Just add salt: opening the floodgates for coastal wetland restoration

A tongue of saltwater inches forward, a gleaming sheet ebbing and flowing with the swell of the rising tide. Standing on the bank above, a group of people watch its progress with avid attention. It’s taken years of work to reach this moment; they intend to savour it.

The group – which includes representatives from Yuwi Aboriginal Corporation, Yuwi People and Queensland Parks & Wildlife – are gathered on Yuwi Country in Cape Palmerston National Park.

This 7,200-hectare national park about 115 kilometres south-east of Mackay in central Queensland is significant for the variety of lowland coastal ecosystems that it protects, including mangroves, dunes, swamps, grasslands and rainforest.

These habitats are home to a vast array of birdlife and other animals, including one of Australia’s rarest rodents, the Water Mouse (Xeromys myoides). The park also protects undeveloped coastline adjacent to the Great Barrier Reef Marine Park. In the right season, the cape is a great place to spot passing humpback whales.

But there’s a problem spot. Before this land became a national park in 1976, some parts were used to graze cattle. Sometime in the 1960s, a bank (or bund) was constructed, blocking tidal flows of saltwater into a coastal wetland area, to create a freshwater-only system for ‘ponded pasture’.

How ‘ponded pasture’ works is that the closed off wetland area is then planted with introduced pasture grasses that grow well in freshwater floodplains. When the water evaporates in the dry season, the cattle can graze the high-quality fodder left behind.

One of the pasture grasses used, introduced from South America, is Olive Hymenachne (Hymenachne amplexicaulis). It’s now considered one of the worst weeds in Australia.

Olive hymenachne is highly invasive and grows in dense stands that block waterways, threaten fish habitat, and exclude all other plants. It is very hard and expensive to remove or control.

New plants can grow from any small fragments left behind, and its tiny seeds spread easily by water, or in mud transported by animals, birds, and vehicles.

The Queensland Parks & Wildlife Service have wanted to do something about this seven-hectare hymenachne ponded pasture in Cape Palmerston National Park for over 20 years. The Yuwi People have wanted to bring this country back to health for a lot longer.

So when Yuwi Aboriginal Corporation RNTBC and Greening Australia won funding from the Australian Government’s Reef Trust for the Yuwi Blue Carbon Wetland Restoration Project, this spot was a priority.

The partners put their heads together to come up with a wetland rescue plan.

After an exhaustive combined effort by 11 organisations over 16 months to model, design and obtain government approvals, a seven-metre gap was excavated in the man-made bund at the end of November 2025.

The first high tide in December sent saltwater flowing through the breach.

You see, hymenachne doesn’t do well in saltwater. Turns out, controlling the invasive weed in a coastal wetland like this one, can be as simple as restoring tidal flows.

Now you can imagine what it means for the group standing on the bank to see that rising tide begin to stream through the gap they’d made. They are seeing their long-laid plans for saving this weed-choked wetland finally in action.

The hymenachne will die off, and the wetland area will gradually transition back into vital coastal ecosystems like mangroves, saltmarsh, and supratidal forest. By 2057, the anticipated area of saltwater inundation will be approximately six hectares.

Within a few short years, all the diversity of wildlife, eerily missing from this wetland before, will begin to return.

Even better, this success goes beyond one wetland. It’s laid the groundwork for Yuwi Aboriginal Corporation and Yuwi People to keep building up coastal wetland restoration and blue carbon projects throughout their Country – and strengthened a vital connection between them and the Queensland Parks & Wildlife Service team.

It’s also increased Greening Australia’s understanding about effective co-design and ways to support other First Nations groups to start up blue carbon projects too.

All in all, that seven-metre gap in a manmade wall represents a big step forward (opening the floodgates, if you will) for recovering coastal ecosystems, and for many more partnerships helping people and nature.

Watch the video

Hear from Yuwi representatives and other partners about the significance of what’s been achieved through this project.

 
Yuwi Aboriginal Corporation RNTBC and Greening Australia co-designed the Yuwi Blue Carbon Wetland Restoration Project, funded by the Australian Government’s Reef Trust.

The project is being developed and delivered with the support of Queensland Parks & Wildlife Service, James Cook University, Civil IQ, Koumala Excavation, Douglas Partners, EcoSure, Everick Heritage, BMT, and Sarina Landcare.

Update: The Queensland Government has funded an extension of this coastal wetland restoration project through its Reef Assist program, as part of the Queensland Reef Water Quality Program.

 
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