Lakes are some of the most biodiverse, yet vulnerable, ecosystems on the planet. K'gari or Fraser Island, the largest sand island in the world, has a large number of permanent lakes and represents one of the few true lake districts on the Australia mainland. The lakes of K'gari/Fraser island are both beautiful and remarkable because many are perched above the regional water table where an impermeable layer separates them from the sand below. These lakes are one of the reasons why the island is listed as a UNESCO World Heritage site. Understanding the history of these lakes and their response to past climate variability is likely to provide insights into their future vulnerability to climate change.
Holocene (i.e. post “ice age”) sediment records have now been analysed from six lakes on K'gari/Fraser Island. There was marked aridity on the island from c. 8000 to 5500 years ago with some lakes drying completely. Interestingly, at some sites there is little to no physical evidence of drying which is instead recorded as a hiatus in the accumulation of highly organic, acidic, lake sediments.
The mid-Holocene dry phase recorded on K'gari/Fraser Island contrasts with evidence from perched lakes on North Stradbroke Island, a sand island approximately 150 km to the south. As a result, there is strong potential to infer the Holocene regional climatology of the Australian subtropics at small spatial scales from these records.
These results highlight a largely unrecognised vulnerability of lakes on K’gari to drying and indicates a need to better understand perched lake hydrology and response to projected future climate change.