Natural Features of Archipelago National Park

Photo: Mikhail Boyarskov
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

The archipelago in the Baltic Sea between Åland and mainland Finland is one of the largest archipelagos in the world. The National Park includes more than 2,000 islands and rocky islets shaped by waves and the ice sheet during the Ice Age. Inside the co-operation area of the park, there are about 8400 islands and islets altogether. The National Park mostly consists of outer archipelago, characterised by windswept pine forests (Pinus sylvestris) on the rocks, low deciduous forests and bare rocky islets which show parts of the 2,000-million-year-old bedrock. However, between the rocks there are hollows with lush vegetation of great diversity.

The windy outer archipelago. Photo: Teemu Köppä / The internet as a virtual destination

Due to the salinity in the brackish water (in the Archipelago about 5-6 per mil), the number of different species living under water is low, but because of abundance of populations of the species, the sea is filled with life.

Large areas of open sea, brackish water, bare outer islets and lush herb-rich forests create the habitat for diversity of plant and animal species. A special feature of the National Park are traditional agricultural landscapes, such as leaf fodder meadows, wooded pastures, dry meadows, coastal meadows and heaths, where the cattle of the inhabitants of the archipelago grazes. There are about 3 of traditional agricultural landscapes in the National Park. The goal of the National Park is to protect the ecosystems and the culture of the Archipelago and the traditional ways of utilising the nature, to preserve the communities of the archipelago, and to promote environmental research.

The Baltic Sea is teeming with life

Underwater Zones

The depth of the water affects the organisms living in it; the deeper you go, the less sunlight the plants receive for photosynthesis. The shore zone (littoral zone) is the part of the underwater shore where there is enough light for photosynthesis, and it has the highest number of species. The shore zone can be divided into three parts according to the fluctuation of the water level: the sublittoral zone is permanently covered with water, the hydrolittoral zone may be exposed when the water level is low, and the geolittoral zone is only covered with water when the water level is high.

Photo: Hedi Arponen.

Seabed vegetation and organisms vary according to the type of bed they inhabit. The species found on soft beds, such as the benthic amphipod (Monoporeia affinis) and the priapulid worm (Halicryptus spinulosus), live burrowed in the sediment. On bottoms with soft gyttja or courser sand and gravel, there are vascular plants, such as various species of water crowfoot (Ranunculus) and watermilfoil (Myriophyllum). Sand gaper (Mya arenaria) and flounder (Platichthys flesus) prefer sand bottoms, as they can burrow into it. On hard rock bottoms, several species, such as blue mussels (Mytilus edulis) and barnacles (Balanus improvisus) attach themselves to the bed and acquire nutrition by filtering water.

Mytilus edulis. Photo: Heidi Arponen.
The pelagic zone is the area of open sea where the foundation of the food chain is the phytoplankton that floats freely in the water. Phytoplankton is food for zooplankton, which in turn is food for many fish species and invertebrates. The plankton feeders are hunted by predatory fish, seals and birds. All dead matter in the open sea sinks into the lower region (profundal zone), where there is not enough light for photosynthesis. The organisms living at the bottom return nutrients into the cycle again. If the amount of oxygen at the bottom is insufficient, the organisms die and the organic matter turns into sediment.

Algae Zones

In water near rocky shores the different algae species create various zones. Blue-green algae are found near the water's surface and by the shoreline.  During a hot summer, when there are plenty of nutrients available, blue-green algae burst into algal bloom. One of the algae in the blue-green algae family, Calothrix scopulorum, forms a slippery film on rock surfaces directly by the shoreline.

Under the water's surface is a zone of filamentous algae that renews annually. These macroalgae include sea felt (Pilayella littoralis), found in the spring, and Cladophora glomerata, which is more common in the summer. Thick canopies of golden sea hair (Dictyosiphon foeniculaceus) and Stictyosiphon tortilis grow on the surface of rocks and bladderwrack (Fucus vesiculosus) in late summer. Sheltered by these filamentous algae are an abundance of gastropods and gammarid shrimps (Gammarus) as well as young Baltic isopods (Idotea).

