Scientists map ancient Great Barrier Reef landscape from 65,000 years ago

Sixty-five thousand years ago, the ocean floor where the Great Barrier Reef now thrives was dry land. The sea level sat eighty metres below where it stands today, and the Southern Great Barrier Reef area was a landscape waiting to be walked on—whether grassland stretching to the horizon, dense rainforest thick with growth, or mangrove swamp thick with water and roots. What it actually was, nobody knew. Until recently.

University of Queensland professor Helen Bostock decided to find out. She assembled a team, boarded the CSIRO research ship RV Investigator, and spent twenty-four days at sea off the Central Queensland coast, working in waters between fifty and two hundred metres deep. The target zone lay between Swain Reef and the Capricorn Bunker Group, near the towns of Yeppoon and Gladstone. The mission was to collect sediment cores from the seafloor—long cylindrical samples that hold, layer by layer, a record of what came before.

What they found was extraordinary. Beneath the thin blanket of modern sediment lay the ghost geography of an ancient world: submerged rivers, lakes, estuaries, and beaches, all preserved in the geological record like pages in a book. Each layer of sediment tells a story. The top layers are newest; dig deeper and you move backward through time. Within those layers lie microfossils—pollen grains and other traces of life—that reveal what plants grew there, what animals lived there, what the climate was like. By reading these layers, Bostock and her team could begin to reconstruct a landscape that vanished beneath the waves thousands of years before humans invented writing.

But this was not purely a scientific expedition. Aboard the RV Investigator were Indigenous Land and Sea Rangers from the Darumbal and Woppaburra traditional owner groups—the descendants of the people who once lived on that dry land. Their presence was deliberate. Bostock had spent years in conversation with Indigenous elders, including Auntie Sally Vea Vea, who carried stories passed down through generations: stories of ancestors walking across to Swains Reef, of hunting and living on country that is now underwater. These were not myths to be filed away. They were knowledge, as real and as valid as any scientific finding. The expedition was designed to merge them.

Tshinta Barney, supervisor of the Woppaburra land and sea rangers, watched the sediment cores come up from the ocean floor and saw something profound. "When you put in the Western science and see the degree that they go to, you can really see where our stories and our family ties all come into one," she said. For her and her colleagues, this was not about proving their ancestors right to outsiders. It was about validating their own knowledge, and about showing the younger generation that this kind of work—this marriage of cultural understanding and scientific rigor—was something they could do, something they could build a life around. Darumbal ranger Nataliah Backo stood on the sea country her ancestors once walked and hunted, and felt the weight of that continuity. "It's just amazing that we got to be on the sea country that our ancestors used to live, walk and hunt on," she said.

The work is far from finished. The oceanographic data—measurements of water temperature, nutrient flows, sediment movement—should be ready within a year. Those findings will help scientists understand how the reef ecosystem functions now, and what it might need to survive the changes ahead. But the sediment samples themselves will take much longer to analyze. Each layer must be examined, each fossil identified, each chemical signature read. The ancient landscape will not reveal itself quickly. Yet for the first time, Western science and Indigenous knowledge are working in genuine partnership to recover it—not to prove one side right and the other wrong, but to build a fuller, truer picture of what was lost when the sea rose, and what that loss means for the people whose stories have kept that memory alive.