International Shark Awareness Day is marked on July 14 to highlight the vital role sharks play within our marine ecosystems and how critical it is that we protect them.
According to BBC Earth, sharks have existed for around 450 million years – with marine experts have found evidence of the oldest known shark scales in Siberian fossil deposits. This was 190 million years before dinosaurs appeared.
Most scientists and marine biologists agree that sharks are living fossils because, other than being much smaller now than their ancient ancestors, sharks have otherwise not evolved much in nearly 23 million years.
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Sharks belong to a group of creatures known as cartilaginous fish as most of their skeleton is composed of cartilage rather than bone. The only part of their skeleton not made from this soft, flexible tissue is their teeth.
The group includes the more well-known animals such as whale sharks and great whites, but also all rays, skates and the little-known chimaeras, also known as rabbitfish or ghost sharks.
Sharks help to maintain the health of various marine ecosystems, including seagrass beds and coral reefs. Healthy oceans depend on sharks.
The Save Our Seas Foundation reported that sharks feeding can affect prey population numbers, but also prey distribution as they select a specific habitat to avoid being eaten.
Scientists have observed that the presence of tiger sharks prevent green turtles from overgrazing seagrass beds which would have negatively affected many other species which depend on the seagrass for food, shelter and as a breeding ground.
By keeping the green turtle populations from exploding, the sharks maintain the balance in that ecosystem. The loss of sharks has led to the decline in coral reefs, seagrass beds and the loss of commercial fisheries.
By removing sharks from a coral reef ecosystem, larger predatory fish such as groupers, increase in abundance and feed on the herbivores.
With fewer herbivores, macroalgae expand and coral can no longer compete, shifting the ecosystem to one of algae dominance, affecting the survival of the reef system.
According to the oceans advocate group, Oceana Europe, sharks as apex predators play an important role in the ecosystem by maintaining the species below them in the food chain and serving as an indicator for ocean health.
They help remove the weak and the sick as well as keeping the balance with competitors helping to ensure species diversity.
Contrary to the ferocious, man-hungry image that society has placed on sharks, they are not as dangerous as they are made out to be. If anything, sharks should be more afraid of humans.
Conservation.org estimates that humans kill up to 100 million sharks annually, and according to the Florida Museum of Natural History's International Shark Attack File, only five human deaths from shark attacks were recorded worldwide in 2018.
Gavin Naylor, director of the Florida Program for Shark Research, which maintains the Shark Attack File, says there is no real evidence that sharks actively hunt humans.
“They generally just ignore people. I think if people knew how frequently they were in the water with sharks, they would probably be surprised.”
The Cape Town-based shark conservation group, Shark Spotters, says there have been a total of 248 unprovoked attacks in South Africa since records began in 1905, with most occurring in the Western Cape, Eastern Cape and KwaZulu-Natal. That equates to an average of just over two reported shark attacks a year.
Three species of shark in South Africa are responsible for most of the attacks – tiger sharks, bull (or Zambezi) sharks and white sharks.
Several shark species are threatened by human activities such as industrial-scale commercial fishing, the huge demand for shark-fin soup, pollution-causing ocean dead zones, and warming oceans due to climate change.
But all is not lost. Sharks are valuable to humans for non-consumptive reasons such as ecotourism, smart design, and management of the ocean’s carbon cycle. These factors are helping push for further shark conservation efforts around the world.
Each and every creature that lives above and below the surface of this planet contributes to sensitive ecosystems, playing an integral part in the balancing act that is life on Earth. As Sir David Attenborough famously said:
“The truth is: the natural world is changing. And we are dependent on that world. It provides our food, water and air. It is the most precious thing we have and we need to defend it.”