Biology
The archipelago is a unique region. The geographical location, its mosaic-like, vast seascape that is studded with small islands and the brackish water have created a special kind of landscape. Here you can find dense fir woods, lush groves, moorland and cliffs. The further out from the mainland the islands are located, the more barren is the landscape. In spite of that, biodiversity is high. Except from the flying squirrel and the hedgehog, most of the mammals that can be found on the mainland of the south-western region of Finland, can also be found here. On the islands, you can observe rare species of birds, insects and plants.
Grazing depending biotopes
On the islands, where cattle have been grazing, the landscape has slowly changed. Through the grazing, some species have disappeared and others have increased. Of our entire vascular plantlife, a large share consists of meadow plants, in the archipelago this share is about 60 per cent. The different types of areas are divided into landscapes:
- The wooded meadow is a meadow, where trees grow. Some pastures may look similar to it,
but the difference is that pastures are not mown. The terrain of the wooded meadow is more flat and lush than the terrain of the pasture. In addition to the mowing, the twigs of the trees on the wooded meadow were often harvested and used to make sheafs, which were given to the cattle as winter fodder. After the haymaking, the cattle were let loose to graze on the wooded meadow.
Coastal meadows are temporarily flooded. The vegetation is low and is maintained through grazing or through mowing.
- Dry meadow: A meadow that is dry and has rich herbal vegetation. Manually kept free from bushes and trees. It is usually not mown.
- Mesk meadow: Open glades with a high and lush vegetation. Grass and flowers have adapted to mowing. Green meadows were earlier used for haymaking and grazing, but nowadays they are only used for grazing. In damper areas, the mesk meadow changes into moist hay meadows and peatland meadows with a different flora, also adapted to grazing and mowing.
- Wooded pastures: Sparsely forest-covered grazing. The terrain is uneven and rocky. Because of this, the grazing ground is not mown. The trees are sparse, since hundreds of years of grazing has prevented the rejuvenation of the trees.
- Moorland: The moor is a treeless sandy heath, created though human activity. An unkempt moor evolves to pine forest. The moor was traditionally maintained by letting lambs and cattle graze there. Some moors have been burned over in hope of better grazing.
The Baltic Sea
The Baltic Sea is the world's largest body of brackish water. Brackish water is a mixture of salt and freshwater. The salinity varies between 0 and 15 psu (practical salinity units).
The Baltic Sea is a young sea that has evolved through different stages since the Ice Age. At times, the Baltic Sea has been cut off from the Atlantic Ocean. The Litorina Sea that evolved 7000 years ago was much larger. The salinity of the Litorina sea was also much higher than the salinity of today's Baltic Sea. During that period, the climate was also much warmer than today. During the different stages, many species have moved into the Baltic Sea, since its formation has created a suitable environment, both for freshwater and saltwater species. Relicts can still be found here, such as the opossum shrimp (
Mysis relicta).
The brackish water affects the flora and fauna in many ways. Many species live under stress. The salt content is too high for freshwater species, while marine species need a higher salinity. Many species have adapted to the environment and new species are introduced from time to time. The increasing naval traffic is a vector, i.e. a means for new species to move from one place to another. It is hard to anticipate the effect these introduced species will have on the fragile ecosystem of the Baltic Sea.
The most well-known of the introduced species (in the middle of the 19th century) is probably the barnacle (
Balanus improvisus) and the recently (1990) introduced predacious cladoceran (
Cercopagius pengoi). The predacious cladoceran sometimes appear in vast numbers and gets tangled up in fishing equipment. The species also affect the original zoo plankton.
The Baltic Sea is a sea of few species, but the species that do exist there often have a high abundancy.
The increased nutrient content that causes a higher biological production favours certain species of fish, such as the roach. An increased nutrient content also favours the production of algae. This is the reason for the increased opacity of the water. In the spring, diatom appears, and as the temperature of the water increases, other algae species appear. Filamentous algae, such as the green algae (
Cladophora glomerata) grows from the waterline down to a depth of 15 meters. When filamentous algae die, they form large floats that sink to the bottom. This can cause oxygen deficiency. Because of the opacity of the water, macro algae such as the bladder wrack (
Fucus vesiculosus) appear in more and more shallow water.