Cross-realm biodiversity profile of the South African coastal zone

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South Africa’s coast is 3 113 km long and includes microtidal shores that experience semi-diurnal tides and mostly high wave energy. From west to east, the cool Benguela Current and the warm Agulhas Current drive steep gradients in climate and environmental conditions, resulting in diverse coastal ecosystem types. Here, we review the biodiversity of South Africa’s coastal zone, focusing on the constituent ecosystem types from the terrestrial, freshwater, estuarine and marine realms, and provide a brief overview of cross-realm biodiversity patterns. We also give guidance on coastal boundaries to improve standardisation in this complex area to support assessment, planning and management. The ecologically determined coastal zone currently comprises 193 ecosystem types: 83 vegetation types (e.g. seashore vegetation, strandveld, duneveld, coastal forest); 22 estuary and 3 micro-estuary ecosystem types; and 85 marine ecosystem types (e.g. shores, islands, reefs, kelp forests, bays), with planned inclusion of freshwater types (e.g. coastal lakes, forested wetlands, dune slacks) in the future. Species richness is generally highest along the south and east coasts, with the highest levels of endemism mostly reported for the south coast. The South African coast is a national asset that warrants careful management for long-term sustainability to safeguard its unique biodiversity and many associated benefits for current and future generations.