Development of a collision impact indicator to integrate in the life cycle assessment of offshore wind farms

Life cycle assessment (LCA) is a robust approach to estimate the environmental impacts of an offshore wind farm (OWF). However, methodological hurdles remain, particularly the lack of appropriate indicators to assess ecosystem impacts during OWF construction and operation and the scarcity of marine ecological data. To address the lack of indicators, this article focuses on developing an impact indicator specifically related to bird collision with OWFs. To assess bird collisions during the operation of OWFs, we adapted a life cycle impact indicator originally developed for onshore wind farms. This indicator combines spatial data on bird species distribution and vulnerability to collisions with OWF technical characteristics (number of turbines, power production, rotor diameter). The results model and map seabird collisions at OWF worldwide and introduce a biodiversity impact characterization factor into LCA. The results are expressed as the potentially disappeared fraction of species (PDF) annually per gigawatt-hour (GWh) and vary between 2.0e−15 and 1.69e−13 PDF.year/GWh. It correlates 1344 bird species distribution with the locations of 226 operational and 181 planned OWFs. The spatial differentiation of the characterization factors highlights the OWF collision impact variability worldwide. Such mapping is crucial for identifying areas with varying levels of risk, which is essential for the strategic planning of OWFs. Projections indicate higher potential collision risks in Asia than in Europe, and future expansion of the OWF into new regions with higher collision potential is expected to increase collision risks. In addition, the main factors affecting collision intensity were statistically identified. Therefore, to mitigate collisions, it is essential to focus on three key aspects: fewer turbines, smaller rotors, and greater distance from the shoreline. In addition, the LC-IMPACT method was employed to compare the collision impacts for two OWF projects in France, with those resulting from climate change. Over the lifetime of these OWFs, the collision impacts are quantified at around 2.0e−7 PDF, where effects attributed to climate change will be six times higher. The development of this collision indicator is a first step towards integrating OWF biodiversity impacts into the LCA framework. It also demonstrates how LCA indicators can inform marine spatial planning in the context of marine renewable energy development.