Abstract
Understanding the global impact of offshore wind farms (OWF) on biodiversity and ecosystem services (ES) is crucial in developing sustainable energy transition pathways. This study takes a holistic approach, coupling a semi-systematic review with a novel analytical methodology, to consider the consequences of construction & operation of OWF deployment on biodiversity and ES. 314 pieces of evidence taken from 132 peer-reviewed studies provide the basis to determine the ecological and ES impacts. The process showed that construction impacts were predominantly negative across the ecological subject groups (52%), compared with positive impacts (8%) with several species of fish (e.g. brill, cod, dab, plaice) and some species of birds (e.g. common guillemot, northern fulmar, redhead) showing strongly negative trends. Operational phase impacts were more variable and could be either negative (32%) or positive (34%) depending on site specific conditions. More detailed investigations into fish, shellfish, humans and air-surface studies recorded a net positive effect of wind farm operations on these subject groups. Translation into ES outcomes identified that 14 ES are impacted by the construction and operation of OWF. The most substantially enhanced ES included effects on commercial fisheries and experiential recreation. Social acceptance toward new and hypothetical OWF was also strongly positive, irrespective of country location. Negative effects on ES, including existence values for culturally important groups, e.g., marine mammals and birds and the spread of non-native species, are potentially of most significance. Overall, this study finds more than 86% of possible offshore wind farm impacts on ES are still unknown. There was also a paucity of studies on the decommissioning of OWF and the impacts of deeper-water floating structures, with a bias in studies toward northern hemisphere and developed countries.