3. Results

3.1. Harbour Porpoise

3.1.1. Scenario HP-01: Maximum Temporal Scenario

  1. Results for the maximum temporal scenario indicate a very small difference in the growth trajectory of harbour porpoise between the unimpacted population and impacted population ( Figure 3.1   Open ▸ ). At all time points, there was little difference in the mean size of the impacted and unimpacted populations, with a maximum difference of 2,048 individuals (approximately 0.59% of the North Sea MU reference population) at time point 9, corresponding to the first year after completion of the piling phase ( Table 3.1   Open ▸ ).

Figure 3.1:
Simulated Harbour Porpoise Population Trajectories in an Unimpacted Versus Impacted Population, for the Maximum Temporal Scenario HP-01

Figure 3.1: Simulated Harbour Porpoise Population Trajectories in an Unimpacted Versus Impacted Population, for the Maximum Temporal Scenario HP-01

 

  1. At time point 7, which represents the end of the piling phase for wind turbine anchors, and corresponding to the six-year reporting period formerly required under the Habitats Directive, the impacted population was predicted to be 1,608 animals smaller than the unimpacted population (approximately 0.46% of the North Sea MU reference population).
  2. At time point 13, which corresponds with six years after the end of the piling phase for wind turbine anchors, and twelve years after the start of the piling phase (aligning with the duration of one and two Habitats Directive reporting periods, respectively) the difference between the impacted and unimpacted populations was 1,869 animals, approximately 0.54% of the reference population.

 

Table 3.1:
Modelled Estimates for the Unimpacted and Impacted Harbour Porpoise Populations and Counterfactuals of Population Size for the Maximum Temporal Scenario HP-01

Table 3.1: Modelled Estimates for the Unimpacted and Impacted Harbour Porpoise Populations and Counterfactuals of Population Size for the Maximum Temporal Scenario HP-01

 

  1. At time point 26, which represents the population at the end point of the iPCoD modelling, 25 years after the start of piling (and 18 years after the completion of the piling phase), this difference is 1,878 animals, corresponding to approximately 0.54% of the reference population ( Table 3.1   Open ▸ ). This suggests that there would not be a long term effect from piling at the Array upon the harbour porpoise population within the North Sea MU.
  2. The median counterfactual for this scenario fluctuated between 1.0000 and 0.9984 through the 26-year simulation, whereas the mean counterfactual reduced to 0.9946 by the end of the simulation. Therefore, given that the differences in disturbed to un-disturbed populations approaches a ratio of 1 there is not considered to be a potential for a long term effect from this piling scenario upon harbour porpoise within the North Sea MU.

3.1.2. Scenario HP-02: Maximum Spatial Scenario

  1. Results for the maximum spatial scenario indicate a very small difference in the growth trajectory of harbour porpoise between the unimpacted population and impacted population ( Figure 3.2   Open ▸ ). At all time points there was little difference in the mean size of the impacted and unimpacted populations, with a maximum difference of 1,371 individuals (approximately 0.40% of the North Sea MU reference population) at time point 9, corresponding to the first year after the completion of the piling phase ( Table 3.2   Open ▸ ).

Figure 3.2:
Simulated Harbour Porpoise Population Trajectories in an Unimpacted Versus Impacted Population, for the Maximum Spatial Scenario HP-02

Figure 3.2: Simulated Harbour Porpoise Population Trajectories in an Unimpacted Versus Impacted Population, for the Maximum Spatial Scenario HP-02

 

  1. At time point 7, which represents the end of the concurrent portion of the piling phase for the Array, and corresponding to the six-year reporting period formerly required under the Habitats Directive, the impacted population was predicted to be 1,142 animals smaller than the unimpacted population (approximately 0.33% of the North Sea MU reference population).
  2. At time point 13, which corresponds with six years after the end of concurrent piling, and twelve years after the start of the piling phase (aligning with the duration of one and two Habitats Directive reporting periods, respectively) the difference between the impacted and unimpacted populations was 1,284 animals, approximately 0.54% of the reference population.

