Did you know that sharks play a role in mitigating Climate Change? Let me show you how . . .
Like good insurance policies, Sharks as Apex predators are directly and indirectly in charge of the health of the ecosystems they patrol. They influence the distribution, behaviour and abundance of their prey and they affect other predator-prey interactions too. They protect fish species from being decimated by mid-range predators, they even protect coral reefs by indirectly protecting algae-eating fish (algae suffocate coral).
When sharks are over-harvested, it literally throws the whole ecosystem out of sync and has an impact on climate change.
Today I will focus on the relationship between Tiger Sharks, Green Turtles and Seagrass to demonstrate one vital role sharks play in the carbon cycle.
But first, allow me to lay down some information foundations…
The world’s Oceans are the biggest and most active carbon sink, absorbing about 40% of the CO² emitted by human activity, which equates to about 4kg of CO², per person, per day…
For eons, the oceans have been absorbing carbon dioxide out of the atmosphere and releasing it again in a steady inhale/exhale rhythm.
Sea grass beds, salt marshes, and mangroves absorb and store far more carbon than equal areas of tropical forest, taking a quarter of a trillion kilograms of carbon out of the atmosphere every year. Most of this ‘blue carbon’ is buried in the mud for hundreds and even thousands of years. Seagrass meadows can store up to 83,000 metric tons of carbon per square kilometre.
Green turtles are one of the Tiger Shark’s favourite prey. And Green Turtles in turn love to feast on seagrass meadows. In the short-term absence of Tiger Sharks, turtles can forage undisturbed, having a great feast in the grass. Then when a Tiger Sharks swims a little too close for comfort, the turtles will stop eating and swim to safer pastures elsewhere. In the event of long-term absence of sharks, turtle populations will be allowed to boom, and since there are no sharks patrolling the meadows, turtles will graze in peace, putting severe pressure on seagrass meadows as inevitable overgrazing will occur. The decimation of these meadows will have severe ramifications in the carbon cycle of the ocean, and more and more stored carbon will be released back into the atmosphere, continuing the current accelerated rate of climate change. Plus, the more acidic the ocean becomes (due to the amount of dissolved CO²), the less CO² it’s able to absorb from the atmosphere. It’s a vicious cycle indeed.
Moral of the story is that sharks need to be protected, respected and left in peace (and in place) to protect our oceans and ultimately, our planet…