Climate change projections for olive yields in the Mediterranean Basin

The olive tree is one of the most important crops in the Mediterranean basin. Given the strong climatic influence on olive trees, it becomes imperative to assess climate change impacts on this crop. Herein, these impacts were innovatively assessed, based on an ensemble of state-of-the-art climate models, future scenarios and dynamic crop models. The recent-past (1989-2005) and future (2041-2070, RCP4.5 and RCP8.5) olive growing season length (GSL), yield, growing season temperature (GST) and precipitation (GSP), potential (ETP) and actual (ETA) evapotranspiration, water demand (WD) and water productivity (WP) were assessed over Southern Europe. Crop models were fed with an ensemble of EURO-CORDEX regional climate model data, along with soil and terrain data. For the recent-past, important differences between western and eastern olive growing areas are found. GSL presents a strong latitudinal gradient, with higher/lower values at lower/higher latitudes. Yields are lower in inner south Iberia and higher in Italy and Greece, which is corroborated by historical data. Southern Iberia shows higher GST and lower GSP, which contributes to a higher ETP, lower ETA and, consequently, stronger WD. Regarding WP, the recent-past values show similar ranges across Europe. Future projections point to a general increase in GSL along with an increase in GST up to 3 degrees C. GSP is projected to decrease in Western Europe, leading to enhanced WD and consequently a yield decrease (down to -45%). Over eastern European, GSP is projected to slightly increase, leading to lower WD and to a small yield increase (up to +15%). WP will remain mostly unchanged. We conclude that climate change may negatively impact the viability of olive orchards in southern Iberia and some parts of Italy. Thus, adequate and timely planning of suitable adaptation measures are needed to ensure the sustainability of the olive sector.