 

Table 3.2:
Modelled Estimates for the Unimpacted and Impacted Harbour Porpoise Populations and Counterfactuals of Population Size for the Maximum Spatial Scenario HP-02

Table 3.2: Modelled Estimates for the Unimpacted and Impacted Harbour Porpoise Populations and Counterfactuals of Population Size for the Maximum Spatial Scenario HP-02

  1. At time point 26, which represents the population at the end point of the iPCoD modelling, 25 years after the start of piling (and 18 years after the completion of the piling phase), this difference is 1,302 animals, corresponding to approximately 0.38% of the reference population ( Table 3.2   Open ▸ ). This suggests that there would not be a long term effect from piling at the Array upon the harbour porpoise population within the North Sea MU.
  2. The median counterfactual for this scenario reduced from 1.0000 to 0.9994 at the end of the 26-year simulation, while the mean counterfactual reduced to 0.9963 by the end of the simulation. This is greater than the corresponding counterfactual from the maximum temporal scenario, suggesting that the maximum spatial scenario may result in a smaller impact.
  3. Given that the differences in disturbed to un-disturbed populations approaches a ratio of 1 there is considered to be no potential for a long term effect from this piling scenario upon the North Sea MU population of harbour porpoise.

3.1.3. Scenario HP-C1: Cumulative Scenario

  1. For scenario HP-C1, in which a total of 306 days of piling were modelled at the Array alongside a total of 273 piling days across Tier 1 cumulative projects (112 days at Berwick Bank, and 161 days at Hornsea Three) these results indicate a small difference in the simulated trajectories of harbour porpoise between the unimpacted population and impacted population ( Figure 3.3   Open ▸ ). This corresponds to a difference of 2,114 fewer animals in the impacted population at time point 26, compared to the un-impacted population ( Table 3.3   Open ▸ ), corresponding to 0.61% of the North Sea MU reference population.
  2. At time point 5, which corresponds to the third year of piling at the Array, the first year after the end of piling at Berwick Bank, and three years after the end of piling at Hornsea Three, the difference between impacted and un-impacted populations is 1,210 animals (0.35% of the reference population). When compared to the equivalent time point from scenario HP-01 (i.e. three years into the maximum temporal scenario for the Array alone: section 3.1.1), this is a difference between scenarios of 733 animals.

Figure 3.3:
Simulated Harbour Porpoise Population Trajectories in an Unimpacted Versus Impacted Population, for Cumulative Scenario HP-C1

Figure 3.3: Simulated Harbour Porpoise Population Trajectories in an Unimpacted Versus Impacted Population, for Cumulative Scenario HP-C1

 

Table 3.3:
Modelled Estimates for the Unimpacted and Impacted Harbour Porpoise Populations and Counterfactuals of Population Size for Cumulative Scenario HP-C1

Table 3.3: Modelled Estimates for the Unimpacted and Impacted Harbour Porpoise Populations and Counterfactuals of Population Size for Cumulative Scenario HP-C1

 

  1. At time point 16, six years after the end of piling at the Array and 12 years after the end of piling at Berwick Bank (both corresponding with the duration of Habitats Directive reporting periods), the difference between impacted and unimpacted populations is 2,108. When compared to the equivalent time point from scenario HP-01 (i.e. six years after the end of piling at the Array alone: section 3.1.1), this is a difference between scenarios of 500 animals.
  2. The median counterfactual of population size for cumulative scenario HP-C1 was 0.9990 at the end of the 26-year simulation, while the mean counterfactual was 0.9940. Therefore, given that the differences in disturbed to undisturbed populations approaches a ratio of 1 there is not considered to be a potential for a long term population-level effect from this cumulative piling scenario upon harbour porpoise within the North Sea MU.

