Marine biodiversity impact pathways for offshore wind farm decommissioning: Implications for Life Cycle impact assessment development

• Review of offshore wind farm decommissioning and biodiversity impacts. • Quantitative assessment methods for impacts on marine biodiversity are missing. • Impact pathways for offshore wind farm decommissioning and marine biodiversity. • Habitat change is especially important for decommissioning impacts on biodiversity. • Baseline for an LCIA method for marine biodiversity in the context of decommissioning. The environmental conditions of the ocean are rapidly deteriorating in many locations, largely due to anthropogenic activities. Previous studies have indicated both negative and positive impacts on marine biodiversity during the construction and operation of OWFs, but the impacts of decommissioning remain largely unknown. Assessments of marine biodiversity impacts are now needed to support science-based decisions as the first OWFs are approaching decommissioning. Life Cycle Impact Assessment (LCIA) offers a quantitative and transparent approach to impact assessment but does currently not adequately cover marine biodiversity impacts. As a first step in developing an LCIA method, we conducted a systematic literature review to identify the links between offshore infrastructure decommissioning activities and their impacts on marine biodiversity. Links were delineated as impact pathways, providing the foundational framework for future LCIA development. We extended the scope of our study to oil and gas (O&G) platforms, given the similarities between the two types of offshore infrastructure and decommissioning activities. Our study identifies numerous impact pathways through which OWF decommissioning affects marine biodiversity. We found many similarities between impacts from the decommissioning of OWFs and O&G, but generally, more pathways were identified for O&G decommissioning. As the structures resemble each other, this study suggests that much knowledge can be brought from O&G decommissioning to OWF. We identified habitat change as particularly important when investigating impacts associated with offshore decommissioning, as several pressures may affect habitat change. The study also identified implications for developing a comprehensive LCIA method, including a scarcity of quantitative studies and empirical data, baseline definitions, as well as inconsistency in biodiversity metrics applied across reviewed studies. Importantly, the identified impact pathways provide the first step toward integrating marine biodiversity into LCIA in the context of the decommissioning of offshore structures.