By examining ancient layers of lake sediment, researchers uncovered evidence that several lakes dried out roughly 7,500 years ago. This period, known as the middle Holocene, came thousands of years after the last Ice Age and was generally wetter than today.

Ancient Lakes Dried During a Wet Climate

"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.

Lake drying is not unusual in Australia, where long periods of low rainfall can cause water levels to fall dramatically. What surprised the researchers was that the ancient drying event on K'gari appears to have occurred during a relatively rainy period.

"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."

The findings suggest that the survival of these lakes may depend on more than the total amount of rain falling across the wider region. Where the rain comes from, how winds carry moisture, and which parts of the landscape receive the water may also be critical.

Wind Patterns May Have Redirected the Rain

Dr. Harald Hofmann, a co-author from the Commonwealth Scientific and Industrial Research Organisation (CSIRO), says ancient wind patterns may explain why heavy rainfall failed to replenish the lakes on K'gari.

Researchers believe south-east trade winds may have directed rain toward nearby Minjerribah rather than K'gari. Trade winds are persistent winds that blow across broad regions and can strongly influence where clouds form and rain falls.

"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.

"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."

That uncertainty is especially important because a future with more powerful rainstorms does not necessarily mean the lakes will receive more usable water. Intense rainfall may fall in the wrong locations, run off too quickly, or fail to recharge the systems that sustain the lakes.

Missing Sediment Reveals a Lost Chapter

The researchers identified the ancient drying event by studying sediment cores taken from some of K'gari's oldest lakes. Over time, material such as pollen, sand, plant remains, and organic matter settles at the bottom of a lake, building a layered record of past environmental conditions.

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

"Pollen from plants in and around lakes can tell us about local vegetation types, and a higher amount of sand might tell us there was more erosion into the lake.

"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."

The absence of sediment across that roughly 2,000-year period indicates that water no longer covered parts of the lake basins. Without standing water, the usual layers of lake sediment could not accumulate.

The Sacred Eyes of K'gari

For the Butchulla people, the Traditional Owners of K'gari, the lakes carry cultural and spiritual importance that extends far beyond their environmental value. They are known as The Eyes of K'gari.

Study co-author and Butchulla man Conway Burns says protecting the lakes is essential so that their beauty, meaning, and connection to Country can continue 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."