Snail shell rings could hold prehistoric cyclone information

Snails could be an unlikely ally in mapping historical weather events, according to a new study.

Researchers from the University of Queensland travelled to Coalstoun Lakes National Park in Queensland's Wide Bay, 350 kilometres north of Brisbane, to study the native land snail known as the Biggenden banded snail (Figuladra bayensis).

Taking tiny samples from dead snail shells, environmental scientist Nicholas Patton said researchers were able to determine the age of the snail, when it lived and the weather conditions during its lifetime.

"It contained elevated levels of radiocarbon from the nuclear tests in Australia in the 1960s, meaning we could date the growth bands and reveal the snail had lived for about 4.5 years," Dr Patton said.

Analysing oxygen and stable carbon isotopes revealed insights into the rainfall the snail had experienced.

"What we saw was the shell did not grow continuously during the snail's life; there were periods of rapid growth separated by periods of little or no growth," he said.

Honorary professor James Shulmeister said researchers assumed they would find summer growth during the wet season and semi-hibernation in winter.

"What we actually found was there were two big growth spurts," Mr Shulmeister said.

"We realised that these were two cyclones or ex-cyclones that passed very close to the site and dumped a lot of water on Coalstoun Lakes."

Portal to historical weather data

Mr Shulmeister said understanding historical rainfall levels, especially from extreme past events, was difficult because official rainfall records in Australia only began in 1900.

"This snail has suddenly given us a possibility for reconstructing past cyclone events, which is a really cool way of actually getting at the history of rainfall in the region," he said.

"If we go back and take cores [samples], we can get older snail shells, and we can then have a look at the window in the past and see what the rainfall events were like back then."

The research has been published in The Holocene, and Mr Shulmeister said he was optimistic about finding preserved snail shells to continue the research.

"Somewhere like Coalstoun Lakes, the sediments preserve things very nicely," he said.

"We have some cores from there, which haven't been analysed, but my expectation is that we will be able to find some shell material in the cores."

John Stanisic, an honorary research fellow at the Queensland Museum, is known as the "snail whisperer".

He said there were 2,500 estimated species of land snails in Australia, with Queensland having the largest per capita range of large snails of any state.

Dr Stanisic was not involved in the research but said it provided insight into a small window of time.

"It looks quite incredible," he said, adding that he hoped the research would spark more of an interest in land snails.

"Snails aren't dumb animals. When it comes to our native species, they can tell us a lot.

"They're part of that suite of invertebrate species that are so critical to the functioning of an ecosystem," he said.

Dr Stanisic said there were snails in museums across the world from the 1850s.

"People could study them, but what that would tell you, I'm not sure."

Mr Shulmeister said the next step would be to take the research, go back and apply it to the past.

"To basically find a site and get a longer record that will allow us to give an insight into the changes in extreme rainfall in the past," he said.

"My expectation is that this should work for most snails because these snails eat vegetation and it appears the snails wait for these big rainfall events."