Blue Carbon: Kelp Restoration in the Atlantic North of Norway

The Trefadder Blue Carbon Kelp Forest Restoration Project is designed to restore degraded kelp forest ecosystems in Troms County, Norway, through the controlled removal of excessive sea urchin populations in order to enhance marine carbon dioxide removal (mCDR) and long-term carbon sequestration. The project seeks to reverse ecological degradation caused by historical overfishing of key sea urchin predators, including coastal cod and Atlantic wolffish, which has resulted in persistent “urchin barrens” where kelp forests have been largely eliminated. Prior to project implementation, coastal marine ecosystems in Troms County, Norway are characterized by extensive “urchin barrens,” resulting from a long-standing ecological imbalance. Overfishing has significantly reduced populations of key sea urchin predators, including coastal cod and Atlantic wolffish. This has led to a substantial increase in sea urchin populations, which actively graze on kelp and prevent its natural regeneration. As a result, historically abundant kelp forests have been largely depleted, reducing ecosystem productivity, biodiversity, and carbon sequestration capacity. Under these conditions, kelp forests are unable to re-establish naturally due to continued grazing pressure, creating a persistent degraded state with limited capacity for marine carbon dioxide removal (mCDR). Under the baseline scenario, sea urchin populations remain uncontrolled, and the project areas continue in an urchin barren state, preventing natural kelp forest re-establishment within the project timeframe. As a result, standing kelp biomass remains limited and the capacity of these areas to support marine carbon dioxide removal and long-term carbon storage remains low. In the absence of project intervention, the degraded ecological condition is expected to persist, with no significant recovery of kelp-driven carbon sequestration. Following sea urchin removal, kelp forests re-establish and as the kelp grows it absorbs dissolved CO₂ through photosynthesis. The resulting amount of carbon stored in standing biomass significantly increases initially and then follows a seasonal pattern of annual growth during the summer followed by winter die-off. Short-term carbon storage in kelp biomass and broader increases in ecosystem carbon as a result of kelp forest re-establishment are conservatively excluded from the project calculations.