Ancient mystery on K’gari: World’s largest sand island lakes dried up during rainy era

By analyzing ancient sediment layers from lakes on K'gari, located off Queensland's south eastern coast, scientists uncovered signs of a major drying period about 7,500 years ago during the middle Holocene.

"Our research shows that about 7500 years ago, at a time of higher rainfall and long after the end of the last Ice Age, some of K'gari's deepest lakes dried out," says lead researcher Associate Professor John Tibby, from the University of Adelaide.

Drying episodes are not unusual in Australia, Associate Professor Tibby explains. However, this particular event stands out because it occurred during a period that was generally wetter than today.

"There are many Australian lakes that dried during the Millenium Drought when there was not enough rainfall to sustain them," says Associate Professor Tibby, whose study was published in Quaternary Science.

"The K'gari lakes we studied have been in existence for between 35,000 and 55,000 years, but the drying event we've identified happened unexpectedly during a time of heavy rainfall."

Wind Patterns and Unexpected Lake Loss

Researchers believe shifting wind systems may help explain the mystery. Dr. Harald Hofmann, a co-author from the Commonwealth Scientific and Industrial Research Organisation (CSIRO), says regional wind patterns likely influenced where rainfall ultimately ended up.

"Prior research shows Minjerribah also experienced heavy rainfall events at this time, but, because of south-east trade winds that were occurring at the time, rainfall from the south only fed into lakes on Minjerribah, not those on K'gari," he says.

According to Dr. Hofmann, the findings raise important questions about how K'gari's lakes might respond to future climate shifts.

"This finding highlights a pressing need to know more about K'gari's beautiful lakes. With a climate that is expected to get drier, but with more intense rainfall, we simply don't know if these lakes are at risk of drying out."

Sediment Records Reveal Missing Water

The team identified the ancient drying event by detecting a noticeable gap in sediment deposits from some of the island's oldest lakes.

"A lake's sediment is like a journal where what happens in and around the lake gets recorded," says Associate Professor Tibby.

Layers of pollen preserved in mud reveal what kinds of plants once grew nearby, while increased sand content can point to greater erosion. When sediment layers are missing altogether, it signals something more dramatic.

"Our study found sediment was missing from some of K'gari's oldest lakes between 7,500 and 5,500 years ago, which tells us that the area of the lakes was not covered by water, meaning the lakes were not there."

Cultural Significance of The Eyes of K'gari

To the Traditional Owners, the Butchulla people, these lakes are known as The Eyes of K'gari. Study co-author and Butchulla man Conway Burns emphasizes the importance of protecting them for future generations.

"K'gari is the name of the dreaming spirit who formed the island, and her eyes are not just water -- they are windows to eternity," Burns says.

"When you stand before the lakes of K'gari, you do not merely see reflections of sky and forest; you see the soul of Country gazing back at you. Her eyes hold ceremony, memory, and the whispers of the Creator. They carry the voices of ancestors and loved ones who have passed, guiding us with permission, wisdom, and reflection.

"These waters are sacred and secret. They are not ours to own, but ours to protect. As we are her children, we are entrusted with a responsibility that is both heartfelt and eternal: to preserve her beauty, her spirit, her voice that whispers through the creeks and her eyes so that future generations may feel the same connection and respect."