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 because there is still nutritious soil type called till to grow on. The 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 nutritious soil from hillsides and lower hilltops, which are 200-280 metres high. 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 harvested as they do not have economic value. Finally, the finest soil material washed up on the seafloor. Due to the land uplift, the old seafloor is nowadays nutritious valleys between the till-capped hills. The valleys have richer spruce forest than the tops of the till-capped hills.
Unlike on the High Coast, spruces are the last trees in the Kvarken Archipelago 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 are mostly 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 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 far apart 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 lake. These lagoons of the Kvarken can form chains, where moraine ridges separate the lagoons. In the first phase of the chain, the land uplift slowly lifts a moraine ridge above sea surface, and it slowly closes 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 turning more into fresh water.
A flad is followed by a glo, where 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 flat, 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.
The shallow isolated basins, flads and gloes offer more sheltered environment for animals when compared to the sea. In spring, the quickly warming shallow waters are popular among spawning fish like pike and perch. The young fish thrive in the lagoons, as there is plenty of zooplankton to eat and 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 nutritious 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 sweet and salty conditions
The High Coast’s and the Kvarken’s waters are part of the Gulf of Bothnia, which in turn is part of the Baltic Sea. The whole Baltic Sea is brackish water, which is a mix between salt seawater and fresh water coming from rains and rivers. The salt content decreases in the north parts of the Baltic Sea. The salinity of the oceans is over 3 percent, whereas the Baltic Sea’s salinity is much lower, only 0,4-0,5 percent.
The Baltic Sea does not have lots of different species, because brackish water is challenging living environment both for freshwater and saltwater species. Surprisingly, the waters of the Baltic Sea have ancient swimmers like a fourhorn sculpin, and marine crustaceans like Sadurias, who originate in the northern Siberia. Sadurias live also in the in the isolated basins of the High Coast. These ancient species are remnants of the times when the Baltic sea was saltier and had more water exchange with the World’s oceans.
Next chapter: the cultural heritage
Living on the rising land has made the people creative and resilient – how?