In the cold waters around Tromsø, volunteers are restoring kelp forests by hand. They dive in to take photographs, monitor species and to remove sea urchins one by one. It is slow work. It is also essential. More than eighty percent of Northern Norway’s kelp forests have disappeared as urchin numbers have increased and predators have declined. The same pattern is seen in many places across the world. When kelp is eaten down, the seabed is left bare and almost nothing grows back on its own.

This local challenge is part of a global story. Ocean Green was created to address it at scale. The project brings together science, technology and community involvement to restore kelp forests and rebuild ecosystems that have been lost.

The newest step in this work is also the most surprising. It is a small activity that feels almost like a game. It is calm, simple and strangely addictive. It is called the Urchin Density Challenge.

A global invitation

Rissa Citizen Science has launched the challenge through the Rissa app. Anyone anywhere can now take part in the research happening in Tromsø. You are given a photograph of a small frame placed on the seabed. Your task is to count the urchins you see inside the square. That is all. Yet each count becomes part of an important dataset used by researchers at the University of Tromsø. These data help them follow changes in the restoration areas over time and understand when kelp is able to return.

Delphin Ruché, founder and director of Rissa Citizen Science, describes it this way:
‘The Urchin Density Challenge takes citizen science to the next level, inviting people around the world to document biodiversity changes in areas where volunteers are restoring kelp forests.’

Some images show many urchins. Others show none. Sometimes a bright starfish appears. Users begin to recognise patterns. They learn what a barren looks like and what recovery looks like.

Why it matters

Ocean Green brings together advanced engineering and hands on monitoring. Ava Ocean is adapting its gentle seabed harvesting system so that urchins can be removed at scale without harming the seabed. NIBIO, NIVA, Hofseth Biocare and Akvaplan niva are studying new uses for the harvested urchins, from food and fertiliser to enzymes and biomaterials. Together they are working to build a circular value chain that supports long term restoration. The project is part funded by Norway’s Green Platform and is endorsed by the UN Ocean Decade.

But citizens remain at the heart of the work.

Dagny Elise Anastassiou, Ocean Green project manager and Chief Impact Officer at Ava Ocean, explains why:
‘We made citizen science a core part of this work because people matter. Many ocean issues stay invisible and are easy to ignore. When people are part of the process, projects are more likely to become long term solutions.’

She adds:
‘The app is easy to use and fun. Some photos show lots of urchins, others none, and suddenly colourful starfish appear. It is quite addictive.’

More than an app

The challenge builds on a wider programme of outreach. Volunteers in Tromsø meet every month to take photos, monitor species and help reduce urchin density by hand. A new permanent exhibition will open on the town jetty in January. It shows the shift from urchin barren to recovering kelp forest in the water below. Schools across Northern Norway have also taken part in screenings of Stone Biter, a visually rich documentary by Ismaele Tortella, followed by discussions about predators and ecosystem change.

Together these activities help make the invisible visible. They give people a direct view of the problem and the solution. They build a shared understanding of what is happening below the surface.

A small action with real impact

The app requires no training. A few minutes is enough. Yet the data collected supports real science and contributes to a growing body of international knowledge. It shows where kelp may return and how quickly. It helps researchers understand how restoration works over time. Anyone can take part. Schools. Organisations. Families. Individuals.

Ocean Green invites the public to join the challenge and become part of the story. The work is serious, but the entry point is light and accessible. A simple count. A global contribution. A small step towards bringing kelp forests back.