Wetlands Work Wonders

Six years ago, Barretts Lagoon near Tully was best described as a weed-choked “disaster”.  But with landholders, agencies and traditional owners working together, the result is a thriving wetland supporting birds, fish and even crocodiles.  

Cane farmers Santo Silvestro and Denis Marsilio’s smiles broaden when they look out over Barrett’s Lagoon. The way it looks now – with its wide expanses of water, birdlife and native vegetation – is a far cry from the weed-covered waters they raised the alarm about back in 2015. 

“You couldn’t see the water – 95 per cent of it was covered in green. We couldn’t believe how quickly an invasive weed like hymenachne could spread both in height and across the water,’’ Denis says.  

“In places it was one and a half metres high and it looked like a huge mat laid out over the water.” 

The pair talked to their industry body Canegrowers who got in touch with natural resource management organisation Terrain NRM and this led to funding and a larger working group including Gulnay Traditional Owners, the Cassowary Coast Regional Council and the Queensland Parks and Wildlife Service. 

“Hymenachne weed was so high we couldn’t begin on land or with boats,’’ Denis says. “Helicopters were used to aerial spray with grass-selective herbicide and that was followed up with land-based work. We had a tractor pump and we dragged a 70m hose through the scrub to areas the helicopters couldn’t get to. Once the spraying took effect and we could use a boat, things got a little easier.” 

Selective herbicides are designed to treat a specific species while leaving other species, like the bullrushes, unharmed. The restoration project also included on-land weed removal by further upstream. 

Gulnay Traditional Owner Clarence Kinjun said rehabilitation work was continuing, with plans for ongoing fish surveys, water quality monitoring, weed management and ecological and cultural assessments as part of proposed project to train up the younger generation and increase wetlands connectivity for fish species. 

“Everything is important here - the fish, the plants, the birds. Everything is connected. We’re bringing bring life back to the lagoon.” 

Wetland ecologist Fernanda Adame has been monitoring the area and studying the effect of lagoons and their aquatic plants in filtering water and removing nitrate that would otherwise flow to the reef.     

“A lagoon network like this, in the lower flood plain area, helps the whole catchment. Removing the weeds and allowing the water to flow brings back diversity in plant and fish life and it also improves the quality of water and the nitrogen removal process,” she said.  

Wetland Fast Facts

  • Queensland has more types of wetlands than any other state in Australia. 
  • Since colonisation, many wetland areas have been modified for agriculture, industry and urban development.  
  • Almost 50% of swamps and 40% of river wetlands have been cleared in the Wet Tropics.  

Other Wetland Projects

  • Figtree Lagoon: Cane farmer Len Parisi won a Reef Champion award for his work restoring seven hectares of cane land with over 9000 trees at Figtree Lagoon with the help of Mulgrave Landcare and Greening Australia.  
  • Mulgrave Landcare have also restored 10 hectares of old cane land with over 10,000 trees next to the Russell River National Park.  
  • Eubenangee Swamp: The rehabilitation of Eubenangee Swamp has been a 30-year labour of love by Queensland Parks and Wildlife Rangers, Terrain NRM and Indigenous Groups.   

Boggy Bits Turned into Treatment Systems  

Wetlands are so effective as water filters that trials have also been undertaken to test whether it is possible to engineer ‘boggy bits’ on farms into water treatment systems. As part of the Wet Tropics Major Integrated Project, an area of low-lying unproductive cane land in Mourilyan has been converted into a 1.2 hectare high performing ‘embellished’ wetland instead - and it is proving that these wet areas can be used to remove high levels of dissolved inorganic nitrogen from farm runoff.  

The project's Chris Argyle said a key success factor in the trial was a high level of vegetation uptake. A thriving ecosystem of plant life established itself in a short timeframe, enabling the denitrification process to occur.  

“This constructed wetland is a great practical example of how a wet piece of land, that’s not productive as farm land, can yield excellent water quality outcomes with the help of a tailored design and relatively minimal earthworks,” said Chris. 

The project has been trialling a range of catchment repair systems across the Tully and Johnstone catchments, including five different bioreactor designs, a landscape wetland, in-drain wetland and three constructed wetlands. The constructed wetlands are yielding the best results, proving that with improved hydrology and the appropriate amount of vegetation they have great potential in reducing nitrate levels. 

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