Frameworks and best practices for cumulative impact accounting in offshore energy development

Offshore renewable energy holds promise for achieving emission reduction targets. However, offshore industries transform land and seascapes with resultant trade-offs for both nature and people. Cumulative impacts have long been a challenging issue for environmental management, creating uncertainty around development limits across scales and risks to financial investments and the environment. This is particularly true for nascent industries and governments striving to meet tight deadlines for international commitments. Here, we provide recommendations for improved accounting of cumulative impacts for offshore development based on scientific best practice including: 1) clear pathways from activity to impact, 2) accounting for the full suite of cumulative impacts, 3) integration across realms and jurisdictions, 4) systematic planning processes to guide fair and equitable development opportunities within and across sectors, and 5) transparent and reproducible assessments. We demonstrate opportunities and challenges of implementing our recommendations using offshore wind project proposals in Australia, where the development of the offshore wind industry is in progress. Our recommendations outline key considerations for cumulative impact accounting in offshore energy development globally and can increase potential for positive outcomes for people and nature across these rapidly expanding sectors. • Available frameworks can improve cumulative impact accounting in offshore industries. • Structured impact-pathway frameworks can provide clear links from activity to impact. • Interdisciplinarity can improve integration across sectors, realms and jurisdictions. • Marine spatial planning can guide fair and equitable development opportunities. • Transparent and reproducible data science practices enable cumulative assessments.