Sejerø Bay
Restoring eelgrass meadows, mussel beds, and stone reefs in northwestern Zealand to boost biodiversity, rebuild fish populations, and support coastal communities.
Sejerø Bay, in northwestern Zealand, is a seascape shaped by ancient ice ages and once rich in eelgrass, mussel beds, and stone reefs. These habitats supported abundant fish populations, seabirds, and marine mammals, while providing coastal protection and livelihoods. Decades of overfishing, stone extraction, and nutrient pollution have degraded these ecosystems, leaving fragmented habitats and depleted stocks of species such as Atlantic cod and European eel.
The Sejerø Bay project aims to restore and reconnect the marine ecosystem, demonstrating how ecological recovery can strengthen biodiversity, build climate resilience, and involve communities in hands-on stewardship.
Sejerø Bay
WWF Denmark
Denmark
Ongoing since 2025
80,000 ha
Eelgrass meadows, Stone reefs, blue mussel beds
Atlantic cod, European eel, European plaice, common sole, European turbot, European flounder, Atlantic herring, European sprat and staging and molting seabirds such as common eider and common scoter
Why this place matters
Sejerø Bayis a seascape shaped by ancient ice ages. Once rich in boulder reefs, eelgrass meadows, and fish like Atlantic cod and European eel, its habitats have been severely degraded by overfishing, stone extraction, and nutrient pollution.
Sejerø Bay spans 80,000 hectares of coastal waters and features boulder reefs, soft-bottom habitats, and historically extensive eelgrass meadows. It is an important nursery for species such as plaice, sole, turbot, and herring, while supporting seabirds like eider and scoter. The bay also sits within a UNESCO Global Geopark and is partly protected as a Natura 2000 site.
Despite these values, ecological degradation has been severe. Between 1960 and 1980 alone, up to 14 million tonnes of stone and gravel were extracted, devastating reef habitats. Nitrogen pollution from agriculture and unsustainable fishing further reduced biodiversity, leaving much of the eelgrass, mussel beds, and cod populations diminished. Yet political momentum, community engagement, and new restoration techniques present a strong opportunity for recovery.
Action on the ground
This large-scale initiative is Denmark’s first marine restoration project of its kind, aiming to reconnect damaged habitats and build resilience to climate change. Planned actions include:
1–2 hectares of eelgrass meadows will be restored through transplantation across different depths.
Atlantic cod will be restocked to strengthen depleted fish populations.
4–6 hectares of blue mussel beds will be established to stabilise sediments and improve water quality.
Communities will be engaged through citizen science, eelgrass planting, and awareness campaigns.
2,000–6,000 cubic metres of stone reefs will be rebuilt to provide habitat for fish and invertebrates.
A long-term recovery plan will be developed to guide future restoration and scaling across Denmark.
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