Part 2. Appendix 2O. Greater Black Backed Gull EIA Analysis

Transcription

1 Part 2 Appendix 2O Greater Black Backed Gull EIA Analysis

2 Greater Black Backed Gull EIA Analysis

3 Introduction Natural England (NE) and JNCC (in their further detailed response to Relevant Representations, 28/03/13) recommended that further consideration was given to the direct (i.e. EA ONE alone) and cumulative impacts (EA ONE and other wind farms) on great blackbacked gull (GBG) at various population scales. It was suggested that population modelling may be useful to predict the thresholds at which GBG (from EA ONE alone and cumulatively) is likely to alter current national / international population trajectories. East Anglia Offshore Wind (EAOW) has considered the comments received from NE / JNCC and a review has been completed as to the most suitable apportionment of the GBG biogeographic populations that may potentially be impacted by EA ONE during each biological period (Breeding, Autumn Migration, Wintering and Spring Migration). In addition to the review of apportioning the population of GBG a revised Collision Risk Model (CRM) to assess the rate when flight height distribution data is used to assess the potential impacts of has also been completed. Biogeographic population The following population estimates for different biogeographic populations have been compiled using Mitchell et al (2004), with detail in Table 1. Total European Flyway Population = 313,878 birds Total East Coast & Western Europe Population = 152,120 birds Total Migrating out through Strait of Dover (Max No. Stienen) = 9,000 birds North Sea Wintering Population = 144,120 birds National (Eng, Sco, Wales, NI & IoM) Population = 51,496 birds 1

4 Table 1. Country populations used to derive the flyway population Total Flyway Population Estimate (AONs) Scotland 14,773 Wales 427 IoM 405 England 1,476 Northern Ireland 71 Republic of Ireland 2,248 Channel Islands 310 Estonia 2,000 Denmark 1,500 Faroe Islands 1,200 Finland 2,800 France 4,382 Germany 19 Iceland 15,000 Netherlands 15 Norway 40,000 Sweden 15,000 Russia 3,000 Total Apparently Occupied Nests (AONs) 104,626 Total Breeding Birds (AONs x2) 209,252 Total Population (including adults, juveniles & immatures) (AONs x3) 313,878 Using the above revised population estimates it has been possible to estimate the population of GBG for each of the four relevant biological periods for the North Sea, the most appropriate regional scale for assessment: Spring / Autumn Migration (incl resident birds) = 153,120 birds Breeding (National Only) = 51,496 birds Wintering = 144,120 birds CRM (Type B) from the Environmental Statement (ES) has been considered in comparison to a new CRM assessment (Type C). The following parameters were applied to the CRM: Both CRM scenarios using 98% avoidance Type B is using original (SOSS based) PCH of 33.1% (as in ES) Type C is using SOSS flight height distribution data Assessments made against baseline rate = 7.0% 2

