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Identifying South African marine protected areas at risk from marine heatwaves and cold-spells

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Abstract

Marine heatwaves (MHWs) and marine cold-spells (MCSs) can negatively impact biodiversity as species distributions are largely governed by temperature linked to physiological tolerances. These extremes have not been considered in South Africa’s Marine Protected Area (MPA) network design, so understanding frequency and severity of extreme thermal events will be important for assessing their impact. This study characterises MHWs and MCSs in MPAs across the six South African marine ecoregions, using a novel index to compare thermal event severity. Thermal events declined in duration and intensity from west to east, with the least severe events recorded in the Delagoa ecoregion. Walker Bay MPA was identified as most at risk due to the combined impact of MHWs and MCSs. These thermal events may threaten the ability of the MPA to meet its conservation objective as a cetacean sanctuary. If past trends in MHW frequency and cumulative intensity persist, the majority of South African MPAs could experience more severe heatwaves in the future. Our approach will help prioritise sites for in situ monitoring of water temperature and studies of the impact of extreme thermal events, as well as identifying areas for expanding refugia and conservation corridors, supporting adaptive management into the future.

Data availability

Data is freely available on Zenodo: Courtaillac et al. (2024) Identifying South African Marine Protected Areas at risk from marine heatwaves and cold spells [Data set]. Zenodo. DOI: 10.5281/zenodo.14900260.

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Acknowledgements

The authors gratefully acknowledge the Marine Heatwaves International Working Group and tools that they make available in support of research into extreme thermal events. Sarah Ackland is thanked for help with the formatting of the map. Three anonymous reviewers are thanked for their insightful and in-depth comments that helped to strengthen this work.

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Authors and Affiliations

  1. Department of Botany and Zoology, Stellenbosch University, Stellenbosch, Western Cape, South Africa

    Kira-Lee Courtaillac & Tamara B. Robinson

  2. Cape Research Centre, South African National Parks, Cape Town, Western Cape, South Africa

    Nicola J. van Wilgen

  3. Centre for Invasion Biology, Stellenbosch University, Stellenbosch, Western Cape, South Africa

    Nicola J. van Wilgen & Tamara B. Robinson

Authors

  1. Kira-Lee Courtaillac
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  2. Nicola J. van Wilgen
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  3. Tamara B. Robinson
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Contributions

Kira-Lee Courtaillac extracted the data, analysed the data, prepared the figures and tables, authored and reviewed drafts of the article and approved the final draft. Nicola van Wilgen conceptualised the study, guided analyses, reviewed drafts of the article and approved the final draft. Tamara Robinson conceptualised the study, analysed the data, prepared tables and figures, authored and reviewed drafts of the article and approved the final draft.

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Correspondence to
Tamara B. Robinson.

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Courtaillac, KL., van Wilgen, N.J. & Robinson, T.B. Identifying South African marine protected areas at risk from marine heatwaves and cold-spells.
Sci Rep (2025). https://doi.org/10.1038/s41598-025-32725-0

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  • DOI: https://doi.org/10.1038/s41598-025-32725-0

Keywords

  • Agulhas current
  • Benguela current
  • Climate change
  • Extreme thermal events
  • Marine conservation planning

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