2.1 The Baltic Sea Area is a globally unique and
sensitive brackish-water ecosystem. It is geologically young, semi-enclosed
and shallow. The exchange of water with the North Sea is limited and
slow, resulting in long residence time of water as well as low and
varying levels of salinity. The climate ranges from sub-arctic to
temperate and large parts of the Baltic Sea are annually ice-covered.
All these factors have resulted in a marine environment with low biodiversity.
Despite the low number of marine species, the area hosts a unique
mix of marine, freshwater and a few true brackish-water species. The
Baltic marine and coastal areas consist of globally important breeding
grounds, nurseries, shelters and food sources for coastal birds and
waterfowl. The diversity of coastal biotopes is high and characterized
by many threatened aquatic and terrestrial species. The disappearance
of single-key species could seriously impede the functioning of the
whole system. Hence, the Baltic marine ecosystem is considered as
particularly vulnerable to man-made disturbances.
2.2 The PSSA Baltic Sea Area is vulnerable to
damage by international shipping activities. The Baltic Sea Area has
some of the densest maritime traffic in the world. During recent decades
the traffic in the area has not only increased but the nature of the
traffic has also changed rapidly. One tendency is the increase in
the transportation of oil and other harmful substances by ships, which
also increases the potential for water pollution. A spill could have
disastrous effects on the vulnerable nature of the area such as fish
spawning areas and breeding, nursery and resting areas for birds and
marine mammals.
2.3 More than 2,000 ships are en route in the
area on an average day, not including ferries, smaller fishing vessels
or leisure craft. Of these 2,000 ships around 200 are oil tankers,
some carrying a cargo of 150,000 tons.