Current procedures for collecting empirical data, modelling effects on demographic rates and translating those effects into projected impacts of offshore wind farms on seabird populations are inadequate. Empirical measurements of effects of offshore wind farms on seabird demographic rates from fieldwork are not sufficiently precise and unbiased. In the case of some important parameters such as turbine avoidance rates and the strength of density-dependent compensation, estimation is rarely even attempted. As a result of these holes in the evidence base, the magnitude of effects of wind farms on seabird demographic rates cannot be estimated accurately and the level of bias and precision in the estimates used cannot be calculated.
To overcome these problems, responsible governments should require the renewable energy industry to co-fund an adequate level of field-based research to estimate effects of wind farms on seabird demographic rates more reliably. The Offshore Renewables Joint Industry Partnership (ORJIP) intends to address this need (Carbon Trust 2015), but the objectives of its project need to be greatly expanded with regard to the number of species covered, proximity to their breeding colonies and robustness of estimation. Further development and deployment of radar, imaging and tracking techniques are likely to be required, including remote download 3D tracking (Cleasby et al. 2015). A defensible approach is then needed to translate these effect measurements, and their uncertainties, into expected impacts on populations. We propose that the counterfactual population ratio from a density-independent Leslie matrix model would be an appropriate method for this translation.
Quite separate from these problems of measurement, estimation and modelling, there is a fundamental logical flaw in the link between scientific assessment and decision-making about the acceptability of wind farm impacts. Modelling approaches have been contrived that seek to define an acceptable threshold for a projected negative impact of a wind farm on seabird populations, below which this negative impact is regarded as causing no adverse effect on site integrity. However, the emperor has no clothes: the thresholds used to define the acceptability of projected offshore wind farm impacts are arbitrary, poorly reasoned, not designed for the purpose and have no valid biological basis. Hence, it is necessary to revise decision-making procedures, regardless of what effect-to-impacts translation procedure is used. At present, inadequate data are being combined with arbitrary and scientifically unsupportable thresholds to argue that wind farms will cause no damage to the integrity of sites designated to restore and maintain Europe's biodiversity.
Population viability analysis indicates that the probability of long-term persistence of an animal population and its mean time to extinction generally increases with its average size (Akçakaya, Burgman & Ginzburg 1999). According to European Commission guidance on managing the network of protected sites established by the EU Birds and Habitats Directives (Natura 2000 sites), Article 6 of the Habitats Directive provides that ‘The integrity of the site involves its ecological functions. The decision as to whether it is adversely affected should focus on and be limited to the site's conservation objectives’ (European Commission 2000). In addition, for the integrity of a site not to be adversely affected, a Court of Justice of the European Union decision (Court of Justice of the European Union 2013; Para. 39) found that the ‘site needs to be preserved at a favourable conservation status’, which entails ‘the lasting preservation of the constitutive characteristics of the site concerned that are connected to the presence of a natural habitat type whose preservation was the objective justifying the designation of that site’. Based upon this reasoning, we argue that some damage to the integrity of a designated site will have been sustained if populations of the seabirds for which it was designated are diminished, even to a small degree, by the effects of a wind farm, compared with what they would otherwise have been. If that is expected to be the case, it does not mean that the competent authority cannot give consent for a wind farm. Article 6(4) of the Habitats Directive sets out tests that determine whether the expected damage can be accepted and compensated for. However, poor science should not be used to avoid those tests by claiming that no damage will occur.