It has been a creeping problem along the coastline of south-eastern Australia for decades, but a breakthrough may be on the way.
Sea urchins, a native species in NSW, have exploded in numbers, grazing on healthy kelp forests until only an eerie moonscape remains.
The urchin barrens already cover 50 per cent of the NSW coast and as ocean temperatures rise, the urchins are now degrading coastal reefs in Victoria and Tasmania.
But a new initiative is bringing together scientists, traditional owners and commercial fishers to selectively harvest urchins from barren areas, while also encouraging a sustainable commercial urchin harvest.
A trial site will be chosen on the far south coast of NSW, the "epicentre" of the sea urchin infestation.
"What we're trying to do is turn those extensive barrens … into a productive mosaic, with enough kelp and seaweed to fatten up the urchins so that we get a commercial harvest," said the project's lead scientist, Professor Adriana Verges from UNSW Sydney.
While roe from healthy urchins is a lucrative delicacy, the urchins in barrens are malnourished and inedible.
The urchins culled in the trial will be crushed up and sold as agricultural fertiliser.
The project is supported by WWF-Australia and comes after a Senate inquiry into climate-related marine invasive species was launched in September 2022.
The Senate committee tabled a progress report this week, requesting an extension of time to report, until July this year.
Australia's other 'great' reef
Australia's Great Southern Reef covers 71,000 kilometres of the Australian coast from NSW to Tasmania and across to Western Australia.
The globally-significant reef supports some of the world's most valuable fisheries — lobster and abalone — worth more than $10 billion each year to the nation's economy.
The loss of kelp forests has been devastating for marine biodiversity on the reef as the sea urchin's predators and competitors decline and urchin numbers proliferate.
Dane Wilmott from the Nature Coast Marine Group, is optimistic that unlike deforestation on land, the loss of kelp forests can be turned around quickly.
"It's a complex issue, but achievable if we address all the key issues that are contributing," Mr Wilmott said.
While the global consensus is that the loss of the sea urchin's natural predators through overfishing, habitat loss and climate impacts is the root cause of the issue, Mr Wilmott said that more research was needed into the interdependence of the different species that inhabit the coastal reefs.
"It's becoming clearer and clearer that when we have these imbalances in the ecosystem, we've put too much pressure on one fish stock or another, the urchins reach a tipping point and they take over," Mr Wilmott said.
Satellite photos of a site in Kurnell in southern Sydney show the potential of kelp forests to regenerate.
White areas in the image below show urchin barrens in 2018.
A photo of the same site in 2021 shows extensive recovery of Golden Kelp and other seaweed after 5,000 urchins were removed.
'Take our science on'
The growing problem of sea urchin infestation is an urgent priority for south coast Indigenous communities, according to Walbunja elder Wally Stewart.
Mr Stewart is a director of Joonga Land and Water Aboriginal Corporation, which was formed to give the local community a greater say in marine conservation and to create employment opportunities.
Last year, Joonga trained a team of six Indigenous scientific divers to address the sea urchin issue, targeting traditional cultural fishing sites.
For Mr Stewart, it is crucial that traditional custodians are not treated as "stakeholders" in conservation decisions, but play a central role in the management of sea country.
"Our mob have been fishing and diving these waters forever. But our science has never been taken seriously," Mr Stewart said.
"We've got an obligation as traditional owners to look after these waters so they're healthy for for for everybody."