5 Collision Risk Model Type B (SOSS PCH) CRM Type B is based on the same basic CRM parameters presented within the ES and using the apportionment principles developed in this technical note in the section above. The CRM Type B uses a PCH of 33.1% that is taken from the SOSS 02 project on flight heights. This value, which has commonly been used by other developers in offshore wind farm application environmental impact assessments (EIAs), has been used for this model run because it is a value that has been derived from a large number of wind farm pre-construction studies in UK waters and the sample size from site-specific data was deemed too small (under 100 birds). Table 2 presents the results of CRM Type B in relation to birds that are associated with the North Sea during each biological period and overall as an annual figure. It considers 98% avoidance rates and uses the SOSS 02 PCH of 33.1%. It does not use any additional proportioning for adults only from the site-specific survey data, as the assessment is against the total population, including adults, immatures and juveniles. CRM Type B has been applied to both an EA ONE alone collision risk assessment (Table 2) and also applied on a cumulative scale to include those developments that are operational, in construction or at an advanced stage of the planning system awaiting consent (Table 3). Collision Risk Model Type C (Band add-on) CRM Type C is based on the same basic CRM parameters presented within the ES and using the apportionment principles developed in this technical note in the section above. The difference in CRM Type C is that the CRM applies the detailed information on flight height distribution data within PCH that is used as an add-on to the standard Band model. That information being taken from the SOSS 02 project. The results of the collision risk assessment for EA ONE alone is presented in Table 2. Predicted mortalities are presented for calculations made on the basis of a 98% avoidance rate and from two CRM Types (B and C) against the North Sea populations during each biological period and overall as an annual figure. It considers 98% avoidance rates, but as with CRM Type B, it does not use any additional proportioning for adults only from the site-specific survey data, as the assessment is against the total population, including adults, immatures and juveniles. Assessment of collision risk impact The predicted annual can be considered against the of individual GBGs that occurs each year (7% annual baseline rate) to produce a figure for the percentage change in the number of individuals subject to each year this gives a measure Relative change in - number of birds that can be used to gauge the scale the effect. In addition, the baseline annual that occurs in the GBG population can be compared to the baseline annual that is predicted to occur as a result of the effect of the wind farm - this gives a second measure Baseline from present to predicted that can be used to gauge the scale of the effect. This has been carried out in Table 2 for GBG populations at the North Sea geographical scale to account for the most appropriate regional scale for EA ONE alone. 3

6 Table 2. EA ONE Alone CRM results (CRM Type B and Type C) Period Baseline Mortality (No. Birds) Type B Type BC Relative change CRM Results (No. Birds) Relative change in Baseline from present (7.0%) to predicted Spring 10, % to 7.02% Breeding 3, % to 7.02% Autumn 10, % to 7.29% Winter 10, % to 7.01% Annual 10, % to 7.32% CRM Results (No. Birds) in Baseline from present to predicted % to 7.005% % to % to 7.07% % to 7.003% % to 7.08% The results of the cumulative collision risk assessment is presented in Table 3. Predicted mortalities are presented for calculations made on the basis of a 98% avoidance rate and from two CRM Types (B and C). A number of the published collision risk predictions for the offshore wind farms used in this cumulative assessment did not provide a seasonal breakdown of their predictions, providing only an annual figure. Accordingly it is not possible to consider in-combination impacts for each season in the manner as has been done for the EA ONE alone analysis above. As with the EA ONE alone collision risk assessment the predicted cumulative annual has been considered for the Relative change in - number of birds and for the Baseline from present to predicted that have both been used to gauge the scale of the cumulative effect. This has been carried out in Table 3 for GBG populations at the North Sea and Total Flyway scales to account for the cumulative impact from the offshore wind farms that are operational, in construction, consented or to have their consent decision made before EA ONE. 4

7 Table 3. EA ONE Cumulative CRM results (CRM Type B and Type C) North Sea Pop Total Flyway EA ONE (CRM Type B) Total North Sea (including EA 1,353 1,353 ONE CRM Type B) Total North Sea Population 153, ,878 Annual Baseline Mortality (7%) 10,718 21,971 Relative change in 12.62% 6.16% Baseline from present (7.0%) to predicted 7.0% to 7.88% 7.0% to 7.43% EA ONE (CRM Type C) Total North Sea (including EA ONE CRM Type C) Total North Sea Population 153, ,878 Annual Baseline Mortality (7%) 10,718 21,971 Relative change in 9.07% 4.42% Baseline from present (7.0%) to predicted 7.0% to 7.63% 7.0% to 7.31% Conclusions With respect to the North Sea population, for all CRM Types the relative change in the number of birds subject to each year is predicted to be an increase of, at most, 9.07%. This is for CRM Type B that uses SOSS 02 PCH data. In no circumstance though is the change in annual baseline approaching a one percentage point difference the maximum increase is from the current 7.0% to 7.63%. It is considered that this level of additional would have little impact on the current population trends of the North Sea GBG population and less on the total flyway population (7.0% to 7.31%). Further analysis of the effect of the predicted EA ONE alone or cumulative, through for instance population modelling, is not justified, as it is considered that the impacts through collision will not have a significant adverse effect on either the North Sea or total flyway populations of GBG. 5