Bladderwrack forms perennial canopies in nearshore waters. It is a keystone species, which means its existence is crucial to the entire Archipelago's ecosystem. It also provides shelter for Baltic prawns and Baltic isopods. Many fish species, such as the nine-spined stickleback (Pungitius pungitius) and the three-spined stickleback (Gasterosteus aculeatus) live among bladderwrack. The abundance of food there attracts predatory fish, such as perches (Perca fluviatilis) and pikes (Esox lucius). On the surface of the bladderwrack live many species of periphyton and other organisms, such as sea mats (Electra crustulenta).
Fucus vesiculosus. Photo: Heidi Arponen.
The red algae zone begins where the bladderwrack zone ends and it may extend to a depth of more than ten metres. The most profuse red algae include Ceranium tenuicorne and forkweed (Furcellaria lumbricalis). Deeper in the water you will find scab-like red algae species, such as Hildenbrandia rubra. Among the red algae, there are other algae too, especially brown algae (Phaeophyta). There are plenty of blue mussels in the red algae zone in places.

The White-tailed Eagle in the Finnish Archipelago 


The white-tailed eagle's distribution area extends from the shore of the Pacific Ocean across Siberia right up to Iceland and Greenland. In Finland, the white-tailed eagle mainly nests in the coastal areas and the archipelago, but it is only a matter of time before it starts to settle further inland. Some nests have already been found near the large lakes and reservoirs in Northern Finland.

Old white-tailed eagles are very loyal to their location; those living in the Finnish Archipelago and the Åland Islands are especially stationary and rarely relocate, unless the freezing of the waters significantly reduces the supply of food. Young birds are more eager than the old ones to move to new locations, and those from Lapland and the Kvarken move closer to the Baltic Sea, to the open waters.


The white-tailed eagle is the largest breeding bird in Finland and the whole of Northern Europe: its wingspan can be as much as 2.5 metres and it can weigh 7 kg. The female is usually larger than the male. The wings are broad, rectangular "barn doors". The silhouette of a flying white-tailed eagle has been compared to a rag rug due to the strongly splayed wing feathers. The tail is short and slightly wedge-shaped. A young bird's dark brown plumage is flecked with lighter feathers on the wings, belly and upper parts of the flanks. The head is dark, as is the tip of the sturdy beak. It takes about five years for the adult plumage to be completed. An old white-tailed eagle has a white tail and a yellow beak, with a more even-coloured plumage. The bird's head and upper body become lighter in colour over time.

Haliaeetus albicilla. Photo: Seppo Keränen


The white-tailed eagle feeds its young with fish, gradually adding gull chicks and ducklings to the diet, occasionally also small mammals, such as muskrats and American minks. An adult white-tailed eagle is happy to feed on dead fish, offal from fish cleaning, carrion and larger water birds – even great cormorants. The white-tailed eagle has good eyesight: it keeps watch from high up on a tree top or quickly flies over the forest edge to the shore, taking its prey by surprise. In wintertime, white-tailed eagles may fly dozens of kilometres from one feeding place to another in no time at all.

Nest and the Young

The white-tailed eagle usually builds its nest in a tree top. It can use the same nest for several years, so the nest gradually turns into a huge edifice of sticks that can weigh as much as a small car – almost a thousand kilogrammes. There are not so many sturdy nest trees available, so artificial nests have been built for white-tailed eagles with the aim of helping the species settle down in undisturbed areas.

The white-tailed eagle usually lays 1–2 eggs, incubated by the female for about five weeks. The egg-laying season lasts from mid-March to early April. The young stay in the nest for some ten weeks before they fledge, staying in the nest under their mother's care for the rest of the summer. In 2009 there were a record number of 349 nestlings in Finland. The oldest ringed white-tailed eagle in Finland lived for 26 years, and the oldest in Europe was a Swedish bird at 28 years and 2 months.


There was a bounty on white-tailed eagles at the turn of the 20th century, which effectively reduced the population. From the 1950s onwards the threat has occurred in the form of environmental toxins, especially DDT, PCB, dioxin and methylmercury. DDT was a potent pesticide and insecticide used in agriculture and gardening. The toxic substances passed through the food chain, ending with the white-tailed eagles at the top, and taking the birds to the brink of extinction. The toxin made the eggshells so thin they did not withstand incubation. Measurements from dead white-tailed eagles' tissue showed such percentages of toxin that the birds were called "flying toxic waste". Today, the use of DDT and PCB is forbidden on the Baltic Sea. Thanks to winter feeding, the white-tailed eagle population is now stronger than it has been for several decades.

