For consent to be granted to construct and operate an offshore wind farm, a Habitats Regulations Assessment of the potential impacts on the features of Special Protection Areas (SPAs) is necessary. If it is not possible to rule out an adverse effect on the integrity of an SPA, consent can be granted only if there are no alternatives to the project and there is an imperative reason of overriding public interest in its consent. In those cases, compensation must be secured to maintain the coherence of the SPA network.
This study identified and answered key biological questions of relevance to assessing the likely efficacy of compensation measures relating to nine qualifying features of eight SPAs in England. The potential for three levels of additional mortality to be compensated at each of three levels of compensation was assessed, using Population Viability Analysis where appropriate.
Recommended methods for compensation included: fisheries bycatch reduction (for northern gannet); control of fox predation (for Sandwich tern and lesser black-backed gull) and the creation of strict marine reserves within SPAs (for non-breeding red-throated diver). Closure of sandeel and sprat fisheries in UK waters was predicted to benefit multiple SPA features (black-legged kittiwake, auks, and Sandwich tern) across several SPAs and to be likely to compensate for high levels of additional mortality. This measure has the potential to be used as strategic level compensation for the offshore wind industry, at least in the North Sea.
In addition to identifying recommended methods for compensation in specific case studies, this study provides a useful guide to the process of: i) identifying key biological questions that must be answered in assessing the likely efficacy of compensation measures, ii) the use of published evidence and bespoke analyses in answering those questions and iii) establishing degrees of confidence in the answers.