1 Introduction

  1. This report presents the method for, and results obtained from, modelling the population consequences of potential impacts to the protected seabird features of Special Protection Areas (SPAs) arising from the proposed Berwick Bank Offshore Development. The modelling informs the assessments and conclusions presented in the Offshore Environmental Impact Assessment Report (EIAR) (volume 2) chapter 11: Marine Ornithology, and in the Report to Inform Appropriate Assessment (RIAA).
  2. The modelling was performed using Population Viability Analysis (PVA) for breeding colonies of seven species of seabirds within multiple SPAs. Stochastic, density independent, age-structured matrix models were used to simulate population trends over time for a range of impacts scenarios.
  3. Collision and displacement / barrier effects are the key impacts on seabird species from the proposed Development and have been quantified in Technical Appendix 11.3: Ornithology Collision Risk Modelling Report and Technical Appendix 11.4: Ornithology Displacement Report. The estimated mortalities for each species were apportioned by age-class and season to relevant SPAs using the methods and weightings set out in Technical Appendix 11.5: Ornithology Apportioning Report and presented in Annex D: Apportioned Mortality.
  4. The species/ SPA combinations modelled were chosen using a threshold approach advised in the Scoping Opinion (MS-LOT, 2022) and confirmed through the Ornithology Roadmap process (Meeting 6, 10th May, 2022) (see Section 2).
  5. Full details of the species and SPAs modelled and the analysis undertaken, including model specifications and demographic rates used, are provided (see Section 2)
  6. In addition, regional calculations are provided for each of the seven species (Section 2.5). In these cases, PVAs for multiple SPAs under a range of impact scenarios were combined to estimate effects on regional population sizes.

2 Methods

  1. PVA modelling here is performed using the Natural England nepva tools (Searle et al. 2019; Mobbs et al. 2020). This software has broadly two implementations, one with a user-friendly GUI, the other a series of code tools for direct use. Both are written in R and are intended to give the same fundamental calculations. Here we have used bespoke R-code directly, with nevpa version 2 tools as a basis (Mobbs et al. 2020) (tool v 2.0, nepva R package: v 4.17), as found within the associated Natural England github repository:  https://github.com/naturalengland/Seabird_PVA_Tool). All analysis was conducted using R version 4.1 for Windows (R Core Team, 2021),
  2. Notably one function from the nepva package was modified (inits.burned) to allow a burn-in period for establishing an initial population age-structure, but also to fix adult numbers as known at the start of simulation. This is not currently catered for within the nepva tools.
  3. While this offers a standardised toolset for PVAs, the underpinnings are projections using commonplace population matrix models. Documentation detailing these models can be found within the repository indicated and are summarised in Section 2.2.

