Science leads the debate against Seismic Surveys
July 22, 2022

The Nature’s Valley Trust is a small community-driven NPO working at the cutting edge of integrated conservation in South Africa. Nestled in the magnificent Garden Route, and situated in the world-renowned Nature’s Valley, we are a passionate group of conservationists that aim to make a practical difference with the work we do. We take a holistic view of people and the environment and use our programmes to help shape how people live, how they view the world around them, and how they as individuals can contribute to conserving the natural world.

Given our research and exposure to conservation issues along the Southern Cape coastline and the Garden Route in particular we are alarmed at the plans by Shell and the South African Department of Energy to go ahead with the seismic exploration off our coastline. Within the current threat of climate change, sea level rise and the extreme loss of biodiversity on a global scale we should in fact be moving toward renewable energy and more sustainable ways of utilising finite resources. 

The generation of underwater noise and sound waves may have significant ecological impacts in an area of high environmental importance. This importance is corroborated by the multitude of environmental statuses the area holds (Important Birding Areas, Hopespots, etc.) as well as the protected areas of national and international importance such as the Robberg, Tsitsikamma, Addo Elephant National Park, Port Elizabeth corals and Agulhas Front Marine Protected Areas. The southern coast of South Africa is also touted for its marine cetacean sightings and birding opportunities, bolstering the South African economy immensely from an eco-tourism perspective. 

Outside of the pure conservation issues scientific research conducted for the fishing industry in Southern Africa shows that seismic surveys may have a significant impact, long surveys of around 6 months, and multiple survey cumulative impact, particularly in 2013, may have cost the industry a lot of money. For example, the report on the impact of Seismic Surveys on the fishing industry (2017) cited below by David Russel on West Coast tuna says that impacts appear to be localized, disrupting fast swimming tunas migration flow by forcing them to move on. But where there are cumulative impacts from repetitive surveys in the same area, as has occurred off Southern Namibia tuna fishing grounds, where catches have severely declined since 2011, and in 2017 dropped off to non-commercial catch rates, there is the ominous possibility that the tunas change their migration path. Environmental factors such as El Nino appear to also have contributed significantly, but combined with regular seismic surveys, the environmental signals are potentially devastating15.

Scientific research shows that many Marine taxa have been shown to be affected by loud, pulsing sounds from seismic surveys. A study conducted in the North Atlantic over 880 000 km2 of marine ecosystem suggested a marked reduction in multiple species of baleen (88%) and toothed whales (53%) when compared to a control site1. Seismic surveys have been shown to cause extended displacement of some whale species, which lasted well beyond the survey length4. An analysis of cetacean responses to 201 seismic surveys in UK waters also exhibited evidence of disturbance5. During active seismic surveying, all small, toothed whales, killer whales, and all baleen whales were found at greater distances from the seismic vessel than when it was not shooting. They also theorized that smaller odontocetes may vacate the area entirely during exposure to seismic pulses5. Seismic noise has been thought to at least contribute to some species’ declines or lack of recovery7,8,9. These surveys have also been shown to reduce singing in humpback whales, displace finback whales by large distances, and disrupt activities vital to foraging and reproduction. In the Pacific, recent seismic noise has been linked to significant reductions in calf survival in western Pacific Gray whales—another endangered baleen whale2.

The South African coastline is also visited by threatened turtle species such as the Green, Loggerhead and Leatherback turtles. Seismic surveys may lead to physical damage and behavioural alterations in turtles. Further ramifications for turtles may include exclusion from critical habitats, damage to hearing and entanglement in seismic survey equipment14.

Seismic surveys do not only affect large cetaceans but also the tiniest animals that form the foundation of a healthy and productive ocean ecosystem. A 2017 study suggests seismic activity at this scale, causes significant mortality events in zooplankton. Zooplankton, which forms a critical link in the marine food and reproductive chain, declined by 64% within three-quarters of a mile of seismic blasts3. Seismic surveys will take many months to complete and involve multiple vessels over the same area, there is the potential for extensive damage to ocean productivity.

This reduction in ocean productivity will have knock-on effects on humans that rely on healthy ecosystems for livelihoods and food. As a result of seismic surveys, fewer fish are caught with reductions of up to 80% of key economic fish species in some places6. These effects can last for days after exposure and at distances of more than 30 km from a seismic survey. Eggs and larval stages of fish may also experience decreased egg viability, increase embryonic mortality, or decreased larval growth when exposed to airgun sound levels of 120 dB re 1 μPa10,11.

