The total area of the Baltic Sea is 422 000 square kilometres. The Finnish territorial waters and the country's exclusive economic zone (EEZ) take up slightly less than one fifth of the total area (82 000 km²). The share of the Baltic Sea of Finland's total area is 19%.

Baltic Sea is only a little more than 10 000 years old. I addition, its history includes several sequential freshwater and marine phases. For these reasons only a few species has had sufficient time to adopt to Baltic Sea's unique conditions. Also, dispersing along natural routes to the Baltic Sea is quite slow for many marine species. Salinity of the Baltic Sea is relatively low, because approximately a half of the Baltic sea water is coming from rivers. Salinity decreases further towards east and north, being lowest in the bottoms of the Gulf of Finland and Bothnian Bay.

Relatively small amount of actual marine species occurs in the Finnish territorial waters because of low salinity of the coastal areas. Only 1 % of well-known species primarily inhabits the Baltic Sea. However, the real share of marine species is in reality greater than this, because a large amount for example micro-algae (approximately 5 000 species) is poorly known and has not been evaluated. Baltic Sea is the most important habitat for many fishes, molluscs, marine mammals, birds and macro-algae.

What and where

The Finnish territorial waters of the Baltic Sea are under main interest in this context. These include the Finnish parts of the Gulf of Bothnia, Gulf of Finland and Archipelago Sea. Gulf of Bothnia is in addition divided into Bothnian Sea, the Quark and Bothnian Bay. This kind of limited examination is ecologically artificial, but can be reasoned from administrative grounds.

The EEZ Act came into operation in Finland in 2005. The law improves the enforcement of environmental crimes since on the EEZ area for example vessels which cause deliberate harm to the environment can be charged in the Finnish court of law. The borders of the exlusive econimic zone are defined by agreements with other countries surrounding the Baltic Sea. The exlusive economic zone could extend as far as 200 nautical miles away from the territorial water border (according to the UN general agreement), but for geographical reasons this is not reached in Finland. At present the whole Baltic Sea is divided to such zones among the surrounding countries.