2.1 Models and Scenarios

  1. The potential impacts of the proposed Berwick Bank wind farm on the population growth and size of seabird species inhabiting SPAs were predicted using PVA.
  2. Additional annual mortality (combined breeding and non-breeding season mortality estimates) was derived by summing the apportioned collision and/or displacement mortality estimates combined for each species / SPA combination. This was done by age class (adult and immature) based on the age class information from the site-specific surveys for gannets, kittiwake and gulls, and asymptotic age distributions for auks. The age-class apportioned total mortality estimates are provided in Annex D of Technical Appendix 11.5: Ornithology Apportioning Report. The complete suite of seasonal apportioned mortality estimates for each species, colony, age class and by impact type (collision or displacement or both) are available electronically as Excel Files: Annex A (breeding season mortalities) and Annex B (non-breeding season mortalities).
  3. Following the advice received through the Ornithology Roadmap Process (meeting 4; Technical Appendix 11.8) breeding season mortality was adjusted downward to account for sabbatical birds: 7% for auks and 10% kittiwakes. For other species, the rates used were as those revised designs in Forth and Tay: 10% for gannet and 35% for herring gull and lesser black-backed gull.
  4. These mortality estimates constituted a number of “Project alone” (i.e., potential additional mortality from the proposed Development) PVA model scenarios (Table 2.1).
  5. Estimates of displacement mortality under the Developer Approach were based on the Applicants review of existing evidence to underpin the use of single species-specific seasonal displacement and mortality rates to identify the mortality estimates from the displacement matrices. The Scoping Approach followed the advice in Scoping Opinion (MS-LOT, 2022) and the displacement and mortality rates advised by NatureScot in their scoping advice (7th December 2021). NatureScot advised two mortality rates (e.g. 3% and 5%) and the lower rate is represented as “Scoping Approach a” and the higher rates as “Scoping Approach b”. Full details are provided in (Technical Appendix 11.4: Ornithology Displacement Report).
  6. Estimates of potential collision mortality under the Developer Approach were based on mean monthly flying seabird densities, whereas maximum monthly flying seabird densities were used for the Scoping Approach. For species only assessed for collision, Scoping Approach a and b are identical. Full details are provided in Technical Appendix 11.3: Ornithology Collision Risk Modelling Report.
  7. PVAs were run for populations where the predicted wind farm associated mortality increased the baseline mortality rate by at least 0.02 percentage point (NatureScot Scoping Advice, 14th December 2021). This was calculated as the predicted additional annual mortality (in terms of the number of adult birds) expressed as a percentage of the number of adult birds in the SPA population (confirmed at meeting 5, Appendix 11.8: Ornithology Roadmap Process). The assessment of annual adult mortality against the threshold is given in Annex C.
  8. The final list of species and SPAs modelled using Project alone mortality estimates are given in Table 2.2. Note that the estimated mortality for some species and SPAs only exceeded the threshold for the Scoping Approach but a Developer Approach model was run for comparative purposes. The estimated mortalities modelled associated with each of the scenarios are given in Section 3.1

Table 2.1: Summary of three Project-alone scenarios used in the PVA models, identifying the causes of mortality for each species and the seasons in which they were assessed; B = breeding season and NBS = non-breeding season

 

Developer approach

Scoping Approach a

Scoping Approach b

 

Collision

Displacement

Collision

Displacement

Collision

Displacement

Gannet

 B + NBS

  B + NBS

  B + NBS

  B + NBS

  B + NBS

  B + NBS

Guillemot

 

  B + NBS

 

  B + NBS

 

  B + NBS

Herring gull *

  B + NBS

 

  B + NBS

 

  B + NBS

 

Kittiwake

  B + NBS

B

  B + NBS

  B + NBS

  B + NBS

  B + NBS

Lesser black-backed gull*

   B + NBS

 

   B + NBS

 

   B + NBS

 

Puffin

 

 B

 

 B

 

 B

Razorbill

 

   B + NBS

 

   B + NBS

 

   B + NBS

Table 2.2:  Project alone species and SPA combinations modelled. Green = threshold was exceeded for both the Developer and Scoping Approach; Orange = threshold was exceeded only for the Scoping Approach

 

Species

SPA

Gannet

Guillemot

Herring gull

Kittiwake

Lesser black-backed gull

Puffin

Razorbill

Buchan Ness to Collieston Coast

 

 

 

 

 

 

 

Coquet Island

 

 

 

 

 

 

 

East Caithness Cliffs

 

 

 

 

 

 

 

Farne Islands

 

 

 

 

 

 

 

Flamborough and Filey Coast

 

 

 

 

 

 

 

Forth Islands

 

 

 

 

 

 

 

Fowlsheugh

 

 

 

 

 

 

 

North Caithness Cliffs

 

 

 

 

 

 

 

St Abb’s Head to Fast Castle

 

 

 

 

 

 

 

Troup, Pennan and Lion’s Heads

 

 

 

 

 

 

 

West Westray

 

 

 

 

 

 

 

 

