Natural Features of Archipelago National Park

A stony shore in the sunset. The sky is partly cloudy and waves can be seen in the background. The sun casting its last rays before setting on the horizon.

The open seas, nostalgic traditional landscapes, underwater depths and lush herb-rich woodlands of this ecosystem swept by the sea winds provide habitat for numerous animal and plant species.
Taking care of nature

Explore the over 2,000 islands

Have you already found your favourite island in the Archipelago Sea? The National Park includes more than 2,000 islands and rocky islets shaped by waves and the ice sheet during the Ice Age.

A Stony peninsula in a summery landscape. The sea is rough.

Jurmo is a unique, flat island formed by a gravel ridge, which is part of the Salpausselkä ridge system. Majority of the vegetation on the island consists of rugged juniper heaths, grazed by the island’s own alpacas. The rough sea continuously shapes Jurmo's gently sloping gravel shores. The island is an excellent destination for observing migratory birds, and there is a bird station in active use in the village.

Utö (, in Finnish) lighthouse island is the final benchmark located at the edge of the main basin of Baltic Sea, just before the vast open sea. In spring, the first migratory birds arriving from the south stop and have a rest on Utö, after flying over the sea.

Located in the middle of Kihti Sea between Ahvenanmaa and mainland Finland, Jungfruskär is the paradise island of the national park. The island is well-known for its orchids and well-maintained traditional landscapes. There is no permanent ferry connection to Jungfruskär, but you can tie your own boat to the visitors’ dock on the island.

Örö Fortress Island was opened for visitors in 2015, when the army ceased its military operations on the island lasting for a hundred years. Limited access to the island has protected its nature from too much wear and tear, while on the other hand, the military operations have stopped the island from becoming overgrown. There are various rare biotypes on the island, such as shiny heaths covered in fragrant wild thyme (Thymus serpyllum), and almost untouched sandy beaches.

In addition to its most well-known islands, there are various other small and large gems hidden in the Archipelago Sea National Park, many of which can only be accessed by a boat or a canoe.

The Baltic Sea is teeming with life

The Baltic Sea is often considered monotonous and lacking in species diversity. In reality, it is both colourful and diverse. An amazing world lies beneath the surface of the water. It is filled with trenches and canyons, crater-like holes, sandbars and rock cliffs.

The Baltic Sea has brackish water, i.e. its salinity is lower than that found in oceans, but greater than that found in inland waters. Even though the Baltic Sea does not contain as many different species as larger seas, the species that do call it home thrive in large numbers. Baltic species are very distinctive. Some are from the sea, while others come from inland waters. Only a few species have specifically adapted to brackish water.

The underwater nature of the Archipelago Sea National Park is built around the countless islands and skerries dotting the sea, ranging from shallow coves to trenches a hundred metres deep. The archipelago has endless shoreline and provides protection for all types of marine organisms. The amount of available light is also a key factor for species success.

Habitat chosen based on the softness of the seabed

Soft seabeds are home to such species as Monoporeia affinis and Halicryptus spinulosus, which burrow their way into the sedimentary deposits.

Vascular plants, such as the water crow-foot (Ranunculus) and watermilfoil (Myriophyllum), grow in soft mud bottoms and coarser sand and gravel bottoms.

Sandy bottoms are the habitat of choice for soft-shell clams (Mya arenaria) and flounder (Platichthys flesus), which prefer to burrow into soft bottoms.

Several species, such as the blue mussel (Mytilus edulis) and bay barnacle (Balanus improvisus), attach themselves to a substrate and feed by filtering water.

Key species play a crucial role

Bladder wrack

Bladder wrack (Fucus vesiculosus) provide a protective environment for many species. The amphipod Gammarus tigrinis, isopod Idotea balthica and several fish species, such as the ten-spined stickleback and three-spined stickleback, thrive among bladder wrack. The abundance of food attracts predatory fish, such as perch and pike. Einhornia crustulenta live on the surface of bladder wrack.

Coral looking seaweed on the seafloor. The sun's rays are sifted through the water.

Blue mussel

Many invertebrates live on and inside the shells of mussels. Blue mussels are an important source of food for many waterfowl and fish species. Blue mussels filter plankton, along with nutrients, particles and environmental toxins, from the water.

Baltic clam

Baltic clams, which burrow into muddy bottoms, increase oxygen transfer in the seabed. This improves water quality and seabed conditions. Baltic clams are the food of choice for flounder.


