Future Scenarios for Aridity under Conditions of Global Climate Change in Extremadura, Southwestern Spain

Aridity conditions in semi-arid lands with warm climates are key variables that must be assessed to properly manage water and plan to minimise the threat of desertification. This study analyses the spatial distribution of aridity in Extremadura, southwestern Spain, using the De Martonne aridity index (I-DM), considering a historical reference period (1971-2005) and three-time intervals: 2006-2035 (near future), 2036-2065 (mid-century) and 2066-2095 (end of the century). Projections were computed using a set of ten global climate model (GCM) and regional climate model (RCM) combinations under two representative concentration pathways (RCPs), RCP4.5, an intermediate anthropogenic radiative forcing scenario, and RCP8.5, a fossil-intensive emission scenario. Progressive strengthening of aridity conditions over Extremadura was evident until the end of the century, mainly under the RCP8.5 scenario. From the predominance of the Mediterranean aridity class in the south of the region during the reference period, semi-arid conditions will soon spread across this zone, occupying most of it during mid-century and later. In the north of Extremadura, less arid conditions will be reduced to the highest elevations, increasing the Mediterranean and semi-arid categories, particularly under the RCP8.5 scenario. Consequently, the projected increase in aridity conditions in Extremadura will make this region more vulnerable to climate change. Policies devoted to adapting to the expected conditions and controlling aridity in vulnerable areas will be necessary to mitigate the negative impacts, with significant environmental and socio-economic implications in the region.