An ecosystem modelling approach to assess potential impacts of offshore wind farms

Abstract Offshore wind energy is in great expansion around the world. Considerable gaps in scientific knowledge on ecological impacts of offshore wind farms (OWFs), including the lack of standardized operational tools to conduct cumulative impact assessment, could lead to delays in the consent process. Ecosystem models are useful tools for cumulative impact assessments because they consider various ecosystem components and their interactions, and therefore are able to provide integrative evaluations. In this study, we improved an existing individual-based ecosystem model (OSMOSE), aiming to assess the cumulative effects of OWFs on various biological groups and fishing activities in the Eastern English Channel (EEC). This work presents substantial technical developments on the existing OSMOSE model application, enhancing its capability to evaluate OWF effects. Technical model improvements included new species, a better representation of the fishing process, prey field forcing updates to include climate change projections, and inter-annual calibration over the period 2002–2021. These developments were essential for improving the depiction of OWFs cumulative impacts, encompassing effects from underwater noise emission, sediment resuspension, and fishing access restriction. We simulated the EEC ecosystem during construction and operational phases under a factorial plan combining OWFs deployment and fishing regulation scenarios. At the scale of the entire EEC ecosystem, total fish biomass and catch were slightly reduced under all scenarios. The most significant biomass declines were observed for cuttlefish, herring, and red mullet, primarily driven by changes in predation and fishing pressure, especially during the construction phase. However, at the local scale (model grid resolution), these changes appear to be OWF-specific, as no consistent spatial patterns in fish biomass were observed across OWFs deployment sites. The differences among scenarios suggest a trade-off between energy production, fishery resource exploitation, and environmental protection goals. The most probable OWF spatial deployment scenario that balanced on regulatory and socio-economic considerations also represented a balance of ecological factors.