Natural Features of Kvarken Archipelago Nature Reserve

A stony archipelago.

Nature in the Kvarken World Heritage Site adapts to constant changes. Land uplift is shaping this maritime archipelago at a world-record pace.

Taking care of nature


UNESCO World Heritage Site 

Due to its geological features, Kvarken was included in UNESCO's World Heritage List as Finland's first natural heritage site in 2006. Together with Sweden's High Coast, it forms the World Heritage Site entitled High Coast - Kvarken Archipelago.
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Landscape formed by the ice age

Rocks, rocks and more rocks. Rocks of all shapes and sizes characterise the Kvarken archipelago.

The Kvarken landscape as you see it today was formed by the latest ice age. The enormous ice sheet that moved over the area scratched the bedrock and swept away dislodged material. When the ice melted, a blend of rocks, gravel and mud was left behind and sometimes the material was deposited in long, low ridge formations. The soil in the Kvarken archipelago consists mostly of this so-called moraine, and rocks are scattered almost everywhere.  

The word moraine is also used to describe the formations consisting of moraine soil. De Geer moraines are a common type of moraine formation in the World Heritage Site area. They are long and narrow moraine ridges, a few metres high and in some cases several hundred metres long. Outside the old fishing port in Svedjehamn the de Geer moraines are particularly noticeable because they are surrounded by water. The terrain in Björköby village also consists of de Geer moraines and if you follow the main road through the village you can see how it is built around the ridge formations. The buildings are built along the ridges (moraines), with long narrow fields and meadows in between. 

An aerial view of an archipelago with long, narrow islands in the foreground with deciduous trees and dense grass vegetation by the beach. In the background a large wooded island.


In the southern part of the Kvarken archipelago, in the outer archipelago around Bergö, the landscape is very different. Out there, enormous rocks and boulders are scattered seemingly everywhere. Some of them are submerged in the water, which is a challenge for anyone attempting to navigate through the area. 


An aerial photo of the rocky archipelago on a windless summer day.


The land is upliftning – for now

In the Kvarken archipelago the land is uplifting eight millimetres every year! The seabed turns into land, the beaches turn into forests. 

During the latest ice age, the glacial ice sheet was at its thickest exactly where the World Heritage Site is located today. The enormous sheet of ice depressed the earth’s crust as much as 800 metres below its original level. When the ice melted, the crust slowly started to uplift. The rebound rate has slowed, but in the Kvarken archipelago the land is still uplifting at world record pace: about eight millimetres a year.  

The landscape in the Kvarken archipelago is flat and the sea is shallow, which makes the rebound more noticeable. The change is not obvious from one year to the next, but the locals are well aware, that a jetty might end up on dry land in just on generation. The World Heritage Site land area grows a hundred hectares every year due to postglacial land uplift. 

The natural environment changes constantly in the archipelago affected by postglacial uplift. When a submerged rock is exposed due to the rebound process, the first coastal plants spread to it quickly. The skerry grows bigger and soon the vegetation will include bushes and trees. The forests in postglacial uplift regions are virgin forests – they are the very first forests growing on (geologically speaking) new land. These types of forests are rare on a global scale and Finland has been given special responsibility to protect them. 

The land should uplift roughly another hundred metres; a process which is expected to take around 10,000 years to accomplish. However, it is possible that global warming and the attendant rising sea levels soon will cancel out the effects of the postglacial rebound. Maybe the next generation of locals in the Kvarken archipelago will have to move their jetties higher up on the beach instead of further out.  

Rocky seascape in early summer. A blossoming rowan on the right.

Sea bays in constant change  

Flads and gloes, the unique lagoons shaped by land uplift along the coast, are typical for the Kvarken Archipelago area. Constant change taking place in the coast joins shallow sea bays with the mainland, triggering the formation of flads and gloes. Flads in the Gulf of Bothnia have been formed in the shallow depressions between moraine ridges shaped by the Ice Age. Flads and gloes are unique to Finland and Sweden, and do not exist anywhere else in Europe.

A summery flad. A forest in the background.

One fascinating aspect of flads and gloes is their constant change. Everything starts from a shallow sea bay, which begins to rise from the sea as a result of land uplift. An almost closed-in sea bay, which still has a regular connection to the sea, is called a flad. When this regular connection little by little disappears, and sea water has only access to the flad when the water level is high enough, a glo has been formed. 
As land uplift continues, saline seawater cannot flow to the glo even on an occasional basis. At this stage, the glo turns into a freshwater lake. If the lake and its catchment area are large enough, they become a permanent water body. Shallow lakes quickly develop into marshland, if their bottom becomes overgrown. After turning into a marsh, the area develops into land, and species development in the area is finally stabilized.

