Marine scientists are lobbying the federal government to ensure protection for Australia’s most endangered – but least known – ocean ecosystem.
Shellfish reefs, formed by millions of oysters or mussels clustering together in or near the mouths of estuaries, have declined by up 99% since British colonisation. Yet they are not formally recognised as a threatened ecosystem under Australian environmental law.
A study led by the Nature Conservancy Australia and published in the peer-reviewed open access journal Plos One on Thursday found that the number of reefs formed by Australian flat oysters, Ostrea angasi, had declined 99% from 118 found in historical records to just one, in Tasmania’s Georges Bay.
The number of reefs formed by rock oysters, Saccostrea glomerata, which are found on coastal banks around Sydney, declined 90% from 60 known historical locations to six surviving reefs.
It is even more drastic than the decline in the Great Barrier Reef, which suffered unprecedented mass bleaching events in 2016 and 2017 that are believed to have killed up to half of the coral, and the shrinking of kelp forests, which have declined 90% off the coast of Western Australia due to successive marine heatwaves.