Humans are depleting the resources on the planet faster than they can be replaced, and are also contributing to climate change. These actions amount to a deadly cocktail that threatens life on earth – a truth that has been evident for many years, but is only now starting to get the attention that may lead to remedial action. Failure to respond could doom life on earth – time is of the essence.
In addition to our concerns about climate change and resource depletion are the unknown effects of marine ecologies rebalancing, thanks to human influences.
Chris Fallows
Apex predators occupy the top feeding level in food chains. Remove the apex predators and there will be a cascade effect down the whole food chain to the bottom level.
Once the Great White sharks were no longer a permanent feature of the marine ecology in the Dyer Island area, it did not take long for Alison Towner and other scientists and observers to notice changes in the local marine ecology. The question is, to what degree are humans responsible? When does natural history become unnatural history?
Bronze Whaler sharks have always been present in the area, but it wasn’t until the threat from Orcas caused the Great Whites to leave that this species seemed to increase in number and started responding to chum around ecotourism boats – the first time this had been noticed in South African waters. The arrival of a semi-resident population of 50 to 70 Bronze Whalers would certainly have some impact on the feeding chain, and this will become apparent with time.
The Great Whites in the Dyer Island area prey on the Cape fur seal colony, so the absence of the sharks means the seals need to be less vigilant. This has the knock-on effect of increasing predation by the seals, mainly the large bulls, on the African Penguin colony. Cape fur seals are not an endangered species, but the African Penguin is listed by the International Union for the Conservation of Nature (IUCN) on its Red List as ‘Endangered’. This new predatory behaviour by the seals on the penguins has caused such concern that the authorities have undertaken limited and selective culling of some seal bulls, known as rogues, to ease the impact.
Abalone harvesting, now regarded as poaching due to the species’ protected status, has long been practised by those in the area who make their living from the sea. The presence of Great Whites has generally had the effect of deterring poachers – not entirely, but it undoubtedly helps keep poaching in check. Once the sharks were absent or their numbers significantly reduced, it didn’t take long for the abalone poachers to start taking advantage of the safer waters. Large numbers of RIBs (rigid inflatable boats) started working around Dyer Island, and as the ecotourist boats came and went, they often saw the telltale bubbles coming from divers working the seabed collecting abalone. Although the poachers’ boats were clearly visible to anyone watching, and it was obvious what they were doing, up to late 2018 little effort was being made by the authorities to stop it.
A well-known resident of Shark Town, who did not want to be named, said: ‘It is completely lawless out there; it’s like a marine wild west and all the sheriffs have left town. Seeing those poachers in such numbers is like standing helplessly by watching while the ocean is being raped. Later the army was called in to bolster law enforcement efforts.’
The whole Great White shark ecotourism industry with its direct and indirect employment has ceased to be the reliable meal ticket it had been for many years. Some of the increase in poaching can be attributed to the safer waters, but it is also a consequence of the decline of ecotourism that has precipitated the need for an alternative pay check.
The scientific name for the abalone is Haliotidae, and the white abalone has been listed as ‘Endangered’ in the United States. In South Africa, abalone is known as ‘perlemoen’, taken from the Dutch meaning ‘mother of pearl’. It is estimated that over the past 18 years poachers have taken at least 96 million abalone from South African waters. This rate of harvesting is considered unsustainable, and in the Dyer Island area the absence of Great Whites appears to be hastening the process of completely stripping the seabed of this valuable natural resource.
Abalone are sea snails and are at the very lower end of the chain in which Great Whites are the apex predators. That the absence of Great Whites is causing the local marine ecology to change is beyond dispute. Time may show that human influence of some kind provided the trigger for Port and Starboard’s behaviour, which led to the dispersal of the sharks, and in turn to safer waters and increased abalone poaching. It looks possible, some say probable, that human meddling is present at both ends of the trophic scale.
It is almost impossible to walk too far along the sandy beach from Hermanus towards De Kelders without coming across the dead bodies of sea creatures. Seals, penguins, seabirds and others are washed up all along the beach, and even a cursory examination often reveals death has been caused by fishing net or line entanglement, oil or other pollution, propeller damage and other human factors.
Our seas are changing, and the evolving situation being studied by scientists in Walker Bay is an example of how changing seas are threatening the marine environment and impacting the lives both of the creatures that live in it and the humans that live off it. It is a constant worry for those most closely involved, who feel the immediate impact. If Shark Town’s problems were unusual or unique, they could be ignored, other than by those involved. But the reality is that Shark Town’s experience is being repeated in different ways and to varying degrees all over the planet. This should be of the gravest concern to us all.
The UK BBC’s Blue Planet II is widely acknowledged as being one of the finest TV wildlife documentaries ever produced. It has been shown by TV channels all over the world, and in the last episode David Attenborough, the programme’s host, spelt out the dangers of plastic pollution in the world’s oceans. His observations significantly increased global awareness that we are strangling our oceans and their inhabitants with plastics. This was perhaps the most effective wake-up call yet, and Attenborough does not think it is too late to clean up our world and save it. It is up to each and every human on earth to do their bit, to prove him right, and save our seas not only for the Orcas, but for all marine species.