Climate change implications for olive flowering in Crete, Greece: projections based on historical data

Climate change is expected to pose major challenges for olive cultivation in many Mediterranean countries. Predicting the development phases of olive trees is important for agronomic management purposes to foresee future climate impact and proactively act toward adaptation and mitigation strategies. In this study, a statistical model was developed based on winter chill accumulation and, in sequence, on heat accumulation to assess the changes in flowering occurrence for Olea europaea cv. Koroneiki, in the island of Crete, Greece. The model was based on and calibrated with long-term phenological observations and temperature data from four different sites in the island, spanning an elevation gradient between 45 and 624 m a.s.l. This model was used to assess the changes in flowering emergence under two Representative Concentration Pathway scenarios, RCP4.5 and RCP8.5, as projected by seven high-resolution Euro-CORDEX Regional Climate Models. Changes in chill accumulation were determined using the Dynamic Model. Reduction rates in chill accumulation for the whole chilling season ranged between 12.0 and 28.3% for the near future (2021-2060) and 22.7 and 70.9% for the far future (2061-2100), in comparison to the reference period of 1979-2019. Flowering was estimated to occur between 6 and 10 days earlier in the near future and between 12 and 26 days earlier in the far future, depending on the elevation and the climate change scenario.