Assessing the long-term impact of climate change on olive crops and olive fly in Andalusia, Spain, through climate indices and return period analysis

The objective of this study is to investigate the long-term effects of climate change on olive crops in Andalusia, one of the most important olive growing areas worldwide, using tailored climate indices and return period analysis. Both the climatic indices and the occurrence probabilities of bad years in terms of olive yield and olive fly risk are being calculated for the reference period 1971–2000 and for the near (2031–2060) and distant future (2071–2100) under two emission scenarios using an ensemble of five high-resolution, bias-adjusted Regional Climate Models. Three threshold-based temperature related indices (SPR32, SU36, SU40) as well as mean temperature and precipitation related climatic indices (SPRTX, WINRR) have been calculated, revealing increasing changes in the near and distant future and pointing out the challenges faced by the olive sector due to climate change; a robust increase of the threshold-based indices are found in central and northern Andalusia, mainly in the provinces of Seville, Cordoba and Jaen. Although the changes of the precipitation-related index are less pronounced for the near future, robust decreases are projected for the distant future period under a high emission scenario. The identification of the bad years is based on observational data from five monitoring stations in Andalusia (Malaga, Granada, Sevilla, Cordoba and Jaen). The role of certain meteorological parameters (precipitation, temperature, relative humidity) is investigated and the return levels of interest for the calculation of the occurrence probabilities are estimated by the upper tail of the reference distribution. The results indicate an overall tendency for increased occurrence probability of bad years in terms of olive yield due to future decreased precipitation; bad year occurrences with return periods of below 2 years may increase by about 20 % by 2060. Spatial variability is also evident with overall larger changes in western Andalusia. The range of the olive fly is expected to decrease in the northern areas of Andalusia.