Predicting the Impact of Climate Change on Olive Cultivation in Southwestern Türkiye under SSP3-7.0 Scenario

It is becoming more and more crucial to comprehend and manage the effects of extreme temperatures in order to preserve agricultural productivity and food security as climate change continues to intensify weather variability. Due to the increasing demand for olive products such as olive oil and olives in the world in recent years, olive cultivation has started to be cultivated economically in countries with a Mediterranean climate. This study investigates the future changes in growing degree days (GDD) for olive in southwestern Türkiye during the 21^st century, using convection-permitting simulations under the SSP3-7.0 scenario. Future climate projections based on the SSP3-7.0 scenario suggest pronounced warming trend, particularly in the summer season. In comparison to the reference period of 1995-2014, temperatures in the 2040-49 period are expected to rise by 2.5°C, and by 3.5°C in the 2070-79 period. The second largest warming trends occur in spring and autumn, approaching those of summer in the second projection decade. After the significant decrease in the winter season, the autumn season is expected to experience the second largest reduction in precipitation, with a similar drying trend extending into the spring months in 2070-79, exacerbating the already reduced winter precipitation. Considering the ten-year average of olive production in Türkiye, our study area contains most of the cities with the highest production. Therefore, GDD is calculated for olives over the period between 1 April and 15 October, using a base temperature of 12^oC. The results show a clear increase in GDD for olives in the future climate projections, especially in the second period. This increase indicates that olives will grow faster and mature earlier due to the accumulation of more heat. If the olives ripen too early, this can affect the yield and quality of the oil. Nevertheless, the relative effects of an increase in GDD across phenological stages may expose the plant to the risk of damage due to higher frequency of extreme weather events (e.g. heatwaves and late spring frosts). Insufficient water can lead to slower growth and smaller fruit sizes, and also lower oil content in olives that reduces the production of high-quality extra virgin olive oil. Olive growers in southwest Türkiye can mitigate some of the negative consequences of climate change while preserving their productivity and quality by focusing on climate-resilient types, water conservation, and sustainable farming methods.

This work is funded by the project titled 'ACLIFS - Assessment of Climate Change Impacts on Food Safety and Enhancing the Resilience of Rural Communities' which is implemented under the “Climate Change Adaptation Grant Program (CCAGP)”.

Key words: Growing degree days, convection-permitting model, COSMO-CLM, future projections, SSP3-7.0