Sharks face adapt, move or die scenario

Tracey Ferrier |

Scientists have suggested baby sharks are right at the edge of what they can tolerate.
Scientists have suggested baby sharks are right at the edge of what they can tolerate.

Climate change could soon force baby sharks out of their shallow coastal nurseries in what could prove to be a profound threat to the apex predators.

Scientists who have been studying such nurseries in French Polynesia have suggested baby sharks are right at the edge of what they can tolerate.

Mangroves and other protected habitats baby sharks rely on to grow and learn to hunt have always been extreme places, says James Cook University marine biologist Jodie Rummer.

Because they are shallow, baby sharks have always had to cope with the strain of high temperatures.

But with climate change driving up sea temperatures and fuelling heatwaves that are more frequent, severe and longer lasting, Dr Rummer says things are about to get worse.

“Adaptation – changes in DNA over generations to accommodate new conditions – may not be possible,” she says.

“This is because sharks are slow to reach sexual maturity compared to most other fishes and do not reproduce as often or have as many babies.

“Therefore, not enough generations can go by fast enough to keep pace with the rate at which we humans are changing their habitats.”

Dr Rummer says studies of nurseries in French Polynesia since 2013 indicate baby sharks are getting by, for now, but could ultimately face an adapt, move or die scenario.

“They are able to cope with the conditions they are experiencing right now, but they are very much at their limits.”

It’s possible newborns might move to cooler nursery-like areas but it’s also possible that some shark populations would disappear.

“This is a real risk. We know sharks are tolerating a lot already. The oceans, their habitats, are getting warmer, lower in oxygen, and lower in pH with climate change” Dr Rummer says.

She says limiting other threats, such as habitat loss, will be crucial in the face of climate change. But like so many other species, the real answer is dumping fossil fuels as quickly as possible.

“Even if we try to protect habitat, yep the water is still warming. Even if we protect the sharks from fishing, yep the water is still warming.

“Even if we watch the agricultural runoff, and make sure the chemicals aren’t going into the water, yep the water is still warming.

“We can keep putting those bandaids on, but at the end of the day we have to do the surgery and reduce our reliance on fossil fuels and move towards 100 per cent renewables.”