The environmental impact from an offshore windfarm: Challenge and evaluation methodology based on an ecosystem approach

International audienceResponding to pressure to combat climate change by cutting greenhouse gasses emission, Offshore Wind Farm (OWF) is currently the most developed of all the renewable energy options that are based in the marine environment. However, despite its perceived benefits, OWF construction will also lead to direct and indirect impacts on the ecosystem. Nonetheless, surprisingly few studies have sought to combine trophic web modelling tools with the framework of OWF impact assessment. The objective of this study was to develop a holistic and integrated ecosystem approach as a complementary methodology to the traditional OWF environmental impact assessment. To that end, trophic web models coupled with Ecological Network Analysis indices were used to study the structure and functioning of three sedimentary types (sandy gravel, gravelly sand, and medium sand), identified on the proposed site for a new offshore wind farm at Dieppe-Le Tréport (Normandy coast). The results from this study demonstrated that the trophic structures are strongly linked to the sedimentary types. The results also highlighted the existence of a maturity gradient moving between the three types of sediment identified. This study underlined the challenge and the need to have detailed biomass data on a maximum of biological compartments to enable an effective OWF impact assessment. We strongly consider that our approach will provide useful and practical information for environmental decision-makers and stakeholders. The same approach can be applied to other new OWF constructions in European or international waters