The challenges currently facing the Baltic Sea include eutrophication and environmental toxins. In addition to these, climate change and littering are causing damage to the sea.

White-tailed eagle - A conservation success story

Just a half hour's boat ride out to the open sea and there they are. The impressive size and steady glide reveal that the pair circling above a nearby island are White-tailed eagles. For the past decade, the White-tailed eagle has charmed visitors to the Archipelago Sea.

Close-up of a white-tailed eagle. The eagle has its beak open.

Fifty years ago, it was an entirely different situation. At that time, the future of the White-tailed eagle looked bleak. It was sheer luck if you were able to spot one circling calmly in the sky. During the darkest years of the Archipelago Sea, only a couple eaglets made it past the fledgling stage. In the 1970s, the White-tailed eagle was plagued by environmental toxins in the food chain that had worked their way up to this apex predator. In addition to this, bounties were paid to hunt the White-tailed eagle at the turn of the last century, thus decimating the population even before environmental toxins were a factor. The combination of these two factors resulted in a fatal decline in the White-tailed eagle population.

Environmental toxins DDT, PCB, dioxin and methylmercury had reached the White-tailed eagle, an apex predator, bringing them to the brink of extinction. The toxins caused the shells of their eggs to be so thin that they could not withstand incubation.

In an effort to save the White-tailed eagle, conservation groups launched comprehensive rescue initiatives under the direction of the WWF in the 1970s. A feeding programme, in which untainted food was given to the eagles, was begun in the 1960s by more active conservation groups. DDT and PCB were banned in the 1990s. The nesting trees used by White-tailed eagle were protected and nature conservation areas were established to provide them with a safe nesting area.

A man sitting in a tree leaning against a pine branch ringing white-tailed eagle chicks. There are two chicks in the nest.

These decades-long active efforts bore fruit. Things started out slowly, but the White-tailed eagle population eventually began to show significant growth. The Archipelago Sea National Park has participated in the White-tailed eagle rescue efforts since its founding. Actually, these efforts began even before the park was founded, as many islands were included in the park expressly for the conservation of the White-tailed eagle. Dense pine forests are already the most common type of forest found in the forty-year-old Archipelago Sea National Park. Metsähallitus assisted with monitoring, feeding and ringing and park personnel actively participated in rescue efforts.

Experience the richness of archipelago nature

The Archipelago Sea landscape is exceptionally diverse. Breaking waves and strong winds keep woody plants in check and provide plenty of room for flowering coastal plants to grow. Lush groves of European ash (Fraxinus excelsior) and meadows with a variety of species grow in rock hollows, clam beds and lime deposits. The rocky ponds and small mire ponds swarm with aquatic life. In the outer reaches of the archipelago, barren skerries rise up out of the sea, offering birds and seals a sunny spot to rest.

If you are interested in plants, the well-maintained islands used for grazing are well worth a visit.  There you can find the bloody cranesbill (Geranium sanguineum) and white swallow-wort (Vincetoxicum hirundinaria). In spring, wooded meadows are filled with blooming elder-flowered orchids (Dactylorhiza sambucina) and cowslip (Primula veris) You might also find the common buckthorn (Rhamnus cathartica) and forest apple trees (Malus sylvestris) in the thick pastures and forests.

There are 25 mammal species living in the Archipelago Sea National Park, most of which are small rodents. You can, however, come across larger animals, such as moose (Alces alces). The rare Baltic ringed seal (Pusa hispida botnica) primarily live in the waters of the Archipelago Sea National Park. The grey seal (Halichoerus grypus), on the other hand, is very common and might even come over to see what boaters are up to.

A grey seal peeking up above the water. Waves hitting a rock in the background.

A birdwatcher will not be disappointed in the archipelago, as 132 species of birds can be spotted in the area. Gulls (Laridae), arctic tern (Sterna paradisaea), common eider (Somateria mollissima), razorbill (Alca torda) and black guillemot (Cepphus grylle) nest on small bird skerries. Mute swan (Cygnus olor), greylag goose (Anser anser) and the common shelduck (Tadorna tadorna) nest within the shelter of the archipelago, while the parasitic jaeger (Stercorarius parasiticus) aim for high rocks. The spotted nutcracker (Nucifraga caryocatactes) and barred warbler (Sylvia nisoria) inhabit the sheltered valleys of treed islands. Even the endangered caspian tern (Hydroprogne caspia) and dunlin (Calidris alpina ssp. schintzii) live in the Archipelago Sea National Park.

