus, the activities will be concentrated within discrete (often small) parts of these wider areas, and within such areas they will not extend over the full duration of the construction phase, so further reducing the potential to which birds may be subject to disturbance effects. For example, cable laying for the Proposed Development export cable will occur over a total of two years, whilst within the Proposed Development array area it is likely that construction activities would be confined largely to discrete areas at any one time.
  7. The potential for disturbance effects during decommissioning is assumed to be the same (or less) as for construction, noting that the duration of the decommissioning phase will not exceed that of construction, and may be shorter.
  8. Given the relatively low sensitivity of puffin to disturbance effects, the relatively small areas that will be subject to activities with the potential to result in disturbance at any given time during the construction period and the fact that these potential effects will be temporary, it is considered that there is no potential for construction or decommissioning related disturbance to lead to an adverse effect on the Forth Islands SPA puffin population.
Displacement
  1. As detailed above, puffin is considered to have a relatively low sensitivity to disturbance, whilst potential effects of disturbance during the construction and decommissioning phases will (at most) only extend across a small part of the wider foraging areas used by the Forth Islands SPA puffin population and be limited to (at most) an eight year period during construction (and a likely similar or shorter period during decommissioning). Furthermore, as detailed above, potential effects of disturbance will not occur simultaneously across the entirety of the Proposed Development array area or Proposed Development export cable corridor but, rather, will be carried out in different areas at different times. Thus, at any given time the potential for disturbance effects that could lead to displacement of puffins from this SPA will be limited to relatively small areas, with the potential effects also being of a temporary nature.
  2. Based upon the above, it is considered that there is relatively little potential for the Forth Islands SPA puffin population to be affected by displacement during the construction or decommissioning phases, with any such effects only extending across relatively small areas and tending to be temporary in nature. Consequently, it is considered that there is no potential for construction or decommissioning related displacement to lead to an adverse effect on the Forth Islands SPA puffin population.
Changes to prey availability
  1. Sandeels are key prey for puffins, with a range of other species taken including clupeids and gadids (del Hoyo et al., 1996). Indirect effects on puffins may arise as a result of changes in the availability, distribution, or abundance of these species during the construction and decommissioning phases of the Proposed Development. Reduction or disruption to prey availability may cause displacement from foraging grounds or reduced energy intake, affecting survival rates or productivity in the Forth Islands SPA puffin population in the short-term.
  2. During construction and decommissioning there are a number of ways in which effects on key prey species may occur including temporary subtidal habitat loss/disturbance, long-term subtidal habitat loss, increases in SSC and associated sediment deposition, underwater noise and vibration, and colonisation of subsea structures (see section on Project Alone: Construction and Decommissioning – Changes to Prey Availability for the St Abb’s Head to Fast Castle SPA kittiwake population and volume 2, chapter 9 of the Offshore EIA Report). Increases in SSC and associated reductions in water clarity may also affect the ability of foraging puffins to locate fish in the water column, thereby reducing prey availability.
  3. It is considered that foraging puffins from the Forth Islands SPA will be largely unaffected by the low-level temporary increases in SSC, as the concentrations are likely to be within the range of natural variability (generally <5 mg/l but can increase to over 100 mg/l during storm events/increased wave heights) and will reduce to background concentrations within a very short period (approximately two tidal cycles). Furthermore, the Proposed Development array area and export cable corridor represent approximately 1% of the total breeding season foraging area that is potentially available to the SPA puffin population, as defined by the species’ mean maximum breeding season foraging range plus 1 SD (i.e. 137.1±128.3 km; Woodward et al., 2019) and assuming that this range is represented by a semicircle to the seaward side of the colony. As outlined in the section on Project Alone: Construction and Decommissioning – Disturbance for the SPA population, data on puffin foraging distributions indicates that the Proposed Development array area and export cable corridor have little overlap with waters that are predicted to be heavily used by birds from the Forth Islands SPA (Bogdanova et al., 2022).
  4. Based upon the above, it is considered that there is relatively little potential for the Forth Islands SPA puffin population to be affected by changes to prey availability during the construction and decommissioning phases, with any such effects being largely intermittent across a relatively small spatial extent, with most effects temporary in nature. Consequently, it is considered that there is no potential for construction or decommissioning related changes in prey availability to lead to an adverse effect on the Forth Islands SPA puffin population. This conclusion is consistent with the outcome of the EIA which concluded that effects from changes in prey availability on puffins during construction and decommissioning were not significant in EIA terms (volume 2, chapter 11 of the Offshore EIA Report).
Project alone: operation and maintenance
Disturbance
