Reflections about blue ecosystem services in cities

Water is of particular importance for cities. Many fast growing megacities are facing serious water-related problems including pollution, eutrophication, missing wastewater treatment and, perhaps most importantly, a severe scarcity of clean water. In the entire urban world, water resources are used in an inefficient way. But there is great potential: this opinion paper discusses ecosystem services provided by waters—hereafter referred to as blue urban ecosystem services—and respective links to green infrastructure and the services they provide for human wellbeing. The messages given illustrate avenues for future research that might help to develop nature-based solutions for water-related challenges in urban regions.