A flock of birds flies close to the water. A rocky island in the background.

Life under the surface

Watch the video (in Finnish).

Traditional Agricultural Landscapes of the Archipelago 

You can travel back in time in the Archipelago Sea National Park. The park’s special features include heritage landscapes: wooded meadows, pastures, coastal meadows and heaths, where island cattle has grazed for centuries.

Wooded meadows are a patchwork of open meadows dotted with clusters of bushes and trees.
Dry and wet meadows are treeless meadows with an abundance of flowering plants.
As its name indicates, coastal meadows are low-growing meadows situated along the shoreline.
Dry meadows are often referred to as fields.
Pastures are grazing land with a minimal number of trees.
Forest pastures have more trees than ordinary pastures.
A heath is a cultivated, treeless shrubland maintained by burn-clearing and grazing.

Highland cattle with horns on a barren and stony pasture.

Their preservation requires management and care. The meadows, dry meadows and heaths of the archipelago are managed by animals grazing on them. As traditional animal husbandry in the archipelago declined, the traditional landscapes were threatened by the overgrowth of shrubs and trees.

A hundred years ago, the wooded meadows were maintained and traditional landscapes cleared as part of the agriculture that made life possible in the archipelago. Today, the management of traditional landscapes in the national park is carried out by various operators in cooperation. In wooded meadows, park masters and conservation biologists work hand in hand with livestock owners, educational institutions, volunteers and contractors. The biggest task, however, is still completed by animals. Today, the park has hundreds of hectares of traditional landscapes.

Volunteer work in a traditional landscape

Today, various voluntary organisations take part in managing the traditional archipelago landscapes. Together, the WWF, Southwest section of Finnish Association for Nature Conservation (Varsinais-Suomen luonnonsuojelupiiri), Arkipelagia association and Metsähallitus organise volunteer camps, where people can take part in clearing and mowing wooded meadows and burn-beating heaths.

Cows lying in the shade of a tree in a summery agricultural landscape. Hikers walking on a sand road next to the field.

Jungfruskär is one of the most valuable destinations with traditional landscapes in Finland, and an excellent example of the diverse cooperation taking place in the national park. The management and care of nature on the island started over 30 years ago, soon after the establishment of the Archipelago Sea National Park.

This care has continued and expanded until today, and the results can be seen both in the landscape and the species. Nowadays, the island is a hub or diversity and an important haven for many species that have become rare elsewhere in the archipelago and on mainland Finland. The carefully maintained and exceptionally nutrient-rich wooded meadows, dry meadows and coastal meadows are home to dozens of endangered plant species and insects living on them.

First of May celebrations on Jungfruskär include “raking a forest”, that is, raking leaves from the wooded meadows and collecting dead branches. This removes the leaves that smother meadow plants and clears branches and twigs to make way for mowing. Summer is the time for mowing followed by raking. After the mowing, cattle is in charge of the aftercare. Just about anyone who wants to join the centuries-long tradition of archipelago meadow management is invited to volunteer.

More information on volunteer camps in the national park can be found on the page 'Vapaaehtoiseksi Saaristomeren kansallispuistoon' (in Finnish).

Cows on summer pasture next to the shore. The shore is rocky and the sea is rough.

Archipelago National Park

  • Established 1983
  • Area 527 km²

The drawn emblem of Archipelago national park. A common a white-tailed eagle with a lighthouse and a sea landscape in the background is depicted inside the oval symbol. The text Saaristomeri kansallispuisto - national park wraps around the outer edge of the emblem.

The Emblem of Archipelago National Park is White-tailed Eagle.

Baltic Sea

  • Average depth: 54 m
  • Deepest point: 300 m on the west side of Åland
  • Salinity: 2.7-6 ‰

Archipelago Sea

  • Average depth: 25 m
  • Deepest point: 245 m
  • Salinity: 5.7 ‰
  • Number of algae species: 261

Part of the Archipelago Sea and Archipelago Biosphere Reserve

The Southwestern Archipelago National Park is part of the Archipelago Sea and Archipelago Biosphere Reserve ( The goal of UNESCO's Man and the Biosphere (MAB) programme is to develop the living conditions of the area's inhabitants while maintaining the protection of nature and the environment.