National Eelgrass Restoration & Blue-Carbon Guidelines (Sweden)

Eutrophication and overfishing — including the loss of cod that once kept algae-grazing crabs in check — drove the collapse of Zostera marina (eelgrass) beds along Sweden's Skagerrak coast. Researchers estimate more than 60%, around 12,500 hectares, of west-coast eelgrass has disappeared since the 1980s, taking with it nursery habitat for fish and significant carbon and nutrient storage.

The University of Gothenburg's interdisciplinary Zorro research group, funded partly by a SEK 14 million grant from the Swedish research council Formas and working alongside the Swedish Agency for Marine and Water Management, developed and published a national restoration handbook (2016, updated 2021) standardising seed-based replanting methods. The team ran restoration trials including a roughly 5-hectare pilot at Kälnäs in Hakefjorden, Bohuslän, and an 8-hectare restoration of a former industrial harbour seabed in Malmö, where toxic bottom sediment was capped and water depth adjusted to allow eelgrass to re-establish.

A 2,000-year sediment record published in Global Biogeochemical Cycles (Dahl et al., 2024) documented substantial historical gains in carbon and nutrient burial following eelgrass colonisation, underpinning the ecological case for restoration; the team's cost analysis put restoration at SEK 1.2-2.5 million per hectare using recommended methods, a figure now used nationally to plan realistic programme budgets.

Restoration remains costly and slow relative to the scale of historical loss: at current per-hectare costs, restoring even a small fraction of the ~12,500 hectares lost would require sustained, large-scale public investment, and the largest completed site (Malmö's 8 ha) remains far below the scale needed to reverse regional decline.