Scientists are warning of a significantly increased risk of collisions between whales and ships off South Africa's south-western coast, following a substantial rerouting of vessels around the region. This rerouting has quadrupled the number of large ships traveling through South African waters at speeds above 15 knots (28 kilometers per hour) between December 2023 and December 2024. The heightened threat to marine life became evident in April this year, when two Bryde’s whales washed up dead on Dyer Island in South Africa’s Western Cape province. The tragic discovery of these two whales showed the immediate and severe consequences of increased maritime traffic in sensitive marine environments.
Reports indicate that the rerouting of ships around South Africa has substantially increased the chances of vessels striking whales in the region. Scientists are specifically warning of this increased risk off South Africa's south-western coast, a critical habitat for various whale species. This particular stretch of coastline is known for its rich biodiversity and serves as key feeding and breeding grounds for numerous marine mammals. The surge in fast-moving shipping traffic has raised concerns among conservationists and researchers monitoring marine ecosystems in the area, prompting urgent calls for mitigation strategies. The potential long-term impacts on whale populations, many of which are still recovering from historical whaling, are a significant worry for the scientific community.
Escalating Maritime Traffic
The rerouting of vessels intensified after Houthi rebel attacks on ships traversing the Red Sea began in 2023. These actions, alongside ongoing conflicts involving the U.S. Israel, and Iran in the Middle East, have led to a significant shift in global shipping routes. The geopolitical instability has effectively transformed the Cape of Good Hope into a primary alternative artery for international trade. Reports indicate that approximately 89 commercial vessels navigated around the Cape of Good Hope between March and April this year. Data from AFP, citing the International Monetary Fund's PortWatch report, supports these figures, noting the dramatic increase in maritime activity in a relatively short period. This surge in traffic represents a substantial deviation from historical shipping patterns, which typically favored the Suez Canal route. The shift has placed unprecedented pressure on the marine ecosystems off South Africa's coast.
The increased maritime traffic became strikingly evident to scientist Els Vermeulen during a flight into Cape Town in 2025. From the air, the sheer volume of vessels traversing the waters was visibly greater than in previous years. "If we have an increased presence of vessels in areas where we have large whales, it’s all we need to know that there’s a problem," Vermeulen stated, emphasizing the direct correlation between shipping activity and potential harm to marine life. The scientist also noted that such incidents lead to "human-wildlife conflict," a term that encapsulates the negative interactions between human activities and animal populations, often resulting in injury or death for the animals involved. This conflict is exacerbated by the fact that many whale species migrate through or reside in these now heavily trafficked waters.
Vermeulen noted that large vessels pose particular risks due to their design. "This is due to the hull masking the noise and the distance between the front of the vessel and the back where the engine is," Vermeulen explained, making it difficult for whales to detect approaching ships until it is often too late to avoid a collision. The massive size and deep drafts of these modern cargo vessels mean that a strike can be catastrophic for a whale, often leading to immediate fatality. The sheer speed at which many of these vessels travel significantly reduces a whale's reaction time, compounding the danger. The combination of masked noise, physical scale, and high speed creates a perilous environment for whales in these newly congested shipping lanes.
Despite the challenges, Vermeulen believes solutions are available. "There are mitigation measures in place, especially in the busy areas in the Northern Hemisphere which will be adapted to the region and the species," Vermeulen commented, pointing to successful examples from other parts of the world. The focus for South Africa, according to Vermeulen, should be on practical implementation of such measures. "It’s about developing guidelines for the shipping industry when operating in our waters that they can realistically adhere to," Vermeulen said, emphasizing the urgency. "We need to start implementing them now, and improve the science as we go." This proactive approach is deemed key to prevent further whale mortalities and to protect the fragile marine ecosystem. The adaptation of existing global best practices to the specific conditions and whale species found off South Africa's coast is a key step.
