Abstract
The multiple uses of marine space and the synergies among their effects require a systematic assessment of cumulative impacts, especially amid the growing blue economy and offshore wind expansion, which interact with existing human activities in an impacted seascape. Cumulative Impact Assessment (CIA) has become essential for systematically managing complex environmental interactions. Clear legal requirements for CIA are crucial to supporting better-informed decision-making, improving environmental governance, and fostering the implementation of CIA into practices. This study aims to compare the legal requirements related to CIA applied to the early planning and development phases of offshore wind energy (OWE) in the United Kingdom, the Netherlands, the United States, and Canada, offering guiding elements for designing or restructuring CIA regulations for offshore wind markets. We conducted a comprehensive scholarly and gray literature review to identify the key federal legislation related to CIA applied for OWE, which was then comparatively analysed using a set of core questions. The key findings are (1) Clear legislation is foundation to CIA practice; (2) Definition of cumulative impacts is key to guiding CIA implementation; (3) CIA requirements are crucial at various planning levels, from marine spatial planning to project-level assessments; (4) CIA regulations should consider collaboration, clear roles, and shared accountability among institutions and sectors; and (5) Stakeholder engagement and public consultation should be ensured throughout all the CIA steps. These elements may be used to support countries that have not yet adopted CIA, as well as those seeking to strengthen its implementation in offshore wind development.