Sydney Harbour is popular with tourists and locals alike. But the sparkling aquatic playground sits upon a world below heavily impacted by centuries of city development, pollution, boating activity and climate change.

Professor Adriana Vergés is a marine ecologist based at the UNSW Sydney School of Biological, Earth & Environmental Sciences. Her research focuses on rewilding the waterways and seascapes in and around Sydney. In doing so, she hopes not only habitats, but the populations of fish, shellfish and other sea creatures they support can start returning to and thriving along our shorelines.

Losing marine habitats and the species within them affects industries but also puts our own survival at risk—marine biodiversity is essential for food and for climate regulation.

Prof Vergés works on re-balancing the seascapes of Sydney’s waters through the Sydney Institute of Marine Science’s Project Restore—one of the largest harbour restoration projects in the world. This collaboration is at the heart of the NSW government’s Seabirds to Seascapes initiative. It combines existing marine restoration programs in NSW including Operation Crayweed and Operation Posidonia, which are both co-founded and led by Prof Vergés.

"Marine conservation is no longer about protecting what remains because too much has disappeared for ecosystems to recover on their own. It’s now about intervention, which means actively restoring what we have lost.” 
- Professor Adriana Vergés, School of Biological and Environmental Sciences, UNSW Science.

Challenges & opportunities

Centuries of intense coastal development, dredging, water pollution and boating activity are taking their toll on Sydney’s waters and its inhabitants. A rapidly warming world only further compounds the problems of poor water quality and urbanisation.

Regulations around the treatment of sewage were improved in the 1990s, to prevent further damage to the waterways and ecosystems. Water quality has slowly gotten better since then—but some habitats did not return.

Seaweeds form highly productive underwater forests. These are the foundation of coastal food webs and provide shelter for hundreds of marine species. They are also more efficient than trees on land are at capturing atmospheric carbon and producing oxygen. But they’re under threat.

“Temperate seaweed forests are in decline worldwide, due to human activities, and that is what we have seen here along Sydney’s beaches,” Prof Vergés said.

Around 70km of forest and meadow habitats off the coast of Sydney disappeared in the 1980s. No one realised until decades later. Crayweed—or, Phyllospora comosa—was a dominant type of marine plant.

Operation Crayweed aims to ‘reforest’ Sydney’s beaches and bays. However, revegetating the seafloor is not an easy process.

The team harvests small amounts of fertile, adult crayweed from existing healthy populations and transplants them into deforested areas. The samples are collected from a wide population, so the new populations are genetically diverse. Once installed, the crayweed starts reproducing (i.e. having sex), producing babies and—as the population grows—helps restore further communities: crayfish, abalone and a huge diversity of other fish and invertebrates.

In the waters closer to the city, seagrasses—particularly the Posidonia australis species—form habitats that provide services such as carbon capture, oxygen production, storm surge protection and water cleaning. They are home to sea horses, cuttlefish, snapper and blue swimmer crabs, as well as nurseries for fishes and prawns. Though seagrasses can live up to hundreds of years, nearly two football fields’ worth is lost each hour across the world.

The once thriving seagrass meadows of Sydney are now much diminished. Part of the problem is that the heavy boat mooring chains used in the harbour dredge up seagrass.

With Project Restore the team aims to replace traditional block and chain moorings with Environmentally Friendly Moorings (EFMs) in Sydney. But the slow growth rate of seagrass means natural recovery is slow. And Posidonia is now officially endangered.

“In some places, it could take more than two decades for the mooring scars to be revegetated by seagrass naturally,” Prof Vergés said. “So we're hoping to give nature a bit of a helping hand.”

Citizen scientists can help through Operation Posidonia. Beachgoers collect fragments of seagrass that are washed ashore following storms, winds and tides. These are then replanted.

“The process is like underwater gardening, where scuba divers take the fragments collected by the public and pin them onto the seafloor to encourage growth,” Prof Vergés said.

“There’s a real risk that, combined with the threat of climate change, seagrasses become locally extinct without intervention."

 - Professor Adriana Vergés

Forward focused

All ecosystems—including those hidden underwater—support life on Earth. With the 2021-2030 UN Decade on Ecosystem Restoration now well underway, the solutions-based research and partnerships led by Prof Vergés are directly restoring healthier oceans, protecting biodiversity and helping mitigate climate change.

Supporting and encouraging healthy marine environments around Sydney also has benefits to snorkelers, fishers, beach goers and seafood lovers alike.

When it started, Operation Crayweed was the fastest environmental project to ever reach its crowdfunding site target. Prof Vergés engages not just with academics but with artists and filmmakers to reach a wider public. The initiative’s success was dependant on working with local communities and communicating achievements with the world.

Operation Crayweed will continue with both restoration and outreach efforts. Not just in restoring underwater forests but ensuring the new plantings are resilient in facing the rapid environmental changes ahead.

“When we did transplant experiments and realised that not only could crayweed now survive in Sydney but that we could also make it reproduce, that’s when we got excited because you don’t often come across many fixable environmental problems,” Prof Vergés said.

The initiative has so far had positive outcomes in several areas along the Sydney coastline including Cabbage Tree Bay, Malabar, Little Bay, Coogee and Freshwater.

The harbour's first Posidonia restoration attempt has started in Balmoral Beach, in collaboration with Mosman Council.

A restoration trial in Port Stephens had a 70 per cent survival success in some areas after one year. After 6 months, many transplants began producing new shoots—expanding into and revegetating the surrounding area. There are new Operation Posidonia restoration sites underway around Sydney. But Prof Vergés hopes to set up more sites within the harbour.

“Enough Posidonia remains that we have a good chance of restoring Sydney Harbour using fragments from surrounding meadows,” Prof Vergés said. “But we must act quickly and while we can if we hope to give the species the best chance to survive.”

"[We are] trying to come up with solutions and bringing people along on that journey."

 - Professor Adriana Vergés

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