Abstract
Potiek et al. (2022) assessed the population level effects of bird collisions in wind farms named in the 'North Sea Programme 2022-2027 (also referred to as KEC 4.0) for a number of relevant bird species. This was an update of Rijkswaterstaat (2019) (KEC 3.0) and included updates of the bird input parameters as well as the wind farm scenarios.
In Potiek et al. (2022), the number of collision victims was predicted using a collision rate model, based on among others bird density maps, assumptions about avoidance and other bird characteristics, and turbine characteristics. This resulted in an estimated number of collision victims per wind farm. For each of the scenarios, the victims were summed for the relevant combination of wind farms. The impact of habitat loss due to wind farms was simultaneously assessed by Soudijn et al. (2022). For northern gannet, the impact due habitat loss was much lower than the impact due to collisions.
Subsequently, the population-level impact was assessed using population models. These population models project the population trajectory for the situation without wind farms (null scenario) as well as for each wind farm scenario. The outcome of these population models was assessed by comparing these to a threshold set by LNV (Acceptable Level of Impact, ALI). These thresholds were based on a method developed by Potiek et al. (2021), in which the probability of a certain decline because of the impact was compared to a threshold set on beforehand.
For northern gannet, the defined ALI threshold was a maximal 50% probability of a 30% decline after 30 years, as a result of the impact. Based on this analysis, the assessed impact on northern gannet resulted in a violation of the ALI threshold for each of the scenarios formulated within the North Sea Programme 2022-2027.
As an extension of the KEC 4.0 study, Rijkswaterstaat asked for a refinement of the cumulative impact assessment for northern gannet, with a focus on the assessment of collision mortality. This consists of several topics:
Collision rate modelling:
1. Literature study to assess whether the input parameters of the sCRM should and could be updated.
2. Literature study of the avoidance rate, combined with assessment of the appropriateness of the use of the avoidance rate in the current model and situation.
3. Assessment of the sCRM input parameters, as well as the results.
Population modelling:
4. Discussion of the used population definition, and the manner of applying the collision victims to this population.
5. Update of the age distribution among victims to match the expected age distribution within individual wind farms.
6. Reassessment of the population effects of collision mortality on northern gannet based on the results from topics 1 to 5.
7. Sensitivity analysis of the population model predictions to life history parameters.