Southern elephant seals are the “canary in the coal mine” for the Southern Ocean, offering insight into how the ecosystem may react to future climate change and human impact, new research shows.
Joint senior author Associate Professor Nic Rawlence, Director of the Otago Palaeogenetics Laboratory, said while elephant seals only inhabited the sub-Antarctic islands and South America, New Zealand beaches were once “heaving” with the colossal animals.
“At the time of human arrival in New Zealand, you would be hard pressed to find room on the beaches, with fur seals on the rocky headlands, prehistoric sealions and elephant seals on the sand, and lots of penguins,” he said.
“It’s a picture that is very hard to imagine today, especially as most New Zealanders wouldn’t think that these majestic giants were once part of our biological heritage.”
The study was undertaken by a group of international researchers, led by postgraduate students Andrew Berg, of the University of Sydney, and Otago’s Megan Askew, and recently published in journal Global Change Biology.
The team used palaeogenetic techniques on specimens dating back thousands of years from New Zealand, Tasmania and Antarctica to show that southern elephant seals used to be spread across the entire Southern Ocean.
Joint senior author Dr Mark de Bruyn, of Griffith University’s Australian Research Centre for Human Evolution, said their whereabouts were heavily impacted by climate change and humans over a short evolutionary period.
“The Ice Ages would have rapidly increased the amount of sea ice surrounding Antarctica, forcing elephant seals to retreat to multiple refugia in South Africa, Australia, New Zealand and South America, before they expanded back out as the climate warmed, including temporarily to the Antarctic mainland.”
Dr Mark de Bruyn
“However, indigenous subsistence hunting and European industrial sealing once again resulted in the contraction of their range, this time to the deep Southern Ocean with their extirpation from Australia and New Zealand.”
Associate Professor Rawlence said knowing how elephant seals responded to these changes would provide insights into how they – and the Southern Ocean ecosystem, which New Zealand and Australia were part of – may be impacted in the future.
“Their dynamic evolutionary history, plus climate change and human impact, strongly suggests that unless measures are taken to mitigate the effects of human-driven climate change and marine ecosystem deterioration, elephant seals and the Southern Ocean ecosystem are in for a rough ride into the future,” he said.
The study ‘Postglacial Recolonization of the Southern Ocean by Elephant Seals Occurred From Multiple Glacial Refugia’ has been published in Global Change Biology.
