Mary River proves Australia's most degraded catchments can be restored

In short:

In the 1990s, the Mary River Catchment was considered one of Australia's most degraded catchments.

Decades of work by the community has helped the environment, reef and endangered species.

What's next?

More effort and investment is needed for the good work to continue.

In the 1980s, Peter and Elke Watson stood out when, instead of cutting down trees, they started planting thousands of them on their land beside south-east Queensland's degraded Mary River.

People were puzzled when they fenced cattle off erosion-prone river and creek banks, installing off-stream water troughs to stop cows fouling waterways with their excrement.

"We were considered the weird greenies … there were hardly any trees here," Ms Watson recalled.

The dairy farmers at Cambroon, near Kenilworth in the Sunshine Coast hinterland, joined the frontline of a quiet revolution in attitudes, working to repair past mistakes and restore the environment.

When the Watsons attended the first management meeting of the Mary River Catchment Coordinating Committee (MRCCC) 31 years ago, the 9,595-square-kilometre catchment was in strife.

"The Mary was described, I think it was post-1990, as one of the most degraded rivers on the east coast of Australia," MRCCC chairman Ian Mackay said.

During floods, the 310-kilometre-long river churns brown with soil and nutrients washed in from its catchment, originating in the Conondale range.

It discharges into the Great Sandy Strait, the southernmost section of the world-heritage-listed Great Barrier Reef.

In 2022, during the second-worst flood on record, plumes of sediment smothered seagrass meadows vital to fish, turtles and dugongs.

An estimated 66 per cent of it came from stream bank erosion; hundreds of hectares of farmland were sliced away.

The MRCCC has built relationships with landholders on more than 850 projects to improve riparian and water health.

New pile field technology has transformed eroded stream banks that the MRCCC once feared could not be fixed.

"We just really didn't know what to do with bad bits like this, and the pile field technology has changed all of that, and it's so exciting," Mr Mackay said.

The Watsons lost 4 hectares of land to one flood in 2013.

They have one of the 16 pile fields installed in the catchment's most challenging sites, with help from the MRCCC, the Burnett Mary Regional Group and Alluvium Consulting.

Eroded creeks and riverbanks have been reshaped, with rows of untreated hardwood poles driven into the earth and native vegetation replanted.

Three years ago, the worst section of Vern and Maxine Gilbert's creek bank at Kidaman Creek looked more like the cliff their neighbour is still dealing with.

A pile field has stopped them losing land with every flood.

"It's really improved to no end. Floods don't worry us like they were," Mr Gilbert said.

The MRCCC's Becky Watson said the pile fields were preventing 27,000 tonnes a year of fine sediment from reaching the reef.

"It's a huge contribution to water quality,"Ms Watson said.

To help the MRCCC keep track of progress, volunteers in a Waterwatch program regularly test water for temperature, pH, salinity, E.coli, dissolved oxygen and turbidity.

The federal and Queensland governments have committed $2 billion to improving reef water quality between 2014 and 2031.

Restoration extends underwater

The catchment is home to the vulnerable Australian lungfish, critically endangered white-throated snapping turtle, bum-breathing Mary River turtle and the endangered Mary River cod.

In 2009, federal environment minister Peter Garrett scuttled the controversial Traveston Crossing dam proposal to save their habitat.

Restoring Mary River cod stocks is a priority as they were fished to near extinction.

To protect the fish and their eggs during breeding season, line fishing is banned between August and October upstream of Gympie.

Cod logs

The MRCCC's Nathaniel Larsen pioneered the use of hollow tree trunks to provide habitat for the endangered cod.

Kabi Kabi and Jinibara rangers are helping him install ethically sourced "cod logs" as nesting sites.

Collaborating with Griffith University, Mr Larsen was elated when they filmed proof that the fish would lay their eggs in them.

"We were stoked. It was spectacular,"he said.

Work continues

Bulk water authority Seqwater has become a major financial backer to improve the quality of drinking water its treatment plants pump from the river.

It is tackling invasive madeira and cat's claw creeper vines, which strangle and kill trees along waterways.

As part of the Upper Mary Rivercare program, Seqwater is working with the MRCCC and dairy farmers to upgrade their effluent systems, manage nutrient and sediment run-off and restore riparian corridors.

The goal is to stop nitrogen, phosphorus, potassium and E. coli flowing into the river and onto the southern barrier reef.

"There's a whole lot of momentum that's gaining as people learn and hear about others around them who have been involved in the program," MRCCC project officer Alana Ebert said.

Effluent upgrades

Twice a day, the Watsons collect hundreds of litres of effluent including spilt milk, faeces, urine and wash-down water from their dairy.

This once-wasted resource helps reduce fertiliser bills; their dairy manager sprays the effluent back onto pasture, which is rested for several weeks.

A wetland on the farm is being restored to filter out excess nutrients.

MRCCC operations manager Brad Wedlock said the multi-pronged approach had been incredibly effective.

"We could see through a couple of flood events that the nutrients from up there to down here dropped by 1,000-fold,"Mr Wedlock said.

Peter and Elke Watson say their work on catchment care has helped their business survive floods, droughts, dairy deregulation and the devastating impacts of $1-per-litre supermarket milk.

"We went through some of those really tough times and pride ourselves on having some of the lowest pasture costs in the dairy industry," Ms Watson said.

"It's also created an environment that you're happy to work in and live in," Mr Watson said.

MRCCC chairman Ian Mackay said that decades of work lie ahead, but he hoped that progress in the catchment would inspire other country communities.

"It's a win-win-win on so many different fronts," Mr Mackay said.

"Fish breeding down in the estuary, bank stabilisation, water quality, it's endless."

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