A new study by European scientists warns that freshwater flowing through rivers into the Mediterranean Sea could decline by as much as 41% due to climate change. The research, published on February 3, 2025, outlines a worst-case scenario in which global temperatures rise by 4°C above pre-industrial levels, drastically altering coastal ecosystems and threatening the region’s fisheries.
The decrease in river flow would reduce freshwater and nutrient inputs, leading to lower primary productivity in the Mediterranean’s marine ecosystem. This would have cascading effects on the food chain, ultimately impacting commercially valuable seafood species.
“The results show that 41% less river flow could slash marine productivity by 10% and fish biomass by 6% in the Mediterranean, leading to annual losses of €4.7 billion for the fishery sector,” stated the European Commission’s Joint Research Centre (JRC). These losses could have severe socio-economic consequences for fisheries and coastal communities that depend on them.
Adriatic and Aegean Seas Face Highest Risk
Among the most vulnerable areas are the Adriatic and Aegean Seas, which are among the most heavily fished waters in the Mediterranean. The study predicts marine productivity could decline by 12% in the Adriatic Sea and by 35% in the Aegean Sea, putting fish stocks at serious risk.
The researchers used the Blue2 Modelling Framework (Blue2MF), developed by the JRC, to analyze the impact of reduced river flow on the Mediterranean’s biogeochemistry, food web, and economy. Their findings suggest that some of the most productive fishing grounds could lose more biomass than they currently land in fishery catches, highlighting the urgent need for action to mitigate climate change and protect marine ecosystems.