Norway Restores Kelp Forests After Decades of Sea Urchin Devastation

Beneath the surface of Porsangerfjord in northern Norway, something profound is unfolding. Where barren rock once stretched across 70 hectares of seafloor, kelp forests now sway in the current, their golden-brown fronds creating cathedral-like canopies where life congregates. This transformation required removing approximately 21 million sea urchins in one of the world’s largest marine restoration projects.

Overfishing of predatory coastal fish during the 1970s coincided with the largest sea urchin bloom observed in the Northeast Atlantic, resulting in the destruction of more than 2,000 square kilometers of kelp forest along Norwegian and Russian coasts. Without natural predators to keep populations in check, green sea urchins multiplied unchecked, reducing thriving ecosystems to underwater deserts that have persisted for nearly five decades.

What disappeared with the kelp was more than scenery. Kelp forests function as spawning, nursery, and feeding areas for many fish species while supporting biodiversity so rich these ecosystems are sometimes called rainforests of the sea. Coastal cod, the fish that built Norway’s economy and culinary traditions, depend on kelp forests during critical life stages.

For centuries, Norwegian coastal communities have transformed cod into stockfish, the air-dried product that Vikings carried on expeditions and that funded the construction of Bergen’s medieval trading empire and Trondheim’s Nidaros Cathedral. Stockfish provided protein for generations in a region with limited salt deposits, where drying rather than salting became the preservation method of choice. This ancient product, in turn, becomes lutefisk when soaked in lye, a dish that has anchored Norwegian Christmas tables for at least 500 years. The fish stocks supporting these traditions require healthy kelp forests to complete their life cycles.

Sámi communities along the coast understood these interconnections through generations of observation. Traditionally, coastal Sámi pursued diverse livelihoods including fishing, hunting marine mammals, and seasonal movement between islands and fjords. Their traditional ecological knowledge recognized the relationships between habitat, fish populations, and sustainable harvest long before modern marine science formalized these concepts.

The restoration work in Porsangerfjord demonstrates what becomes possible when intervention targets the root cause. In 2013, researchers used 200 tons of quicklime to reduce sea urchin populations, and kelp recovered within a year at treated sites. The treatment proved remarkably selective; non-target species remained largely unaffected. Within months, divers documented lumpfish laying eggs among the new kelp stands, cod and pollock schools returning, and the gradual recolonization of invertebrates and crustaceans.

Interestingly, an invasive species has aided the recovery. Red king crabs, introduced to Russian waters decades ago and now expanding westward, prey heavily on sea urchins. The king crab contributed to kelp recovery even in untreated areas by keeping new generations of sea urchins at low levels, though native predators would be preferable for long-term ecosystem balance.

This resilience carries implications for marine restoration globally, but also demands humility. The recovery depends on maintaining predator populations, which means rethinking harvest pressures on species we’ve historically viewed as commodities rather than ecological keystones (cod, wolffish, haddock). It means recognizing that traditional foodways and marine ecosystem health are not competing interests but intimately linked expressions of coastal abundance. It’s the possibility of repair, the capacity of damaged systems to remember themselves back into being when we give them room to do so.

Written by: Junior Thanong Aiamkhophueng.

Attribution: This article draws from peer-reviewed research published in Marine Biology documenting the large-scale kelp forest restoration experiment in Porsangerfjord, northern Norway, where 200 tons of quicklime successfully removed sea urchin populations across 70 hectares. Historical context on the 1970s sea urchin bloom and overfishing of predatory coastal fish sourced from PMC research analyzing the depletion of cod, wolffish, and haddock populations along Norwegian coasts. Kelp forest ecosystem services and ecological functions documented through Norway’s integrated ocean management white paper and Frontiers in Marine Science research on Laminaria hyperborea populations. Stockfish cultural traditions and lutefisk preparation informed by Visit Norway culinary heritage documentation and Norwegian intangible cultural heritage records on dried cod traditions. Sámi coastal livelihoods and traditional ecological knowledge sourced from University of Texas research on Coastal Sámi history and Visit Norway Indigenous culture documentation. Restoration monitoring and red king crab impacts documented by NIVA (Norwegian Institute for Water Research). Photography courtesy of Oleksandr Sushko via Unsplash and Manxruler via Wikimedia Commons (public domain).