How does climate change affect soil salinity? The case study of a Mediterranean pasture with saline groundwater

Abstract The case study is located in an agricultural area of alluvial origin, approximately 10 km northeast of Lisbon (Portugal). The area is a peninsula surrounded by River Tejo, its estuary, and by River Sorraia. The peninsula lies 1 to 2 m above sea level, with saline groundwater arising from the estuarine tides. The soil is typically clayey and homogeneous. The future climate projections for the Mediterranean region show a decrease in precipitation, increase in mean temperature, and increase in sea water level. These conditions aggravate the processes leading to salt-affected soils (increased evapotranspiration, decrease in salt leaching during the rainy season, and increase of the groundwater salinity). This work evaluates the influence of climate change on soil salinity and water content in a rainfed spontaneous pasture, using Hydrus-1D. Three climate scenarios, comprising series of 30 years obtained with a regional climate model, were used: reference scenario (referent to 1971-2000), RCP4.5, and RCP 8.5 (both for 2011-2040). The results show an increase in the soil salinity in the RCP scenarios compared to the reference and a decrease in the mean yearly water content of the topsoil. Both effects limit the productivity of the pasture and even compromise the plants’ growth.