Photo: Teemu Köppä / Internet virtuaaliseksi retkikohteeksi

Even in this millennium, hatred for predators is expressed through killing white-tailed eagles and not letting them nest in peace. The white-tailed eagle is a protected species and killing it is a punishable act, with a possible fine of 7,400 euro. Another threat to the white-tailed eagle is the changing use of land: summer cottage construction in the archipelago, increased boating and other recreational activities, and clear-cuttings all reduce the number of peaceful nest sites and suitable nest trees.

Experience the richness of archipelago nature


Photo: Teemu KöppäThe exceptional diversity of the vegetation at the Archipelago Sea arises from the small features of the landscape, and the variety of rock basement. Although the park for most part consists of bare and rocky outer islands, calciferous soils nourished by shell remains and deposits of limestone can support luxuriant groves between the rocks. For example, ash (Fraxinus excelsior) often grows in the hollows.

Around dry pasture meadows grow the Bloody Cranesbill (Geranium sanguineum) and the Swallowwort (Vincetoxcium hirundinaria). On leaf fodder meadows bloom the Elder-flowered Orchid (Dactylorhiza sambucina) and the Nettle-leaved Bellflower (Campanula trachelium), and on the edge of the forest grow the Common Buckthorn (Rhamnus catharticus), and the Crab Apple (Malus sylvestris).


In the Archipelago area live 25 species of mammals, the most common ones being small rodents. Also large animals, such as mooses (Alces alces), can be seen. Most part of the declining population of the Baltic Ringed Seal (Phoca hispida botnica) in the archipelago lives inside the National Park. The Grey Seal (Halichoerus grypus ) is becoming more common, and it may turn up to watch boaters almost anywhere in the National Park.

Photo: Jevgeni Usov

The Grey Seal. Photo: Markku Lappalainen

There are 132 breeding bird species in the Archipelago. Gulls (Larus), arctic terns (Sterna paradisaea), eiders (Somateria molissima), razorbills (Alca torda) and black guillemots (Gepphus grylle) nest on small bird islets. The mute swan (Cygnus olor), greylag goose (Anser anser) and shelduck (Tadorna tadorna) build their nests in the peaceful archipelago, while the arctic skua (Stercorarius parasiticus) looks out on the high rocks.

The nutcracker (Nucifraga caryocatactes) and barred warbler (Sylvia nisoria) live in the shelter of leafy trees. These days it is also possible to see the white-tailed eagle (Halliaeetus albicilla) gliding up in the sky. It has been saved from exctinction by active conservation measures. Threatened species in the area include the caspian tern (Sterna caspia) and a subspecies of the Dunlin (Calidris alpina schinzii).

Life under the surface

Watch the video (in Finnish).

Traditional Agricultural Landscapes of the Archipelago 

Traditional agricultural landscapes are an important part of the archipelago

In addition to the open sea and the rocky shores, there are coastal meadows, dry meadows and wooded pastures, which are an important part of the landscape in the archipelago. However, the traditional agricultural landscapes will disappear, if they are not managed. In the old days, the meadows, pastures and heaths in the Southwestern Archipelago were shaped by farmers and grazing animals. Nowadays, when cattle keeping has become less common in the archipelago, overgrowing threatens the traditional agricultural landscapes: they are becoming covered with bushes or forest.

Photo: Laura Lehtonen

Different kinds of traditional agricultural landscapes

Traditional agricultural landscapes are meadows and pastures, which are managed in the traditional way. They are also called traditional (semi-natural) biotopes. A wooded meadow is a mosaic of meadow patches, and groups of trees and bushes. A mesic meadow is an open, lush meadow patch. A coastal meadow is located on the shoreline, and its vegetation is low. A dry meadow usually has a rich set of grass species. On a wooded pasture grows a thin forest. On a forest pasture, the forest is denser than on a wooded pasture. A heath is treeless, and covered with twigs. It has been created by human activity.

