One of the key messages of ‘On Sharks & Humanity’ is that sharks are an integral part of the marine ecosytstem. Their existence as apex predators means they regulate species that are lower down on the food chain. This regulation is multifold. Firstly, their predation of other carnivorous species such as seals, large fish and rays means that numbers of these species are regulated. Without sharks, these carnivorous species would boom in number, which would deplete stocks of species further down the chain, such as planktivores and filter feeder. These smaller species, in turn, regulate marine plants and algae, which is one of the reasons that the disappearance of sharks would results in a much greener, unhealthy ocean. Secondly. large planktivores such as whale sharks and basking sharks compete with other planktivores (such as jelly fish.) Without this competition, jellyfish would see a rise in numbers.
Ultimately, what this would result in is a green sea, filled with jellyfish.
This sort of thing isn’t limited to sharks. The extinction of many different species could have adverse effects. Worryingly, Harvard biologist Edward O Wilson predicts that the world’s present course will lead to the extinction of half of all plant and animal species by 2100.
For a really indepth piece about the effects of extinction, have a look at the link.
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