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Study finds sharks ‘critical’ to restoring climate damaged ecosystems

Apex predators or protectors? New studies suggest that sharks are absolutely crucial in helping ecosystems recover from damaging climate events.

We all know that removing animals from the food chain can have drastic knock on effects, but I doubt many foresaw sharks as being bastions of biodiversity. They just eat everything, right?

On the contrary, new studies have revealed that sharks are nothing short of crucial when it comes to restoring ocean ecosystems from extreme climate events.

This conclusion was drawn by a cohort of scientists from the Florida International University, the University of Washington, and the Deakin University in Australia.

Studying an extreme marine heatwave in 2011 – which happened to wipe out a quarter of the world’s largest and most diverse seagrass meadows in Shark Bay, Australia – the team wanted to isolate factors that may prolong the damage caused by climate change years on.

Why? Because 10 years on, Shark Bay has still yet to meaningfully recover.

Before long, the team found themselves looking into a mass exodus of sharks in the area and discovered it could’ve been intrinsically linked to the bay’s stuttering recovery.

‘We wanted an answer to the question: can the absence of large predators cause an already bad situation to spiral downwards?’ said the lead author of the study, Rob Mowicki.

After the heatwave killed off most of the seagrass in 2011, the area’s dugong (sea lion) population temporarily left, along with their formidable hunters the tiger sharks. This allowed Mowicki’s researchers to set up a unique field experiment directly within a damaged area of the bay, free from unwanted visitors.

Using calculations based on the grazing rate of dugongs, the team was able to artificially simulate a seagrass bay free of sharks. They quickly found that the quantity of seagrass being consumed by the herbivores and the rate at which plants were being disturbed made it almost impossible for canopies to fully recover.

In-case you’re wondering, no, the team wasn’t eating seagrass at the rate of 600lb dugongs. Instead, through a process called ‘underwater gardening,’ scuba divers periodically uprooted seagrass at pre-determined grazing rates.

‘This allowed us to mimic the behaviour dugongs would have if the sharks in the bay magically disappeared, or were overfished,’ said Nowicki.

As we previously eluded, the harsh truth was that without predators around to hunt dugongs, the damage caused by the climate would be prolonged indefinitely. Chiefly then, this study serves as further evidence that interfering with the natural order of any marine ecosystem will always lead to bad news.

Bearing that in mind, now consider that seventeen out of the 39 types of pelagic shark species are currently threatened with extinction by overfishing. Often caught unintentionally by destructive fishing methods like trawls and seine nets (which we covered in detail here), these majestic and vital animals are regularly discarded.

In summary, if we really are beginning a decade of climate action now, marine ecosystems will need just as much attention as those on land.

 

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