Are urchins an invasive species?

No. the urchins that have overgrazed Norway’s kelp forests – mostly green sea urchin (Strongylocentrotus droebachiensis) – are native and the goal is not to get rid of them. When in balance with their surroundings, these creatures play an important role in their ecosystems. That’s what Ocean Green’s regenerative harvesting is all about: harvesting the right number of urchins in order to allow kelp forests to return.

What is an urchin?

Small, spiky sea creatures – maybe green, pink or purple – urchins are found in every ocean of the world – from shallow tidal pools to depths of up to 7,340 metres. Since they can’t swim, you’ll typically find them on rocks or the sea floor. Their main diet is algae – of which kelp is one type – but they will also reportedly eat sea cucumbers, mussels and sea sponges, scraping food into their mouth – which is on their underside.

They are also voracious eaters: research has shown they typically eat between 1.3% and 4.1% of their body weight a day but, depending on factors such as food availability, this could range from 18% of their body weight per day, to nothing. They have been shown to live for a long time in a ‘zombie’ state, with almost no nutrients – meaning urchin barrens don’t go away by themselves simply because the food has run out.

This has led to urchin barrens becoming an ecosystem challenge across multiple regions: from California to Japan, Norway to New Zealand, scientists and policymakers and researchers are trying to come up with solutions to the problem, which is caused in some cases by overfishing, but might also be due to disease, changing ocean temperatures and other effects of climate change.

Historic overfishing

In northern Norway, the main culprit is historic overfishing. While it is important to stress that the urchins we see covering the sea floor in many parts of northern Norway are native to the region, it is as important to explain why they have managed to reproduce to such scale. And the problem goes back decades. Overfishing of urchin predators meant not enough of these animals were eaten. This led to a boom in numbers and the decimation of kelp forests. In fact, the largest overgrazing events ever observed in the North East Atlantic were seen in the early 1970s – and the problem of urchin barrens has persisted since.

How bad is the problem?

Researchers from Ocean Green partner NIVA compared the loss of kelp to what we see in the world’s most important land forests. ‘We all think about deforestation and the devastating disappearance of forests on land, from the burning of the Amazon to wildfires in southern Europe, Siberia and California,’ they wrote in a 2021 paper. ‘But something similar has happened under the ocean completely out of view that destroyed Norway’s kelp forests across an estimated 8,400 km2.

‘There is no doubt that if Norway lost all its trees today, there would be a public outcry over their disappearance and calls for immediate restoration actions; a perception that must be adopted for kelp forest ecosystems to firmly establish their conservation and restoration as an integral part on political agendas,’ they added.

For regenerative harvesting to work, there should be around two urchins per square meter – down from around 30 today. You can do your bit to join the urchin count using the ‘urchin sudoku’ app.

What is Ocean Green doing?

With funding from Norway’s Green Platform – a vehicle providing support for research- and innovation-driven green transition in business – Ocean Green has brought together science and research, engineers, commercial seafood and citizen science to deliver a new approach to the urchin-kelp challenge.

Led by Ava Ocean, which uses patented technology to gently harvest scallops from the Barents Sea, the team are working to adapt that technology for urchin removal. But the goal goes well beyond removal. As they work on the technology, Ocean Green partners are also going inside the urchins, exploring products that could turn an abundance of urchins into a new, economically viable fishery. One such example has seen promise as NIBIO researchers turn urchins into a biostimulant to boost lettuce growth – something that could offer a nutritional boost to people spending months of every year in the dark of northern Norway.

Haven’t I eaten urchin?

You might well have. Urchins have long been fished – and prized. But this isn’t a viable solution to the urchin barren problems, mostly because these ‘starved’ urchins have little flavour or nutrient value.

If you do get hold of some high-quality urchin roe – or more specifically gonads – you might want to try it in the Japanese style as sashimi or on rice, Italians also have a taste for sea urchin, added to risotto or a creamy pasta.

Safeguarding restoration

‘The long-term hope is that, once urchin numbers are controlled and kelp has returned, natural checks and balances will do the hard work, without the need for human intervention,’ says Dagny-Elise Anastassiou, chief impact officer at Ava Ocean and management lead for the Ocean Green project. But that is a big ask – especially since the drivers of urchin overpopulation go beyond overfishing. Still, overfishing can be better managed locally than climate change and NIVA researchers have suggested setting up protected areas where kelp restoration is happening. This would control fishing activities, allowing for the established return of larger predators, giving local ecosystems more time to really rebound.

‘Given the likelihood of some degree of monitoring and removal – Ocean Green funding was originally designed to support the project for three years – we are also working hard to secure self-sufficiency. One avenue is blue carbon credits, but establishing an economically viable fishery that makes real use of harvested urchins is key to the zero-waste, circular goal of restorative harvesting,’ adds Anastassiou.