Advances in country-level assessments of South Africa’s estuaries
Over the last few years, South Africa has been on a drive to consolidate and publish its national-level assessments and management tools. Two recent publications that support this initiative are an assessment of key estuarine pressures at the country-level to better inform management and resource protection (Van Niekerk et al 2022a) and a Vulnerability Assessment of South African Estuaries to Climate Change at a regional scale (Van Niekerk et al. 2022b). Collectively these two recent publications highlight the high level of current and future pressures on these important ecosystems that are already in a poor state (Van Niekerk et al. 2013). Overall, the decline in estuary conditions stems from multiple escalating pressures managed across several key sectors. Approximately 15% of the national estuarine extent is under severe flow modification pressure. Land-use and development result in severe pressure on 40% of the extent. About 15% of inlets are artificially manipulated which impacts 60% of estuarine extent. Pollution places 34% extent under severe pressure and 78% extent is severely impacted by overfishing. Invasive terrestrial vegetation has infested a third of estuaries, while aquatic invasive plant species occur in 8% of estuaries. Alien or extralimital (translocated) fish cause severe pressure in 35% of the estuarine area.
To support country-level assessments, South Africa’s estuaries were recently reclassified into 9 functional types across 4 biogeographical regions, resulting in 22 estuarine ecosystem types (Van Niekerk et al. 2020). This represents a high diversity of estuary types stemming from the wide array of climatic, oceanographic and geological influences prevalent in South Africa. The refined types align well with the IUCN Global Ecosystem Typology.
This ongoing work is also complemented by efforts to facilitate land-sea integration at the country-level, both from the freshwater aquatic side with the identification of river-estuarine ecotones that represents the transition zone between rivers and estuaries (Van Deventer et al. 2020) and efforts to integrate coastal ecosystem typology and maps (Harris et al. 2019).
Efforts were also made to consolidate advances in environmental flow requirement methods (e.g., Van Niekerk et al. 2019; Adams & Van Niekerk et al. 2020) and approaches to quantify water quality change in data-limited estuaries (Taljaard et al. 2022) for South Africa’s estuaries. Ongoing endeavours are being made to address the need for estuary restoration at the national scale, for example, identifying priority areas for saltmarsh restoration at the national-scale (Adams et al. 2021).
All of the above advances in assessment methods and approaches aim to improve South Africa's ability to manage estuaries from the strategic to the local level in a socio-ecological systems approach (Adams et al. 2020).
References (In order of use):
Van Niekerk L, Taljaard, S, Lamberth, SJ, Adams, JB, Weerts, S, MacKay, F (2022a). Disaggregation and assessment of estuarine pressures at the country-level to better inform management and resource protection - the South African experience. African Journal of Aquatic Science. DOI: 10.2989/16085914.2022.2041388
van Niekerk L, Lamberth SJ, James NC, Taljaard S, Adams JB, Theron AK, Krug M. The Vulnerability of South African Estuaries to Climate Change: A Review and Synthesis. Diversity. (2022b.) 14(9):697. https://doi.org/10.3390/d14090697.
Van Niekerk L, Adams JB, Bate GC, Forbes AT, Forbes NT, Huizinga P, Lamberth SJ, MacKay CF, Petersen C, Taljaard S, Weerts SP, Whitfield AK and Wooldridge TH. (2013). Country-wide assessment of estuary health: An approach for integrating pressures and ecosystem response in a data limited environment, Estuarine, Coastal and Shelf Science, 130: 239-251.
Van Deventer, H, van Niekerk, L, Adams, JB, Ketelo Dinala M., Lötter, M., Gangat, R., Lamberth, SJ, Lötter, M, Mbona, N., MacKay, F, Nel, J, Ramjukadh C-L, Skowno, A., Weerts, SP (2020). National Wetland Map 5: An improved spatial extent and representation of inland aquatic and estuarine ecosystems in South Africa. Water SA, 46(1): 66–79.
Harris, L., Bessinger M., Dayaram, A., Holness S., Kirkman S., Livingstone T.-C., Lombard A.T., Lück-Vogel M., Pfaff M., Sink K.J., Skowno A.L., van Niekerk L. (2019). Advancing land-sea integration for ecologically meaningful coastal conservation and management. Biological Conservation, 237: 81-89.
Van Niekerk L., Taljaard S, Adams JB, Lamberth SJ, Huizinga P, Turpie JK, Wooldridge TH (2019). An environmental flow determination method for integrating multiple-scale ecohydrological and complex ecosystem processes in estuaries. Science of the Total Environment, 656 (15): 482-494.
Taljaard S, Lemley DA, Van Niekerk L (2022). Method to Quantify Water Quality Change in Data-limited Estuaries. Estuarine, Coastal and Shelf Science. Volume 272: 107888. https://doi.org/10.1016/j.ecss.2022.107888.
Adams, JB and Van Niekerk, L, 2020. Ten Principles to Determine Environmental Flow Requirements for Temporarily Closed Estuaries. Water, 12, 1944.
Adams, JB; Raw, JL; Riddin, T; Wasserman, J; Van Niekerk, L (2021). Salt Marsh Restoration for the Provision of Multiple Ecosystem Services. Diversity 2021, 13, 680. https://doi.org/10.3390/d13120680