Worldwide, water obtained from tidal rivers for human use is threatened by saltwater intrusion. This is the result of a recent study by an international research team led by the University of Maryland in the US, which has now been published in the journal Environmental Science & Technology Letters and in which the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) also participated. The main causes are the effects of climate change, such as prolonged periods of drought and sea level rise. In addition, local human activities affecting tidal rivers directly contribute to an increase in salinity in these vital freshwater resources.