Abundance of species on the meadows

Many species living on the meadows of the archipelago need an open habitat. Plants of the coastal meadows include the Dune Gentian (Gentianella uliginosa), the Northern Grass of Parnassus (Parnassia palustris), the Strawberry Clover (Trifolium fragiferum), the Narrow-leaved Yellow Rattle (Rhinanthus serotinus) and the Saltmarsh Flat-sedge (Blysmus rufus). Nesting birds of the coastal meadows include the Barnacle Goose (Branta leucopsis), the Greylag Goose (Anser anser), the Northern Shoveller (Anas clypeata), the Common Redshank (Tringa totanus) and a subspecies of the Dunlin (Calidris alpina schinzii).

The glory of the flowers on the dry meadows is impressive, and so are the butterflies and the other insects there. The Middle Lace Border (Scopula decorata) is a rare moth which lives on the dry meadows. Many butterflies and moths depend on certain plants of the dry meadows. For example, the larvae of the Apollo (Parnassius apollo) feeds on the Orpine (Sedum telephium), and the larvae of the Large grizzled skipper (Pyrgus alveus) on the Cinquefoils (Potentilla) and the Agrimony (Agrimonia eupatoria).

Traditional working practices

In the Southwestern Archipelago, patches were temporarily cleared for cultivation futher from the villages, too, when needed. At first, trees and bushes were cut down, then the ground was hoed, and finally the surface soil was burnt. This kind of fields were still made by farmers and crofters in the archipelago until the beginning of the 1900s.

In the pasturing era, meadows became overgrown just as well as nowadays. Junipers, heathers, roses, sprout forest and sapling stand grew on wooded pastures, heaths and wooded meadows. Usually in the spring, the islanders made joint efforts to clear the pastureland. Sometimes, the overgrown meadows and pastures were burned over. Clearing, burning over, and pasturing kept the meadows open.

Hundreds of cloven hoofs maintain the traditional agricultural landscape

Traditionally, the meadows in the archipelago have not been used only for haymaking. After the hay was cut, cattle grazed on the meadows. Heaths, dry meadows, wooded pastures and forest pastures were not suitable for haymaking at all, so they were only used as grazing land. The primary use of the traditional agricultural landscapes has been pasturing. Nowadays, cooperation between the authorities and the farmers is needed, so that the traditional agricultural landscapes can be maintained. Since the end of 1900s, a couple of hundred sheep and more than 70 head of cattle have pastured on the islands of Archipelago National Park. Human activities cannot substitute for the work done by animals in restoring traditional agricultural landscapes.

Read more about traditional agricultural landscapes of the archipelago in the book "Island pastures" by Leif Lindgren. The book can be ordered from the postal order service of Metsähallitus.

Photo: Matti Peltonen

Traditional agricultural landscapes restored by volunteers

Nowadays, the traditional agricultural landscapes are often restored and managed by volunteers. The aim is to restore the habitat back to its original state, and to manage it yearly so that the outcome is as much as possible like the former meadow or pasture. The traditional working practices are being revived, where it is possible.

In an overgrown traditional agricultural landscape, restoration begins with clearing the deciduous bushes and junipers. Rare and valuable bushes, and tree-like or column-shape junipers are saved. The next step is to space out the forest. In future, spring clearing, mowing and pasturing are needed every year on a restored meadow or pasture.

Volunteers, who take part in restoration camps, have done spring clearing on wooded meadows, for example. In the spring, leaves are raked and sticks are collected, because otherwise the leaves suffocate the meadow plants, and the sticks make mowing difficult. In the summer, mowing is carried out according to the local traditions, using scythes and a small mowing machine.

Photo: Laura Lehtonen

Archipelago National Park

  • Established 1983
  • Area 500 km²

The Emblem of Archipelago National Park - White-tailed Eagle

The Emblem of Archipelago National Park is White-tailed Eagle

Part of the Archipelago Sea and Archipelago Biosphere Reserve

The Southwestern Archipelago National Park is part of the Archipelago Sea and Archipelago Biosphere Reserve (www.skargardshavetsbiosfaromrade. fi). 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.

Publications of Archipelago National Park (


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