Australia recycled 150,000 wheelbarrows of oyster shells to rebuild a lost underwater ecosystem |

Before European settlers arrived on Australia’s coastlines, vast oyster and mussel reefs stretched across the southern half of the country all the way north to the edges of the Great Barrier Reef. These shellfish reefs filtered seawater, fed fish populations, stabilised sediment, and protected shorelines from wave damage. Then, over the course of a century, they were almost entirely wiped out. Commercial dredging, pollution, coastal development, and disease collectively destroyed more than 90% of them. Today, less than 10% of Australia’s natural shellfish reefs remain. A restoration effort led by The Nature Conservancy and backed by the Australian Government and the UN Environment Programme is now trying to change that one recycled shell at a time.

How Australia’s shellfish reef restoration programme recycles shells to rebuild lost marine habitat

The method is deceptively simple. Conservationists collect used oyster and mussel shells from restaurants, fish markets, and seafood processors, shells that would otherwise end up in landfills and return them to the ocean. Once deposited on the seafloor, they form a hard, textured base over existing rubble. Baby oysters, known as spat, need exactly this kind of firm surface to attach themselves and begin growing. Without it, they can’t establish. With it, a reef can begin to build itself back from almost nothing.“What we’re really doing is sort of kick-starting that recovery process,” said Simon Branigan, Marine Restoration Lead at The Nature Conservancy Australia. “Since 2014, we’ve recycled like 150,000 wheelbarrows of shells.”That figure, 150,000 wheelbarrows, is roughly the equivalent of thousands of tonnes of shell material redirected from waste streams into ecosystem recovery. The programme, known as the Reef Builder initiative, was a $20 million partnership between The Nature Conservancy and the Australian Government, running between 2021 and 2023. It built on restoration trials that TNC had been running since 2015, and it expanded the project to 13 geographies across Western Australia, South Australia, Victoria, Tasmania, New South Wales, and Queensland.

Fish species richness and water filtration: what the restored oyster reefs are actually delivering

The restored reefs are already showing results that go well beyond what was expected for sites still in their early years of recovery. According to UNEP, the areas rebuilt so far are adding an estimated 50 tonnes of fish to local stocks every year a number that could double by 2030 as more reefs mature. Researchers monitoring the sites have recorded around 250 species of fish and mobile invertebrates on the restored reefs, compared to 175 species in nearby unrestored areas. That includes crabs, sea stars, and a wide range of native fish that depend on the reef’s complex structure for food and shelter.The water quality benefits are equally significant. The restored reefs are filtering up to 125 billion litres of seawater every year and removing as much as 14 tonnes of nutrient pollution in the process. Excess nutrients from agricultural runoff, stormwater, and wastewater are a major driver of harmful algal blooms, which can suffocate marine life and make water unsafe. Shellfish are among the most effective natural filters on the planet, and at scale, they can meaningfully reduce this problem.As published in npj Ocean Sustainability, shellfish reef ecosystems deliver what the authors call “outsized biodiversity benefits” relative to their physical size: fish production, nutrient removal, sediment stabilisation, and shoreline protection, all from a relatively small footprint of restored habitat.

The IUCN Red List and the target to make Australia the first country to recover a critically endangered marine ecosystem

The goal the programme is working toward is unusually specific and unusually ambitious. The aim is to restore oyster reefs across 30% of the bays and estuaries where they once dominated, which means 60 reef systems in total, covering 300 hectares across 60 locations by 2030.If that target is reached, it would trigger a formal reassessment of the oyster reef ecosystem’s status on the IUCN Red List of Ecosystems, which currently classifies the Oyster Reef Ecosystem of Southern and Eastern Australia as critically endangered. Achieving a reclassification to a lower threat category would, in effect, make Australia the first country in the world to have formally recovered a critically endangered marine ecosystem.As of April 2024, 21 shellfish reefs had been restored at sites around the country, covering 62 hectares. The South Australian Government, meanwhile, began delivering 26 community recycled shell reefs across Eyre Peninsula, Yorke Peninsula, Kangaroo Island, and Largs Bay in 2026, with plans for a large-scale limestone reef of around 16 hectares in the Gulf of St Vincent.

Economic benefits of shellfish reef restoration: jobs, fisheries, and coastal resilience

Marine restoration isn’t usually pitched in economic terms, but the benefits here are concrete enough to count. UNEP estimates the programme could create thousands of jobs, support hundreds of local businesses, and generate close to 14 million Australian dollars, roughly $10 million, in ongoing annual economic benefits. The Reef Builder project alone generated 425 new employment opportunities for local communities during its 2021–2023 delivery phase, which was more than twice the original employment target.The communities that stand to gain most are those along Australia’s southern coastline, fishing towns, coastal tourism operators, Indigenous communities with deep cultural connections to shellfish, and local businesses that depend on healthy marine environments. “They may not be as famous as Australia’s Great Barrier Reef, but these ecosystems are just as important for maintaining the health of our oceans,” said UNEP’s Natalia Alekseeva. “This initiative shows that when nature is given a helping hand, it can come roaring back, for its own sake and for ours.”Reef Builder was named a UN World Restoration Flagship in 2025, only the third project in the award’s history to receive that designation, and the only Australian conservation project ever to be recognised with it.What makes this programme worth watching isn’t just the science or the scale. It’s the logic of it that the shells piling up outside seafood restaurants are also the raw material for rebuilding one of Australia’s most productive and long-lost marine habitats. The waste stream and the restoration effort are, quite literally, the same thing. That’s the kind of closed loop that’s hard to argue with.