  1. Vessel use within the Proposed Development array area and export cables corridor during the operation and maintenance phase may lead to direct disturbance of puffins from the Forth Islands SPA. As described in section on Project Alone: Construction and Decommissioning – Disturbance for the SPA population, puffins are considered to have low sensitivity to such sources of direct disturbance at sea (Garthe and Hüppop 2004, Furness et al., 2013).
  2. The maximum design scenario is for up to 3,393 vessel round trips per year over the operational lifetime of the project. Vessel types which will be required during the operation and maintenance phase include those used during routine inspections, repairs and replacement of equipment, major component replacement, painting or other coatings, removal of marine growth, replacement of access ladders, and geophysical surveys (Table 4.1).
  3. Based on information presented in the section on Project Alone: Operation and Maintenance – Disturbance for the St Abb’s Head to Fast Castle SPA kittiwake population and in the Offshore EIA Report, volume 2, chapter 13, baseline levels of vessel traffic in the Offshore Ornithology study area are relatively high. In the context of the baseline levels of vessel traffic across the Offshore Ornithology study area, the increase during the operation and maintenance phase is considered to be relatively small. Vessel movements will be within the Proposed Development array area and export cable corridor and will follow existing shipping routes to/from ports. In addition, Project Codes of Conduct included as a part of the NSVMP (Offshore EIA Report, volume 4, appendix 25) will be issued to all project vessel operators to avoid sudden changes in course or speed which will minimise the potential for disturbance. Within the Proposed Development array area, movements and associated maintenance activities will be restricted to individual wind turbines over a period of days to weeks.
  4. The size and noise outputs from vessels during the operation and maintenance phase will be similar to those used in the construction phase. However, the number of vessel return trips per year and their frequency will be much lower for the operation and maintenance phase compared to the construction phase. In addition, activities during the operation and maintenance phase will not occur simultaneously across the entirety of the Proposed Development array area and export cable corridor but intermittently within discrete (often very small) parts of these wider areas.
  5. Given the discrete areas relative to the species’ foraging range that will be subject intermittently to potential disturbance from vessel use and maintenance activities (Woodward et al., 2019), and the fact that these potential effects will be reduced compared to the construction and decommissioning phases, it is considered that there is no potential for disturbance during operation and maintenance to lead to an adverse effect on the Forth Islands SPA puffin population.
Displacement/barrier effects
  1. As outlined above, displacement effects on the Forth Islands SPA puffin population are estimated using the SNCB matrix approach, as applied to the Proposed Development array and two kilometre buffer (SNCBs 2022, Offshore EIA Report, volume 3, appendix 11.4). Thus, throughout this section, mortality from displacement is assumed to refer to that which results from both displacement and barrier effects. The approach used to derive predicted levels of mortality is as described in the section on Project Alone: Operation and Maintenance – Displacement/Barrier Effects for the St Abb’s Head to Fast Castle SPA kittiwake population above (and in the Offshore EIA Report, volume 3, appendix 11.4).
  2. On the basis of the advice provided in the Scoping Opinion (volume 3, appendix 6.2 of the Offshore EIA Report), displacement effects on puffin are estimated for the breeding period only (see above). The displacement and associated mortality rates advised in the Scoping Opinion (subsequently termed the Scoping Approach) for puffin are:
  • Breeding period: 60% displacement with lower and upper mortality rates of 3% and 5%.
    1. As with other species for which displacement effects are assessed (see above), the approach to estimating puffin displacement effects advocated by the Scoping Opinion was considered overly precautionary in relation to both the displacement and mortality rates that were proposed, with these rates being higher than is considered to be justified on the basis of the available evidence (even when allowing for the incorporation of precaution in the assessment - volume 3, appendix 11.4, annex G of the Offshore EIA Report). Furthermore, the mortality rates advocated by the Scoping Opinion represented a marked change from the assumptions applied in assessments for other recent Scottish offshore wind farms (Marine Scotland 2017a,b,c) with no clear evidence apparently being available to justify such a change.
    2. Based upon a consideration of the available evidence for puffin displacement, the potential consequent mortality, previous precedent and a need to incorporate precaution within the assessment, an alternative Developer Approach to estimating displacement effects was determined (volume 3, appendix 11.4, annex G of the Offshore EIA Report). The rates adopted by the Developer Approach are:
  • Breeding period: 50% displacement with a mortality rate of 1%.
    1. Estimates of puffin mortality were produced using the SNCB matrix on the basis of both the Scoping Approach and the Developer Approach (Offshore EIA Report, volume 3, appendix 11.4), with these estimates then apportioned to the Forth Islands SPA puffin population during the breeding season according to the NatureScot (2018) approach (Offshore EIA Report, volume 3, appendix 11.5, Table 5.76). The resulting mortality estimates for the breeding season were apportioned to age classes on the basis of the asymptotic age distribution of the population model used for the Forth Islands SPA puffin PVAs in this assessment (Offshore EIA Report, volume 3, appendix 11.6). Based on advice provided by NatureScot and Marine Scotland Science following Roadmap Meeting 4 (G. Holland, email 26/01/2022), it was also assumed that 7% of the breeding adults in the SPA population miss breeding in any given year (i.e. sabbatical birds) so that the number of estimated adult deaths during the breeding season was adjusted accordingly.