3.2. Bottlenose Dolphin

3.2.1. Scenario BND-01: Maximum Temporal Scenario

  1. Results for the maximum temporal scenario indicate a small difference in the growth trajectory of bottlenose dolphin between the unimpacted population and impacted population ( Figure 3.4   Open ▸ ). At all time points there was little difference in the mean size of the impacted and unimpacted populations, with a maximum difference of seven individuals (approximately 3.13% of the Coastal East Scotland MU reference population) at time point 25 and 26, corresponding to 24 years after the start of piling, and 18 years after the completion of piling for wind turbine anchors ( Table 3.4   Open ▸ ), and both aligning with the duration of Habitats Directive reporting periods.

Figure 3.4:
Simulated Bottlenose Dolphin Population Trajectories in an Unimpacted Versus Impacted Population, for the Maximum Temporal Scenario BND-01

Figure 3.4: Simulated Bottlenose Dolphin Population Trajectories in an Unimpacted Versus Impacted Population, for the Maximum Temporal Scenario BND-01

 

  1. At time point 7, which represents the end of the piling phase for wind turbine anchors, and corresponds to the six-year reporting period formerly required under the Habitats Directive, the impacted population was predicted to be three animals smaller than the unimpacted population (approximately 1.34% of the Coastal East Scotland MU reference population).
  2. At time point 13, which corresponds with six years after the end of the piling phase for wind turbine anchors, and twelve years after the start of the piling phase (aligning with the duration of one and two Habitats Directive reporting periods, respectively) the difference between the impacted and unimpacted populations was four animals, approximately 1.79% of the reference population.

 

Table 3.4:
Modelled Estimates for the Unimpacted and Impacted Bottlenose Dolphin Populations and Counterfactuals of Population Size for the Maximum Temporal Scenario BND-01

Table 3.4: Modelled Estimates for the Unimpacted and Impacted Bottlenose Dolphin Populations and Counterfactuals of Population Size for the Maximum Temporal Scenario BND-01

  1. At time point 26, which represents the population at the end point of the iPCoD modelling, 25 years after the start of piling (and 18 years after the completion of the piling phase), this difference is seven animals, corresponding to approximately 3.13% of the reference population ( Table 3.4   Open ▸ ). This suggests that there would not be a long term effect from piling at the Array upon the bottlenose dolphin population within the Coastal East Scotland MU.
  2. The median counterfactual for scenario BND-01 remained at 1.0000 throughout the 26-year simulation, whereas the mean counterfactual fluctuated between a maximum of 1.0000 and a minimum of 0.9868, to finish at 0.9882 by the end of the simulation. Given that the differences in disturbed to un-disturbed populations approaches a ratio of 1 there is considered to be no potential for a long term effect from this piling scenario upon bottlenose dolphin within the Coastal East Scotland MU.

3.2.2. Scenario BND-02: Maximum Spatial Scenario

  1. Results for the maximum spatial scenario indicated a small difference in the growth trajectory of bottlenose dolphin between the unimpacted population and impacted population ( Figure 3.5   Open ▸ ). At all time points there was little difference in the mean size of the impacted and unimpacted populations, with a maximum difference of four individuals (approximately 1.79% of the Coastal East Scotland MU reference population) at time points 21 to 26, corresponding to 20 years after the start of piling, and 18 years after the end of the piling phase, respectively ( Table 3.5   Open ▸ ).

Figure 3.5:
Simulated Bottlenose Dolphin Population Trajectories in an Unimpacted Versus Impacted Population, for the Maximum Spatial Scenario BND-02

Figure 3.5: Simulated Bottlenose Dolphin Population Trajectories in an Unimpacted Versus Impacted Population, for the Maximum Spatial Scenario BND-02

 

  1. At time point 7, which represents the end of the concurrent piling portion of the piling phase and corresponds to the six-year reporting period formerly required under the Habitats Directive, the impacted population was predicted to be three animals smaller than the unimpacted population (approximately 1.34% of the Coastal East Scotland MU reference population).
  2. At time point 13, which corresponds with six years after the end of the concurrent piling phase, and twelve years after the start of the piling phase (aligning with the duration of one and two Habitats Directive reporting periods, respectively) the difference between the impacted and unimpacted populations was three animals, approximately 1.34% of the reference population.