  1. PVA models and scenarios were also run for in-combination additional mortality. A summary of the approach taken to collation of mortality estimates for in-combination assessment is provided in Annex E.
  2. Mortality estimates were collated and assigned to each of the three approaches for each of the in-combination scenarios (Table 2.3) and the mortality totals are given in Annex D.
  3. Mortality estimates for the in-combination models were identified for plans/projects for two regions: i) Forth and Tay and ii) North Sea. Estimated mortality totals were collated for consented and as-built designs, where available, for each region. The scenarios considered were:
  • Forth and Tay: Consented – Developer Approach; Consented – Scoping Approach A; Consented – Scoping Approach B
  • North Sea: Consented – Developer Approach; Consented – Scoping Approach A; Consented – Scoping Approach B
  • North Sea: As-built – Developer Approach; As-built – Scoping Approach A; As-built – Scoping Approach B
  1. In the Forth and Tay, there were no differences between the consented and as-built mortality totals for any species and therefore, only consented mortality estimates were modelled.
  2. In the UK North Sea, mortality totals for as-built and consented projects were compared, and where the difference between estimates was greater than 5%, then both were modelled. When less than 5%, consented totals only were modelled.
  3. The estimated Project alone mortalities were added to the in-combination estimated mortalities under each scenario for each species/SPA combination.
  4. There were no in-combination totals available for lesser black-backed gull. The SPA populations screened in are the Forth Islands, Farne Islands and Coquet Islands SPA and Project effects are limited to breeding season. No existing/consented/in-planning projects are considered to have effects on Farne Islands and Coquet Island SPA populations during the breeding season. For Forth Islands SPA population there is potential for breeding season effects from the consented Forth & Tay projects. However, no estimates of effects are available from the assessments of the 2017 revised designs of these projects because the respective scoping opinion excluded consideration of the species. The most relevant information pertaining to effects on the Forth Islands SPA population derives from the 2014 MS AA for the Forth & Tay projects. This states that a predicted effect of < -0.1% decline in adult survival was identified on this SPA population as a result of the NnG project and concludes no adverse effect on site integrity. Therefore, it is assumed that existing in-combination effects are inconsequential and can be ignored.
  5. In total, PVA models were run for 40 species/SPA combinations and given the scenarios identified below, this resulted in 234 model runs. The mortality estimates for each are provided in the summary tables in section 3.

Table 2.3:  Summary of the species and SPAs that were modelled using in-combination mortality estimates from as-built and/or consented projects in the Forth and Tay and UK North Sea

Species

SPA

Forth and Tay

UK North Sea

Consented

As-built

Consented

Gannet

Forth islands

Y

 

Y

Flamborough and Filey Coast

N/A

Y

Y

North Rona & Sula Sgeir

N/A

 

Y

Fair Isle

N/A

 

Y

Noss

N/A

 

Y

Hermaness, Saxa Vord & Valla Field

N/A

 

Y

Kittiwake

Forth Islands

Y

 

Y

Fowlsheugh

Y

 

Y

St Abb's Head to Fastcastle

Y

 

Y

Buchan Ness to Collieston Coast

Y

Y

Y

East Caithness Cliffs

N/A

Y

Y

North Caithness Cliffs

N/A

Y

Y

Troup, Pennan & Lion's Head

N/A

Y

Y

Farne Islands

N/A

 

Y

Coquet Island

N/A

 

Y

Flamborough and Filey Coast

N/A

Y

Y

West Westray

N/A

Y

Y

Herring gull

Forth Islands

 

 

Y

Fowlsheugh

Y

 

Y

St Abb's Head to Fastcastle

 

 

Y

Guillemot

Forth Islands

 

N/A

Y

Fowlsheugh

 

N/A

Y

St Abb's Head to Fastcastle

 

N/A

Y

Buchan Ness to Collieston Coast

Y

N/A

Y

Troup, Pennan & Lion's Head

N/A

N/A

Y

East Caithness Cliffs

N/A

N/A

Y

Farne Islands

N/A

N/A

Y

Razorbill

Forth Islands

Y

N/A

Y

Fowlsheugh

Y

N/A

Y

St Abb's Head to Fastcastle

Y

N/A

Y

Troup, Pennan & Lion's Head

N/A

N/A

Y

East Caithness Cliffs

N/A

N/A

Y

Farne Islands

N/A

N/A

Y

Flamborough and Filey Coast

N/A

N/A

Y

Puffin

Forth Islands

 

N/A

Y

North Caithness Cliffs

N/A

N/A

Y

Farne Islands

N/A

N/A

Y