 

Table 5.76:
The Mean Peak Abundance Estimates of Puffin in the Proposed Development Array Area and 2 km Buffer During the Breeding Season, Together with the Proportion of Birds Estimated to Belong to the Breeding Adult Age Class and to be from the Forth Islands SPA Population

Table 5.76: The Mean Peak Abundance Estimates of Puffin in the Proposed Development Array Area and 2 km Buffer During the Breeding Season, Together with the Proportion of Birds Estimated to Belong to the Breeding Adult Age Class and to be from the Forth Islands SPA Population

 

  1. Based upon the estimates and assumptions detailed above, the potential annual mortality amongst the SPA puffin population as a result of displacement is estimated as 18 adult and 21 immature birds based on the lower mortality rates for the Scoping Approach (i.e. Scoping Approach A) and as 30 adult and 36 immature birds based upon the higher mortality rates for the Scoping Approach (i.e. Scoping Approach B) (Table 5.77). For the Developer Approach, the predicted annual mortality is five adult and six immature birds, equating to approximately 28% and 17% of the mortality predicted for the lower and upper range of the Scoping Approach, respectively (Table 5.77).

 

Table 5.77:
Estimated Potential Annual Mortality of Forth Islands SPA Puffins as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach

Table 5.77: Estimated Potential Annual Mortality of Forth Islands SPA Puffins as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach

 

