Shell Seismic Surveying: What's all the fuss about?
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Dutch energy giant, Shell, will soon be embarking on four to five months of geographic seismic surveying off the coast of the Eastern Cape and parts of the Western Cape provinces.
Thousands of South Africans are protesting against the planned survey with demonstrations taking place around the country and an online petition which garnered around 286 000 signatures as of Thursday morning.
But what is all the fuss about? What exactly is seismic surveying and why is it bad for the marine environment?
Dr Judy Mann at South African Association for Marine Biological Research (SAAMBR) explained that “seismic surveys are used by mining companies to find and estimate the size of offshore oil and gas reserves.
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A ship tows multiple air gun arrays that emit thousands of high-decibel explosive impulses to map the seafloor and rock strata. Hydrophones attached to long cables pick up the signal reflected off the seafloor.
Based on the return time of the reflected or refracted impulses to the hydrophones, the underlying structure of the ocean floor can be mapped in 3D.”
Marine seismic exploration provides mining companies with an accurate picture of any gas or oil pockets that may be trapped beneath the ocean floor. If these pockets are large enough, then the drilling will commence.
Unlike air, water is extremely acoustic. This means it is highly efficient at carrying sound waves through itself. Dr Mann states that “sound travels extremely efficiently in seawater, and marine mammals and many fish and invertebrates depend on sound to find mates, find food, avoid predators, navigate and communicate.”
It is well known that the South African east coast is home to a host of marine and coastal habitats. These are extremely diverse and unique biomes that support countless sea creatures including those which are endemic to South African oceans. Deep-water habitats, deeper than 500 metres, in particular, are largely unexplored ecologically, meaning not much is known about exactly what occurs or what ecological processes take place there.
SAAMBR said that “internationally, seismic surveys have been demonstrated to have negative impacts on a range of marine organisms, from smaller creatures which live in sediments or as plankton, to larger animals such as ﬁshes and marine mammals. Marine mammals, in particular, appear to be the most impacted by seismic surveys because of their reliance on sound for communication, to find food and to navigate.”
Another important factor of concern is the Agulhas current, one of the fastest and most powerful oceanic currents in the world. Offshore oil and gas extraction comes with a myriad of negative impacts including leaks and spills on scales we cannot begin to comprehend. The Agulhas current could potentially carry an oil spill all along the east coast of South Africa in a matter of days and would make cleanup efforts next to impossible.
Research has shown that although the impact of seismic surveying on fish populations themselves are localised, they may have serious consequences for the long-term health of fisheries with different fisheries being impacted in different ways. Decreases in the overall catch were observed in some areas according to SAAMBR.
In a statement for SAAMBR, Dr Mann shared that “it is our opinion that the best way forward for environmental sustainability and local job creation is to expand technology which makes use of renewable energy.
“The global market is moving away from fossil fuels given the catastrophic eﬀects of human-induced climate change. Indeed, if South Africa and the world are to meet the goals set by COP26 which has recently been concluded in Glasgow, to limit global warming to less than 1.5°C, it is urged that we move away from our reliance on fossil fuels.
“We thus consider that the potential short-term, non-sustainable beneﬁts to be gained from oil and gas are largely outweighed by the environmental risks posed by exploring for, and using these non-renewable energy resources, especially along this vulnerable coastline.”
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