 

Table 3.5:
Modelled Estimates for the Unimpacted and Impacted Bottlenose Dolphin Populations and Counterfactuals of Population Size for the Maximum Spatial Scenario BND-02

Table 3.5: Modelled Estimates for the Unimpacted and Impacted Bottlenose Dolphin Populations and Counterfactuals of Population Size for the Maximum Spatial Scenario BND-02

 

  1. At time point 26, which represents the population at the end point of the iPCoD modelling, 25 years after the start of piling (and 18 years after the completion of the piling phase), this difference is four animals, corresponding to approximately 1.79% of the reference population ( Table 3.5   Open ▸ ). This indicates that there would not be a long term effect from piling at the Array upon the bottlenose dolphin population within the Coastal East Scotland MU.
  2. The median counterfactual for scenario BND-02 remained at 1.0000 throughout the 26-year simulation, whereas the mean counterfactual fluctuated between a maximum of 1.0000 and a minimum of 0.9907, to finish at 0.9916 by the end of the simulation. This is greater than the corresponding counterfactual from the maximum temporal scenario, suggesting that the maximum spatial scenario may result in a smaller impact.
  3. Given that the differences in disturbed to un-disturbed populations approaches a ratio of 1 there is considered to be no potential for a long term effect from this piling scenario upon bottlenose dolphin.

3.2.3. Scenario BND-C1: Cumulative Scenario

  1. For scenario BND-C1, in which a total of 306 days of piling were modelled at the Array alongside a total of 112 piling days at Berwick Bank, these results indicate a small difference in the simulated trajectories of bottlenose dolphin between the unimpacted population and impacted population ( Figure 3.6   Open ▸ ). This corresponds to a difference of 10 fewer animals in the impacted population at time point 26, compared to the un-impacted population ( Table 3.6   Open ▸ ), corresponding to approximately 4.46% of the Coastal East Scotland MU reference population.
  2. At time point 5, which corresponds to the third year of piling at the Array and the first year after the end of piling at Berwick Bank, the difference between impacted and un-impacted populations is three animals (1.34% of the reference population). When compared to the equivalent time point from scenario BND-01 (i.e. three years into the maximum temporal scenario for the Array alone: section 3.2.1), this is a difference between scenarios of two animals.

Figure 3.6:
Simulated Bottlenose Dolphin Population Trajectories in an Unimpacted Versus Impacted Population, for Cumulative Scenario BND-C1

Figure 3.6: Simulated Bottlenose Dolphin Population Trajectories in an Unimpacted Versus Impacted Population, for Cumulative Scenario BND-C1

 

  1. At time point 16, six years after the end of piling at the Array and 12 years after the end of piling at Berwick Bank (both corresponding with the duration of Habitats Directive reporting periods), the difference between impacted and unimpacted populations is seven animals. When compared to the equivalent time point from scenario BND-01 (i.e. six years after the end of piling at the Array alone: section 3.1.1), this is a difference between scenarios of four animals.
  2. The median counterfactual of population size for cumulative scenario BND-C1 was 1.0000 throughout the 26-year simulation, while the mean counterfactual was varied between a maximum of 1.000, and a minimum of 0.9820 at time point 11, increasing to 0.9824 at the end of the simulation. Therefore, given that the differences in disturbed to undisturbed populations approaches a ratio of 1 there is not considered to be a potential for a long term population-level effect upon bottlenose dolphin.

 

Table 3.6:
Modelled Estimates for the Unimpacted and Impacted Bottlenose Dolphin Populations and Counterfactuals of Population Size for Cumulative Scenario BND-C1

Table 3.6: Modelled Estimates for the Unimpacted and Impacted Bottlenose Dolphin Populations and Counterfactuals of Population Size for Cumulative Scenario BND-C1