Lagoons with a variety of species 

Flads and gloes offer a small and sheltered environment in comparison to the challenging conditions of the sea. In spring, water that warms more quickly than the sea tempts spring spawning fish to the area. Such species include the northern pike (Esox lucius), perch (Perca fluviatilis) and various cyprinids (Cyprinidae). In addition to warm water, the large quantities of zooplankton, as well as aquatic flora that offers protection against predators, create good conditions for young fish to grow. New generations of insects are born throughout the summer and grow protected by the flad. Large quantities of insects also benefit the species feeding on them, such as many birds and bats. In addition to food, the shallow sea bays provide birds with places to rest and build a nest.

Underwater jungle

Looking at the flad from the shore, it is hard to believe how enchanting its underwater landscape is. Sago pondweed or fennel pondweed (Stuckenia pectinata), claspingleaf pondweed (Potamogeton perfoliatus) and watermilfoils (Myriophyllum) sway towards the sun, forming thick, jungle-like growth. Every now and then, a lucky diver comes across a meadow of stonewort (Charales) glowing in green, which is a highly endangered biotope. Stoneworts bind nutrients from the water, making it clearer and helping sunlight reach the bottom. Vegetation thrives in clear water, as also water plants photosynthesise and require light to grow. In a sheltered environment, the coral stonewort (Chara tomentosa) may create miniature forests spreading as far as the eye can see. Coral stonewort is an indicator species providing valuable information on the state of the environment.

An underwater picture where Spiny water nymph can be seen growing on the seafloor.

Valuable habitats

Flads and gloes belong to habitats protected in the Natura 2000 project. Well-developed bottom vegetation, presence of spawning coastal fish and an unaffected catchment area are proof of the well-being of these water areas. The biggest threat to the shallow sea bays is caused by eutrophication, pollution, dredging, construction work on the shore, boating, and drainage in the catchment area.

A dive into brackish water 

Large, sharp-edged rocks and erratic boulders pierce the water’s surface, and require boaters to be very careful when navigating the Kvarken Archipelago. Glaciated rocks sanded by masses of ice represent a softer design. However, the view above the sea surface gives only a hint of the landform underwater. A diver enters a kingdom of rocks and hills. Shaped by the Ice Age, the undulating moraine ridges offer an excellent soil for different algae, aquatic mosses and rockweed (Fucaceae). Amidst the boulders scattered here and there, it feels as though you have arrived at an underwater labyrinth.  

A fibrous, light-green aquatic plant against the rocks, dabbed by sunlight.

Salty and fresh conditions

The shallow and narrow sea area of Kvarken is exceptional in many ways. In Kvarken, both saline and fresh water species live side by side, as it is located where the fresh water of Bothnian Bay meets the more saline water of the Bothian Sea. On the other hand, for many sea species, the water in Kvarken is not salty enough, while for many freshwater species, it is too salty. Due to its low saline levels, Kvarken is the northernmost habitat for various sea species.
Land uplift rapidly changes the Kvarken landscape. Each year, the sea moves further and further, as approximately 100 hectares of new ground appear. Species living in Kvarken have to be able to adjust to the changing conditions.

A kingdom of algae

Benefiting from eutrophication, filamentous algae have taken over areas from other species. From the ecosystem’s point of view, however, they are important survivors. Filamentous algae can live in conditions impossible for other species, thus protecting the invertebrates in the area. Slightly deeper, we are met by gold-coloured bladder wrack (Fucus vesiculosus) swaying in the water. Bladder wrack is one of the most important species in the Baltic Sea, as it provides food and shelter for a large number of plants and animals. Red algae (Rhodophyta) also form important habitats for other species, as they survive in very low light, and are therefore able to live deeper than other algae.  

Bladderwrack growing beneath the water surface.

Charophyte algae (Charophyta), a group of freshwater green algae, live in sea bays and other calm areas, and provide important information on water quality. Spotting vast fields of charophyte algae delights the friends of the Baltic Sea, as this type of algae is the first of its kind to disappear. The most common vascular plants include sago pondweed or fennel pondweed (Stuckenia pectinata), claspingleaf pondweed (Potamogeton perfoliatus) and different types of watermilfoil (Myriophyllum). Their communities are valuable spawning grounds and growing areas for fish. In addition, the plants filter water flowing from the coast to the sea and stabilize the seabed with their roots.

