Restoring Norway's underwater forests

A strategy to recover kelp ecosystems from urchin barrens.

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. But something similar has happened under the ocean completely out of view that destroyed Norway’s kelp forests across an estimated 8400 km2.

The loss of sea urchin predators led to a population explosion of the green sea urchin, Strongylocentrotus droebachiensis, causing the largest overgrazing events ever observed in the NE Atlantic around the early 1970s. Highly productive kelp forests were transformed into desert-like urchin barrens that have persisted for many decades, impeding coastal communities from fully benefitting from the goods and services these habitats provide.


Norwegian kelp forests are important carbon sinks and nutrient filters, as well as focal points for high biodiversity and abundances of commercial fish species, generating an estimated €16.7 million per km2 per year. In comparison, boreal forests are valued at about €0.24 million per km2, which makes kelp forests 70 times more valuable than their terrestrial counterparts. Today, urchin barrens still dominate around 5000 km2 and if restored back to kelp forests would provide an extra $83.6 billion per year – a value 3 times as high as all of Norway’s terrestrial forests combined.

Many international and national commitments and laws call for action to restore coastal and marine environments. The OSPAR convention states to “restore marine areas which have been adversely affected” and the Nature for Life (Norwegian action plan for biodiversity) demands that Norwegian government policy is to achieve “good condition of the ecosystem”. It also calls for “knowledge-based management” and “tailor-made solutions for various ecosystems” to which this report contributes.

An important prerequisite for the restoration of natural habitats is a well-functioning toolbox, with well-established and scientifically tested methods. This report provides guidance for the restoration of kelp forests, specifically in Northern Norway. It addresses the main benefits of kelp forests and the need for their restoration, and provides strategies for practitioners and policymakers on how to achieve this. Target groups of the report are primarily natural resource managers and policymakers, restoration practitioners from national and regional organisations, commercial urchin enterprises and local communities with interest in the restoration of productive coastal habitats and their socioeconomic benefits. The work also supports the needed public enlightenment of the problems that sea urchin barrens and the loss of kelp forests present for the health and productivity of Norway’s marine coastal systems.

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Executive summary

Kelp forests are highly productive underwater seascapes and are among the most ecologically and socioeconomically important habitats on the planet. These marine forests are important carbon sinks and nutrient filters, and focal points for high biodiversity. Kelp forests support productive fisheries, are attractions for recreational ocean users, protect coastlines and provide biomass for commercial kelp harvesting, among other services. Globally, kelp forests generate an estimated €515 billion annually in economic benefits with a per-area value of Laminaria forests in the North Atlantic of €16.7 million per km2 per year which is considered an underestimation of their true value.

Laminaria hyperborea and Saccharina latissima form dense forests along the shallow coastal zone in Norway and are the two most important species in terms of their spatial extent, habitat provision, biomass production and revenue to commercial kelp harvesting. The loss of urchin predators led to a population explosion of the green sea urchin, Strongylocentrotus droebachiensis, causing large scale overgrazing events around the early 1970s. Highly productive kelp forests were transformed into desertlike urchin barrens across an estimated 8400 km2 and have persisted for many decades, especially in northern parts of Norway.

These large-scale losses are now reversing in some regions, attributed to climate change and increasing crab predation. In the Norwegian Sea, around 50% of the previously lost kelp forests have recovered whereas in the Barents Sea region north of Tromsø no noticeable recovery has occurred. Here only 20% of the original kelp forest extent exist today.

Albeit the observed recovery, the remaining urchin barrens are still extensive and provide an enormous potential for commercial exploitation and recovery of kelp forests together with their economic benefits. In Nordland and Troms/Finnmark, an estimated 14780 km of coastline are dominated by urchin barrens that should be targeted by future restoration initiatives. Re-growing these extensive habitats across an estimated 5000 km2 would generate economic benefits of around €83.6 billion annually, making kelp forest restoration attractive for both public and private investment.

Urchin density control has been identified as one of the most effective management measures to rebuild kelp forest ecosystems today. The purpose of this publication is to provide a science-based strategy for the restoration of kelp forests from urchin barrens in Norway by providing information on both the legal framework as well as key concepts and practical approaches for implementing restoration actions.

An ideal scenario for the recovery of kelp forests from urchin barrens

The most feasible solution to recover kelp forests from urchin barrens is a stepwise approach using efficient harvesting methods for subsequent commercial roe enhancement as well as other commercially or socially beneficial uses. Our proposed solution is based on strong cross-sectoral collaborations between key stakeholders, with gradual upscaling and expansion of restored kelp forest habitats. With the development of an economically sustainable urchin fishery, the approach moves kelp restoration from academia to industrial and municipal management which is a key requirement to upscale restoration efforts and ensure the long-term persistence of newly formed kelp forests through ongoing management actions.


The various approaches to recover kelp forests are managed under several laws found at Some methods suggested in this report are not under any laws and can be done by anyone, anytime and at any extent. Whereas other methods need to be generally approved (i.e. specific tools) and/or an application sent for each area treated (i.e. use of CaO). An overview of the legal framework practitioners need to follow in order to plan and implement restoration actions is presented.

Policy recommendations

Substantial financial resources and strong institutional support are needed to achieve kelp forest restoration at desired scales. Government needs to encourage restoration through cross-sectoral dialogue and financial incentives. Perhaps one of the best incentives that government can provide are tax incentives. Charitable donations to kelp restoration programs should provide additional tax benefits, creating an incentive to donate more to this cause. In the longer run, government should establish blue carbon and blue biodiversity credits, that can be used to further fund restoration.

Besides the need for policymakers to enable restoration actions, they must tackle the underlying causes that led to the disappearance of kelp forests in the first place. An adequate policy framework must be in place that encourages restoration while avoiding perverse policies that drive degradation. The implementation of marine protected areas (MPAs) or no-fishing zones and quota reductions for known urchin predators are effective management strategies to facilitate urchin predator recovery and maintain low urchin abundances to sustain restoration efforts.


Jan Verbeek, Inês Louro, Hartvig Christie, Pernilla M. Carlsson, Sanna Matsson, Paul E. Renaud (2021): Restoring Norway's underwater forests. Report by SeaForester, NIVA, Akvaplan-niva.

Last updated 10.06.2021