On the world’s largest sand island, K’gari, there are significant freshwater lakes. A recent study by the University of Adelaide has revealed that even the largest and deepest lakes on the island could disappear under certain climatic conditions.

Ancient Changes in K’gari’s Lakes

Analysis of ancient lake sediment layers showed that about 7,500 years ago, several lakes on the island dried up. This period, known as the mid-Holocene, occurred thousands of years after the last ice age and was characterized by a wetter climate compared to today.

The drying of lakes in Australia is not uncommon, as prolonged periods of low rainfall can lead to significant drops in water levels. However, the study found that the ancient drying on K’gari happened during a relatively wet period, which is different from modern cases where lakes dry up due to drought.

The Influence of Winds and Rainfall

The data indicate that the survival of the lakes depends not only on the total amount of rainfall, but also on the direction of incoming rains, the movement of moisture by winds, and how water is distributed across the landscape. Researchers suggest that southeast trade winds may have directed rain toward the neighboring island of Minjerribah instead of K’gari. Trade winds are steady winds that play a significant role in cloud formation and precipitation.

It was previously established that during the same period, Minjerribah also received abundant rainfall, but due to wind direction, the rains nourished only the lakes on that island, not those on K’gari.

The Uncertainty of the Lakes’ Future

The study highlights the need for deeper research into K’gari’s lakes. With a climate expected to become drier but with more intense rainfall, it remains unclear whether these lakes are at risk of drying out. A future with heavier downpours does not necessarily mean the lakes will receive more usable water, as rainfall may fall elsewhere, run off quickly, or fail to replenish the systems that sustain the lakes.

Research Methods

Scientists identified an ancient episode of drying by studying sediment cores from K’gari’s oldest lakes. Over time, materials such as pollen, sand, plant remains, and organic matter settle on the lakebed, forming a layered record of past ecological conditions. Lake sediments capture all events that occurred in and around the lake. Plant pollen helps determine the types of local vegetation, while large amounts of sand indicate increased erosion.

In some of K’gari’s oldest lakes, there are no sediment layers from between 7,500 and 5,500 years ago, indicating the absence of water in those areas at that time. Without standing water, the usual lake sediment layers could not accumulate.

Cultural Significance of the Lakes

For the Butchulla people, the traditional owners of K’gari, the lakes hold cultural and spiritual significance that goes beyond their ecological value. The lakes are called the Eyes of K’gari. It is believed that protecting the lakes is essential for preserving their beauty, meaning, and connection to the land for future generations.

The name K’gari is linked to the spirit of the Dreaming who created the island, and the lakes are seen as windows into eternity. The waters of the lakes are considered sacred and precious, and their preservation is viewed as a responsibility passed down from generation to generation, so that future generations can maintain the same connection and respect for these places.