The intrusion of seawater into freshwater bodies, such as rivers and streams, is increasing somewhat across Europe and threatening the biodiversity of these ecosystems.
According to a study led by the Catalan research group FEHM-Lab (comprising the University of Barcelona, the Spanish National Research Council and the Institute of Agro-Food Research and Technology), more than 23,000 kilometres of the region’s river network (about 2%) exceed the salinity level defined as the international standard for protecting aquatic life.
Published in the journal Nature Communications, the research analyzes data from 1970 to 2024 on the water quality of rivers in 35 European countries. In 28 of them, there are rivers where salinity has more than doubled compared with what would occur under natural conditions, i.e., without human influence.
The researchers explain that the rise in salinity levels in European river ecosystems results from both natural and anthropogenic factors. Climate, geology and hydrology are all natural drivers that influence the salinity of rivers, but the way humans, for example, use land, is also strongly associated with increasing salinization.
Beyond environmental and ecological consequences, salinization can also impact human communities and important economic sectors, as it affects sources of drinking water, agricultural irrigation, and use in industrial activities.
Based on estimates, the researchers indicate that 26% of Europe’s rivers and streams exhibit low levels of salinization and 14% moderate levels. However, 9% of these flowing water bodies show severe levels and 1% extreme.
Furthermore, the analysis reveals that salinity exceeds the limits set for drinking water in about 1% of the river network and those for irrigation and industrial use in about 3%.
In a statement, the Joint Research Centre (JRC), the research arm of the European Commission, says that although salinization is considered a growing pressure on European freshwater ecosystems, with increasing ecological and socioeconomic impacts, secondary salinization continues to be largely “ignored” in the current water policies of the European Union and its member states.
“Twenty-five years after the adoption of the EU Water Framework Directive, which requires Member States to achieve ‘good ecological and chemical status’ of surface waters, most countries still do not have specific salinity standards and do not monitor or systematically report the impacts of salinity,” notes the JRC.