  1. The additional annual mortality of adult puffin from the Forth Islands SPA population predicted due to displacement from the Proposed Development array represents less than 0.01% of the current adult breeding population at this colony (i.e. 87,240 individuals – Table 3.3 in the Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach, and between approximately 0.02 – 0.03% of this population as determined by the lower and upper estimates from the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.099 – see Table 2.17 in volume 3, appendix 11.6 of the Offshore EIA Report), the estimates of adult mortality equate to an increase of less than 0.1% for the Developer Approach and of 0.2 – 0.3% for the lower and upper estimates from the Scoping Approach.
  2. The potential levels of impact on the Forth Islands SPA puffin population resulting from the mortality predicted from displacement and barrier effects associated with the Proposed Development array during the operation and maintenance phase are considered in more detail below in the Project Alone: Population-Level Impacts section. This presents the outputs from PVAs of the potential effects of predicted displacement mortality on the SPA population.
Changes to prey availability
  1. Potential impacts on key prey species for puffins breeding at Forth Islands SPA during the operation and maintenance phase have been assessed in volume 2, chapter 9 of the Offshore EIA Report using the appropriate maximum design scenarios for these receptors. Reduction or disruption to prey availability through temporary and long-term subtidal habitat loss/disturbance, increased SSC and deposition, reductions in water clarity, EMF from subsea electrical cabling, and colonisation of subsea structures, could affect puffin survival and productivity in the Forth Islands SPA population.
  2. During the operation and maintenance phase, there is potential for temporary habitat loss/disturbance for up to 989,000 m2 as a result of the use of jack-up vessels during any component replacement activities and during any cable repair activities. These impacts will be similar to those identified for temporary habitat loss/disturbance during the construction phase (as discussed in the section on Project Alone: Construction and Decommissioning – Changes to prey availability for the SPA population) and will be highly restricted to the immediate vicinity of these operations.
  3. As outlined in the section on Project Alone: Operation and Maintenance – Changes to prey availability for the St Abb’s Head to Fast Castle SPA kittiwake population, the presence of infrastructure within the Proposed Development, will result in long-term habitat loss of up to 7,798,856 m2 during the operation and maintenance phase. These areas of habitat loss will be discrete, either in the immediate vicinity of foundations, or relatively small isolated stretches of cable, representing a very low proportion of available habitat for key prey species (0.7% of the Proposed Development fish and shellfish ecology study area).
  4. Increased SSC could occur as a result of repair or remedial burial activities during the operation and maintenance phase, as outlined in the section on Project Alone: Operation and Maintenance – Changes to prey availability for the St Abb’s Head to Fast Castle SPA kittiwake population. The assessment in volume 2, chapter 9 of the Offshore EIA Report considered that any suspended sediments and associated deposition and water clarity reduction during operation and maintenance will be of the same magnitude, or lower, as for construction.
  5. The presence and operation of inter-array, interconnector and offshore export cables will result in emissions of localised EMF, however there is no evidence to suggest that the key prey species of auks (e.g. sandeel and clupeids) are electrosensitive and would respond to electrical and/or magnetic fields (volume 2, chapter 9 of the Offshore EIA Report).
  6. Artificial structures introduced to the marine environment provide hard substrate for settlement of various organisms, which can increase local food availability for higher trophic levels. Whilst there is mounting evidence of potential benefits of artificial structures in marine environment (Birchenough and Degrae 2020), the statistical significance of such benefits and details about trophic interactions, particularly in relation to key prey species for puffin, remain largely unknown (Peschko et al., 2020; BOWL 2021a, 2021b; Scott, 2022). Overall, any change in prey abundance and/or distribution through the presence of subsea structures of foundations is likely to be small relative to the area over which breeding SPA puffins forage.
  7. It is therefore considered that there is relatively little potential for the Forth Islands SPA puffin population to be affected by changes to prey availability during the operation and maintenance phase, with any such effects being largely intermittent across a relatively small spatial extent. Consequently, it is considered that there is no potential for operational or maintenance related changes in prey availability to lead to an adverse effect on the Forth Islands SPA puffin population. This conclusion is consistent with the outcome of the EIA which concluded that effects from changes in prey availability on puffins during operation and maintenance were not significant in EIA terms (volume 2, chapter 11 of the Offshore EIA Report).
Project alone: population-level impacts
  1. As determined above, the effects from the Proposed Development alone which could lead to an adverse effect on the Forth Islands SPA puffin population are limited to displacement (inclusive of barrier effects) during the operation and maintenance phase. For other effect pathways, there is considered to be no potential for an adverse effect on this population as a result of the Proposed Development alone, with any such effects likely to be small and of little, or no, consequence in terms of impacts at the population level.
  2. Given this, PVA was undertaken on the mortality to the adult and immature age classes predicted due to the displacement effects associated with the Proposed Development, as determined by both the Scoping and Developer Approaches (see Table 5.77 above). The population model for the SPA population was a stochastic, density independent, matrix model, based upon the demographic parameters specified in Table 2.17 of volume 3, appendix 11.6 of the Offshore EIA Report. The starting population size was the 2017 – 2021 count for the SPA, with the projected population trends considered over a 35 year timescale (volume 3, appendix 11.5 of the Offshore EIA Report). The approach and methods to undertaking the PVA are as described in the section on Project Alone: Population-Level Impacts for the St Abb’s to Fast Castle SPA kittiwake population above (with further details provided in volume 3, appendix 11.6).
  3. Outputs from the PVA are summarised according to the median predicted population-sizes at the end of the projection period, and the three metrics which the Scoping Opinion (volume 3, appendix 6.2 of the Offshore EIA Report) advised should be used for the interpretation of outputs and which have been shown to have relatively low sensitivity to factors such as varying population status and the mis-specification of the demographic rates underpinning the population model (Cook and Robinson 2015, Jitlal et al., 2017). These metrics are:
  • The CPS – the median of the ratio of the end-point size of the impacted to un-impacted (or baseline) population, expressed as a proportion;
  • The CPGR - the median of the ratio of the annual growth rate of the impacted to un-impacted population, expressed as a proportion; and
  • The centile of the un-impacted population that matches the median (i.e. 50th centile) of the impacted population (based upon the distribution of the end-point population-sizes generated by the multiple replications of the model runs, the value should always be less than 50 because the median for the impacted population is not expected to exceed that for the un-impacted population).

