Scientists say the surprising discovery that North Stradbroke Island's Ferngully Lagoon dated back more than 200,000 years, and other wetlands on the island more than 40,000 years, could reshape climate change research on the Australian continent.
Researchers from the University of Queensland and the University of Adelaide made the discovery after they took core samples from the 16 wetlands on North Stradbroke Island.
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| John Tibby and Cameron Barr take core samples from Duck Lagoon, North Stradbroke Island. Photo: Tony Moore |
The discovery showed North Stradbroke Island was an exception.
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| Researchers John Tibby, Lydia McKenzie, Jonathan Marshall and Cameron Barr take core samples from Duck Lagoon, North Stradbroke Island. Photo: Tony Moore |
The South Australian lead researcher John Tibby released the results on Monday, with Queensland government scientist Jonathan Marshall.
Dr Marshall, the principal scientist with the Queensland Department of Science, Information Technology and Innovation, said the research demonstrated North Stradbroke Island was "an Australian exception" during those dry times.
"We cored and dated 16 wetlands on the island and found six dating to the ice age or earlier, with one being more than 200,000 years old," Dr Marshall said.
Dr Tibby, from the University of Adelaide, said there were more wetlands on North Stradbroke Island dating back to the Ice Age than anywhere else in Australia.
"Australia was much drier during the last Ice Age than it is today, as most of the water was held in large ice sheets in the Northern Hemisphere," he said.
“Right across Australia, there were few wetlands during this time, which raises the question: Where and how did plants and animals survive that needed permanent water?
"The island, and possibly even the region itself, may have been a refuge from dry climates.”
The Moreton Bay side of North Stradbroke Island has a string of wetlands.
Dr Tibby said their research showed Ferngully Lagoon, to the north of Blue and Brown Lakes on the bay side of North Stradbroke Island, was 200,000 years old.
"The instinctive thing is that you would expect that lakes and swamps that exist on sand, because North Stradbroke Island is a sand island, is that they are likely not to have existed for a long period of time," he said.
"So the fact that these lakes and swamps have existed for a long time suggests that on average it has been wet in the region for most of that period of time, which is in contrast to what we think we know about the rest of the Australian continent.
"We have very, very few locations where we have wetlands that have persisted through since the end of the last Ice Age."
The Ice Age began slowly about 100,000 years ago, reached its peak between 15,000 and 20,000 years ago and gently warmed.
The discovery would allow researchers to study the history of vegetation changes, eventually over the past 200,000 years, by looking at fossilised pollens.
This research would be compared to other research, which was "inferring" past rainfall in the region.
Dr Tibby said researchers would use core samples to look into the impact of human arrival in south-east Queensland and the impact on vegetation.
"Whether those two things together had a role in causing the extinction of the giant animals, the megafauna and then what happened to fire practices with Indigenous people using the landscape," he said.
"It has been hard to get good answers to those questions because we have had so few good sites."
The science suggested the island may have had permanent wetland areas when Australia’s climate was at its driest.
Dr Tibby said the persistence of these wetlands were linked to the island’s groundwater systems, which acted as water reservoirs during periods of rainfall deficit.
“During what was otherwise a particularly dry period in Australia’s ancient past, these persistently moist regions are thought to have played a unique role in maintaining biodiversity,” he said.
Dr Tibby said being able to research the North Stradbroke Island wetlands further would help understand longer-term climate change.
“It will greatly improve our understanding about the drivers of both local and regional climate variability.”
Quandamooka Yoolooburrabee Aboriginal Corporation traditional owner Darren Burns said the new scientific evidence confirmed the existence of local natural resources – local spring and water supplies - which the Quandamooka people used to live on the island they knew as Minjerribah.
Science Minister Leanne Enoch, herself a Quandamooka women from Minjerribah, said the research had the potential to change thinking about how climate changed in south-east Queensland.
“Until now, few Australian sites had offered detailed information about what was happening at wetlands since the last great ice age, which peaked around 15,000 years ago,” Ms Enoch said.
“...The significance of this research is that it greatly adds to our understanding of the ancient climatic changes that shaped our country, our wildlife and our first peoples.”
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