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Scottish Marine and Freshwater Science Report Volume 2 Number 13

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Approach

As was the case in the development of the Draft Plan for Offshore Wind Energy in Scottish Territorial Waters, and the Scoping Study for the Saltire Prize programme for wave and tidal power development, Marine Scotland has worked with The Crown Estate to use MaRS for the identification of potential areas for offshore wind development .

As previously mentioned, in order to apply the MaRS tool, it is necessary for the user to make a number of decisions regarding the data to be included in the models and the way in which the data are to be handled. These decisions include factors such as:

  • The factors that require consideration when locating offshore wind developments and the availability of spatial data that can be included in the models.
  • Whether particular activities or uses should be considered as incompatible with wind farm development, or whether activities or uses should be considered as presenting gradations of limitation to development potential.
  • The relative importance (weighting and scoring) that should be applied to the different layers of data in the final integrated model.
  • The relative quality and reliability of data layers.

The Sensitivity Analysis noted that some of the sensitivity of the final outputs had probably arisen through the use of a single model of environmental constraints. This required that relative weightings are developed for very diverse types of data ( e.g. the relative weighting of seabird colonies, wrecks, fish landings, and basking shark sightings). This is very difficult to apply without some clear additional frame of reference, such as consenting risk. Alternatively, grouping the data layers into themes ( e.g. industrial, environmental, heritage etc) would present fewer conceptual problems, and assessing the sensitivity of the outputs to variation in the overall weighting between themes could be achieved. This latter approach had previously been used successfully in the Scoping Study for the Saltire Prize. A similar approach has therefore been adopted in the current study, grouping constraints layers into themes representing constraints arising from industrial activity, environmental factors and heritage interests.

The purpose of the Sensitivity Analysis was explore the sensitivity of the outcome of the MaRS modelling used to identify the medium term options within The Draft Plan to the selection of data layers to use in the model, and the scoring/weighting applied to them. A number of technical improvements to the data handling processes were identified, as below, and these were implemented in the current Scoping Study.

a) Transfer some heavily weighted data layers from the constraint models to the exclusion models. This had the effect of allowing other layers in the constraint models to have greater influence on the outcome of the modelling.

b) Amend the scoring system to match the recommendations of the model owners, ie The Crown Estate. This was done for statistical reasons, which are beyond the scope of this report. However, adherence to the MaRS guidelines is likely to give greater confidence in the outputs.

c) Amend the weightings given to different data layers to better reflect the degree of risk to consenting that experience suggests might arise from the subject covered by each layer during the licensing process.

d) Amend the classification/scoring system for statistically skewed data sets. This had the effect of enabling these data layers to have more appropriate influence on the final integrated models and to enable improved discrimination between areas,

Furthermore, in undertaking the sensitivity analysis, it was noted that improvements could be made in some of the data layers to better reflect their significance for wind farm development. Examples include:

a) The analyses use the JNCC seabird at sea data set. It would be better to use the more comprehensive European Seabird at Sea ( ESAS) data and to distinguish between species according to their sensitivity to wind farm developments. It should be noted that these data were not available in a suitable form at the time of the original MaRS modelling work undertaken by the consultants.

b) The fish spawning and nursery ground data are now more than 10 years old and are in the process of being revised.

c) The fish (fisheries) value combines across all gears and all vessels. A better analysis could be developed using VMS data for >15m vessels, distinguishing between gear types (and perhaps species). There is a significant lack of detailed information on <15 m vessels, which are likely to be important in some of the proposed areas.

d) Some of the data layers used by the SG Consultants in the MaRS models on the distribution of wildlife, such as seals, basking sharks, etc, although the best available at the time, had been derived from non-systematic survey methods and may therefore have been biased by the distribution of observer effort.

e) All SACs and SPAs are treated equally, while the risk arising from wind farms will differ between species and habitats. A more risk-based approach could improve the targeting of the assessment.

f) A broad range of conservation sensitivities could be taken into account by consideration of the distribution of SNH Priority Marine Features. Maps of these are in preparation.

Where possible, improved or updated data layers were used in the current Scoping Study.