Shark experts will gather in Sydney on Tuesday to discuss new safety measures, as new research warns the culling of sharks could indirectly accelerate climate change.
The New South Wales premier, Mike Baird, will launch the shark summit at Taronga zoo, featuring more than 70 experts from Australia and around the world.
The summit will highlight emerging technologies that can repel sharks, after a spate of attacks along the NSW coast. There have been a total of 13 shark attacks in NSW so far this year – up from three in 2014 – with one surfer, 41-year-old Tadashi Nakahara, killed near Ballina.
Shark deterrents such as underwater gates that release electro-magnetic fields and flexible plastic nets will be discussed at the summit as well as shark-detecting buoys and real-time tracking of tagged sharks.
NSW already has nets installed at 51 popular beaches between Newcastle and Wollongong and has launched a shark tagging program to better understand the behaviour of the ocean predators. The outcome of a review into shark deterrent technology will be addressed at the summit.
Niall Blair, NSW minister of primary industries, said the state government is “leaving no stone unturned to make sure we look at new and innovative ways to protect our beaches.”
However, some surfers have called for more drastic action to be taken, such as a partial cull of sharks seen near beaches.
This stance has been opposed by environmentalists, and most policymakers, as being cruel or inappropriate. But new research suggests that killing sharks also exacerbates climate change.
A paper published in Nature Climate Change warns the removal of top ocean predators such as sharks causes a “trophic cascade” throughout the food chain that results in the release of carbon into the atmosphere.
With about 90% of the world’s sharks and other large predator fish wiped out through overfishing and culling, potential prey such as sea turtles, stingrays and crabs have flourished.
As a result, turtles have been free to munch their way through larger amounts of seagrass and crabs have been able to disturb a greater amount of seabed sediment. Such consequences have “far reaching consequences on carbon cycling and, by implication, our ability to ameliorate climate change impacts” the paper warns.
The research, conducted by academics from Deakin University, University of Technology Sydney and Griffith University, said vegetated coastal habitats store 50% of the carbon buried in all ocean sediments, representing about 25bn tonnes.
There are no exact estimates of how much of this carbon is being released by animals free from shark harassment, but the paper points out if just 1% of this vegetation is lost, 460m tonnes of carbon dioxide would be released – the equivalent emissions of 97m cars.
“Once you remove large ocean predators you get strange indirect impacts, there is a meltdown in the ecosystem that influences the release of carbon,” said Dr Peter Macreadie, co-author of the report.
“That’s definitely a problem here in Australia. We have massive potential to offset our emissions by maintaining these ecosystems but we’ve lost a lot of our seagrass and salt marshes. Whenever you remove those keystone fish and birds that sit at the top of the ecosystem, everything falls apart.”
Macreadie said shark culling should be rejected as a way to protect swimmers and surfers visiting Australia’s beaches.
“For me it’s a no brainer,” he said. “There’s a risk when you drive a car or if you go into an area that has lions. There is a natural order of things. We have to get used to the idea there are things out there that can harm us, as rare as that is.”