Impacts of climate change on olive crop evapotranspiration and irrigation requirements in the Mediterranean region

The Mediterranean basin is the largest world area having specific climatic conditions suitable for olive cultivation, which has a great socio-economic importance in the region. However, the Mediterranean might be particularly affected by climate change, which could have extensive impacts on ecosystems and agricultural production. This work focussed on the climate change impact on olive growing in the Mediterranean region considering the possible alterations of cultivable areas, phenological dates, crop evapotranspiration and irrigation requirements. Monthly climate data, with a spatial resolution of 0.25°×0.25° (latitude by longitude), have been derived from Regional Climate Models driven by ECHAM5 for the A1B scenario of the Special Report on Emissions Scenarios (SRES). The data used in the analysis represented two time periods: (i) present, called year 2000 (average values for the period 1991–2010), and (ii) future, called year 2050 (average values for the period 2036–2065). The areas suitable for olive cultivation were determined using the temperature requirements approach known as the Agro Ecological Zoning method. Crop evapotranspiration and irrigation requirements were estimated following the standard procedure described in the FAO Irrigation and Drainage Paper 56. Results showed that the potentially cultivable areas for olive growing are expected to extend northward and at higher altitudes and to increase by 25% in 50 years. The olive flowering is likely to be anticipated by 11±3 days and crop evapotranspiration is expected to increase on average by 8% (51±17mmseason−1). Net irrigation requirements are predicted to increase by 18.5% (70±28mmseason−1), up to 140mm in Southern Spain and some areas of Algeria and Morocco. Differently, effective evapotranspiration of rainfed olives could decrease in most areas due to expected reduction of precipitation and increase of evapotranspirative demand, thus making it not possible to keep rainfed olives’ production as it is at present.