Transforming Australia’s urban rivers with mud crabs

Along the banks of Australia’s most polluted urban river, a different species of mud crab scurries along the flats. Named for the plastic pincers they use to pick up rubbish, a 600-strong clan of eco-warriors, aka The Mudcrabs, is comprised predominantly of retirees from suburbs surrounding Sydney’s Cooks River.

Peter Munro, 73, helped found the Landcare group 20 years ago. He has seen a dramatic improvement in the river’s health.

“At different points on the river, you could once almost walk across the floating litter,” he told AAP.

The Cooks (as locals call it) has been notorious as a toxic sewer. Its 23 kilometres is a brown and murky snake that weaves past residences and industry. The Cooks River winds from its source in the southwest to its artificial mouth at Botany Bay.

The work of the volunteers in restoring the watercourse to its natural state has brought wildlife back to its banks, once dominated by endangered ironbark forests.

One of their successes is the revitalisation of wetlands at Cup and Saucer Creek – formerly a barren concrete drain that now houses native animals and filters stormwater of harmful chemicals.

Munro, who lives two blocks from the river, runs a survey of different birds spotted returning to the renewed ecosystem. The most exciting finds include tawny frogmouths and honeyeaters.

Urban rivers are “massively important” refuges for animals, University of Queensland conservation ecologist Michelle Ward says.

“(Rivers) often meander through cities connecting urban ecosystems like floodplains and wetlands but also nature reserves and parks. They all play a vital role in threatened species recovery,” she says.

The federal government’s latest State of the Environment report, published in July, highlighted the importance of waterways to the myriad species living in the middle of large cities.

It found that 46 per cent of Australia’s threatened species inhabit towns and cities, with several solely reliant on urban river ecosystems.

Urban river systems could be thriving

The western swamp tortoise, Australia’s most critically endangered reptile, was once found in swampland throughout central Perth. However, overdevelopment has reduced the tiny terrapins to just two populations.

In a recent report card co-authored by Dr Ward for WWF, Australia was given an F for species conservation.

But not all is lost, she says.

Protecting habitat from destruction and filtering pollution out of stormwater drains are crucial, but communities can also make a big difference.

“Spaces for urban conservation don’t have to be large. Just one old tree on a riverbank can be a lifeline for many different species,” Ward says.

Having grown up on the Macquarie River in central western NSW, Wiradjuri woman Jennifer Newman struggled to feel the same beloved connection to the Cooks. Part of that came from it being constrained, as it is in part, within concrete walls.

“When you grow up in a town on the river bank, you learn to swim in the river. You fish in the river, walk along the river,” she says.

“The river is a constant presence in your landscape, in your sense of the country.”

Now an executive of the Cooks River Valley Association, Newman believes conservation groups give residents a sense of custodianship over the river.

“It’s a breeding ground, a home, a protection zone, and what waters the trees and shrubs and bushes,” she says.

“As we become more tuned in to the growing population of non-human residents, we can understand this watercourse to be a living river rather than a drain.”

The Gameygal, Wangal, and Cadigal clans had stewardship of the land before colonisation. Their culture lives on through practices like the Blak Markets ceremonies held at La Perouse to guide whales as they migrate up the NSW coast.

Indigenous knowledge key for urban river revival

Newman considers the Bare Island ritual a reminder of humanity’s involvement in the whales’ journey.

Everyone has a responsibility to ensure the water that washes off their properties, down the river, into Botany Bay and out to the whale lines is free of chemicals and waste. Hence, they continue to come back, she says.

The Mudcrabs carry on this practice of stewardship by using Indigenous-grown seedlings. They also harness traditional planting techniques to revegetate the riverbanks.

More than just healing natural ecosystems, river care groups are also improving waterways for their human inhabitants.

At Deep Rock in Melbourne’s inner city, locals brave the frigid, murky water to plunge into the Yarra River. Decades of work have gone into reducing pollution and making swimming safe. It is still not recommended in the CBD.

Formed during the city’s COVID-19 lockdown, when locals rediscovered neighbourhood parks and waterways, environmental alliance Regen Melbourne plans to make all of the Yarra fit for a dip by 2030.

Munro still hopes one day, people will be able to swim in the Cooks River. However, that might be hard to achieve.

In the meantime, he’s not sitting idly by.

“The river is such a unifying bit of geography,” he says.

“It gives you the drive to bring it back to health.”