Harris, LRVan Niekerk, LaraHolness, SDSink, KJSkowno, ALDayaram , AVan Deventer , HeidiJob, NLamberth , SJAdams, JBRaw, JLRiddin, TMacKay , CFPerschke, MJ2025-05-122025-05-122025-041873-524X0964-5691https://doi.org/10.1016/j.ocecoaman.2025.107586http://hdl.handle.net/10204/14249Conservation planning and implementation are typically applied in land and sea areas separately, placing already impacted coastal biodiversity – which spans the divide – at risk of being inadequately managed and conserved. In South Africa, we tested how well existing land-based and marine biodiversity priority areas cover coastal priorities that we identified cross-realm using Marxan with >1000 biodiversity features. Existing priorities covered 83% of coastal priorities, indicating good but incomplete coverage. Proportionately, the seashore (foredunes, shores) and estuaries had greatest selection as coastal priorities, confirming their important biodiversity value. Finally, we developed a map of Critical Biodiversity Areas for the South African seashore and estuaries, with management recommendations. To include coastal biodiversity in real-world planning, we propose: co-developing data and targets for cross-realm features; identifying broad coastal priorities that can be used in land-based and marine plans; and developing dedicated seashore and estuary priorities to seamlessly align land-based and marine prioritisation maps.FulltextenCoastal conservationIntegrated coastal zone managementLand-sea planningMarxanSustainable useArticleN/A