Fossil Shorebirds Unveil Past Wetland Climates at Naracoorte Caves

Unveiling the Ancient Wetlands of Naracoorte: A Glimpse into Australia’s Pleistocene Past

The Naracoorte Caves, a World Heritage site in South Australia, hold valuable clues about ancient ecosystems and the impact of climate change over millennia. Recent investigations into the fossil-rich deposits of these caves have uncovered a significant presence of shorebird remains, providing insight into the region’s prehistoric wetlands and their eventual disappearance.

Shorebirds, typically scarce in the fossil record, have been found in abundance in the Naracoorte Caves, especially in Blanche Cave. This discovery highlights how wetlands and mudflats, once thriving during the last Ice Age, have since vanished due to climatic shifts. The study, conducted by a team of researchers including Flinders University Ph.D. candidate Karl Lenser, suggests that a pronounced drying event around 17,000 years ago led to the decline of several shorebird species.

“Shorebirds are rare in the fossil record, so finding so many in one cave (Blanche Cave) was a surprise,” said Lenser. This suggests that habitats supporting species like plovers, sandpipers, and snipes were more widespread in this region during the Ice Age.

Currently, shorebird populations in Australia face challenges due to climate change and diminishing habitats. The historical data from Naracoorte could be crucial for anticipating how these species might respond to future environmental changes.

Among the fossils, the plains-wanderer, a small endangered bird native to Victoria and New South Wales, was notably prevalent. It accounted for over half of the nearly 300 bones analyzed, indicating that the species once thrived in woodland environments, unlike the treeless grasslands they inhabit today. This significant presence at Naracoorte suggests a dramatic population decline over the past 14,000 years, likely due to habitat loss.

“Living plains-wanderers are now very selective about their habitat, but other fossils from Naracoorte show that the area was probably a woodland… a far cry from the treeless open grasslands plains-wanderers inhabit today,” Lenser explained.

Furthermore, the cave’s fossil collection includes migratory species that journey from the northern hemisphere to Australia, such as sandpipers of the Calidris genus and Latham’s snipe (Gallinago hardwickii). The double-banded plover, known for migrating between Australia and New Zealand, was also found among the remains, with two young birds documented as having flown from New Zealand to Naracoorte before being preyed upon by an owl.

Dr. Trevor Worthy of Flinders University noted, “This sample of shorebirds is also extra special as it documents migratory species that annually fly from the northern hemisphere to spend the boreal winter in Australia.”

Despite these findings, much remains unknown about Australia’s avian life during the Ice Age. Still, the Naracoorte Caves continue to reveal essential details about ancient biodiversity, as noted by Dr. Liz Reed from Adelaide University. “The Naracoorte Caves preserves a half million-year record of biodiversity in southeast South Australia,” Reed stated, emphasizing their importance for understanding pre-European landscapes and modern conservation efforts.

The study was published in the journal Palaeontologia Electronica, offering a window into the past that informs present-day ecological challenges.