Chara tomentosa algae photographed underwater.

An irreplaceable home 

The shallow open waters and bays of the Kvarken Archipelago are crucially important for many fish. Approximately 40 to 50 fish species live in the area and Kvarken is the northernmost habitat for many species including the great sand eel (Hyperoplus lanceolatus) and broadnosed pipefish (Syngnathus typhle). The rarest species of fish in the area is the critically endangered grayling (Thymallus thymallus). This type of grayling spawns in brackish water and is native to the Gulf of Bothnia, which is its only habitat in the world. 
If you spot a glistening grey lump sticking up from the water or notice a stone with an unusually soft outline on a rock in the outer archipelago, you should pay close attention. Both the grey seal (Halichoreus grypus) and the less common Baltic ringed seal (Pusa hispida botnica) live in the Kvarken Archipelago. The grey seal is particularly fearless, and as a curious animal, it may well come and check out what is going on. One of Finland’s seven seal protection areas is located in the Kvarken area.

A spring spectacle created by spawning fish

In spring, as soon as the ice has melted, nature provides the stage for a fascinating play. Numerous fish, such as the northern pike (Esox lucius), perch (Perca fluviatilis), ide (Leuciscus idus) and other cyprinids (Cyprinidae) swim to the coastal waters of the Kvarken Archipelago to spawn. 
Perfect places for spawning can be found in estuaries, and flads and gloes, which have been playfully named fish nurseries. They are shallow and sheltered, and warm up faster in the spring sunshine than deeper water areas. In addition to the warm water, fish are lured to the area by the aquatic flora, which offers protection for the developing eggs and young fish. The spawning grounds should also have enough zooplankton, as it provides food for young fish. 

Close-up of a fish turning toward the photographer, with its large jaws and eye in the foreground. Bare bushes can be seen in the background above the water.

Swimming up to the spawning ground is a life-threatening journey, and only the strong and lucky ones survive. Nevertheless, in the spring, streams are filled with shiny scaled fish on their journey to spawn, as they have such a strong urge to procreate. Many birds, such as the white-tailed eagle (Haliaeetus albicilla), common crane (Grus grus), hooded crow (Corvus corone cornix) and gull (Larinae) stay close to shallow waters in the hope of catching easy prey. Streams and shallow waters separating the flads from the sea offer birds an easy meal, which is welcome after the scarcity of food in winter. 

Hustle and bustle in the spawning ground 

Fish are gallant on their spawning journey and take turns, as there is not enough space and food for all simultaneously. At first, the northern pike arrive, swimming in and out of the fallen reeds and looking for a suitable place to spawn. The northern pike are followed by perch, and at last, cyprinids find their way to the scene. In the case of most fish, the female of the species lay dozens of eggs, which is necessary, as only very few young survive the first stages of their life.  
After hatching, young pike or ‘jack’ stay in the shelter of the reeds, hiding and hunting for prey. Young perch, in turn, spread themselves boldly into the open waters of the spawning ground in search for zooplankton. During their first summer, the young perch already spread across the entire archipelago. The everyday life of young fish consists of alternately seeking for protection and food. There is a tough competition for zooplankton, as it may not suffice for all. Left without food, young fish starve to death in a few days. Many young fish also end up eaten by bigger fish. 
However, some of the young fish survive the trials of their first summer, and swim out to the sea in the hope of finding better food and a place to stay over winter. The circle closes when the fish reach maturity at the age of two to eight years, and set off on their own spring time spawning trip towards the temptingly warm coastal waters. 

Small fishes swim among aquatic plants.

Curious fish-lovers and shy creatures – mammals in the Kvarken archipelago

Wild mammals rarely show themselves, but they are out there. If you are out and about at dusk or dawn you might meet an elk (Alces alces) emerging from the mist or a fox (Vulpes vulpes) hunting voles in a meadow. 
In the Kvarken archipelago you might come across more than half of the approximately 60 species of mammals in Finland. Some of the large predators, such as wolf (Canis lupus), brown bear (Ursus arctos), lynx (Lynx lynx) and wolverine (Gulo gulo), are only temporary visitors. Badger (Meles meles), fox and otter (Lutra lutra) are predators that have settled in the area. 

