It’s 20°C in the water, but it feels like 12! We descend onto the familiar reefscape of Bass Point Reserve, but something has changed. The kelp arms that once waved us over a metropolis of fish and crustaceans have been chewed away. Remnants cling to a white moonscape, empty except for sea urchins clambering over each other to advance their frontier. We have never seen them in such high densities! I shiver, and it’s not from the cold.

The term ‘urchin barrens’ describes areas where high densities of sea urchins overgraze kelp, creating large expanses of bare rock inhospitable to many high-value fish and crustacean species.

The formation of urchin barrens is broadly described as an environmental problem, unpacked in a recent Great Southern Reef documentary called White Rock. However, the nature of urchin barrens is hotly debated! The NSW Department of Primary Industries describes urchin barrens as a “typical and distinctive habitat of NSW rocky reef ecosystems” characterised by specific assemblages of sponges, sea squirts, urchins, limpets and fish.

“It’s a very divisive topic,” says Yuin Walbunja woman Kyah Chewying, a marine scientist working toward her PhD at the University of Wollongong. “Some stakeholders support efforts to reduce the population, while others don’t see the issue as so clear-cut and believe it requires a more considered approach.”

Kyah is assessing interactions between native long-spined sea urchins (Centrostephanus rodgersii) and kelp in southeastern Australia through habitat mapping, biodiversity surveys and oral histories. She has identified urchin barrens across the South Coast, with study sites in Bushrangers Bay, Ulladulla, Stoney Creek, Nullica Bay, Fingal Bay, and Port Stephens.

“I’d heard increasing worries [within Indigenous communities] about the urchin barrens and their proliferation on the coast, specifically because the community that I belong to are very avid abalone divers, and they were finding a very large reduction in the abalone population due to urchins invading the spaces and crevices where the abalone and lobsters used to be.

“I’m reading recent reports and studies about how the barrens are static and they’ve been there for up to 50 years, and then when I go and talk to community, they say, 'No, when I was growing up, it was a completely different environment'.

“It was fascinating to me that people can perceive an environmental issue so differently, depending on what side of the fence they’re on.”

The different ways that urchin barrens are perceived provided the inspiration for Kyah’s research, which braids western science and traditional knowledge.

“Braiding these Knowledge Systems together can shed more light on an issue and facilitate a balanced discussion, and this hasn’t been done yet for the urchin barrens in NSW," Kyah says.

“Traditional Owners look at the environment very locally, so they go to their dive spot and see the effect that urchins are having, whereas then you have the NSW Government, and they’re looking at it from a state-wide or nation-wide perspective.”

But what does Kyah think – are urchin barrens a problem on the Illawarra coast?

“I think it’s an issue that needs to be addressed, but that there are nuances to the discussion which make it more complex,” she says. "I don’t think ignoring it will make it go away. It’s not just the Indigenous community; the wider community is concerned as well.”

The local diving community shares Kyah’s concerns. Emerging from the apocalyptic dive I described earlier with their eyes down, my companions just kept repeating,“They were everywhere” and “There’s nothing left”.

Kyah says: “I think there’s a few factors causing this. Climate change is causing them [urchin barrens] to expand. The larvae are very adaptable and are able to live in the water column, especially warmer waters, for a very long time. One possible theory is they are the result of mismanagement and overfishing. If you remove the top predators like snapper and grouper, it allows for proliferation of prey species. Also, Centro don’t need much sustenance and keep reproducing in really starved conditions. It’s the perfect storm.”

Solving the ‘urchin barren’ problem may be as complex as the cumulative impacts driving their expansion.

“A lot of people jump just to remove the urchins. However, it’s not addressing the reason that they’re there. If this is a result of overfishing or climate change, then they’re going to come back.

“We need a multi-prong approach. Yes, remove the urchins to restore local environments. Also, allow Traditional Owners to have more control of their cultural waters. We have an issue with not consulting Traditional Owners and there’s a lot of fear when it comes to Indigenous People taking control of ocean issues because of historical distrust in the Government. We need to build trust between the community and decision-makers. Also, this issue is not just affecting us anymore. We need more communication with other states.”

Kyah published her Honours study in April this year and is working hard to publish additional results by the end of this year.

A Recipe for Sea Urchin Butter

Sea urchin butter is an incredibly versatile ingredient that can be easily stored in the freezer and used as needed. Packed with umami, it's the perfect substitute for regular butter in dishes featuring garlic prawns, mussels, or other seafood. Try spreading it on toast or placing a slice atop your favourite cooked fish while resting.

Note: Use a good-quality butter to get the best outcome.

Ingredients

• 250g salted butter (Pepe)
• 50g sea urchin
• Zest 1 lemon
• Juice ½ lemon
• 1 bunch chives, chopped
• 1-2 sprigs lemon thyme

Dice the butter and leave it in a warm place to soften.

Method

Place the sea urchin into a blender or food processor and blend until smooth. Add the butter, lemon zest and juice, then blend until smooth and well combined. Stir in the chives and lemon thyme. Roll into a log using baking paper and foil, chill in the fridge or freeze until needed.

Source: Recipe by Sea Urchin Harvest from Port to Plate: South Coast New South Wales (2025, porttoplate.com.au)