Baltic Sea -

Key indicators for fish stocks, waterbirds, and marine mammals have failed to meet health thresholds. The Baltic harbour porpoise population is critically low, with only about 500 individuals remaining.

In early 2026, experts noted a rapid loss of water (275 billion tonnes), leaving levels 67 cm below average due to atmospheric factors. Maritime & Economic Activity baltic sea

Approximately 94% of the sea is impacted by excessive nutrients, leading to "dead zones" roughly 1.5 times the size of Denmark. Key indicators for fish stocks, waterbirds, and marine

Often called the "most polluted sea in the world," its slow water turnover (roughly 30 years for a full exchange) causes toxins to linger for decades. Key indicators for fish stocks

State of the Baltic Sea – Third HELCOM holistic assessment