 

Table 5.78:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Forth Islands SPA Puffin Population Under Different Impact Scenarios for the Proposed Development Alone

Table 5.78: Projected 35 Year Population Sizes and Associated PVA Metrics for the Forth Islands SPA Puffin Population Under Different Impact Scenarios for the Proposed Development Alone

 

  1. The PVA predicted that the Forth Islands SPA puffin population would increase over the 35 year projection period irrespective of the effects from the Proposed Development. Thus, the population is predicted to be almost three times larger than the current estimate of 87,240 adult birds under baseline conditions (i.e. no wind farm effects) and under each of the impact scenarios (Table 5.78). Given that the PVAs are based on density independent models, which assume all mortality from the wind farm effects is additive and that there are no compensatory mechanisms operating within the population, the predicted increases are inevitably greatest for the baseline scenario and least for the scenario involving highest annual mortality (i.e. Scoping Approach B). However, the differences between the scenarios in terms of the predicted increases and eventual 35 year population sizes are small. The predicted levels of increase are unlikely to occur in reality (and are, in part, a consequence of the absence of any compensatory density dependence within the models – as discussed in the section on Project Alone: Population-level impacts for the St Abb’s Head to Fast Castle SPA kittiwake population), and whilst the prediction for an increasing trend is consistent with the overall long-term trend for this SPA population it does not reflect the more recent decline in numbers (Figure 5.23).
  2. The predicted population-level impacts are small, irrespective of whether these are determined using the Developer or Scoping Approaches. Thus, for the upper range of the Scoping Approach the CPS value indicates that the predicted mortality associated with the Proposed Development alone would result in a reduction of approximately 1% in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects (Table 5.78). The associated reductions in annual population growth rate (relative to that predicted under baseline conditions) are not detectable (at least when the CPGR value is expressed to three decimal places) and the centile values are all above 48.0, indicating a considerable overlap in the distributions of the predicted impacted and un-impacted population sizes and, hence, a high likelihood of the impacted population being of a similar size to the un-impacted population after 35 years (Table 5.78).
Project alone: conclusion
  1. For both the Developer and Scoping Approaches, the potential effects from the Proposed Development alone on the Forth Islands SPA puffin population are predicted to be small, with the resultant population-level impacts also predicted to be small. In addition, the PVA metrics indicate a high chance of the population being of a similar size to that which would occur in the absence of the Proposed Development after 35 years. Given this, it is concluded that the effects from the Proposed Development alone would not result in an adverse effect on this population (with this conclusion being irrespective of whether these effects are determined by the Scoping or Developer Approach).
Effects in-combination
Effects of relevance to the in-combination assessment
  1. As detailed above, any effects from the Proposed Development alone on the Forth Islands SPA puffin population during construction and decommissioning and resulting from disturbance and changes to prey availability during operation and maintenance will be small and highly localised. As such, there is considered to be no potential for these effect pathways to add to impacts at the population-level that might result from other effects pathways associated with the Proposed Development or from the effects due to other plans and projects.
  2. Therefore, the potential for effects of the Proposed Development to act on the Forth Islands SPA puffin population in-combination with other plans and projects is limited to the displacement (inclusive of barrier effects) effect pathway during operation and maintenance. Following advice from NatureScot provided through the Ornithology Roadmap process (at meeting 3, 8th December 2021), the following sections consider these potential effects for (i) the Proposed Development in-combination with the other Forth and Tay wind farms and (ii) the Proposed Development in-combination with the other UK North Sea wind farms (noting that scenario (ii) includes those plans and projects which comprise scenario (i)).
Displacement/barrier effects – operation and maintenance
  1. As described in annex E of the Offshore EIA Report, volume 3, appendix 11.6, estimates of breeding season displacement mortality which had been attributed to the Forth Islands SPA puffin population were extracted from the existing assessments for offshore wind farms that are in planning, consented, under construction or in operation. As for the potential displacement mortality estimated for the Proposed Development, the mortality attributed to the SPA population from other offshore wind farms was estimated using the SNCB matrix approach, with details on the displacement and mortality rates that had been applied being available in each case. Thus, it was possible to adjust the estimated mortalities from each of the other projects to align with the displacement and mortality rates on which the Scoping and Developer Approaches are based.

