2022, North West Wildlife Trust, Marine Internships, Marine Net Gain Research and Evidence Project series https://portal.medin.org.uk/portal/start.php?tpc=015_4b76ee69-0073-4545-9f1b-006ca61f8f4a This report was produced as part of the Marine Futures Internship, a collaborative project between Natural England, Ørsted, The Crown Estate, and the North West Wildlife Trusts, funded by The Crown Estate and managed by Cumbria Wildlife Trust. The project aims to support the UK Governments development of the "Marine Net Gain" (MNG) policy, which requires developers to leave marine biodiversity in a better state than before development. This policy is crucial for expanding the offshore renewable energy sector whilst aiding marine nature recovery. Using data from the Walney Extension Offshore Wind Farm, the report tests various scenarios to highlight the advantages and challenges of using a metric to calculate biodiversity value in marine environments. It identifies key issues such as the scarcity of knowledge on marine habitats, the difficulty of restoring marine environments, and the need for strategic significance in habitat restoration. The report provides recommendations for improving the metric and suggests involving developers and stakeholders in its development to ensure a smooth transition into policy. 20221230 20221202