Biodiversity in the Baltic Sea has undergone major changes during the past decades. However, the lack of comprehensive data and the natural variability in biodiversity makes it difficult to specify the human contribution to these changes.
The Baltic Sea is inherently a highly dynamic system and concurrently with the observed changes in biodiversity, large-scale climate fluctuations have influencer the Baltic. This has caused changes in the salinity and oxygen concentrations in the deep basins, as well as in sea-surface temperature, which in turn have affected the distribution of species and the ecosystem structure. The changes in climate, whether natural or anthropogenic, thus make it challenging to distinguish natural variation from human-induced modifications of the Baltic Sea biodiversity. Nevertheless, there is no doubt that various human pressures have contributed to the observed changes in biodiversity. While many of the observed changes in biodiversity are slanting towards a deteriorating state, there are also positive trends reported for selected species.
The biodiversity assessment will be updated periodically as described in the:HELCOM Monitoring and Assessment Strategy
Eutrophication thematic assessment
Hazardous substances thematic assessment