Invertebrates such as squid, bivalves and crabs are not excluded from the impacts of seismic surveys. There have been records of mass strandings of squid as well as major internal injuries and damage12. The bivalve, paphia aurea, showed acoustic stress as evidenced by hydrocortisone, glucose, and lactate levels when subjected to seismic noise13. Additionally, crabs exposed to seismic noise showed sediments in their gills and statocysts and changes consistent with a stress response compared with control animals.

Due to the risk posed to our marine ecosystem, marine wildlife, fish populations and human livelihoods, we urge the South African authorities and the extraction industry to align with the global movement that is calling for our oceans to be protected from increasing levels of pollution including noise pollution. The rising anger amongst South Africans against these surveys echoes the objections from our global community as the threat of seismic surveys has become increasingly prevalent across the globe. The fragility of all our critical ecosystems requires all of us to take due care of them and not place them at further risk.

We, therefore, implore all conservation NGOs, organizations and individuals along the Garden Route and across Southern Africa to object to this issue by signing this petition.


  1. Kavanagh, A.S., Nykänen, M., Hunt, W., Richardson, N. and Jessopp, M.J., 2019. Seismic surveys reduce cetacean sightings across a large marine ecosystem. Scientific reports, 9(1), pp.1-10.
  2. New England Aquarium blog, 29 November 2021:
  3. McCauley, R.D., et al: Widely used marine seismic survey air gun operations negatively impact zooplankton. Nature Ecology & Evolution 1, 0195 (2017) 
  4. Castellote, M., Clark, C.W., and Lammers, M.O. 2012. Acoustic and behavioural changes by fin whales (Balaenoptera physalus) in response to shipping and airgun noise. Biological Conservation 147: 115–122
  5. Stone, C.J., and Tasker, M.L. 2006. The effect of seismic airguns on cetaceans in UK waters. J. Cetacean Res. Manag. 8: 255–263.
  6. Weilgart, L., 2013, November. A review of the impacts of seismic airgun surveys on marine life. In CBD Expert Workshop on Underwater Noise and its Impacts on Marine and Coastal Biodiversity. London, United Kingdom (pp. 1-10).
  7. Weller, D.W., Rickards, S.H., Bradford, A.L., Burdin, A.M., and Brownell, R.L., Jr. 2006. The influence of 1997 seismic surveys on the behavior of western gray whales off Sakhalin Island, Russia. Paper No. SC/58/E4 presented to the International Whaling Commission Scientific Committee, Cambridge, UK.
  8. Weller, D.W., Tsidulko, G.A., Ivashchenko, Y.V., Burdin, A.M., and Brownell, R.L., Jr. 2006. A reevaluation of the influence of 2001 seismic surveys on western gray whales off Sakhalin Island, Russia. Paper No. SC/58/E5 presented to the International Whaling Commission Scientific Committee, Cambridge, U.K
  9. IWC (International Whaling Commission). 2007. Report of the scientific committee. Annex K. Report of the Standing Working Group on environmental concerns. J. Cetacean Res. Manag. 9 (Suppl.): 227–296.
  10. Kostyuchenko, L.P. 1973. Effects of elastic waves generated in marine seismic prospecting of fish eggs in the Black Sea. Hydrobiol. Jour. 9 (5): 45-48.
  11. Booman, C., Dalen, J., Leivestad, H, Levsen, A., van der Meeren, T. and Toklum, K. 1996. Effects from airgun shooting on eggs, larvae, and fry. Experiments at the Institute of Marine Research and Zoological Laboratorium, University of Bergen. (In Norwegian. English summary and figure legends). Fisken og havet No. 3. 83 pp.
  12. Guerra A, González AF, and Rocha F. 2004. A review of records of giant squid in the north-eastern Atlantic and severe injuries in Architeuthis dux stranded after acoustic exploration. ICES CM 2004/CC: 29.
  13. Moriyasu, M., Allain, R., Benhalima, K., and Claytor, R. 2004. Effects of seismic and marine noise on invertebrates: A literature review. Canadian Science Advisory Secretariat. Research document 2004/126.
  14. Nelms, S.E., Piniak, W.E., Weir, C.R. and Godley, B.J., 2016. Seismic surveys and marine turtles: An underestimated global threat? Biological Conservation, 193, pp.49-65.
  15. Russel, D. 2018. Assessing the impacts of seismic surveys on South African fisheries. ( – 29 November 2021)

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