Community
30 January, 2022
The future for sharks: adapt, move or die
A new study suggests sharks will need to adapt, move, or die as climate change could soon render their nurseries uninhabitable.
Baby sharks rely on coastal nursery-like spaces such as shallow lagoons and mangroves for food and protection from predators.
But they also need to be robust enough to cope with the challenging conditions these environments throw at them - conditions that may soon become unbearable in a warming world.
ARC Centre of Excellence for Coral Reef Studies at James Cook University’s researcher and author of the study Dr Ian Bouyoucos said there are already many challenges for baby sharks that global warming could make unbearable.
“In shallow coastal habitats, baby sharks already have to tolerate the strain of high temperatures,” Dr Bouyoucos said.
“The temperatures can also fluctuate dramatically daily. It’s the constant change that makes these environments ‘extreme’.”
Dr Bouyoucos said nursery areas are essential for sustaining the local shark populations, serving as ‘safe havens’ for newborns and juveniles to learn critical survival and foraging skills. But the impacts of climate change are increasingly becoming a problem for their survival.
“We don’t know if sharks can adapt and can continue to use these important habitats early in life, or whether they will be able to find new nurseries, or whether populations will die off,” he said.
Co-author and Associate Professor Jodie Rummer from Coral CoE at JCU said this is a case of adapting, moving or dying.
“Heatwaves due to climate change are becoming more frequent and severe, and lasting longer with climate change,” Dr Rummer said.
She said more work is needed to find current tolerance limits for newborn sharks to survive and thrive in shallow, warm nursery habitats.
“The temperature thresholds that limit their performance today can help us predict how future populations might fare as the waters continue to warm with climate change,” she said.
“But adaptation - changes in DNA over generations to accommodate new conditions - may not be possible. 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 said there was a possibility newborn sharks could move to new nursery-like areas that are not as warm.
“Or, we might just see these shark populations disappear,” she said.
“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.”
As predators, sharks are essential for healthy ocean ecosystems. Without predators, whole ecosystems can collapse.
“We need to keep studying and protecting sharks,” Dr Bouyoucos said.
“Our sharks, ecosystems, and our futures all depend on us urgently cutting greenhouse gas emissions to curb climate change.”
