In the near future, climate change will likely increase pressures on transition zones such as deltas and coastal areas (IPCC, 2013). This special issue focuses on how to “climate proof” these zones with special concerns for the stresses stemming from droughts and salinization. Coastal zones and Deltas are under pressure worldwide. High water demand in these regions put pressure on the availability of freshwater resources and on coastal ecosystems. This leads to problems like water shortage, overexploitation of groundwater resources, saltwater intrusion, and degradation of wetlands. Economic growth, population increase, and climate change may potentially intensify these problems. This, therefore, is of strategic importance for Europe, which has a long coastline where many human activities are concentrated. Coastal aquifer development is often intensive and prone to induce salinization because of seawater intrusion, up-coning of deep saline water, and residual salinity in aquitards (Custodio 2010). Severity and frequency of droughts appear to have increased in the southern European countries. Minimum river flows are projected to decrease significantly not only in southern and southeastern Europe, but also in many other parts of the continent, especially in summer (EEA 2012). The Mediterranean region is particularly stressed (e.g. Giorgi 2006), due to the combined effect of rising sea levels, increased water demand due to global warming, and reduced aquifer recharge.