Harris, Linda R.Van Niekerk, LaraHolness, Stephen D.Sink, Kerry J.Skowno, Andrew L.Dayaram, AnishaVan Deventer, HeidiJob, NancyLamberth, Stephen J.Adams, Janine B.Raw, Jacqueline L.Riddin, TarnMackay, C. FionaPerschke, Myriam J.2025-05-132025-05-132025-04Harris, L.R., Van Niekerk, L., Holness, S.D. et al. 2025, 'Conserving cross-realm coastal biodiversity when real-world planning and implementation processes split the land and sea', Ocean and Coastal Management, vol. 263, art. 107586, pp. 1-13, doi : 10.1016/j.ocecoaman.2025.107586.0964-5691 (print)1873-524X (online)10.1016/j.ocecoaman.2025.107586http://hdl.handle.net/2263/102364DATA AVAILABILITY : The map of coastal priorities is available at: https://doi.org/10.6084/m9.figshare.22463890.v1 and the Seashore and Estuary CBA Map is available at https://doi.org/10.6084/m9.figshare.22461901.v1.Conservation 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.en© 2025 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by- nc/4.0/).Coastal conservationIntegrated coastal zone managementLand-sea planningMarxanSustainable useSystematic conservation planning (SCP)Article