Salt Level Rise in Freshwater Rivers Causing Biodiversity Loss, Says Study

A new study by Australian and European researchers highlights the growing environmental problem caused by increasing salt levels in the world's rivers.

The researchers reveal that salinity is posing a major threat to the freshwater river systems, as organisms thriving in such rivers can tolerate only certain ranges of water salinity. Secondary salinisation (increase in salt levels caused by human interventions) is impacting at the individual, population, community and ecosystem levels, thus ultimately leading to biodiversity losses and apparently allowing alien species to thrive in these ecosystems, according to the researchers.

"In low salinity rivers there is a much greater diversity of species, with each site having a different set of species, but as salinity increases the same limited set of species get found at all sites. Eventually if salinity increases enough the number of species at a site decreases," study co-author Ben Kefford, from the University of Technology, Sydney, said in a statement.

High levels of salinity are affecting freshwater invertebrates such as the mayflies, stoneflies and caddisflies. These organisms play a significant role in recycling the terrestrial vegetation like leaves that fall into streams and providing food for fish and birds, Kefford said.

Various factors such as irrigation, mining activity or the use of salts as de-icing agents for roads, are cited as reasons for the human-induced rise in salt levels in freshwater rivers. In particular, the main causes attributed to river salinisation in Australia are dryland and irrigation agriculture and mining.

While there are water quality guidelines in Australia, no such quality standards exist in Europe, where salinity is not seen as a major problem. With the increase in global temperatures and human demand for water consumption, freshwater rivers that have already been affected by salinisation might potentially cause huge environmental and economic costs, the researchers concluded.

They insisted on integrated catchment strategies and identifying threshold salt concentrations to manage secondary salinisation and preserve the ecosystem integrity.

The details of the study, "Salinisation of rivers: An urgent ecological issue", are published in Environmental Pollution.