 

Table 5.79:
Estimated Annual Mortality of Forth Islands SPA Puffins as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach, In-Combination with other Forth and Tay Wind Farms and UK North Sea Wind Farms

Table 5.79: Estimated Annual Mortality of Forth Islands SPA Puffins as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach, In-Combination with other Forth and Tay Wind Farms and UK North Sea Wind Farms

 

  1. Virtually all of the mortality associated with the other plans and projects was attributable to the other Forth and Tay wind farms, with the Kincardine and Hywind farms being the only other projects considered to have potential displacement effects on this SPA population (Table 5.79, annex D of Offshore EIA Report, volume 3, appendix 11.6). Given this, the Forth and Tay and UK North Sea in-combination scenarios are essentially the same and further consideration is limited to the Proposed Development in-combination with the other UK North Sea wind farms.
  2. Incorporating the potential mortality predicted from the displacement effects associated with the other UK North Sea wind farms leads to a near ninefold increase in the predicted displacement mortality compared to the Proposed Development alone for each of the Developer and Scoping Approaches (Tables 5.77 and 5.79).
  3. The resultant additional annual mortality of adult puffins from the Forth Islands SPA population predicted due to the in-combination displacement effects represents 0.05% of the current adult breeding population at this colony (i.e. 87,240 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach, and between approximately 0.18 – 0.30% of this population as determined by the lower and upper estimates from the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.099 – see Table 2.17 in the Offshore EIA Report, volume 3, appendix 11.6), the estimates of adult displacement mortality equate to an increase of 0.5% for the Developer Approach and of 1.8 – 3.1% for the lower and upper estimates from the Scoping Approach.
  4. The potential levels of impact on the Forth Islands SPA puffin population resulting from the mortality predicted from displacement and barrier effects associated with the Proposed Development in-combination with the other UK North Sea wind farms during the operation and maintenance phase are considered in more detail below in the Effects In-Combination: Population-Level Impacts section. This presents the outputs from PVAs of the potential effects of predicted displacement mortality on the SPA population.