Scientific Concerns and Evidence
Both whales found dead in April this year carried severe injuries, with reports indicating their vertebrae had been shattered. These types of injuries are highly indicative of blunt force trauma consistent with a vessel strike, leaving little doubt as to the cause of death. In the same month, Dr. Els Vermeulen presented a preliminary study to the International Whaling Commission (IWC) regarding the increased risks. This presentation served to alert the global scientific and conservation community to the emerging crisis off South Africa's coast. The IWC, as the pre-eminent international body for whale conservation, was an appropriate forum for noting these urgent findings and seeking collaborative solutions.
Vermeulen's team developed distribution models for whale species around the Western Cape, which they overlaid with current shipping routes to identify areas of heightened collision risk. This sophisticated modeling allowed researchers to pinpoint geographical hotspots where the likelihood of a whale-ship encounter is significantly elevated. The research specifically combined ship movement records with these species distribution models, concentrating on six different baleen whale species. These species, which include large filter feeders, are particularly vulnerable due to their size, surface feeding behaviors, and often slow movements. By focusing on these specific species, the study provided a targeted assessment of the most at-risk populations. The integration of real-time shipping data with long-term whale distribution patterns offered a strong scientific basis for the warnings issued by the research team.
Quantifying the exact number of whales struck by vessels proves challenging due to a general lack of current data, reports indicated. This data deficiency makes it difficult to ascertain the true scale of the problem. Most collisions, according to reports, often occur in deep offshore waters, resulting in the affected animals sinking to the ocean floor rather than washing ashore. This phenomenon, where mortalities largely go unobserved, is referred to as 'cryptic mortality'. Cryptic mortality means that the reported incidents, such as the two Bryde's whales found on Dyer Island, likely represent only a fraction of the actual number of whale deaths caused by ship strikes. The hidden nature of these mortalities makes it harder to assess population impacts and to generate public and political will for immediate action. Therefore, the visible incidents serve as critical indicators of a much larger, unseen problem.
Mitigation and Future Steps
Dr. Els Vermeulen's study has modeled alternative shipping routes that could reduce the relative strike risk by between 20% and 50% across all whale species examined. These models provide concrete, actionable proposals for the shipping industry to consider. Vermeulen suggested adjusting shipping routes and lowering vessel speeds during specific times of the year to mitigate risks. These recommendations are based on established practices in other regions facing similar challenges. For example, on the U.S. East Coast, a 10-knot (18.5 km/h) speed limit is already in place to reduce collisions with North Atlantic right whales, a critically endangered species. This precedent demonstrates that such measures are not only feasible but also effective in protecting vulnerable whale populations. Implementing similar seasonal speed restrictions or rerouting protocols in South African waters could significantly reduce the incidence of catastrophic collisions.
Humpback whale populations have shown an increase in South African waters, forty years after a global whaling moratorium was introduced. This recovery notes the success of international conservation efforts and shows the importance of protecting these rebounding populations from new threats. During the Southern Hemisphere spring, specifically in October and November, large groups of whales, known as supergroups, congregate within the Benguela Upwelling System. This area is recognized for its rich marine biodiversity and is a vital feeding ground for these magnificent creatures. The presence of these large aggregations of whales in an area that is now experiencing increased shipping traffic creates a particularly dangerous scenario, making targeted mitigation efforts during these months especially critical. The Benguela Upwelling System's ecological significance further amplifies the need for protective measures, as it supports a vast array of marine life beyond just whales.
Vermeulen and her team plan to conduct a systematic survey of offshore whale populations using either aircraft or boats. This full survey aims to gather more precise data on whale distribution and abundance, particularly in the offshore areas where cryptic mortalities are most likely to occur. The findings from this research are expected to contribute to more informed mitigation strategies, allowing for the refinement of shipping routes and speed regulations. The ongoing commitment to scientific research is key for adapting to the evolving challenges posed by increased maritime traffic. The current publication date for this information is May 11, 2026, indicating the long-term nature of these research and conservation efforts. The ultimate goal is to ensure that both global trade and marine life can coexist sustainably, protecting South Africa's precious marine heritage for future generations.
