Australia’s longest dune system stretches 190 kilometres from the mouth of the Murray River to South Australia’s south-east, part of the thin strip of coastline that separates the wetlands of the Coorong from the crashing waves of the Southern Ocean.

The coastline here is rugged, remote and beautiful, accessible only to the lucky few who can come in by 4WD and boat.

It’s also eroding and changing at an alarming and accelerating rate, which scientists say should be a lesson for coastal communities around the country as they prepare for the effects of sea-level rise.

Flinders University professor Patrick Hesp first came to the area around 42 Mile Crossing, near Salt Creek, in the 1970s as a young PhD student.

He returned in 2013 as a world expert in coastal-dune geomorphology and was shocked to see the amount of change that had taken place.

“In 1978, when I drove along here you had 100 metres more of beach and dunes with a 60m-wide foredune. Entirely gone now,” he said.

The rate of erosion and dune movement was tracked with drones, and historical and satellite photos.(ABC South East SA: Caroline Horn)

With PhD student Marcio DaSilva he began to visit regularly and examine historical photographs and satellite data.

“Every few months we come, two or three months and it’s gone more, and the dunes are rapidly, massively changing.”

They found that an initial rate of erosion of 1 to 1.5m per year in the 1990s had accelerated and is currently 3.5m per year.

As the shoreline erodes, the dunes move inland towards the wetlands.(Supplied: Patrick Hesp)

As the beach disappears the foredunes become cliffs and collapse and the sand is moved over those behind, smothering vegetation and destabilising them.

“In the last 10 years or less, a new dune field has developed that’s gone up to 200m wide across the older dune system and continuing to expand landwards,” Professor Hesp said, adding that the erosion sites were also becoming wider.

Coastal communities could see ‘remarkable change’

The dramatic changes here are thought to be due to a combination of increasing wave power in the Southern Ocean, a rise in sea levels, and breaking down of an offshore limestone reef that once absorbed the power of the waves before they crashed onto the coast.

Professor Hesp said if the major shoreline erosion he was seeing in the Coorong started to be seen elsewhere, Australian coastal communities could see “remarkable change” and would need to consider how to protect their assets.

“Especially where you’ve got decent dune systems. They’re extremely good at translating upwards and landwards with sea-level rise and erosion but if you’ve got infrastructure in the way then there’s going to be huge problems,” he said.

“I don’t see that government is doing enough anywhere in the world to really mitigate climate change and to make coastal communities think more about retreat options, for example, which we seem to hate to do.”

What does this mean for the future of the Coorong?

The Coorong is a long, shallow estuary at the bottom of the Murray River, known to many Australians through the iconic book and film Storm Boy.

It is divided into the North and South lagoons at its narrowest place and was designated as a Ramsar-listed wetland of international importance in 1985.

The Coorong is known to many through the iconic Storm Boy book and films.(ABC South East SA: Caroline Horn)

The South Lagoon has experienced considerable environmental degradation since the 1980s.

It sits behind the dunes being observed by Professor Hesp, which he says are moving inland at a rate of about 10m every year.

Faith Coleman, an ecologist based in the South Lagoon of the Coorong, was drawn to the area after being brought up “on a diet of Storm Boy”.

An initial six-month stay has turned into 30 years of watching, caring and advocating for the region.

Faith Coleman is researching the history of the Coorong.(ABC News: Guido Salazar)

Ms Coleman said records showed while the Coorong was always in a state of change, the speed and way the dunes were moving now was unique and showed a “slightly faster” rate than normal.

“The funny thing about climate change is that things are exponential,” she said.

“So he’s documented this rate and then what’s going to happen is it’s going to get faster and faster and the question is how fast?

“Slow change we can all deal with. We have dealt with it for thousands of years. Fast change we’re not evolved to deal with.”

Professor Hesp’s work indicates if the dunes continue to move in their current speed they will start to invade the South Lagoon in about 30 years.

Ms Coleman said of more immediate concern to locals was the “atrocious” environmental state of the South Lagoon, which she said was in desperate need of government action and decisions between several infrastructure options.

A special place

The lagoons and dunes of the area have been the home of the Tanganekald people of the Ngarrindjeri Nation for thousands of years.

“This is a very special place to our family,” elder Mark Koolmatrie said.

“When the Coorong is sick, so are we.”

Darryl and Mark Koolmatrie want any exposed remains to be treated with respect.(ABC News: Guido Salazar)

Both Mr Koolmatrie and his brother Darryl hope, as the dunes continue to shift and change, any uncovered remains or artefacts are treated with respect by visitors and reported to the Ngarrindjeri Aboriginal Corporation and South Australian Police.

They also hope that governments will take note and learn from the environmental impacts being felt in their ancestral home.

“We don’t have to look after everything globally but if we care for significant areas that are important to us as individuals, we cannot help but look after the whole environment globally,” Mark Koolmatrie said.

“Nature will have its way. It doesn’t matter what we believe in, who we believe in, but nature will have its way,” Darryl Koolmatrie added. 

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