Understanding the complex ways that biodiversity change influences Nature’s Contributions to People (NCPs) is at the heart of current debates on coastal conservation, as researchers and practitioners seek to translate ecological shifts into meaningful impacts for society and policy. Specifically, we often lack quantitative evaluations of this relationship. We address this gap through a survey of biodiversity experts, focusing on the Wadden Sea located along the coasts of Germany, Denmark, and the Netherlands, as well as Algoa Bay in South Africa. We asked the experts to assess which changes in Essential Biodiversity Variables (EBVs) of selected marine organism groups (phytoplankton, macrozoobenthos, birds, and fish) link to which NCP category. Expert opinions indicated a significant influence of biodiversity changes on non-material NCPs compared to material and regulating NCPs. Specifically, experts perceive significant impacts on experiences, learning, inspiration, and cultural identities derived from the marine environment. However, there is a lack of conservation focus on non-material NCPs with regards to marine biodiversity change, indicating a gap between stakeholder perceptions policy priorities. Our study emphasises the importance of integrating relational values into conservation strategies and calls for knowledge co-production involving diverse stakeholders to address power imbalances and develop more inclusive and effective management approaches for marine biodiversity.