In July and August 2022, at least 300 tons of dead fish were pulled out of the Oder River, which forms part of the border between Poland and Germany. 

According to the European Commission and the European Environment Agency, the incident was one of the biggest ecological disasters involving a European river in recent history.

Investigations show that a combination of factors led to the environmental crisis: an increase in salinity, which caused blooms of toxic golden algae, heat waves, low water levels and nutrient spillage from agriculture. 

But it wasn't just the environment that took a hit: Local tourism in north-western Poland — a region known for water sports, fishing and kayaking — has declined dramatically over the last two years.