The elk (Alces alces) is our largest mammal. The elk have developed an annual pattern similar to that of people living in coastal areas: it likes to spend the summer in the archipelago but returns to the mainland for the winter. The elk is a good swimmer and can easily move from one island to another. The same is true of the much smaller roe deer (Capreolus capreolus), which has become more common in recent years. 

The bats are one of our smallest mammals. We rarely see bats, despite the fact that they often live right among us. They are active at dusk and throughout the night. Bats use echo sounding both to locate prey and to move without bumping into objects in the dark. They produce a sound that bounce off objects, such as insects, in their vicinity. The sound is art-specific, but not audible to the human ear. A bat detector can convert the sound to an audible signal. Many bat species move between their reproductive grounds and their wintering areas just like migratory birds. 

Two species of seal live in the Kvarken archipelago. The grey seal (Halichoerus grypus) is the more common of the two, while the Baltic ringed seal (Pusa hispida) is still endangered. The grey seal is rather fearless and can often be seen resting on low rocks and cliffs in the outer archipelago. Seals like fish in general and Baltic herring (Clupea harengus membras) and three-spined stickleback (Gasterosteus aculeatus) in particular. The grey seal also enjoys whitefish (Coregonus lavaretus) and salmon (Salmo salar), and unfortunately for the fishermen in the area it does not hesitate to have a little snack when it finds these fish caught in fishing nets. Seals are clever animals and the quickly learn how to get hold of the delicacies. 

The World Heritage Site Kvarken archipelago has a dedicated seal reserve ( Seal hunting is prohibited, and visitor access is restricted within the reserve.  

Close-up of a seal. The seal is looking directly at the camera with its nostrils flared.

A paradise for birdwatchers all year round

Migratory birds every spring and autumn, nesting birds throughout the summer, a great white-tailed eagle slowly soaring high in the clear blue winter sky. Birdwatching is a thrilling experience any season!

Every spring hundreds of thousands of migratory birds pass through the Kvarken archipelago on their way north to the Arctic Ocean or to the Norwegian and Swedish fell regions. Migrating white-tailed eagles (Haliaeetus albicilla), rough-legged buzzards (Buteo lagopus), greylag geese (Anser anser), velvet scoters (Melanitta fusca), common scoters (Melanitta nigra) and loons (Gavia sp.) are strongly linked to spring in the Kvarken archipelago. As the ice melts and winter loses its grip, more and more of the archipelago’s own winged inhabitants return and the air is filled with the twitter of small birds, the trumpeting calls of cranes and the screeching of gulls.

In time, nature calms down when the birds retire to nest. The rocky waters and the many shallow bays in the Kvarken archipelago offer excellent nesting grounds for the archipelago birds. Razorbills (Alca torda) and black guillemots (Cepphus grylle) nest in holes between rocks, while tufted ducks (Aythya fuligula), common eiders (Somateria mollissima) and velvet scoters (Melanitta fusca)  build their nests in the grass and arctic terns and gulls prefer open rocky beaches and coastal meadows. Finland's largest predatory bird, the white-tailed eagle (Haliaeetus albicilla), builds its enormous nest in a tall spruce or pine, or even sometimes a birch. Active protective measures have brought the white-tailed eagle back from near extinction and it is now a common sight in the archipelago. Many small birds also nest in the forests along the postglacial rebound coast. Woodpeckers and other hole nesters thrive in the coastal forests with lots of deciduous trees and decaying trees. 

In the autumn, many migratory birds rest in sheltered areas in the Kvarken archipelago. Whooper swans (Gygnus gygnys) and mute swans (Gygnus olor) stay until the sea freezes over.

During the winter months, the Kvarken archipelago is quiet, but in the coastal forests you can hear the calls of various tits and goldcrests as well as the quiet drumming of great spotted woodpeckers (Dendrocopos major) looking for food. Old white-tailed eagles do not leave their nesting grounds in the winter. Mild winters even the younger white-tailed eagles stay in the Kvarken archipelago. 

Four black birds are sitting on a stone.

A flying White-tailed eagle.

Grazing sheep at work 

Many of the islets and skerries in the Kvarken archipelago were used for grazing and fodder harvesting in times past. Almost every household kept sheep and they were transported to the islands for the summer. That way the pastures in the village could be harvested for important winter fodder. 

