An international team of scientists analysed the biases and gaps in studies of freshwater salinisation. They present a research agenda to advance the understanding of the effect of salts on lakes and streams. Most importantly, they propose several research priorities on different time and space scales that need to be tackled by multidisciplinary approaches as a joint effort by the international scientific community.

Salt pollution in lakes and streams appears to strongly change ecosystems and may seriously impair essential services to human societies. Human activities such as mining, intensive agriculture, water withdrawal and climate change are pushing salt concentrations in our inland waters to higher, partly unprecedented levels. This may not only make water undrinkable and unusable for industry, but have many other serious consequences ranging from loss of salt-sensitive species and spread of invasive species to the alteration of nutrient cycling and transfer of organic matter through the food webs and rise in greenhouse gas emissions.

Despite increasing evidence of dramatic effects from salinisation, present knowledge is not enough to predict consequences of salinization on freshwater ecosystems. To challenge this lack, a team of scientists from 10 countries joined their efforts to determine the most urgent research needs. The review paper published in Trends in Ecology and Evolution emerged as a spin-off from a webinar series on Grand Challenges in Aquatic Ecology in the European Network Project AQUACOSM-plus. Due to COVID-19, the meeting had to be adapted to a webinar format, which allowed a greater international participation and therefore inspired a more global message.

After reviewing several hundred papers published in the last 5 years, the authors show an uneven geographical coverage of current knowledge with the focus on North America and Europe and neglected regions such Africa or South America where salinization drivers are intensifying. Most of current research also neglects small freshwater habitats like ponds that are very important for regional biodiversity. There is little information about effects of different types of salts, the consequences at regional and landscape scales, the impact on ecosystem level processes such as greenhouse gas emissions or nutrient removal. Most studies focus on aquatic invertebrates while knowledge of the effect of salinization on microorganisms that drive nutrient cycling and the top of the aquatic food pyramid with fish, reptiles and amphibians is poor.

“We elaborated a research agenda with the most urgent gaps to fill and proposed several ways to tackle them across several perspectives. For each perspective we list three main focuses and suggest experiments, methods or aspects that will foster new studies advancing the field”, – explains David Cunillera-Montcusí, the lead author from WasserCluster Lunz, Austria 

The global tendency of salinization of lakes and streams is a great challenge for freshwater biodiversity, ecosystems functioning and the human societies that depend on them. To address this challenge a joint effort of the scientific community, practitioners, local communities and policy makers is needed. The collaborative effort of the international team of scientists that published the review paper tries to facilitate this joint effort by targeting paths to advance as well as raising the interest for this global-scale problem that will bring a saltier world for which we must prepare.

“This is very important message that closes the gap between freshwater and saline lakes studies. Indeed, the worldwide salinization trend makes the knowledge produced by saline lakes research community highly relevant and demanded”, – adds Egor Zadereev, one of co-authors, leading research scientist at the Institute of Biophysics, Krasnoyarsk, Russia, the President of the International Society for Salt Lake Research.