Selkämeri

Selkämeri National Park protects the internationally significant coastal archipelago of the northern Bothnian Sea along the western coast of Finland, spanning the provinces of Satakunta and Southwest Finland. Established in 2011, making it one of Finland's newest national parks, the park covers approximately 91,800 hectares of sea area, islands, and skerries—making it the country's largest national park by area. The park encompasses the diverse coastal zone from the Kokemäenjoki delta in the north to Airisto in the south, including over 2,500 islands and skerries. The name 'Selkämeri' means 'open sea' or 'Bothnian Sea' in Finnish, reflecting the park's maritime character.

The park's diverse coastal and archipelago habitats support a rich marine and coastal fauna. Grey seal has a significant breeding population in the outer archipelago, recovering strongly since the banning of seal hunting. White-tailed eagle nests on several larger forested islands. Eider duck, velvet scoter, goosander, and long-tailed duck nest throughout the skerries. The park's waters support Baltic herring, pike-perch, perch, and pikeperch. Harbour porpoise is occasionally observed in the outer waters. Migratory wading birds including ruffs, curlews, and sanderlings congregate on the coastal meadow islands during spring and autumn. The park is a key staging area for Baltic migratory bird movements.

The park's vegetation reflects the gradient from exposed outer skerries to sheltered inner archipelago. Outermost rocky skerries support sparse lichen communities and colonising vegetation. Sea buckthorn thickets are characteristic of gravelly shores on outer islands. Coastal meadows on grazed islands support rare plant communities including seaside centaury, Baltic rush, and shore plantain, maintained by traditional cattle grazing that Metsähallitus has reintroduced on several islands. Old coastal pine forest covers the larger islands. Submerged vegetation in sheltered bays includes eelgrass beds—critical nursery habitat for fish—and various pondweeds.

Selkämeri's geology reflects both the ancient Precambrian bedrock of the Fennoscandian Shield and the dynamic processes of post-glacial land uplift. The islands and skerries are composed primarily of Precambrian granites and gneisses, shaped by glacial erosion into rounded, ice-smoothed forms. Post-glacial isostatic rebound is lifting the land at approximately 6–8 mm per year in this area—one of the highest rates in Finland—gradually transforming submerged reefs into emergent skerries and creating new land. The Kokemäenjoki delta is actively prograding seaward, depositing river sediments across the shallow sea floor.

The park's maritime climate is moderated by the Bothnian Sea, which stores summer heat and moderates winter cold. The sea freezes along the inner archipelago in most winters but the outer waters remain ice-free or nearly so. Summer temperatures average 17–19°C, and the growing season is extended by the maritime influence. Winter storms from the southwest bring strong winds and high seas. The park experiences the full range of Baltic weather including summer fog, autumn storms, and the dramatic spring breakup of sea ice in the inner skerries.

The Selkämeri archipelago has been inhabited since prehistoric times, with Bronze Age burial cairns visible on several islands. The coastal communities of Satakunta and Southwest Finland were traditionally fishing and farming communities that exploited both the sea's resources and the archipelago islands for summer grazing. Swedish cultural influence is strong along the coast, and the area was part of the broader Swedish-Finnish maritime cultural sphere. Pilot stations, lighthouses, and fishing villages dot the archipelago. The town of Rauma, adjacent to the park, is a UNESCO World Heritage Site for its well-preserved wooden architecture.

Selkämeri became Finland's 38th national park in 2011 following years of planning and consultation with local communities, fishermen, and municipalities. The creation of a large marine national park on the Finnish west coast was driven by recognition of the biological significance of the Bothnian Sea and the need to protect coastal habitats from increasing recreational and development pressure. The park has promoted sustainable maritime tourism and fishing practices as part of its management approach. Cooperation with Swedish protected areas across the Bothnian Sea is part of the broader Baltic Sea conservation framework.

The park is best explored by boat—private vessels, kayaks, or seasonal tour boats from Rauma, Pori, and Uusikaupunki. Marked water trails connect main island groups. Several islands offer marked hiking trails through coastal habitats. Birdwatching from designated observation points is outstanding during spring and autumn migration. Grey seal watching tours operate from Rauma. The coastal meadow islands managed by restoration grazing provide picturesque and ecologically rich day trip destinations. Fishing and sailing within the park follow Metsähallitus regulations that protect sensitive breeding areas seasonally.

Access to the park is primarily by boat from the gateway towns of Rauma, Pori, Eurajoki, and Uusikaupunki. Seasonal passenger boats run to the most popular islands in summer. Metsähallitus maintains campfire sites, lean-to shelters, and landing stages on designated islands. The park's extensive sea area means private boat users make up the majority of visitors. Visitor centres are located in Rauma and Uusikaupunki. The park is open year-round; summer is the main visitor season, though winter sea ice provides unusual access to the inner archipelago in cold years.

Selkämeri's conservation priorities focus on maintaining water quality in the increasingly eutrophied Bothnian Sea, protecting grey seal and eider breeding colonies from disturbance, and restoring traditional coastal meadow habitats through reintroduction of grazing. Fisheries management within the park aims to maintain sustainable fish populations and prevent destructive gear use in sensitive habitats. Nutrient runoff from agricultural land along the Satakunta and Southwest Finland coasts is the primary driver of coastal eutrophication. Climate change is altering sea ice patterns and water temperatures, with implications for cold-water fish species and the timing of biological events.