Future aridity and Drought Risks for Traditional and Super-Intensive Olive Orchards in Portugal

Assessing drought and aridity risks can help olive growers make informed decisions and plan effective management strategies to mitigate climate-related challenges. Portugal is a major producer of olive oil, with six regions designated as Protected Denomination of Origin (PDO), each characterized by varying olive orchard (OR) densities, ranging from traditional rainfed to superintensive irrigated systems. This study aimed to evaluate future drought and aridity trends and their potential effects on ORs within these PDO regions. To achieve this, drought and aridity indicators were analyzed for both historical (ERA5: 1981–2000) and projected future periods (2041–2060; 2081–2100) under two climate scenarios (RCP4.5 and RCP8.5), using a 7-member ensemble of global climate models. Spearman’s correlation analysis identified Annual Mean Aridity (AIA) as the most representative climate indicator influencing ORs. Readily Available Soil Water (RAW, mm) was used to assess the soil’s capacity to retain moisture for olive trees. Additionally, the Olive Drought and Aridity Risk Index (ODAR) was developed to estimate future risks for each OR by weighting AIA and RAW based on orchard density. Projections indicate that southern Portugal will experience greater aridity (0.69) compared to central and northern regions (0.60). Moreover, southern PDOs are expected to have lower RAW levels (<60 mm), whereas central and northern areas will retain higher soil water content (>90 mm). These findings suggest that southern ORs will be more vulnerable to water stress than those in the north. According to ODAR, ORs in central PDOs will face both low and high risks, while northern regions will mostly experience moderate to high risk. However, in the south, very high risk levels are expected, which could adversely impact olive tree growth, fruit production, and olive oil quality. To enhance the resilience of the sector, targeted adaptation strategies will be necessary. This work is supported by National Funds by FCT –Portuguese Foundation for Science and Technology, under the projects UID/04033 and LA/P/0126/2020 (https://doi.org/10.54499/LA/P/0126/2020).