Coastal communities and ecosystems along the South African coast are facing unprecedented challenges due to alarming rates of sea-level rise (SLR), driven partly by climate change and exacerbated by local geological factors. A comprehensive study investigating sea-level trends from 1993 to 2022 reveals SLR rates near Cape Town reaching 6.3 mm per year—almost double the global average of 3.3 mm per year. This study highlights the importance of utilizing precise measurements from both tide gauges and advanced radar altimetry to gain insights on regional variability.
The authors of the study, published recently, emphasized the pressing necessity for effective coastal management as southern Africa grapples with rising sea levels and the potential loss of significant cultural heritage sites. By 2035, projections suggest over 143 million people will live within 100 kilometers of the South African coast, heightening their vulnerability to flooding, erosion, and storm surges.
This alarming situation is worsened by subsidence rates of over 2.2 mm per year. Cape Town, along with other cities, faces significant risks, with the potential for up to 80 cm of rise by 2100 if current trends continue. This compounded risk highlights the urgent need to prioritize adaptive strategies, ensuring these vulnerable communities can withstand future challenges.
The findings of the study are based on data collected over three decades, which involved 10 credible tide gauges and advanced XTRACK altimetry processed using the Coastal Altimetry Approach. This technique aims to minimize shortcomings connected to conventional coastal altimetry data, providing solid evidence of SLR trends. The results indicate regions of accelerated sea level rise, particularly near the Agulhas Bank, which could experience rates similar to those observed around Cape Town.
"The rates of sea-level rise we've documented reveal a serious escalation of the challenges faced by coastal ecosystems and communities," stated the authors of the article. They explored the underlying mechanisms of sea-level variability, linking SLR with significant oceanographic changes driven by the Agulhas and Benguela currents. These currents play pivotal roles, impacting local ocean climates and leading to individualized experiences of sea-level rise along the coast.
The interaction of rising sea levels, combined with extreme weather events like cyclones and flooding—exacerbated by climate change—poses serious risks to urban infrastructure and local economies. Notably, tropical storms have caused significant destruction along South Africa's coast, emphasizing the urgency of adaptive planning and risk mitigation.
Further complicative factors include seismic activity, which leads to subsidence and can result in apparent changes to sea levels. Between 1993 and 2022, South Africa recorded 1102 earthquakes, predominantly situated near coastal cities. Even though earthquakes do not directly influence SLR, they can result in significant land elevation changes, aggravate coastal erosion, and introduce additional burdens to already vulnerable regions.
"Our study portrays the urgent need for targeted research and proactive measures to safeguard coastal communities from SLR impacts," the authors added. With rising sea levels threatening infrastructure, livelihoods, and biodiversity, this research highlights the necessity of integrated coastal zone management and innovative financing mechanisms to protect these vulnerable regions.
Continued monitoring and research are imperative for projecting future sea-level changes. By integrating data from various measurement techniques such as altimetry and tide gauges, researchers aim for enhanced precision, providing coastal authorities with the necessary insights to craft effective responses to the realities of climate change.
Overall, the convergence of human activity, natural processes, and climate change signifies the need for collective actions and adaptive strategies as coastal cities across South Africa prepare for an uncertain future influenced by rising seas.