Syndey, Feb 1 (IANS): Mining and other industrial activities are turning freshwater rivers into saline systems not only in Australia but also in other parts of the world, threatening species such as the mayflies, stoneflies and caddisflies, says a study.

"Our study shows that the increasing salt levels in freshwater river systems are causing severe bio-diversity losses and may make it easier for alien and exotic species to get a foothold in these ecosystems," says Ben Kefford, study co-author from the University of Technology's Sydney Centre for Environmental Sustainability.

"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," says Kenfford, the journal Environmental Pollution reports.

"High salinity levels are particularly detrimental to key groups of freshwater invertebrates the mayflies, stoneflies and caddisflies which are critical in the recycling of terrestrial vegetation like leaves that fall into streams and providing food for fish and birds," adds Kenfford, according to a Syndey statement.

Kefford said that there were a variety of factors causing the worsening of human-induced river salinisation but that in Australia the main causes were mining, dryland and irrigation agriculture.

The researchers said that in the context of global warming and increasing human demand for water for consumption, agriculture and industry, areas affected by river salinisation will increase with potentially huge environmental and economic costs.