The grazing sheep in forests and coastal meadows, haymaking in glades and on marshland as well as foliage gathering have all made their mark on the environment and the landscape. Gnarled old birch trees and an open pasture-like forest are signs that an area has been used for grazing. When walking in the forest you may come across the remains of an old fodder barn, where hay and bunches of leafy branches were stored until they could be transported home on the ice in winter. 

You can see sheep grazing on some islands still today. Grazing cattle is also kept at Bodvattnet on Björkö. The grazing helps keep the coastal meadows, heaths and pastures open. Many wild animals and plants thrive on the grazed land. Many of them also depend on this method of maintenance. The grazing animals are important nature and landscape conservationists. 

Close-up of two sheep.

The Kvarken archipelago is a national landscape 

National landscapes are particularly valuable landscape areas that have been selected as the most representative of certain nature and culture characteristics in Finland. The Kvarken archipelago is one of 27 such landscapes in Finland. The archipelago villages are living and prosperous communities, where the buildings and the environment are well maintained. On the islands in the outer archipelago the locals try to preserve the old fishing cabins. The forests surrounding the villages are managed through small-scale forestry. A modern lifestyle is mixed with elements from days gone by. 


An archipelago landscape with boats, buildings and sea.

Uninvited guests

Some animals and plants do not belong in the archipelago. These species have spread in nature due to human activity. Some of the species can cause great harm to the original fauna and flora. 

The small predators, mink (Neovison vison) and raccoon dog (Nyctereutes procyonoides)  are common in the Kvarken archipelago. Neither species is indigenous to Finland. Their populations originate from animals escaped from fur farms. The raccoon dog with its thick fur and the smaller mink both like to eat eggs laid by ground nesting birds. The mink thrives near and in the water, and the raccoon dog can also easily swim between islets and skerries. When a mink comes to an islet it will destroy and eat all the eggs it can find. These two species are at least partly to blame for the fact that many birds are failing to reproduce these days. Hunters do an important job keeping the mink and raccoon dog populations in check.

A raccoon dog in the reeds, with its gaze turned toward the photographer.

Certain plants are also harmful for the environment. The hardy rugosa rose (Rosa rugosa) with its abundant flowers is a popular plant in gardens as well as in city parks and green areas. The species has spread to the archipelago only in the past few decades. Despite the beautiful flowers and the edible hips, the plant must not be allowed to spread any further, or it will soon cover all our beaches in dense thickets of thorns. The rugosa rose must be kept in check if our beaches are to keep their original flora and fauna. 

A red flower, thick with wrinkly green leaves.

It is difficult enough to get to grips with non-indigenous species on land. The problem is compounded when the unwanted, non-indigenous species are in the sea. These invasive species reach the Baltic Sea mainly with foreign ships, in their ballast water or attached to the hull. The Baltic Sea is a very different habitat than the sea outside, because of the much lower salinity. That is why most new species find it difficult to survive here. 

The bay barnacle (Amphibalanus improvisus) arrived in our waters a long time ago and it is annoyance to boat owners who have to scrape the barnacles off their boats. The bay barnacle spends its entire adult life attached to its surface, but despite this it is actually a crustacean. The shell is the barnacle's house. In order to catch plankton to eat, the barnacle waves its legs through an opening in the shell.

Three species of polychaete of the family Merenzelleria have spread to the Kvarken archipelago this century. These polychaetes belong in northern regions, where they live in estuaries. They have adapted to life in brackish water with low salinity, such as the Baltic Sea. As these species are new to our waters, we do not yet know exactly how they will affect the ecosystems in the sea. There are examples of areas where they have displaced the original fauna. However, it is also a fact that polychaetes prefer oxygen-deficient soft sea-beds, which they help to aerate as they dig holes in the sediment. 
The has recently arrived in the Baltic Sea. The minuscule animals have barbed tails, which they attach to each other to create a sticky mess on fishing tackle. As the fishhook waterflea (Cercopagis pengoi) is new to our waters, we do not yet fully know how it will affect the ecosystem or how much it will spread.


The High Coast and the Kvarken Archipelago

The High Coast is a UNESCO world heritage site.

Municipalities: Kramfors and Örnsköldsvik in Sweden, and Korsholm, Korsnäs, Malax, Vaasa and Vörå in Finland.


  • The High Coast: 140,000 hectares, of which 60,000 ha are land areas
  • Kvarken Archipelago: 194,400 hectares, of which 29,300 ha are land areas

Nature protection at Kvarken Archipelago


Videos about High Coast and Kvarken Archipelago

World Heritage Site High Coast and Kvarken Archipelago (