Changing nature
The entire landscape of the World Heritage Site is shaped by the latest Ice Age and the land uplift. The nature in the High Coast and in the Kvarken Archipelago is quite the same, because both sides are on the same latitude by the brackish Baltic Sea. It is the altitude differences that can make a big difference for flora and fauna. The land uplift also lifts up new and ever-changing habitats from the sea.
Forests of the World Heritage area
In the High Coast, spruce forests grow on the tops of the till-capped hills and in some protected places where sediments have gathered. The till soil on the tops of the till-capped hills has stayed untouched since the Ice Age because the tops were never under water. On the other hand, the waves washed away the finer sediments from hillsides and lower hilltops, when they were at the sea level. Only small and slow-grown pine trees can grow on the hillsides, and the oldest pine trees can be over 500 years old. These pine forests have not been cut down as they do not have economic value. Finally, the finest soil material settled on the seafloor. Due to the land uplift, the old seafloor is nowadays the valley bottoms. The valleys have a richer spruce forest than the tops of the till-capped hills.
In the Kvarken Archipelago spruces are the last trees that start to grow on the new land rising from the sea. This is because vegetation zones follow the land that rises from the sea. First, coastal meadows grow closest to the shoreline. Then comes shrubbery or bushes, which are followed by alders, then birch and finally, spruce. These changes in vegetation are called succession, and the vegetation zones can be tens of metres wide on the flat beaches. In the steep High Coast, the succession mostly occurs in narrow belts and the spruces can grow almost on the shoreline.
Living on the edge
The shores of the World Heritage Site are beautiful but rough habitats for plants. In the Kvarken Archipelago, the stony shorelines are flat, whereas the shores of the High Coast often are steep and rocky. All the same, the shores are exposed to elements like storms, winter ice and erosion caused by these. The plants must endure both the elements and the brackish sea water. Especially seed-spread annual plant species have a hard time to root to the areas that are exposed to the elements.
Lush Lagoons of the land uplift coasts
All the lakes or lagoons of the World Heritage Site are created by the land uplift, but the lakes look different in Sweden and in Finland. The lagoons are formed when the rising land cuts the sea bays off from the sea.
In the High Coast, the lagoons are called isolated basins. They usually form large lakes that can be up to 50 metres deep. Isolated basins form quite slowly one at a time in the steep High Coast, so they are often located some distance from each other.
In the Kvarken Archipelago, the cut off bays are called flads, gloes or glo-lakes, depending on the development stage of the lagoon. These lagoons of the Kvarken can form chains, where moraine ridges separate each lagoon. In the first phase of the chain, the land uplift slowly lifts a moraine ridge above sea surface, and it slowly closes the mouth of the bay off from the sea. At this stage, the bay is called a flad. A flad still has a connection to the sea, but the water is slowly changing into fresh water.
A flad turns into a glo, when the connection to the sea is nearly closed. Sea water no longer enters the glo except when there is a strong wind, or the water level is high. When the connection to the sea is completely closed, the glo turns into a glo-lake or an inland lake. Since the Kvarken Archipelago is very shallow, the flads and gloes are also very shallow. The flat terrain allows the bays to be cut off from the sea in a matter of decades.
Sheltered habitats
The shallow isolated basins, flads and gloes offer a more sheltered environment for different species compared to the sea. In spring, The shallow waters quickly warms in spring and are important for spawning fish like pike and perch. The fish fry thrive in the lagoons, as there is plenty of zooplankton to eat and dense vegetation that provides hiding places from the predators. The fish-rich lagoons, in turn, provide food for birds, and many birds nest around the lagoons.
Sheltered locations in the High Coast have become very lush as nutrient-rich sediments washed away from the shores and ended up on the seafloor. Due to the land uplift, the previous seafloor has become sheltered valleys. These valleys can be extremely lush with nutrient-demanding plants such as fly-honey suckle, February daphne, alder buckthorn and blue anemone. Some places have layers of mussel and seashells in the soil. These shells contain a lot of lime which benefits more unusual flowers such as fairy slipper, ghost orchid and other orchids.
Underwater life in brackish conditions
The High Coast is part of the Bothnian Sea, while Kvarken Archipelago is situated in the shelf area between the Bothnian Sea and the Bothnian Bay. The whole Baltic Sea, including the Bothnian Sea and Bothnian Bay have brackish water, which is a mix between salt seawater and fresh water coming from rains and rivers. The salt content decreases in the northern parts of the Baltic Sea. The salinity of the oceans is over 3 percent, whereas in the World Heritage area the salinity is much lower, only 0,3-0,6 percent.
The Baltic Sea does not have lots of different species, because brackish water is challenging environment both for freshwater and saltwater species. The Baltic Sea is also a young sea, without enough time for species adapted to the brackish waters to evolve. What can be found in the World Heritage area and the Baltic Sea in general, are relic species trapped here since times when the Baltic Sea had more water exchange with the oceans and saltier water. Surprisingly, the waters of the Baltic sea was saltier and had more water exchange with the World’s oceans. Among this glacial relicts are a fourhorn sculpin, and marine crustaceans like Sadurias and Mysis, which also live in some of the isolated basins of the High Coast.
Next chapter: humans and land uplift
Living ina landscape that is continously rising has affected the people here – how?