The expansion of offshore wind farms (OWFs) is central to global decarbonization strategies, yet their effects on marine biodiversity are only partially understood. This systematic review synthesizes 221 publications up to June 2025 to assess the ecological impacts of OWFs on marine fauna living below the sea surface. The evidence base is uneven, heavily focused on North European waters, fish, and invertebrates, while expanding OWF regions and marine mammals remain underrepresented. Most studies examine short-term, individual-level responses, limiting inference on long-term effects. Impacts vary widely by stressor, taxon, and biological outcome. Invertebrates often show positive responses linked to reef effects, though key functional traits are vulnerable. Fish responses are largely neutral except under noise, while marine mammals exhibit the most consistent negative impacts. The impact score developed here highlights taxon-specific vulnerability and offers a scalable risk-assessment tool for data-poor regions. The review calls for standardized, long-term field monitoring to support OWF expansion while safeguarding biodiversity.
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